Dissertations / Theses on the topic 'Hadronic jet'
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Kallweit, Stefan. "Precision calculations for Gauge-Boson pair production with a hadronic jet at Hadron colliders." Diss., kostenfrei, 2008. http://edoc.ub.uni-muenchen.de/9362/.
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Fong, Che Ping. "Jet fragmentation at small momentum fractions in quantum chromodynamics." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239209.
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Newton, Warrick Miles. "Measurement of the inclusive one-jet and two-jet cross-sections in two-photon interactions at #sq root#=91 GeV." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267065.
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Tsang, Wai Yeung. "Hadronic jet production at the CERN UA2 detector : an experimental test of QCD." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254216.
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Chen, Xuan. "Hadronic production of a Higgs Boson in association with a jet at next-to-next-to-leading order." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11158/.
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In this thesis the production of a Higgs boson in association with a hadronic jet at the Large Hadron Collider is studied using the effective interaction between the Higgs boson to gluons induced by a heavy quark. The Leading Order (LO), Next- to-Leading Order (NLO) and Next-to-Next-to-Leading Order (NNLO) perturbative QCD corrections are studied for all of the parton channels. The infrared (IR) diver- gent behaviour of the various contributions to the partonic cross section is regulated using the antenna subtraction formalism. This method has previously been used at NNLO in the calculation of three jets production in the e+e− annihilation and for the gluonic dijet production via proton collision. The research presented in this thesis extends the antenna formalism to include scattering processes in which the initial state parton changes its identity. All contributions to the pp → H+jet pro- cesses are calculated at LO, NLO and NNLO and numerically tested to demonstrate the convergence between the matrix elements and the antenna subtraction terms in the various unresolved limits. As an example of the phenomenological impact of this work, numerical results for the total and differential Higgs plus one jet cross sections are presented for the purely gluonic subprocesses.
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Winter, Jan-Christopher. "QCD jet evolution at high and low scales." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1208912443778-27732.
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This thesis deals with a broad range of aspects that concern the simulation of QCD jet physics by Monte Carlo event generators. Phenomenological work is presented in validating the CKKW approach for merging tree-level matrix elements and parton showers. In the second part the main project is documented comprising the definition, realization and verification of a new QCD colour-dipole cascade. Finally, a new cluster-hadronization model is introduced.
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Gupta, Shaun. "A study of longitudinal Hadronic shower leakage and the development of a correction for its associated effects at √s = 8 TeV with the ATLAS detector." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:3f37bd18-d4d2-40c5-b231-e193060ec218.
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In the high energy environment of the Large Hadron Collider, there is a finite probability for the longitudinal tail of the hadronic shower represented by a jet to leak out of the calorimeter, commonly referred to as longitudinal hadronic shower leakage, or jet 'punchthrough'. This thesis prescribes a method for identifying such 'punch-through' jets via the use of muon activity found behind a jet in the ATLAS muon spectrometer, finding an occurrence rate of up to 18% in the worst affected regions. 'Punch-through' jets were found to degrade the measured jet energy scale by up to 30%, and jet energy resolution by a factor of 3. A correction to remove these effects was developed in Monte Carlo and validated in data, with associated systematic uncertainties derived. The correction was found to negate the degradation of the measured jet energy scale, improving the jet energy resolution by up to 10% in the worst affected regions, and up to 1.6% overall. The correction was integrated into the final 2012 ATLAS jet energy calibration scheme as the fifth step of the Global Sequential corrections. The prescription developed in this thesis to derive the correction is currently being used by ATLAS in Run II of the Large Hadron Collider.
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Winter, Jan-Christopher. "QCD jet evolution at high and low scales." Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A23602.
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This thesis deals with a broad range of aspects that concern the simulation of QCD jet physics by Monte Carlo event generators. Phenomenological work is presented in validating the CKKW approach for merging tree-level matrix elements and parton showers. In the second part the main project is documented comprising the definition, realization and verification of a new QCD colour-dipole cascade. Finally, a new cluster-hadronization model is introduced.
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Bravo, Gallart Sílvia. "Measurements of the Strong Coupling Constant and the QCD Colour Factors using Four-Jet Observables from Hadronic Z Decays in Aleph." Doctoral thesis, Universitat Autònoma de Barcelona, 2001. http://hdl.handle.net/10803/3335.
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En aquest treball es presenten dues mesures, una de la constant d'acoblament forta i l'altra d'aquesta mateixa constant conjuntament amb els anomenats factors de color. Les dades foren recollides pel detector ALEPH durant els anys 1994-95 a energies al voltant dels 91.2 GeV.Per a les dues mesures s´usaren obervables de quatre jets. La mesura de la constant d´acoblament forta a partir de la taxa de sucesos a quatre jets fou la primera realitzada a partir d´un observable de quatre jet i en resultà una de les mesures més precises fins avui.
La mesura conjunta de la constant d´acoblament i els factors de color representa un prova rigorosa de la teoria de les interaccions fortes, la cromodinàmica quántica. Els resultats, amb incerteses molt competitives, estan en acord absolut amb els valors esperats per la teoria i també amb els resultats d'altres col·laboracions.
In this work two measurements are presented. One is the measurement of the strong coupling constant alone, and the other the combined measurement of the strong coupling constant and the, so called, colour factors. Data were collected by the ALEPH detector during years 1994-95 at energies around 91.2 GeV.
Both measurements made use of four-jet observables. The measurement of the strong coupling constant from the four-jet rate was the first ever made from a four-jet observable, and represents one of the most precise measurements at present.
The combined measurement of the strong coupling constant and the colour factors is a stringent test of the theory, quantum chromodynamics. The results, with very competitive uncertainties, are in exact agreement both with the values expected by the theory and the results from other collaborations.
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Grahn, Karl-Johan. "Measurement of Multi-Jet Production in Proton-Proton Collisions at 7 TeV Center-of-Mass Energy and Hadronic Calibration Studies with the ATLAS Detector at CERN." Doctoral thesis, KTH, Partikel- och astropartikelfysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-29111.
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The ATLAS experiment – situated at the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Geneva – took its first collsion data in 2010. Physics topics include finding the Higgs boson, heavy quark physics, and looking for extensions of the Standard Model of Particle Physics such as supersymmetry. In this thesis, inclusive multi-jet production has been studied with the ATLAS detector in proton-proton collisions at a center-of-mass energy of 7 TeV, using an integrated luminosity of 17 nb−1. The anti-kt algorithm with distance parameter ℝ = 0.6 is used to identify jets. The inclusive multi-jet cross section is measured, as well as the ratio ofcross sections for inclusive production of n − 1 and n jets for n ≤ 6. The differential cross sections of the first, second, third and fourth leading jets as a function of transverse momentum, and the differential cross section as a function of the scalar sum of the pT of selected jets, HT, for different jet multiplicities are presented. The ratio of the differential cross section as a function of HT for 3-jet and 2-jet events is also measured. The results are compared to expectations based on leading order QCD, which agree with the data. In addition, a new method for calibrating the hadron response of a segmented calorim-ter is developed and successfully applied to 2004 ATLAS combined beam test data. It is based on a principal component analysis of the calorimeter layer energy deposits, exploiting longitudinal shower development information to improve the measured energyresolution. For pion beams with energies between 20 and 180 GeV, the particle energy is reconstructed within 3% and the energy resolution is improved by 11% to 25% comparedto the response at the electromagnetic scale. Multi-mode optical readout cables for the ATLAS liquid argon calorimeters, about one hundred meters in length, were installed between the main ATLAS cavern and the counting room in the USA15 cavern. Patch cables were spliced onto the ribbons and the fiber attenuation was measured. For 1296 fiber pairs in 54 cables, the average attenuation was 0.69 dB. Only five fibers were found to have losses exceeding 4 dB, resulting in a failure rate of less than 2 per mill. In the ATLAS liquid argon barrel presampler, short circuits consisting of small pieces of dust, metal, etc. can be burned away in situ by discharging a capacitor over the high voltage lines. In a burning campaign in November 2006, seventeen existing short circuits were successfully removed. An investigation on how to implement saturation effects in liquid argon due to high ionization densities resulted in the implementation of the effect in the ATLAS Monte Carlo code, improving agreement with beam test data. The timing structure of hadronic showers was investigated using a Geant4 Monte Carlo. The expected behavior as described in the literature was reproduced, with the exception that some sets of physics models gave unphysical gamma energies from nuclear neutron capture.QC 20110125
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Jammes, Jérôme. "Mesure de la section efficace de production de paires de quarks top dans le canal comportant un muon, un tau, des jets dont au moins un jet de b, et de l'énergie manquante auprès de l'expérience Dzero du Tevatron." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2011. http://tel.archives-ouvertes.fr/tel-00840859.
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Le but premier de la physique des hautes énergies est d'améliorer notre connaissance de la structure fondamentale de la matière, et notamment des particules qui constituent le monde. L'une d'entre elles est le quark top, qui fut découvert en 1995 par les collaborations CDF et D0 auprès du collisionneur protons-antiprotons Tevatron. Un des buts principaux du Tevatron a été depuis l'étude fine des propriétés du quark top, et en particulier de la section efficace de production de paires top-antitop. Différentes analyses ont été menées dans les canaux leptons, dileptons, et tout hadronique afin de déterminer le plus précisément possible les valeurs de ces paramètres, et ainsi de tester la validité du Modèle Standard. Le but principal de cette thèse est de vérifier une des prédictions théoriques du Modèle Standard de la physique des particules, à savoir la section efficace de production top-antitop, auprès du collisionneur Tevatron. Le canal étudié est constitué d'un muon, d'un lepton tau, de leurs neutrinos associés, de de deux jets de quark b (l'un d'entre eux provenant d'un quark b, l'autre d'un anti-quark b). La reconstruction et l'identification des jets , des muons, des leptons taus (en particulier par l'utilisation d'un réseau de neurones dédié), et l'étiquetage des jets de b, représentent les éléments fondamentaux de cette étude. Au final, un bon accord entre les données et la simulation Monte Carlo est obtenu à la dernière étape de cette analyse. En outre, la mesure finale de la prédiction théorique au niveau NLL + NLO du calcul des pertubations sont compatibles.
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Fletcher, Gregory. "A Measurement of W+jets Z+jets with the ATLAS Detector." Thesis, Queen Mary, University of London, 2015. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8047.
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A study is presented on the production of vector boson (W and Z0) events in association with recoiling hadronic activity in the form of hadronic jets, using proton-proton collisions at the LHC. The dataset was taken by the ATLAS detector during the 2011 data-taking run, at a centre of mass energy p s = 7 TeV, and corresponds to an integrated luminosity of 4.6 fb 1. A measurement of the cross-section ratio of W+jets Z+jets events is de ned, reducing the large systematic uncertainties inherent in the experimental measurement of such events. Inclusive and di erential cross-sections are presented for W+jets Z+jets , as a function of a range of kinematic variables, and are compared to state-of- the-art theoretical predictions.
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Hayward, Scott Kelly. "A study of the retention of quark quantum numbers in hadron jets." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28775.
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The retention of quantum numbers in hadron jets was studied, and a model was constructed
to infer the quantum numbers of the leading quark and antiquark in the the reaction e⁺e⁻ → qoqo → hadrons, from the quantum numbers of the final state particles. The method used involved taking a weighted average of the quantum numbers of the hadrons in the jet, with the weight assigned to each particle dependent on its kinemat-ical variables. The model was tested using the Lund Monte Carlo JETSET 7.1 at 80 GeV. It was found that in two jet events, it was possible to determine the sign of the charge of the leading partons with SO percent accuracy overall, and with greater than 94 percent accuracy in 41 percent of the events (using cuts on the weighted average to select the events). In light quark events (dd, uu, and ss), it was found that the quark jet and its flavour could be determined with about 48 percent precision and heavy quark tagging of cc and bb could be achieved in 38 and 63 percent of events respectively. In 15 percent of the light quark events, selected by consistency between the two back to back jets, successful determination of the quark jet and its flavour were obtained in 85 percent of events, with heavy quark contamination reduced to 12 and 6 percent of cc and bb events respectively. The model was also run on three jet events at 80 GeV. Although it was possible to identify one jet as a non-gluon jet (in particular the jet which subtends the largest angle with the other two jets) in 90 percent of events, it was not possible to determine which of the two remaining jets was the gluon jet. The sign of the electric charge of the non-gluon jet could be determined in 70 percent of events overall, and in 90 percent of a smaller group of 20 percent of events again using cuts on the weighted charge for the jets. The flavour of the non-gluon jet could be determined in 42 percent of events overall, and in 65 percent of a smaller group of 18 percent of events using consistency between the non-gluon jet and the other two jets, although heavy quark contamination was more significant. Finally, the accuracy with which the sign of the electric charge and flavour could be determined in two jet events at energies in the range 20 to 100 GeV was studied. It was found that as the centre of mass energy increased, the precision with which these properties could be inferred showed a marked increase.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Williams, Peter Howard. "Hadronic Higgs production with forward jets." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/3131/.
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The production of a Higgs boson with central rapidity, decaying to bb and accompanied by two jets that are forward in rapidity is presented as an important class of events at the Large Hadron Collider. Specifically, we study central Z boson production accompanied by rapidity gaps on either side as a way to gauge Higgs production via weak boson fusion at the LHC. We analyse the possible backgrounds for the bb decay mode and show that these can be substantially reduced. Special attention is paid to the evaluation of the gap survival factor, which is the major source of theoretical uncertainty in the rate of H, Z and W central production events with rapidity gaps. More generally, in relation to Higgs plus forward jet production, we consider the hadronic radiation patterns for the generic process of bb plus two forward jet production at the LHC, where the (centrally produced) bb originate either from a Higgs, a Z or from standard QCD production processes. A numerical technique for evaluating the radiation patterns for non-trivial final states is introduced and shown to agree with the standard analytic results for more simple processes. Significant differences between the radiation patterns for the Higgs signal and the background processes are observed and quantified. This suggests that hadronic radiation patterns could be used as an additional diagnostic tool in Higgs searches in this channel at the LHC. We also study the applicability of an equivalent photon/gluon approximation in describing events with a central system accompanied by two forward jets.
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Jouttenus, Teppo T. (Teppo Tapani). "Jet production at hadron colliders." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76979.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 101-104).
Hadronic jets feature in many final states of interest in modern collider experiments. They form a significant Standard Model background for many proposed new physics processes and also probe QCD interactions at several different scales. At high energies incoming protons produce beam jets. Correctly accounting for the beam and central jets is critical to precise understanding of hadronic final states at the Large Hadron Collider. We study jet cross sections as a function of the shape of both beam and central jets. This work focuses on measuring jet mass but our methods can be applied to other jet shape variables as well. Measuring jet mass introduces additional scales to the collision process and these scales produce large logarithms that need to be resummed. Factorizing the cross section into hard, jet, beam, and soft functions enables such resummation. We begin by studying jet production at e + e- collisions in order to focus on the effects of jet algorithms. These results can be carried over to the more complicated case of hadron collisions. We use the Sterman-Weinberg algorithm as a specific example and derive an expression for the quark jet function. Turning to hadron colliders, we show how the N-jettiness event shape divides phase space into N +2 regions, each containing one central or beam jet. Thus, N-jettiness works as a jet algorithm. Using a geometric measure gives central jets with circular boundaries. We then give a factorization theorem for the cross section fully differential in the mass of each jet, and compute the corresponding soft function at next-to-leading order (NLO). We use a method of hemisphere decomposition, which can also be applied to calculate N-jet soft functions defined with other jet algorithms. Our calculation of the N-jettiness soft function provides the final missing ingredient to extend NLO cross sections to resunmmed predictions at next-to-next-to-leading logarithmic order. We study the production of an exclusive jet together with a Standard Model Higgs boson. Based on theoretical reasons and agreement between our calculation and data from the ATLAS collaboration, we argue that our results for the jet mass spectrum are a good approximation also for inclusive jet production and other hard processes.
by Teppo T. Jouttenus.
Ph.D.
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Martini, Till. "The Matrix Element Method at next-to-leading order QCD using the example of single top-quark production at the LHC." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19288.
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Hochenergiephysikanalysen zielen darauf ab, das Standardmodell—die gemeinhin akzeptierte Theorie—zu testen. Für überzeugende Schlüsse, sind Analysemethoden nötig, welche einen eindeutigen Vergleich zwischen Daten und Theorie ermöglichen und zuverlässige Abschätzung der Unsicherheiten erlauben.
Die Matrixelement-Methode (MEM) ist eine Maximum-Likelihood-Methode, welche speziell auf Signalsuche und Parameterschätzung an Beschleunigern zugeschnitten ist. Die MEM hat sich durch optimale Nutzung vorhandener Information und sauberer statistischer Interpretation der Ergebnisse als vorteilhaft erwiesen.
Sie hat jedoch einen großen Nachteil: In der Originalformulierung ist die Berechnung der Likelihood intrinsisch auf die erste störungstheoretische Ordnung in der Kopplung limitiert. Höhere Ordnungskorrekturen verbessern die Genauigkeit theoretischer Vorhersagen und erlauben eindeutige feldtheoretische Interpretation der gewonnen Informationen.
In dieser Arbeit wird erstmalig die MEM unter Einbezug der Korrekturen der nächstführenden Ordnung (NLO) der QCD-Kopplung durch Definition von Ereignisgewichten für die Berechnung der Likelihood präsentiert. Diese Gewichte ermöglichen auch die Erzeugung ungewichteter Ereignisse, welche dem in NLO-Genauigkeit berechneten Wirkungsquerschnitt folgen.
Der Methode wird anhand von Top-Quark-Ereignissen veranschaulicht.
Die Top-Quark-Masse wird aus den erzeugten Ereignissen mithilfe der MEM in NLO-Genauigkeit bestimmt. Die erhaltenen Schätzer stimmen mit den Eingabewerten aus der Ereigniserzeugung überein. Wiederholung der Massenbestimmung aus denselben Ereignissen, ohne NLO-Korrekturen in den Vorhersagen, führt zu verfälschten Schätzern. Diese Verschiebungen werden nicht durch abgeschätzte theoretische Unsicherheiten berücksichtigt, was die Abschätzung der theoretischen Unsicherheiten der Analyse in führender Ordnung unzuverlässig macht.
Die Resultate unterstreichen die Wichtigkeit der Berücksichtigung von NLO-Korrekturen in der MEM.Analyses in high energy physics aim to put the Standard Model—the commonly accepted theory—to test. For convincing conclusions, analysis methods are needed which offer an unambiguous comparison between data and theory while allowing reliable estimates of uncertainties. The Matrix Element Method (MEM) is a Maximum Likelihood method which is especially tailored for signal searches and parameter estimation at colliders. The MEM has proven to be beneficial due to optimal use of the available information and a clean statistical interpretation of the results. But it has a big drawback: In its original formulation, the likelihood calculation is intrinsically limited to the leading perturbative order in the coupling. Higher-order corrections improve the accuracy of theoretical predictions and allow for unambiguous field-theoretical interpretation of the extracted information. In this work, the MEM incorporating corrections of next-to-leading order (NLO) in QCD by defining event weights suited for the likelihood calculation is presented for the first time. These weights also enable the generation of unweighted events following the cross section calculated at NLO accuracy. The method is demonstrated for top-quark events. The top-quark mass is determined with the MEM at NLO accuracy from the generated events. The extracted estimators are in agreement with the input values from the event generation. Repeating the mass determinations from the same events, without NLO corrections in the predictions, results in biased estimators. These shifts may not be accounted for by estimated theoretical uncertainties rendering the estimation of the theoretical uncertainties unreliable in the leading-order analysis. The results emphasise the importance of the inclusion of NLO corrections into the MEM.
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Hammad, Grégory. "Data-driven multi-jet and V+jets background estimation methods for top quark pair production at CMS." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209884.
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The analysis presented in this thesis focuses on two methods developed to estimate, from data, the multi-jet and the V+jets background processes for top quark pair production occuring during proton-proton at LHC. Top quark paires are reconstructed using the CMS detector, exploiting the semi-leptonic decay channel. Both methods have been developed and studied using Monte-Carlo simulated data.Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Tripathee, Aashish. "Jet substructure at the Large Hadron Collider." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/111882.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 57-60).
In this thesis, we use the CMS Open Data to study the 2-prong substructure of jets. We use CMS's particle flow reconstruction algorithm to obtain jet constituents, which we then use to perform various jet substructure studies. After validating our basic kinematics and substructure results through a comparison to results from parton shower generators, we extract the 2-prong substructure of the leading jet using the soft drop algorithm. We find good agreement between the results from the Open Data and those obtained from parton shower generators. For the 2-prong substructure, we also compare to analytic calculations performed to modified leading-logarithmic accuracy. To our best knowledge, this is the first ever physics analysis based on the CMS Open Data.
by Aashish Tripathee.
S.B.
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Tripathee, Aashish. "Jet substructure at the Large Hadron Collider." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111882.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 57-60).
In this thesis, we use the CMS Open Data to study the 2-prong substructure of jets. We use CMS's particle flow reconstruction algorithm to obtain jet constituents, which we then use to perform various jet substructure studies. After validating our basic kinematics and substructure results through a comparison to results from parton shower generators, we extract the 2-prong substructure of the leading jet using the soft drop algorithm. We find good agreement between the results from the Open Data and those obtained from parton shower generators. For the 2-prong substructure, we also compare to analytic calculations performed to modified leading-logarithmic accuracy. To our best knowledge, this is the first ever physics analysis based on the CMS Open Data.
by Aashish Tripathee.
S.B.
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Mao, Yaxian. "Mesure des corrélations gamma-hadrons et hadrons-hadrons dans les collisions pp à 7 TeV pour l'étude de la fragmentation des jets avec l'expérience ALICE du LHC." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00622562.
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L'expérience ALICE, qui utilise les collisions d'ions lourds ultra-relativistes produites par le LHC au CERN, est dédiée à l'étude d'un nouvel état de la matière nucléaire, qui pourrait se présenter sous la forme d'un plasma de quarks et de gluons (QGP). Parmi les sondes portant des informations sur les propriétés de ce milieu, celles relatives à la production des jets de grande impulsion transverse sont particulièrement intéressantes. L'analyse présentée dans cette thèse s'intéresse aux évènements photon-jet, qui comportent un photon de grande impulsion transverse avec un jet émis dans la direction opposée. Ce dernier est issu de la fragmentation d'un parton, une fois qu'il a traversé le QGP. La thèse comprend une étude des observables pertinentes pour la mesure des corrélations photon-hadron ainsi qu'une analyse des premières données du LHC en collisions proton-proton. Des résultats préliminaires sur l'impulsion transverse des partons incidents et la fonction de corrélation ont ainsi été obtenus.
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Doglioni, Caterina. "Measurement of the inclusive jet cross section with the ATLAS detector at the Large Hadron Collider." Thesis, University of Oxford, 2012. http://doi.org/10.1007/978-3-642-30538-2.
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This thesis presents the measurement of the inclusive jet cross section using data collected in 2010 by the ATLAS detector, with a particular focus on the reconstruction and calibration techniques used for jets in this measurement and on the estimate of the systematic uncertainty on their energy scale. The inclusive jet cross section measurement is used as input to fits of parton distribution functions. Although the PDF analysis in this thesis is preliminary and its main purpose is to serve as a proof of principle for future studies, improvements in the knowledge of the gluon density are observed thanks to the inclusion of ATLAS data.
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Valéry, Loïc. "Recherche de sgluons dans des états finals multitops avec le détecteur ATLAS auprès du LHC à √s = 8 TeV." Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22470/document.
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En dépit de nombreuses confirmations expérimentales, le Modèle Standard, théorie décrivant les particules élémentaires et trois des interactions fondamentales souffre de difficultés théoriques et expérimentales. Ces dernières motivent l’existence d’une physique non décrite jusqu’alors : la Nouvelle Physique. Ce travail se focalise sur la recherche de gluons scalaires, appelés communément sgluons, nouvelles particules prédites dans plusieurs théories de Nouvelle Physique. Une étude phénoménologique considère les différents états finals (de un à quatre quarks top) et signatures (un ou deux leptons chargés) qui peuvent être engendrés par l’existence de sgluons. La sensibilité d’une expérience comme Atlas à ce signal est estimée et montre que l’un des états finals les plus prometteurs est celui contenant quatre quarks top, dans la signature à deux leptons porteurs de la même charge électrique (électron ou muon). La recherche de sgluons dans l’expérience Atlas s’appuie sur les états finals à quatre quarks top dans une signature à deux leptons porteurs de la même charge électrique, des jets étiquetés b et de l’énergie transverse manquante. Elle représente la première recherche mondiale de sgluons dans cet état final. Les principaux enjeux de l’analyse (estimation des bruits de fond, optimisation de la sélection, interprétation statistique) sont détaillés. La comparaison avec les données enregistrées pendant la première partie de l’année 2012 (L = 14:3 fb..1) ne montre pas d’excès significatif. La limite inférieure sur la masse du sgluon est alors de 0.80+0:02..0:03 TeV. L’extension de cette analyse avec le lot complet de données enregistrées en 2012 par Atlas est également présentée dans ce document et permet une sensibilité accrue jusqu’à des masses de sgluons de 0:94 0:03 TeV. Ce document présente également les analyses et résultats relatifs à des études de performances. La première s’attache au système de hautes tensions du calorimètre hadronique à tuiles du détecteur Atlas (TileCal). Elle conclut notamment, au regard des critères établis, que seuls 7 canaux de hautes tensions du TileCal (sur un total de 9852) ont un comportement problématique. La deuxième étude est liée à la réjection de l’effet d’empilement au moyen d’une sélection sur la variable JVF (Jet Vertex Fraction). L’efficacité de cette sélection, calculée dans les données et dans la simulation montre des différences, nécessitant l’apport d’une correction à la simulation. La détermination de facteurs correctifs et de leurs incertitudes systématiques associées est présentée dans ce documentDespite its experimental confirmations, the Standard Model, which describes both the elementary particles and three of the fundamental interactions, has some theoretical and experimental limitations. As a consequence of these limitations, a Physics not described in the context of the Standard Model could exist : the New Physics. This work focuses on the search for scalar gluons, commonly dubbed sgluons, predicted in various New Physics theories. A phenomenological study considers various final states (containing between two and four top quarks) and signatures (with one or two charged leptons) that could arise from sgluon production. The sensitivity of an Atlas-like experiment to this signal is estimated and the results indicate that one of the most promising final states contains four top quarks in a signature with two charged leptons (electron or muon) of the same electric charge. The search for sgluons within the Atlas experiment uses the previous results. Thus, it only investigates the 4-top topology in a signature containing two same-sign charged leptons, b-jets and missing transverse energy. It represents the first search ever for sgluons in this final state. The main steps of the analysis (background estimation, selection optimisation and statistical interpretation) are detailed. The comparison with the data recorded in the first months of 2012 (L = 14:3 fb..1) shows no significant excess and is interpreted in terms of a limit on the sgluon mass. The latter is found to be 0.80+0:02..0:03 TeV. The extension of this analysis to the full 2012 Atlas dataset is also presented in this document and shows an increased expected sensitivity to sgluon masses up to 0:94 0:03 TeV. Finally, this document also presents the analyses and results of performance studies. The first one is related to the high voltage system of the Atlas Tile Calorimeter (TileCal). The main conclusion is that only 7 channels out of the 9852 TileCal ones are fond to be problematic. The second study focuses on the rejection of the pile-up effect by the means of a selection applied on the so-called JVF (Jet Vertex Fraction) variable. The efficiency of this selection is computed both in data and simulation and shows some differences that have to be corrected in the simulation. The derivation of the correction factors and their associated systematic uncertainties is detailed in this document
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Fiascaris, Maria. "W Boson production in association with hadronic jets at ATLAS." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543477.
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Crispin, Ortuzar Mireia. "High jet multiplicity physics at the Large Hadron Collider." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:68af3867-1488-48d1-9738-73397ba3399d.
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The Large Hadron Collider at CERN completed its first data-taking phase in 2013, after three years of remarkable performance. The high-energy proton-proton collisions recorded by the ATLAS experiment provide a gateway to the world of subatomic particles. This thesis presents two analyses of the full 8 TeV dataset taken by ATLAS, inspired by two of the major physics goals of the experiment. The first analysis is a search for new phenomena that could explain the nature of Dark Matter and solve the hierarchy problem. In particular, the search is optimised to look for heavy supersymmetric particles decaying to large numbers (7 to ≥10) of jets. The events are further classified according to the number of jets identified as originating from a b quark. No evidence is found for physics beyond the Standard Model, so the results are interpreted in terms of exclusion limits on various simplified supersymmetry-inspired models where gluinos are pair produced, as well as a mSUGRA/CMSSM model. The main background to the search is due to multi-jet production via the strong force. This motivates the second analysis presented in this thesis, which is a measurement of the cross section of four-jet events. The measurement is performed differentially in a series of variables which describe the kinematics and spatial configuration of the events. The results are compared to existing theoretical predictions.
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Dreyer, Frédéric. "Precision physics at the large hadron collider." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066170/document.
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L'avènement du LHC marque le début d'une ère de haute précision en physique des particules. Dans cette thèse de doctorat, nous abordons avec des outils innovants deux processus clés des collisionneurs de hadrons: la production inclusive de jets, et la production du boson de Higgs par fusion de bosons vecteurs (VBF). Dans la première partie de cette thèse, nous montrons comment resommer les premiers ordres logarithmiques de rayon de jet R, et appliquons ce formalisme à une étude approfondie du spectre inclusif des jets. Nous étudions les termes dépendant de R au troisième ordre non-nul (next-to-next-to-leading-order, NNLO), et les intégrons dans notre calcul. Nous examinons les éliminations dans la dépendance d'échelle, conduisant à une nouvelle prescription pour l'évaluation des incertitudes, et vérifions l'impact d'effets non-perturbatifs. Dans la deuxième partie de cette thèse, nous étudions les corrections de chromodynamique quantique dans la production de Higgs par VBF. En utilisant l'approche des fonctions de structure, nous calculons les corrections de quatrième ordre non-nul (NNNLO) à la section efficace inclusive. Nous calculons ensuite les corrections NNLO entièrement différentielles à la production de Higgs par VBF. Nous montrons que ces contributions sont significatives après coupures VBF, se trouvant en dehors des bandes d'incertitude d'échelle NLOWith the advent of the LHC, particle physics has entered an era where high precision is required. In this thesis, we tackle two of the key processes at hadron colliders using innovative tools: inclusive jet production and Higgs production through vector-boson fusion (VBF). In the first part of this thesis, we show how to resum leading logarithmic terms of the jet radius R, and apply this formalism to a detailed study of the inclusive jet spectrum. We study subleading R-dependent terms at next-to-next-to-leading order (NNLO), and incorporate them into our calculation. We investigate cancellations in the scale dependence, leading to new prescriptions for evaluating uncertainties, and examine the impact of non-perturbative effects. In the second part of the thesis, we study QCD corrections in VBF-induced Higgs production. Using the structure function approach, we compute the next-to-next-to-next-to-leading order (NNNLO) corrections to the inclusive cross section. We then calculate the fully differential NNLO corrections to VBF Higgs production. We show that these contributions are substantial after VBF cuts, lying outside the NLO scale uncertainty bands
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Pozo, Luis Andres del. "Tests of QCD from jet and hadron production at LEP." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320401.
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Khelifa, Kerfa Kamel. "QCD resummation for high-pT jet shapes at hadron colliders." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/qcd-resummation-for-highpt-jet-shapes-at-hadron-colliders(16fdf645-238d-4979-8239-155f9ba07001).html.
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Exploiting the substructure of jets observed at the LHC to better understand and interpret the experimental data has recently been a very active area of research. In this thesis we study the substructure of high-pt QCD jets, which form a background to many new physics searches. In particular, we explore in detail the perturbative distributions of a certain class of observables known as non-global jet shapes. More specifically, we identify and present state-of-the-art calculations, both at fixed-order and to all-orders in the perturbative expansion, of a set of large logarithms known as non-global logarithms. Hitherto, these logarithms have been largely mis-treated, and in many cases ignored, in the literature despite being first pointed out more than a decade ago. Our work has triggered the interest of many groups, particularly Soft and Collinear Effective Theory (SCET) groups, and led to a flurry of papers on non-global logarithms and related issues. Although our primary aim is to provide analytical results for hadron-hadron scattering environments, it is theoretically instructive to consider the simpler case of e+e- annihilation. We thus examine, in chapters 4, 5 and 6, the the said jet shapes in the latter environment and compute the full next-to-leading logarithmic resummation of the large logarithms present in the distribution for various jet definitions. We exploit the gained experience to extend our calculations to the more complex hadronic environment in chapter 7. We provide state-of-the-art resummation of the jet mass observable in vector boson + jet and dijet QCD processes at the LHC up to next-to-leading logarithmic accuracy. The resultant distribution of the former (vector boson + jet) process agrees well, after accounting for hadronisation corrections, with standard Monte Carlo event generators and potential comparisons to data from the LHC will be made soon.
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Brooks, Helen Marguerite. "Multi-jet phenomenology for hadron colliders in the high energy limit." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/12313/.
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We have incorporated next-to-leading logarithmic corrections into the High Energy Jets (HEJ) formalism and parton-level Monte Carlo generator for $W$ plus inclusive dijet production. This has involved an analytic demonstration of factorisation for the relevant configurations, an extraction of the effective current and proof of its gauge invariance. We have thoroughly validated our numerical implementation and matching of the cross section to leading order accuracy. We have studied the impact of these corrections upon transverse momentum distributions and found a significant improvement in the description of data. We also present a new merging algorithm, inspired by the CKKW-L method, for combining high energy and soft-collinear logarithms. This has been implemented for HEJ+\textsc{Pythia}. Multiple parton interactions and hadronisation effects are also accounted for, allowing for an accurate description of jets shapes. We find good agreement with data for observables such as the average number of jets and gap fractions which are relevant for understanding the impact of jet vetoes.
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Harman, Cates Michael Cates-Harman. "p0-Hadron Jet Correlations in He + Au Collisions at 200 GeV." Ohio University Art and Sciences Honors Theses / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ouashonors1462295771.
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Cockburn, James David. "Subleading corrections to hadronic cross-sections at high energies." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/29519.
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The Large Hadron Collider (LHC) has provided, and will continue to provide, data for collisions at the highest energies ever seen in a particle accelerator. A strong knowledge of the properties of amplitudes for Quantum Chromodynamics in the High Energy Limit is therefore important to interpret this data. We study this limit in the context of the High Energy Jets (HEJ) formalism. This formalism resums terms in the perturbative expansion of the cross-section that behave like αn/s log (s/-t)ⁿ¯¹, which are enhanced in this limit. Understanding this region is particularly important in certain key analyses at the LHC: for example, Higgs-boson- plus-dijet analyses where cuts are applied to pick out events with a large mjj and in many searches for new physics. In this thesis, we discuss two directions in which HEJ's accuracy has been improved. Firstly, we look at adding descriptions of partonic subprocesses which are formally sub-leading in the jet cross-section but Leading Logarithmic (LL) in the particular subprocess itself. This required the derivation of new effective vertices that describe the emission of a quark/anti-quark pair in a way that is consistent with the resummation procedure. The inclusion of such processes reduces HEJ's dependence on fixed-order calculations and marks an important step towards full Next-to-Leading Logarithmic (NLL) accuracy in the inclusive dijet cross-section. The second extension was to improve our description of events involving the emission of a Higgs boson along with jets. Specifically, we derive new effective vertices which keep the full dependence on the quark mass that appears in the loops that naturally arise in such amplitudes. The formalism is also simple enough to allow for any number of extra nal state jets in the process. Therefore, HEJ is unique in its ability to provide predictions for high-multiplicity Higgs-plus-jets processes with full nite quark mass e ects. Such a calculation is far beyond the reach of any xed order approach.
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Ohlson, Alice Elisabeth. "Investigating Parton Energy Loss in the Quark-Gluon Plasma with Jet-hadron Correlations and Jet Azimuthal Anisotrophy at STAR." Thesis, Yale University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3578426.
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In high-energy collisions of gold nuclei at the Relativistic Heavy Ion Collider (RHIC) and of lead nuclei at the Large Hadron Collider (LHC), a new state of matter known as the Quark-Gluon Plasma (QGP) is formed. This strongly-coupled, deconfined state of quarks and gluons represents the high energy-density limit of quantum chromodynamics. The QGP can be probed by high-momentum quarks and gluons (collectively known as partons) that are produced in hard scatterings early in the collision. The partons traverse the QGP and fragment into collimated "jets" of hadrons. Studies of parton energy loss within the QGP, or medium-induced jet quenching, can lead to insights into the interactions between a colored probe (a parton) and the colored medium (the QGP).
Two analyses of jet quenching in relativistic heavy ion collisions are presented here. In the jet-hadron analysis, the distributions of charged hadrons with respect to the axis of a reconstructed jet are investigated as a function of azimuthal angle and transverse momentum (pT). It is shown that jets that traverse the QGP are softer (consisting of fewer high-pT fragments and more low-p T constituents) than jets in p+p collisions. There are also indications that the shapes of the distributions of charged hadrons about the jet axis are modified by interactions with the QGP. The results are quantitatively consistent with two models of medium-induced radiative parton energy loss.
A measurement of jet v2, defined as the correlation between reconstructed jets and the reaction plane or 2nd-harmonic participant plane (approximated by the 2nd-harmonic event plane), provides information about the medium-induced pathlength-dependence of parton energy loss. The event plane is reconstructed with detectors at forward pseudorapidity in order to reduce the artificial jet – event plane bias, which results from jet fragments being included in the event plane calculation. A non-zero jet v2 is measured, indicating that more jets are reconstructed with a higher energy in-plane compared to out-of-plane, which demonstrates that the parton energy loss depends on the length of the parton's path through the QGP.
The data analyzed here were collected in [special characters omitted] = 200 GeV Au+Au and p+p collisions at the STAR detector at RHIC. A novel method for measuring jet v2 is also proposed and tested in simulation.
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DIltz, Christopher S. "Time Dependent Leptonic and Lepto-Hadronic Modeling of Blazar Emission." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1459506010.
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Cass, A. J. "A search for jets in direct photon events from hadronic collisions at 280GeV/c." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234824.
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Sanguinetti, Grégory. "Calcul de la production d'une paire de bosons de jauge faible associée à un jet à l'approximation au-delà des logarithmes dominants." Phd thesis, Chambéry, 2008. http://tel.archives-ouvertes.fr/tel-00331294.
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En 2008, le futur collisionneur du CERN, le Large Hadron Collider (LHC), commencera à récolter les données issues des collisions entre protons à l'échelle du TeV, dans le but de comprendre la brisure de la symétrie électro-faible. Un grand nombre de réactions incluant de nombreuses particules dans l'état final doit être étudié avec précision. Ces possibilités de découverte du LHC ne pourront être pleinement exploitées que si le bruit de fond de la Chromodynamique Quantique est bien maîtrisé. Parmi les réactions comprenant plus de quatre particules, la production associée d'une paire de bosons de jauge faible (W, Z) associée à un jet constitue un des bruits de fond pour la recherche du boson de Higgs au LHC. Il est important de calculer cette réaction à l'approximation dite "au-delà des logarithmes dominants", qui consiste à ajouter à l'ordre dominant le plus bas les deux contributions suivantes : la correction virtuelle (c'est un calcul d'amplitudes à une boucle) et l'émission réelle (c'est un calcul d'amplitudes à l'arbre mais avec un parton de plus dans l'état final). Des expressions analytiques suffisamment compactes pour être évaluées numériquement ont été obtenues et sont en parfait accord avec les résultats de deux autres groupes de recherche indépendants. Quant à l'émission réelle, toutes les contributions ont été évaluées à l'aide de programmes de génération automatique d'amplitudes à l'arbre. Ainsi, nous sommes en mesure de présenter des prédictions précises concernant les corrections à l'ordre supérieur de la section efficace totale de cette réaction au LHC.
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Barter, William James. "Z boson and associated jet production at the LHCb experiment." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707943.
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Scott, Patrick Aaron. "Search for medium effects with jet-like hadron correlations at ALICE at the LHC." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4542/.
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We present an analysis of the properties of jets in proton-proton and lead-lead collisions at the ALICE experiment at the CERN Large Hadron Collider. The jet width and transverse momentum imbalance were studied in minimum bias proton collisions. The width was found to be independent of hadron transverse momentum and to have a larger value than measurements from earlier experiments at lower beam energies, consistent with theoretical expectations. The imbalance was found to increase with collision energy and also with the transverse momentum of the hadrons in the jet. The dependence of jet yield on the produced multiplicity was studied in proton and ion collisions, with a view to identifying suppression through interaction with a quark-gluon plasma. This suppression was identified in lead collisions as expected, but no suppression was observed in high multiplicity proton collisions. The jet width and tranverse momentum imbalance were also studied as a function of multiplicity. In proton collisions, the jet width was measured to be independent of multiplicity and hadron transverse momentum and consistent with minimum bias measurements. The width was observed to decrease in lead collisions of increasing centrality; this was interpreted as a suppression of the high momentum hadrons in the jet.
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Abeloos, Baptiste. "Recherche de particules supersymétriques dans le canal hadronique et calibration des jets avec le détecteur ATLAS du LHC." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS200/document.
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Le Modèle Standard de la physique des particules est un modèle décrivant très bien les particules élémentaires et leurs interactions mais plusieurs raisons motivent les physiciens à rechercher de la physique au-delà de ce modèle. La supersymétrie correspond à une des extensions les plus prometteuses. La thèse est axée sur deux sujets, et repose sur les données acquises en 2015 et 2016 avec le détecteur ATLAS du LHC (CERN):La première partie est un travail de performance permettant d'améliorer la mesure de l'énergie des jets de particules. Ces objets sont générés par l'hadronisation des quarks et des gluons par interaction nucléaire forte et sont difficiles à reconstruire. Ma contribution correspond à la dernière étape et repose entièrement sur les données. La méthode se base sur les mesures effectuées sur les photons qui servent d'objets de référence. Mon travail a consisté à mettre en place la méthode, estimer les corrections en énergie et évaluer les incertitudes. Les corrections obtenues sont de l'ordre de 2-3% en fonction de l'énergie des jets. L'incertitude sur l'échelle en énergie des jets est estimée à environ 1% pour les trois types de jets étudiés. Les résultats sont actuellement utilisés par la collaboration ATLAS. Cette méthode permet également de mesurer la résolution en énergie des jets du détecteur. Une résolution de l'ordre de 17%-22% est obtenue à 40 GeV en fonction du type de jet étudié, et 4% à 1 TeV, avec une incertitude de l'ordre de 10%.La deuxième partie de la thèse porte sur la recherche d'un signal de supersymétrie. Le signal recherché correspond à la production d'une paire de squarks ou de gluinos et comprend des jets et de l'énergie transverse manquante dans l'état final. Mon travail porte principalement sur l'optimisation des critères de sélections en se basant sur plusieurs modèles simplifiés de supersymétrie. Neuf nouvelles régions de signal ont été introduites dans l'analyse. Les limites tracées au cours du Run 1 sur la masse des squarks et gluinos ont ainsi été augmentées pour atteindre une valeur maximale respective de l'ordre de 1.6 TeV et 2 TeV sur les modèles étudiésThe Standard Model of particle physics is a very precise model describing the elementary particles and their interactions. However, some issues lead physicists to search for physics beyond the Standard Model. Supersymmetry is an extension of the Standard Model providing solutions to the current issues. In this thesis, results are obtained using the data collected in 2015 and 2016 with the ATLAS detector at the LHC (CERN). The thesis is based in two parts:The first part is a performance analysis improving the energy measurement of high energy objects called "jets". They are generated by the hadronization of quarks and gluons in the detector via the strong nuclear interaction. My contribution is the last step of the the reconstruction and calibration chain and is fully based on data. The method uses the very precise measurement of the photon energy, and provides corrections to the jet energy scale. My contribution consists in set-up the method, estimate the corrections, measure the jet energy scale and evaluate the uncertainties. Corrections are at the order of 2-3% as a function of the jet energy scale. The uncertainty of the jet energy scale is estimated to be at the order of 1% for the three jet types. Results are now used by the ATLAS Collaboration. This method is also used to estimate the jet energy resolution. A resolution at the order of 17%-22% at 40 GeV depending on the jet type, and 4% at 1 TeV is obtained with an uncertainty at the order of 10%.The second part of the thesis corresponds to the search for supersymmetry. The signal corresponds to a pair of supersymmetric particles called squarks and gluinos and corresponds to jets and missing transverse energy in the final state. My contribution mainly corresponds to the optimisation of the selections using several simplified models of supersymmetry. Nine signal regions have been introduced in the analysis. Limits on the mass of squarks and gluinos computed during the Run 1 have been greatly improved to reach a maximal value respectively at the order of 1.6 TeV and 2 TeV
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Williams, Ciaran. "Hadronic productions of a Higgs boson in association with two jets at next-to-leading order." Thesis, Durham University, 2010. http://etheses.dur.ac.uk/414/.
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We present the calculation of hadronic production of a Higgs boson in association with two jets at next-to-leading order in perturbation theory. We consider amplitudes in an effective theory in which the Higgs couples to gluons in the limit of a large top quark mass. We treat the Higgs as the real part of the complex field φ that couples to the self-dual field strengths. We use modern on-shell inspired methods to calculate helicity amplitudes and we give a detailed review of unitarity based and on-shell methods. Using these unitarity methods we derive the cut-constructible pieces of the general φ-MHV amplitudes in which the positions of the two negative gluons are arbitrary. We then generate the cut-constructible pieces of the φ-NMHV four parton amplitudes. We generate the rational pieces of these amplitudes and the four-gluon φ-MHV amplitude using Feynman diagrams. For the φ-MHV amplitude we also use the unitarity-boostrap method to calculate the rational pieces. We then implement these, and analytic results from previous calculations, into MCFM. Using this program we are able to perform some phenomenological studies at the Tevatron and LHC.
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Caucal, Paul. "Jet evolution in a dense QCD medium." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP002.
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Afin de sonder les propriétés du plasma quarks-gluons créé dans les collisions d’ions lourds, on mesure des observables associées à la propagation de jets en son sein. Un jet est une gerbe collimatée de hadrons de haute énergie générée par des émissions successives de partons à partir d’un quark ou d’un gluon virtuel produit par la collision. Quand de telles gerbes se propagent dans le milieu dense créé par la collision des noyaux, leurs interactions avec ce milieu entraînent une modification dans leurs propriétés, phénomène appelé "réduction des jets". Dans cette thèse, nous développons une nouvelle théorie permettant de comprendre la réduction des jets. Nous calculons pour la première fois les effets du milieu dense sur les émissions de type vide dans les jets, c’est à dire les émissions déclenchées par la virtualité initiale du parton source. Une nouvelle image physique pour l’évolution des jets est présentée, dans laquelle les émissions de type vide sont factorisées en temps par rapport à celles induites par le milieu. Cette image est markovienne, donc adaptée pour une implémentation Monte-Carlo des cascades de partons que nous développons dans le programme JetMed. Nous nous intéressons ensuite aux prédictions de notre théorie sur des observables de jets, et en particulier le facteur de modification nucléaire des jets RAA, la distribution Soft Drop zg et la fonction de fragmentation. Ces prédictions se révèlent être en bon accord avec les mesures du LHCTo probe the properties of the quark-gluon plasma created in heavy-ion collisions, a very useful class of observables refers to the propagation of energetic jets. A jet is a collimated spray of particles generated via successive parton branchings, starting with a virtual quark or gluon produced by the collision. When such a jet is produced in the dense environment of a nucleus-nucleus collision, its interactions with the surrounding medium lead to a modification of its properties, phenomenon known as jet quenching. In this thesis, we develop a new theory to describe jet quenching. We compute for the first time the effects of the medium on multiple vacuum-like emissions, that is emissions triggered by the virtuality of the initial parton. We present a new physical picture for jet evolution, with notably a factorisation in time between vacuum-like emissions and medium-induced emissions. This picture is Markovian, hence well suited for a Monte Carlo implementation that we develop in the parton shower JetMed. We then investigate the phenomenological consequences of our new picture on jet observables and especially the jet nuclear modification factor RAA, the Soft Drop zg distribution and the jet fragmentation function. Our Monte Carlo results prove to be in good agreement with the LHC measurements
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Wanotayaroj, Chaowaroj. "Search for a Scalar Partner of the Top Quark in the Jets+ETMiss Final State with the ATLAS detector." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22275.
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This dissertation presents searches for direct pair production of a scalar partner of the top quark in events with only jets and \acrlong{met} in proton--proton collisions recorded during LHC Run 1 and Run 2 with the ATLAS detector. In the supersymmetry scenario, the partner is called top squark or stop. The stop ($\stop$) is assumed to decay via $\stop \to t \ninoone$, $\stop\to b\chinoonepm \to b W^{\left(\ast\right)} \ninoone$, or $\stop\ra bW\ninoone$, where $\ninoone$ ($\chinoonepm$) denotes the lightest neutralino (chargino). Exclusion limits are reported in terms of the stop and neutralino masses.
The LHC Run 1 analysis uses an integrated luminosity of 20.1~{\ifb} at $\acrshort{sqrts}=8~\tev$ to exclude top squark masses in the range $270$--$645~\GeV$ for $\ninoone$ masses below $30~\GeV$, assuming a 100\% $\stop \to t \ninoone$ \gls{br}. For a \gls{br} of $50\%$ to either $\stop \to t \ninoone$ or $\stop\to b\chinoonepm$, and assuming $m_{\chinoonepm} = 2 m_{\ninoone}$, stop masses in the range $250$--$550~\GeV$ are excluded for $\ninoone$ masses below $60~\GeV$.
The LHC Run 2 analysis uses an integrated luminosity of 13.3~{\ifb} at $\acrshort{sqrts}=13~\tev$. Assuming a 100\% $\stop \to t \ninoone$ \gls{br}, stop masses in the range $310$--$820~\GeV$ are excluded for $\ninoone$ masses below $160~\GeV$. For $\mstop\sim m_t+\mLSP$ scenario, the search excludes stop masses between $23$--$380~\GeV$. Additionally, scenarios where stops are produced indirectly through gluino decay but have very low $p_T$ signature due to a very small $\Delta (\mstop, \mLSP)$, have been considered. The result is interpreted as an upper limit for the cross section in terms of the gluino and stop masses. This excludes all models considered which include $m_{\gluino}$ up to 1600~\GeV\ with $\mLSP<560~\GeV$ at 95\% CL.
Finally, the analysis strategy from the LHC Run 1 search is applied in the broader scope of supersymmetry called \gls{pmssm}. This dissertation presents a summary of the results that related to the stop search.
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Lattaud, Hugues. "Photon et jets avec l'expérience CMS du LHC : de la calibration à la mesure." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1137/document.
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Cette thèse présente deux analyses réalisées avec des évènements où un photon est produit en association avec un jet obtenus avec l'expérience CMS au LHC. Le première analyse présente l'extraction de la calibration de l'échelle en énergie des jets en utilisant la balance en impulsion présente dans ce type d'évènements, la seconde analyse présente la mesure de la section efficace différentielle de production d'évènement ou un photon est émis en association avec un jet de saveur lourde dans les collisions proton proton du LHCThis PhD thesis presents two analysis using photon + jet events with the CMS experiment at the LHC. The first analysis presents the extraction of the jet energy calibration using the momentum balance between the jet and the photon in such events, the second analysis presents the photon + heavy flavored jet differential production cross section with proton proton collision at LHC
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Hendricks, Khalida. "Jets + Missing Energy Signatures At The Large Hadron Collider." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563367019906869.
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Hassan, Hadi. "Modélisation et mesure des facteurs de modification nucléaire des jets issus de quarks beaux dans les collisions p-Pb à 5.02 TeV avec l'expérience ALICE auprès du LHC." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY008/document.
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Dans les collisions Pb-Pb au LHC, un milieu chaud et dense formé de quarks et de gluons déconfinés est formé, communément appelé Plasma de Quarks et de Gluons (PQG). Le PQG est l’état hypothétique de l’univers primordial quelques microsecondes après le Big Bang et constituerait encore à ce jour le cœur des étoiles à neutrons. Une des signatures les plus frappantes de l’occurrence du PQG lors de collisions d’ions lourds est la suppression des jets. Ce phénomène appelé étouffement des jets est attribué au mécanisme de perte d’énergie du parton à l’origine du jet lors de son trajet au travers du milieu formé par le PQG.Les deux dernières décennies ont vu l’émergence d’une formulation théorique du phénomène d’étouffement des jets dans le cadre de la Chromo Dynamique Quantique. La perte d’énergie étant le plus fréquemment attribuée dans la littérature à des processus radiatifs et collisionnels. Un nouveau mécanisme de perte d’énergie à été étudié dans ce travail de thèse qui outre la description des effets de diffusions multiples, met en œuvre une perte d’énergie radiative induite par un champ chromomagnétique, de sorte qu’un parton rapide se propageant au travers du milieu ressentira l’effet des champs magnétique et de couleur tout en subissant des diffusions multiples avec les particules du milieu.De plus, les modèles théoriques prédisent une dépendance de la perte d’énergie avec la charge de couleur et la masse du parton issu d’une diffusion à grand transfert d’impulsion lors de sa traversée du milieu.Une telle dépendance en masse peut être étudiée en mesurant la production de hadrons et de jets contenant des quarks lourds dans les collisions pp, p-Pb et Pb-Pb au LHC. Dans cette thèse, un modèle original du milieu est présenté, décrit comme un ensemble de centres de diffusion statiques colorés en présence d’un champ chromomagnétique, de même qu’une description du mécanisme de perte d’énergie associé. Enfin, la mesure de la production de jets issus de quarks beaux avec le détecteur ALICE dans les colllsions pp et p-Pb à l’énergie de 5.02 TeV au LHC à l’aide d’une méthode d’étiquetage utilisant le paramètre d’impact des traces est présenté dans cette thèseIn Pb-Pb collisions at the LHC, a hot and dense medium of deconfined quarks and gluons is formed, the so-called Quark-Gluon Plasma (QGP).The QGP is conjectured to be the state of matter of the early Universe up to few microseconds after the Big Bang and may still exist in the core of neutron stars. One of the most striking signatures of the QGP formation in heavy-ion collisions is the suppression of jet production. This phenomenon, called jet quenching, is ascribed to the energy lost by the initial parton while traveling through the QGP medium.In the last two decades, many theoretical developments of the theory of jet quenching have been formulated within pQCD.The main energy loss mechanisms proposed in the literature are attributed to radiative and collisional processes. Another kind of energy loss is developed in this work comprises a background field induced radiative energy loss which besides that besides scattering effects. Under the suggested model, a fast parton propagating through the medium will feel the effect of the color magnetic and the color electric fields while undergoing multiple scatterings with the particles in the medium.Besides, theoretical models predict that energy loss depends on the color charge and mass of the hard-scattered parton traversing the medium. Such mass dependence can be studied by measuring the production of hadrons and jets containing heavy-quarks in pp, p-Pb and Pb-Pb collisions at the LHC.In this thesis report, a new model for the medium is presented, which is described as a collection of static colored scattering centers in the presence of a chromomagnetic field, together with the description of the related energy loss mechanism. The ALICE measurement of b-jet production in pp and p-Pb collisions at $sqrt{s_{mathrm{NN}}}=5.02$ TeV using an impact parameter based tagger is also presented
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Zhang, Fengwangdong. "Measurement of jet production in association with a Z boson at the LHC and jet energy correction calibration at high level trigger in CMS." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/251804.
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This PhD dissertation presents the measurement of the cross section of jet production in association with a Z boson in proton-proton collisions at the Large Hadron Collider in CERN, with a center-of-mass energy of 8 TeV in 2012 and of 13 TeV in 2015. The data used for this analysis were collected by the Compact Muon Solenoid (CMS) detector, with an integrated luminosity of 19.6 fb-1 in 2012 and of 2.25 fb-1 in 2015. The differential cross section is measured as a function of jet multiplicity, jet transverse momentum and rapidity, and the scalar sum of jet transverse momenta. The rapidity correlations between the Z boson and jets are also measured benefiting from the large statistics of data taken in 2012. All distributions of measured observables are obtained after correcting detector effects using unfolding approach, and the results of two leptonic decaying channels of Z boson are combined. Coming along with the systematic and statistical uncertainties, the measurement is compared to different theoretical predictions at different accuracy levels. The predictions are from MADGRAPH 5, SHERPA 2 (for 8 TeV analysis only), MADGRAPH_AMC@NLO, and fixed next-to-next-to-leading order (for 13 TeV analysis only). Thanks to the unprecedented high energy and the large statistics of data, precision measurement is accomplished in a physical phase space never reached before. This measurement provides precise systematics for different theoretical models. It also quantifies the improvement with higher order of perturbative quantum chromodynamics calculations on matrix elements relative to the leading order multi-leg approach. In particular to the rapidity correlation study, new matching schemes (FxFx and MEPS@NLO) for next-to-leading order matrix elements and parton shower show significant improvements with respect to the MLM matching scheme for leading order multi-leg matrix elements and parton shower. This measurement also gives precise background estimation for the measurements of many other processes in Standard Model like top quark production and gauge boson couplings, and for new physics searches such as Supersymmetry. In this thesis, the jet energy correction and calibration for the high level trigger system of CMS are also depicted. From 2012 to 2015, the Large Hadron Collider was upgraded, not only with the center-of-mass energy of the beams enlarged, but also with the instantaneous luminosity increased. The time distance between two particle bunches in a beam is reduced. As a result, the reconstructed momenta of the jets produced in each bunch crossing are significantly contaminated by multiple interactions. A dedicated technical approach has been developed for correcting the reconstructed jet momenta. The corrections have been calibrated and configured for the data taking in 2015 and 2016.Cette thèse présente une mesure de la section efficace de production de jets associés à un boson Z dans les collisions proton-proton du Grand Collisionneur de Hadron (LHC) situé au CERN, avec des énergies dans le centre de masse de 8 TeV et 13 TeV, respectivement pour les années 2012 et 2015. Les données utilisées pour cette analyse ont été collectées par le détecteur Compact Muon Solenoid (CMS). Elles constituent des échantillons de luminosités intégrées de 19.6 fb⁻¹ et 2.25 fb⁻¹, respectivement pour 2012 et 2015. Nous mesurons la section efficace différentielle en fonction de la multiplicité de jets, de l’impulsion transverse et de la rapidité des jets, et en fonction de la somme scalaire des impulsions transverses des jets. La corrélation entre les rapidités du boson Z et des jets est aussi mesurée et bénéficie de la large statistique prise en 2012. Toutes les distributions d’observables mesurées sont obtenues après corrections pour les effets détecteurs et les résultats des canaux de désintégration muonique et électronique du boson Z sont combinés. Tenant compte des incertitudes statistiques et systématiques, les mesures sont comparées à différentes prédictions théoriques ayant différents niveaux de précision. Les prédictions sont obtenues de MADGRAPH 5, SHERPA 2 (pour l’analyse à 8 TeV uniquement), MADGRAPH_AMC@NLO, et un modèle fixé au NNLO (pour l’analyse à 13 TeV uniquement). Par ces mesures de précisions, et en particulier celle de la corrélation de rapidités, nous avons acquis une compréhension plus approfondie de la chromodynamique quantique dans son régime perturbatif. Grâce à la plus haute énergie jamais atteinte en laboratoire, et à la grande statistique disponible, nous avons sondé avec précision des endroits de l’espace des phases jusque là inaccessibles.Dans cette thèse, les corrections et la calibration de l’énergie des jets pour le haut niveau de sélection de CMS est également présentée. Durant la période de 2012 à 2015, le LHC a été amélioré, non seulement l’énergie dans le centre de masse a augmenté, mais la luminosité instantanée a aussi été amplifiée. L’écart temporelle entre deux paquets de particules dans les faisceaux du LHC a été réduite. L’une des conséquences est que l’impulsion reconstruite pour les jets produits lors d’un croisement de faisceau à une contribution significative venant des multiples interactions ayant lieux lors du croisement des paquets. Une approche technique dédiée a été développée pour corriger l'impulsion des jets. Les corrections obtenues ont été calibrées aux données prises en 2015 et 2016.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Hill, P. V. "A model insensitive determination of the strong coupling constant and a measurement of the energy spread of quark jets in electron positron annihilation." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379148.
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Mahmoudi, Farvah. "Chromodynamique quantique aux collisionneurs hadroniques : vers une automatisation du calcul des processus multi-particules à l'ordre d'une boucle : application à la production de deux photons et un jet." Chambéry, 2004. http://www.theses.fr/2004CHAMS013.
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Le futur collisionneur du CERN (le LHC) possède un fantastique potentiel de découverte à condition d'avoir une prédiction quantitative de la QCD. Pour ce faire, il est nécessaire d'effectuer des calculs dans l'approximation NLO de manière à réduire la dépendance de la section efficace en fonction des échelles non physiques. Pour obtenir des résultats dans cette approximation, il faut calculer les sections efficaces des sous-processus partoniques contribuant à la réaction étudiée à l'ordre le plus bas ainsi que les corrections virtuelles (une boucle) et réelles. Le calcul des corrections virtuelles reste très compliqué si le nombre de particules externes est supérieur à quatre ou si les particules externes (internes) sont massives. Dans cette thèse est proposée une méthode automatique pour effectuer les calculs à une boucle et à cinq pattes, et qui peut être généralisée aux cas de particules massives. Dans une première partie, nous décrirons divers outils et méthodes nécessaires à de tels calculs. Nous les appliquerons ensuite au calcul de la réaction (gluon + gluon -> photon + photon + gluon), qui intéresse les expérimentateurs des expériences ATLAS et CMS comme bruit de fond à la recherche du Higgs, notamment pour décrire correctement la queue de la distribution transverse du boson de Higgs. Sera alors présenté le résultat explicite de cette amplitude pour chaque configuration d'hélicités sous une forme compacte et une représentation clairement invariante de jauge. Nous terminerons par une étude phénoménologique de cette réactionThe future CERN collider (LHC) bas a fantastic potential of discovery, provided QCD can be quantitatively predicted. To do so, it is necessary to work at NLO approximation in order to reduce the dependence of the cross-section on the non-physical scales. To obtain results in this approximation, one has to calculate the cross-sections of the partonic subprocesses contributing to the studied reaction at the lowest order, and also the virtual corrections (loop corrections) and the real corrections. The calculation of the virtual corrections remains very complicated if the number of external particles is greater than four or if the external (internal) particles are massive. Ln this thesis, an automatic method which enables to calculate one loop diagrams with five external legs and which can be generalized to the case of massive particles is presented. Ln a first part, we describe different tools and methods necessary to such calculations. We then apply them to the calculation of the (gluon + gluon -> photon + photon + gluon) reaction, which interests the ATLAS and CMS experimentalists as the background for the Higgs boson search. We also give the explicit result for this amplitude for each helicity configuration in a compact form and a clearly gauge invariant representation. We finally present a phenomenological study of this reaction
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Klein, Jochen [Verfasser], and Johanna [Akademischer Betreuer] Stachel. "Jet Physics with A Large Ion Collider Experiment at the Large Hadron Collider / Jochen Klein ; Betreuer: Johanna Stachel." Heidelberg : Universitätsbibliothek Heidelberg, 2014. http://d-nb.info/1180033094/34.
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Tiras, Emrah. "Characterization of 900 four-anode photomultiplier tubes for use in 2013 hadronic forward calorimeter upgrade." Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/3392.
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The first 900 four-anode Photomultiplier Tubes (PMTs) have been evaluated for use in the 2013 Hadronic Forward (HF) calorimeter upgrade. HF is a part of the Compact Muon Solenoid (CMS), which is one of the two large general-purpose particle detectors of the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland. HF requires 1728 PMTs. These small tubes are the sensitive light detectors that provide the output signals of HF. Before installing PMTs in HF, their quality control demands need to be satisfied. These tests, done at the University of Iowa, are designed in three categories to test seventeen different parameters for each PMT. The three most basic and most important groups of parameters are: dark current, gain (anode and cathode), and timing. There are secondary tests which are performed on a smaller percentage of the PMTs such as surface uniformity, double pulse and single photo-electron resolution. The PMTs that meet the specifications of HF will be sent to CERN where they are expected to be in use for at least a decade.
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Rodrigues, Eduardo. "Azimuthal angle asymmetries of hadrons and jets in deep inelastic scattering at HERA." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247646.
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Bhauruth, Yaadav. "Beam density functions in van der Meer scans and leptonically decaying off-shell Z bosons in association with two hadronic jets." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/beam-density-functions-in-van-der-meer-scans-and-leptonically-decaying-offshell-z-bosons-in-association-with-two-hadronic-jets(a81f2cb5-9235-4d6b-8b60-014a51884918).html.
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At present, high energy particle colliders, like the Large Hadron Collider (LHC), are used to investigate the nature and interactions of the elementary particles that make up matter. The precise determination of an interaction cross section at the LHC relies heavily on a robust determination of the delivered luminosity over a given time period. Two analyses are documented in this thesis. The first analysis comprised an investigation of the LHC beam density functions during van der Meer (vdM) scans. vdM scans are used by the ATLAS experiment to calibrate the visible interaction rates measured by a number of luminosity monitoring detectors to the absolute luminosity scale. The vdM scan methodology assumes that the beam density functions factorise in the horizontal and vertical directions. An investigation was carried out to test this assumption by using experimentally determined luminous region parameters, together with data from luminosity monitors in ATLAS, to constrain beam models defined as the sum of two or three Gaussian functions. The impact of the vertex-position resolution on this analysis was also investigated. The vdM scans analysed were performed during the 2012 proton-proton and 2013 proton-lead and lead-proton data-taking runs of the LHC. The second analysis reported is a feasibility study centred on the extraction of the cross section of the electroweak production of a leptonically decaying high mass off-shell Z boson in association with two hadronic jets (Zjj). The study used a dataset corresponding to $32.9 \,\mathrm{fb^{-1}}$ collected by ATLAS during the proton-proton data-taking run in 2016. The analysis was carried out in two channels, comprising Z boson decays to either a pair of muons or to a pair of electrons. The analysis first measured the on-shell electroweak Zjj cross section in the muon and electron channels using Zjj events in which the dilepton invariant mass was close to the rest mass of the Z boson. The analysis techniques were then extended to Zjj events in which the invariant mass of the dilepton pair was higher than the Z boson rest mass. The signal significance of high mass electroweak Zjj production was found to be around five sigma in the combined muon and electron channels for the dataset analysed. The study therefore demonstrated how, and to what degree of precision, the high mass electroweak Zjj production cross section could be measured using the dataset analysed and future LHC datasets.