Dissertations / Theses on the topic 'Quark and lepton masses'
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1
Malinsky, Michal. "Quark and Lepton Masses and Mixing in Supersymmetric Grand Unified Theories." Doctoral thesis, SISSA, 2005. http://hdl.handle.net/20.500.11767/4198.
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The material is organized as follows: the first chapter is devoted to several remarks
on the two basic supersymmetric GUTs - first the minimal SUSY SU(5) is considered
and the main shortcomings are pointed-out in brief, and in the second part these issues
are addressed concerning a general class of SO(lO) models. This provides a natural
motivation to approach and describe shortly the minimal SUSY SO(lO) scheme in the
second chapter. The third chapter is dedicated to a detailed study of the correlations
among the quark and lepton masses and mixing within the framework with dominant
triplet seesaw contribution. An extended framework, a setup with an additional,
quasidecoupled Higgs multiplet transforming as 120 of 50(10), is introduced and studied
in detail in chapter 4. Chapter 5 is devoted to a class of alternative seesaw schemes
emerging in theories with a spinorial 16 in the Higgs sector of SUSY and split-SUSY
SO(lO) GUTs. Finally, a set of Appendices is added to coment on technical points in
the main text.
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Ferrara, Valentina. "Extraction of the top quark mass from the total top quark pair production cross section in the single lepton channel." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16727.
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In dieser Arbeit wird eine Messung des totalen {\ttb} Produktions-Wirkungsquerschnitts im Einzellepton-Kanal vorgestellt. Der Wirkungsquerschnitt wird mittels einer Profile-Likelihood-Anpassung von Templates bestimmt, welche \"uber einen Lieklihood-Klassifikator unter Benutzung von vier kinematischen Variablen konstruiert werden. F\"ur ein Top-Quark der Masse $m_t=172.5$ GeV ergibt sich ein gemessener Wirkungsquerschnitt von $178.9 \pm 12$ pb, welcher innerhalb einer Standardabweichung mit den aktuellsten theoretischen Vorhersagen \"uberein stimmt. Um die Massenabh\"angigkeit des experimentellen Wirkungsquerschnitts zu bestimmen, wird die Messung f\"ur sieben weitere Werte der Top-Quarkmasse im Bereich zwischen 140 GeV und 200 GeV wiederholt. Mittels Vergleich dieser Massenabh\"angigkeit mit theoretischen Vorhersagen h\"oherer Ordnung wird die Top-Quarkmasse ermittelt. Diese Methode erlaubt die Bestimmung von zwei verschiedenen theoretischen Massenparametern: der Top-Quarkmasse im On-Shell-Schema $m_t^{\mathrm{pole}}$ sowie der Masse im $\overline{MS}$-Schema $\overline{m}_t(\overline{m}_t)$. Der Messwert mit der h\"ochsten erhaltenen Genauigkeit liegt bei $m_t^{\mathrm{pole}} = 171.2\pm 4.5$ GeV, und wird durch Verwendung der derzeit pr\"azisesten Berechnungen h\"oherer Ordnung im $\overline{MS}$-Schema erhalten. Dieser Wert stimmt innerhalb einer Standardabweichung mit den derzeitig besten Mittelwert von Messungen der Top-Quarkmasse am Tevatron \"uberein.A measurement of the total {\ttb} production cross section in the single lepton channel is presented. The cross section is extracted in a profile likelihood fit of templates constructed from a likelihood classifier using four kinematic variables. For a top quark of mass $m_t=172.5$ GeV, the measured cross section is $178.9 \pm 12$ pb. The measurement agrees within one-standard deviation with the latest theoretical predictions. The cross section measurement is repeated for seven other values of the top quark mass ranging from 140 GeV to 200 GeV to obtain the mass dependence of the experimental cross section. By comparing this with the mass dependence of different higher-order predictions, the top quark mass is extracted. This method allows the determination of two different theoretical mass parameters: the top quark mass in the on-shell scheme $m_t^{\mathrm{pole}}$ and in the $\overline{MS}$ scheme $\overline{m}_t(\overline{m}_t)$. The most precise measurement obtained is $m_t^{\mathrm{pole}} = 171.2\pm 4.5$ GeV, obtained when employing the most precise higher-order calculations in the $\overline{MS}$ scheme. This value agrees within one-standard deviation with the latest Tevatron average of the best top quark mass measurements.
3
Capelli, Laurent. "Étude des dimuons de la région des masses intermédiaires produits dans les collisions d'ions lourds auprès du SPS du CERN." Lyon 1, 2001. http://www.theses.fr/2001LYO10041.
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Dans cette thèse, nous étudions la production des dimuons dans une région de masse entre les résonances et j/ (région des masses intermédiaires, imr) dans les collisions proton-noyau et noyau-noyau de haute énergie. L'expérience Na50, installée auprès de l'accélérateur SPS du CERN, détecte les paires de muons émises dans ces interactions au moyen d'un spectromètre spécifique. La mesure de la centralité des collisions repose sur trois détecteurs indépendants : un calorimètre électromagnétique, un détecteur de multiplicité et un calorimètre a zéro degré. Les résultats des analyses proton-noyau fournissent une valeur de référence pour l'étude des intéractions noyau-noyau. Les distributions expérimentales, corrigées de l'acceptance et de la résolution par une méthode quadri-dimensionnelle, des dimuons IMR sont correctement reproduites par la superposition des processus conventionnels drell-yan et dd (désintégration des mesons charmes). L'extrapolation linéaire avec le nombre de masse des noyaux des résultats p-a aux collisions s-u et pb-pb, sous-estime systématiquement les spectres mesures dans la région des masses intermédiaires. Cet excès de dimuons imr augmente avec la centralité des collisions. Plusieurs modèles théoriques sont présentés et comparés aux données noyau-noyau. Nous montrons qu'un modèle base sur la diffusion des mesons d et d dans l'état final ne reproduit pas les distributions expérimentales. Finalement, cette étude permet de proposer deux explications possibles de l'excès observe. Les spectres noyau-noyau peuvent être reproduits soit par une augmentation de la production de charme soit par la présence de dimuons thermiques émis par un milieu dense et chaud.
4
Wang, Ping. "Studies of lepton and quark interactions." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/53614.
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Part I
Proposed Experimental Tests of the Right-handed Weak Current
All possible experiments which test the SU(2)L x U(1)R x U(1)B-L model and SU(2)L x SU(2)R x U(1)B-L model using the LEP e⁺e⁻ collider and HERA e⁻p collider are calculated and the most sensitive experiments are examined.
Part II
Semi-Phenomenological Theory of (Qq̅) System
The (QQ̅) and (Qq̅) mesons are calculated using a QCD motivated potential model. It is discovered that by including a long distance relativistic correction term derived by Grome, the Coulomb + Linear potential works not only for c and b quarks, but s quark as well. The leptonic decay constants of various (Qq̅) mesons together with their masses are predicted. The topponium states are also discussed.Ph. D.
5
Souchlas, Nicholas. "Quark Dynamics and Constituent Masses in Heavy Quark Systems." Kent State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=kent1248013809.
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Kimchi, Itamar. "Quark masses : an environmental impact statement." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44761.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.Includes bibliographical references (leaves 63-65).
We investigate how the requirement that organic chemistry be possible constrains the values of the quark masses. Specifically, we choose a slice through the parameter space of the Standard Model in which quark masses vary so that as many as three quarks play a role in the formation of nuclei, while keeping fixed the average mass of the two lightest baryons (in units of the electron mass) and the strength of the low-energy nuclear interaction. We classify universes on that slice as congenial if they contain stable nuclei with electric charge 1 and 6 (thus making organic chemistry possible in principle). Universes that lack one or both such stable nuclei are classified as uncongenial. We reassess the relationship between baryon masses and quark masses, using information in baryon mass differences in our world and the pion-nucleon sigma term [sigma]IIN. We generalize the Weizsacker semi-empirical mass formula through a degenerate Fermi gas model that handles the kinetic energy of new baryonic species as they begin to participate in the nucleus, and derive an expression for the asymmetry energy equivalent in the SU(3) limit through a minimization procedure on the quadratic Casimir operator. We spell out the conditions for decay by weak nucleon emission. Finally, we study the congeniality of various regions in the quark mass space, primarily by direct comparison to analog nuclei in our universe. Considering only two light quarks u and d, we find a band of congeniality roughly 29 MeV wide in mu - md, with our universe living comfortably away from the edge. We find multiple congeniality regions in the three quark mass space. For an important region around the SU(3) limit, we have not determined conclusive results but we have constructed the machinery to aid in its analysis and formulated the relevant problems. We have succeeded in formulating a well defined question about congeniality, and have made concrete progress toward answering it.
by Itamar Kimchi.
S.B.
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Ogasahara, Atsushi. "Discrete flavor symmetry for lepton mixing and quark mixing." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/189340.
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Antusch, Stefan. "The running of neutrino masses, lepton mixings and CP phases." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969430248.
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Rimmer, Steven. "Neutrino masses and lepton flavour violating phenomena in the MSSM." Thesis, Durham University, 2007. http://etheses.dur.ac.uk/2521/.
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The most general supersymmetric model with minimal particle content and an additional discrete Ƶ(_3) symmetry, which allows lepton number violating terms, is considered. In this model, we calculate at the level of one-loop the resulting Majorana neutrino masses and the flavour violating radiative decays of charged leptons, ﺎ→ﺎ’γ. We first study the neutral scalar sector of the model, performing a calculable rotation of the scalar fields to a basis in which the sneutrino vacuum expectation values are zero. Lagrangian parameters are initialised without recourse to assumptions concerning trilinear or bilinear terms, CP-conservation or intergenerational mixing and one-loop corrections to the neutrino masses are analysed. We present scenarios in which the experimental data are reproduced. We find that with bilinear lepton number violating couplings in the superpotential of the order 1MeV the atmospheric mass scale can be reproduced. Certain trilinear superpotential couplings, usually of the order of the electron Yukawa coupling can give rise to either atmospheric or solar mass scales and bilinear supersymmetry breaking terms of the order 0.1 GeV(^2) can set the solar mass scale. Taking parameters which correctly describe the neutrino sector, we consider their repercussions in flavour violating radiative lepton decays. Such decays have not been observed and upper bounds on their branching ratios exist. We note that certain parameter sets, which correctly describe the neutrino sector, will also generate observable branching ratios and suggest four such sets as Benchmarks scenarios. We present as Appendices the full set of Feynman Rules for the general super- symmetric standard model with minimal particle content and details of the loop calculations in the Weyl spinor notation.
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Mes, Alexes K. "Light Quark Masses from QCD Finite Energy Sum Rules." Master's thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/30901.
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Due to quark-gluon confinement in QCD, the quark masses entering the QCD Lagrangian cannot be measured with the same techniques one would use to determine the mass of non-confined particles. They must be determined either numerically from Lattice QCD, or analytically using QCD sum rules. The latter makes use of the complex squared energy plane, and Cauchy’s theorem for the correlator of axial-vector divergences. This procedure relates a QCD expression containing the quark masses, with an hadronic expression in terms of known hadron masses, couplings, and lifetimes/widths. Thus, the quark masses become a function of known hadronic information. In this dissertation, the light quark masses are determined from a QCD finite energy sum rule, using the pseudoscalar correlator to six-loop order in perturbative QCD, with the leading vacuum condensates and higher order quark mass corrections included. The systematic uncertainties stemming from the hadronic resonance sector are reduced, by introducing an integration kernel in the Cauchy integral in the complex squared energy plane. Additionally, the issue of convergence of the perturbative QCD expression for the pseudoscalar correlator is examined. Both the fixed order perturbation theory (FOPT) method and contour improved perturbation theory (CIPT) method are explored. Our results from the latter exhibit good convergence and stability in the window s0 = 3.0 − 5.0 GeV2 for the strange quark and s0 = 1.5 − 4.0 GeV2 for the up and down quarks; where s0 is the radius of the integration contour in the complex s-plane. The results are: ms(2 GeV) = 91.8 ± 9.9 MeV, mu(2 GeV) = 2.6 ± 0.4 MeV, md(2 GeV) = 5.3 ± 0.4 MeV, and the sum mud ≡ (mu + md)/2, is mud(2 GeV) = 3.9 ± 0.3 MeV. They compare favourably to the PDG and FLAG world averages. Further in this dissertation the updated series expansion of the quark mass renormalization group equation (RGE) to five-loop order is derived. The series provides the relation between a light quark mass in the modified minimal subtraction (MS) scheme defined at some given scale, e.g. at the tau-lepton mass scale, and another chosen energy scale, s. This relation explicitly depicts the renormalization scheme dependence of the running quark mass on the scale parameter, s, and is important in accurately determining a light quark mass at a chosen scale. The five-loop QCD β(as) and γ(as) functions are used in this determination.
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Oliveira, Jorge Miguel Da Silva Borges. "Lepton flavour violation, Yukawa unification and neutrino masses in supersymmetric unified models." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340363.
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Wirén, Jens. "Higgs Lepton Flavour Violation and Radiative Neutrino Masses in the Zee Model." Thesis, KTH, Fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210307.
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Abazov, V. M., B. Abbott, B. S. Acharya, M. Adams, T. Adams, J. P. Agnew, G. D. Alexeev, et al. "Measurement of top quark polarization in t ¯ t lepton + jets final states." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/622747.
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We present a measurement of top quark polarization in t (t) over bar pair production in p (p) over bar collisions at root s = 1.96 TeV using data corresponding to 9.7 fb(-1) of integrated luminosity recorded with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing a lepton and at least three jets. The polarization is measured through the distribution of lepton angles along three axes: the beam axis, the helicity axis, and the transverse axis normal to the t (t) over bar production plane. This is the first measurement of top quark polarization at the Tevatron using lepton + jet final states and the first measurement of the transverse polarization in t (t) over bar production. The observed distributions are consistent with standard model predictions of nearly no polarization.
14
Napoletano, Davide. "Treatment of quark masses in b-associated production at the LHC." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/12409/.
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With the discovery of the Higgs boson at the Large Hadron Collider (LHC), and no signs of new physics to current date, precise theoretical predictions are of increasing importance. It is now essential to study in details the properties of the newly found boson, in particular its coupling to other particles and itself, as this unveils further the mechanism of symmetry breaking. In this thesis, we extend the currently used methods to deal with heavy quarks in hadron collision processes, the four-flavour and the five-flavour scheme, to con- sistently include mass effects as well as resummation of collinear logarithms. This is done using two complementary approaches. At the inclusive level, we extend a method used to include mass effects in parton densities evolution, known as FONLL. At the differential level, we devise a five-flavour scheme that includes mass effects consistently and systematically up to MC@NLO accuracy. We study the impact of such schemes on two phenomenologically relevant pro- cesses at the LHC: the production of a heavy boson, a Z or a Higgs, in association with heavy quarks. For these processes, in fact, the two standard schemes, have been known to largely disagree. In both new schemes, mass effects are found to have a few percent effect, with the bulk of the difference between a completely massless and a completely massive picture, residing in the resummation of collinear logarithms.
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Rasmussen, Rasmus Westphal. "Implications of physics beyond the Standard Model in the quark and lepton sectors." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19174.
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Das Standardmodell (SM) der Teilchenphysik hat sich in der Praxis als vielseitige Theorie bewährt, dennoch deuten nichtverschwindende Neutrinomassen, dunkle Materie und Baryonenasymmetrie auf Physik jenseits des SM (BSM) hin. Um also ein mit den Beobachtungen konsistentes Modell zu entwickeln, ist eine umfassendere Theorie nötig. Experimentell kann entweder in Abweichungen von den Vorhersagen des SM nach neuer Physik gesucht werden. So kann jedes BSM-Szenario getestet werden.
In dieser Arbeit werden BSM-Szenarien im Quark- sowie im Leptonen-Sektor und deren phänomenologische Konsequenzen auf messbare Observablen betrachtet. Ein konkretes Beispiel in dieser Dissertation sind Neutrino massen modellierung mit der Einführung von sterilen Neutrinos. Wir untersuchen die phänomenologische Konsequenz ihrer Einführung auf verschiedenen Massenskalen im Zusammenhang mit symmetriegenerierten oder strukturlosen Neutrinomassenmodellen. Unter den geschmacksabhängigen aktivsterilen Mischungen in den durch Symmetrie erzeugten Massenmodellen finden wir deutliche Hierarchien, die als Modelldiskriminator für zukünftige Experimente dienen.
Ähnlich wie beim Ausnutzen von Symmetrien im Neutrinosektor, kann man Symmetrien auch in Modellen für Quarkmassen nutzen. In dieser Arbeit werden Symmetrien behandelt, die den Cabibbo-Winkel für Quarkmischung in führender Ordnung quantisieren können. Dies führt zu einer Vielzahl möglicher Symmetrien, welche genutzt werden können um spezifische Modelle für Quarkmassen zu entwickeln.
BSM-Physik indirekt mit Hilfe astrophysikalischer Neutrinos zu testen stellt eine Alternative zur direkten Detektion dar, und führt bei Betrachtung der Zusammensetzung des NeutrinoFlavours zu klaren Abweichungen von den Erwartungen. Neben der Behandlung verschiedenster BSM-Szenarien wird auch das Potenzial zukünftiger Experimente betrachtet, vor Allem im Hinblick auf deren Effektivität Physik jense.The Standard Model (SM) of particle physics is a well-tested and predictive theory, however non-zero neutrino masses, the existence of dark matter, and the baryon asymmetry suggest physics beyond the SM. Thus, in order to have a model consistent with observations, a more complete theory is needed. Experimentally, one can search for new physics, thereby differentiate different BSM scenarios. We consider BSM scenarios in the quark and lepton sectors, and study their phenomenological consequence on measurable observables. A specific example is neutrino mass modeling with the introduction of sterile neutrinos. We study the phenomenological consequence of introducing them at different mass scales in the context of symmetry-generated or structureless neutrino mass models. We find distinct hierarchies among the flavor-dependent active-sterile mixings in the symmetry-generated mass models, which acts as a model discriminator for future experiments. Similarly as using symmetries in the neutrino sector, one can also use symmetries in quark mass models. This thesis consider symmetries capable of quantizing the Cabibbo quark mixing angle to leading order. As a result, a variety of possible symmetries are obtained, which can be used to build specific quark mass models. Probing BSM physics indirectly via astrophysical neutrinos, acts as an alternative to direct detection, and using the neutrino flavor composition as observable, BSM physics leads to clear deviations from expectation. Additional information comes from other effects, and it helps in constraining the parameter space further. Beside discussing different BSM scenarios, we illustrate the potential of future experiments, emphasizing their effectiveness to test and discriminate BSM physics.
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Kajfasz, Eric. "Quelques expériences gravitant autour du problème de génération de masses." Habilitation à diriger des recherches, Université de la Méditerranée - Aix-Marseille II, 2002. http://tel.archives-ouvertes.fr/tel-00002687.
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Gluckman, Gary Richard. "Determination of the charm- and beauty-quark masses from QCD sum rules." Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/17051.
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Bibliography: pages 58-59.Ratios of Laplace QCD sum rules are used in order to determine the on-shell charm- and beauty-quark masses. After confronting the experimental data in the charmonium and bottonium systems with theory, we obtain mc = 1.46 ± 0.07 GeV and mb = 4.70 ± 0.07 GeV. The error is due to the uncertainties in the values of Λ and the gluon condensate.
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Bielski, Rafal. "Top quark pair production measurements in the single lepton channel using the ATLAS detector." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/top-quark-pair-production-measurements-in-the-single-lepton-channel-using-the-atlas-detector(ff46d1b0-0102-47d5-a60c-3a9e4ae07c07).html.
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Three measurements of top-quark pair production cross sections in proton-proton collisions at sqrt(s) = 13 TeV using data collected by the ATLAS experiment are presented. The single-lepton final states are used, where one electron or muon, two b-jets and two other jets can be identified. The inclusive ttbar production cross section is measured to be sigma(ttbar) = 817 +/- 13 (stat.) +/- 103 (syst.) +/- 88 (lum.) pb, which is in good agreement with predictions and with other measurements. Absolute and relative differential cross sections of ttbar production are also measured, showing an overall good agreement with predictions, except for the top-quark transverse momentum distribution. As already reported in measurements at lower proton-proton collision energies, this distribution is shifted towards higher momenta in all predictions with respect to the observations. Total and differential fiducial cross sections of ttbar production in association with heavy-flavour jets are also presented. All tested models are found to agree with data within the uncertainties of these measurements.
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Kämpfer, Burkhard, André Peshier, G. Soff, and O. P. Pavlenko. "An new effective model of the quark-gluon plasma with thermal parton masses." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-32370.
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Kämpfer, Burkhard, André Peshier, G. Soff, and O. P. Pavlenko. "An new effective model of the quark-gluon plasma with thermal parton masses." Forschungszentrum Rossendorf, 1994. https://hzdr.qucosa.de/id/qucosa%3A22065.
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Hasan, Nesreen [Verfasser]. "A lattice QCD study of nucleon structure with physical quark masses / Nesreen Hasan." Wuppertal : Universitätsbibliothek Wuppertal, 2020. http://d-nb.info/1207005657/34.
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Jackson, David John. "Investigations into tau lepton and charm quark creation by electron-positron interactions at 91 GeV." Thesis, Lancaster University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358151.
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De, Vasconcelos Corga Kevin. "Étude du couplage du boson de Higgs au quark top dans les canaux avec deux leptons de même signe avec l’expérience ATLAS au LHC." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0316.
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Le Grand Collisionneur de Hadrons (Large Hadron Collider, LHC), au CERN (European Organisation for Nuclear Research), permet de sonder la matière à l’échelle subatomique. Après deux ans d’arrêt pour raison de maintenance et mises à jour, le LHC a redémarré en juin 2015 avec une augmentation de luminosité et d’énergie dans le centre de masse de 8 à 13 TeV. La première partie de ce document traite de la mesure de l’efficacité de reconstruction des électrons dans le détecteur ATLAS avec 27:7 fb−1 de données collectées en 2016. L’environnement hadronique des collisions voit les leptons être des marqueurs caractéristiques d’évènements d’intérêt. La mesure de leur efficacité de reconstruction est par conséquent cruciale. Méthode de mesure et d’estimation des bruits de fond sont présentées pour les électrons et les efficacités sont calculées dans les données et simulations. Les électrons sont reconstruits avec une efficacité variant de 97% à 99%. La précision de la mesure est de l’ordre du pourcent à bas ET et du pour mille pour ET > 20 GeV. Les résultats ont été utilisés par l’ensemble des analyses de l’expérience ATLAS utilisant des électrons. La seconde partie est consacrée à l’étude du couplage yt entre le boson de Higgs et le quark top. L’étude présentée dans ce document cible une mesure directe du couplage yt grâce au mode de production du boson de Higgs en association avec une paire de quark top (t¯tH). Sept canaux multileptoniques, visant principalement les décroissances du boson de Higgs H → WW∗ et H → fifi, ont été étudiés avec les 36:1 fb−1 de données collectées par l’expérience ATLAS au cours des années 2015 et 2016. Ce document décrit l’étude du canal le plus sensible au couplage, comptant deux leptons de même charge électrique dans l’état final. La discrimination du bruit de fond repose sur des analyses multivariées et l’apprentissage de la machine. La stratégie d’optimisation est présentée et les résultats détaillés pour le canal 2‘SS. La combinaison de tous les canaux associés à la production t¯tH a rendu possible la mise en évidence, puis l’observation de ce processus par les expériences ATLAS et CMS. L’analyse multileptonique pour la recherche de production t¯tH a été adaptée à la recherche de changement de saveur du quark top avec émission de courant neutre, interdit à l’ordre de l’arbre. Les canaux 2‘SS et 3‘ sont étudiés et leurs résultats combinés. Les limites supérieures posées sur les rapports d’embranchement des processus B(t → Hu) et B(t → Hc) sont de 0.19% et 0.16%, respectivement, et les plus basses à l’heure de leur obtentionThe Large Hadron Collider (LHC) at CERN (European Organization for Nuclear Research) enables physics exploration at subatomic level. After shutting down for planned maintenance in early 2013, the LHC restarted in June 2015, increasing luminosity and centre of mass energy from 8 to 13 TeV. The first part of this document is dedicated to the electron reconstruction efficiency measurement with the ATLAS detector using 27:7 fb−1 of data collected in 2016. In the intense hadronic environment, leptons are markers of interest for many processes. Precise measurements of their reconstruction efficiency are then crucial. Measurement method and background estimates are detailed for electrons, and results are computed in both data and Monte Carlo simulation samples. Electron reconstruction efficiency varies from 97% to 99%. The measurement accuracy is at the percent and per mille level at low energy and ET > 20 GeV, respectively. Those results have been used in all ATLAS physics analyses involving electrons. The second part of this manuscript focuses on the Higgs boson coupling yt to the top quark. The analysis aims at a direct measurement of the coupling yt from the associated production of the Higgs boson with a top quark-antiquark pair (t¯tH). Seven multileptonic channels, mainly targetting Higgs boson decays H → WW∗ and H → fifi, have been studied using 36:1 fb−1 of proton-proton collision data collected in 2015 and 2016. This document focuses on the most sensitive one for the measurement, characterized by a final state with two same-charge leptons. Background discrimination is based on machine learning with multivariate analysis (MVA) techniques. The optimisation strategy is described and results detailed for the 2‘SS channel. Combining all t¯tH studied decay channels, the ATLAS and CMS experiments independently claimed an evidence, and then observation for the t¯tH process. The same methodology has been used in the search for flavour changing neutral currents in top-quark decays, forbidden at tree level. The 2‘SS and 3‘ channels are optimized and their results are combined. The current best upper limits on the branching ratios B(t → Hu) and B(t → Hc) have been set to 0.16% and 0.19%, respectively
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Jeong, Yu Seon. "Quark and lepton mass effects and the observational constraints on the high energy neutrino cross sections." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/1233.
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The cross sections of neutrino-nucleon scattering at high energies are evaluated with quark masses at next-to-leading order in strong interaction corrections. We compare the results with two kinds of schemes for treating the heavy quarks, the fixed flavor number scheme and the variable flavor number scheme for muon neutrino-nucleon interaction, and discuss which scheme is more relevant. The optimized parton distribution functions (PDF) for the flavor number schemes are also evaluated. The tau mass, much larger than the muon mass, suppresses the cross sections at low energies. We calculate the tau neutrino and antineutrino cross sections including the lepton mass corrections with low Q-extrapolated structure functions. Uncertainties due to the factorization scale, PDF choice, and the momentum transfer cutoff for the structure functions are also discussed with total theoretical errors. At ultra high energies (UHE), the same cross sections can be used for all flavors. We applied our evaluated cross sections to estimate the UHE neutrino event rates from lunar detection. The effective lunar aperture depends on the frequency and the minimum detectable electric field. We evaluate the effective aperture for a range of inputs. The event rates for both neutrino and cosmic rays are calculated in the standard model and compared with the enhanced neutrino-nucleon cross section for mini-black hole production. Lunar detection of UHE neutrino fluxes in the standard model will be challenging because low event rates are predicted.
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Green, Jeremy Russell. "Studies in hadron structure using lattice QCD with quark masses that almost reach the physical point." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84184.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 93-100).
Lattice QCD allows us to study the structure of hadrons from first-principles calculations of quantum chromodynamics. We present calculations that shed light on the behavior of quarks inside hadrons in both qualitative and quantitative ways. The first is a study of diquarks. We bind two quarks in a baryon with a static quark and compute the simultaneous two-quark density, including corrections for periodic boundary conditions. Defining a correlation function to isolate the intrinsic correlations of the diquark, we find that away from the immediate vicinity of the static quark, the diquark has a consistent shape, with much stronger correlations seen in the scalar diquark than in the axial-vector diquark. We present results at pion masses 293 and 940 MeV and discuss the dependence on the pion mass. The second set of calculations is a more quantitative study that covers a wide range of (mainly isovector) nucleon observables, including the Dirac and Pauli radii, the magnetic moment, the axial charge, and the average quark momentum fraction. Two major advances over previous calculations are the use of a near-physical pion mass, which nearly eliminates the uncertainty associated with extrapolation to the physical point, and the control over systematic errors caused by excited states, which is a significant focus of this thesis. Using pion masses as low as 149 MeV and spatial box sizes as large as 5.6 fm, we show the importance of good control over excited states for obtaining successful postdictions -- which we achieve for several quantities -- and we identify a remaining source of systematic error that is likely responsible for disagreement with experiment in the axial sector. We then use this understanding of systematics to make predictions for observables that have not been measured experimentally.
by Jeremy Russell Green.
Ph.D.
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Ferrara, Valentina [Verfasser], Ulrich Akademischer Betreuer] Husemann, Hermann [Akademischer Betreuer] [Kolanoski, and Wolfang [Akademischer Betreuer] Lohmann. "Extraction of the top quark mass from the total top quark pair production cross section in the single lepton channel / Valentina Ferrara. Gutachter: Ulrich Husemann ; Hermann Kolanoski ; Wolfang Lohmann." Berlin : Humboldt Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://d-nb.info/1034123718/34.
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Linacre, Jacob Thomas. "A top quark mass measurement using a matrix element method." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:c716f985-1913-46fb-a11b-1ef973ba4e6f.
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A measurement of the mass of the top quark is presented, using top-antitop pair (t-tbar) candidate events for the lepton+jets decay channel. The measurement makes use of Tevatron proton-antiproton collision data at centre-of-mass energy 1.96 TeV, collected at the CDF detector. The top quark mass is measured by employing an unbinned maximum likelihood method where the event probability density functions are calculated using signal (t-tbar) and background (W+jets) matrix elements, as well as a set of parameterised jet-to-parton mapping functions. The likelihood function is maximised with respect to the top quark mass, the fraction of signal events, and a correction to the jet energy scale (JES) of the calorimeter jets. The simultaneous measurement of the JES correction (ΔJES) provides an in situ jet energy calibration based on the known mass of the hadronically decaying W boson. Using 578 lepton+jets candidate events corresponding to 3.2 inverse femtobarns of integrated luminosity, the top quark mass is measured to be 172.4 ± 1.4(stat+ΔJES) ± 1.3(syst) GeV/c², one of the most precise single measurements to date.
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Kurth, Thorsten [Verfasser]. "Precision Physics from the Lattice Calculation of the Hadron Spectrum, Quark Masses and Kaon Bag Parameter / Thorsten Kurth." Wuppertal : Universitätsbibliothek Wuppertal, 2011. http://d-nb.info/1018298673/34.
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Gottardo, Carlo Alberto [Verfasser]. "Search for charged lepton-flavour violation in top-quark decays at the LHC with the ATLAS detector / Carlo Alberto Gottardo." Bonn : Universitäts- und Landesbibliothek Bonn, 2019. http://d-nb.info/1198933267/34.
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Lefeld, Anthony J. "Search for Enhancements of Associated Top Quark Production in Multiple Lepton Final States in the Context of Effective Field Theories." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574427195392083.
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Tourneur, Stéphane. "Search for top pair production in the dilepton decay channel with tau lepton at the CDF experiment." Paris 6, 2006. http://www.theses.fr/2006PA066422.
Full textAbstract:
La recherche des désintégrations du quark top impliquant un lepton tau au détecteur CDF, dans les collisions p/pbar \à 1. 96 TeV du Tevatron, a deux finalités principales : observer l'un des derniers canaux t/tbar et rechercher d'éventuels excès par au modèle standard. Le signal est ténu et difficile à extraire dans un bruit de fond dominé par des événements Z->TauTau+ 2 jets, et W+3 jets où un jet est identifié par erreur comme un tau hadronique. L'une des avancées de ce travail est le développement d'une méthode d'estimation rigoureuse du fond dominant de W+jets dans un environnement à haute énergie transverse manquante, un électron ou muon, un tau hadronique. L'analyse se fait sur deux échantillons de données successifs, de 350/pb et 1/fb de luminosité intégrée. Après contrôle de la cohérence de la méthode, une évidence de 92\% est trouvée pour le signal. L'excès relatif de signal top en tau comparé au modèle standard est mesuré tel que R<1. 5 à 95% de degré de confianceThe search for top quark decays with tau leptons in p/pbar collisions at sqrt(s)=1. 96 TeV using the CDF detector has two main goals: To observe one of the last top decay channels yet to be observed and to search for possible excesses over the standard model expectations. The signal is tiny and difficult to extract from a high background dominated by Z->TauTau+2 jets events, and W+3 jets in which a jet is misidentified as a hadronic tau. One of the main original of this work is the development of a rigorous estimation method of the tricky W+jets background in an environment characterized by a high missing transverse energy, one electron or muon, and one hadronic tau. The analysis makes use of two successive data samples with 350/pb and 1/fb of integrated luminosity. After a thorough control of the method, a 92\% signal evidence is established with 1/fb of data. The relative excess of the top in tau signal is also constrained down to R<1. 5 at 95% confidence level
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Schieferdecker, Philipp. "Measurement of the Top Quark Mass at D0 Run II with the Matrix Element Method in the Lepton+Jets Final State." Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-44217.
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Moch, Paul [Verfasser], Martin [Akademischer Betreuer] Beneke, and Andreas [Akademischer Betreuer] Weiler. "Loop-induced lepton and quark dipole transitions in Randall-Sundrum models / Paul Moch. Betreuer: Martin Beneke. Gutachter: Andreas Weiler ; Martin Beneke." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1081768010/34.
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Hepburn, Derek John. "Light hadron spectrum, quark masses and meson decay constants from lattice QCD with O(a)-improved dynamical Wilson fermions." Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/15009.
Full textAbstract:
In this thesis I present results for the light hadron spectrum, light quark masses and meson decay constants from numerical simulations of lattice QCD. The simulations were performed on a 163 x 32 space-time lattice using the standard Wilson gauge field action and a fully O(a)-improved Sheikholeslami-Wohlert fermion action with Nj = 2 degenerate flavours of dynamical fermions. A subset of these simulations were performed at fixed lattice spacing, as determined through the Sommer scale parameter, ro, in order to investigate the effects associated with a finite sea quark mass whilst keeping cutoff and finite size effects fixed. A quenched simulation was also performed at this lattice spacing for comparative purposes. No clear evidence of unquenching was found in the light hadron spectrum at the quark masses used in the matched simulations studied here. Light quark masses were determined from chiral extrapolations of pseudoscalar and vector meson masses to both the standard and PCAC definitions of the quark mass. The bare strange quark mass was fixed through the K, K* and ø meson masses for comparison. Renormalised quark masses have been determined in the ? scheme at a reference scale of 2GeV with matching performed at two values of the scale parameter, m = 1/a and m = p/a, in order to study the systematic effects.
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Meinel, Stefan. "Lambda(c) -> Lambda l(+)nu(l) Form Factors and Decay Rates from Lattice QCD with Physical Quark Masses." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/623030.
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The first lattice QCD calculation of the form factors governing Lambda(c) -> Lambda l(+)nu(l) decays is reported. The calculation was performed with two different lattice spacings and includes one ensemble with a pion mass of 139(2) MeV. The resulting predictions for the Lambda(c) -> Lambda e(+)nu(e) and Lambda(c) -> Lambda mu(+)nu(mu) decay rates divided by vertical bar V-cs vertical bar(2) are 0.2007(71)(74) and 0.1945(69)(72) p(s-1), respectively, where the two uncertainties are statistical and systematic. Taking the Cabibbo-Kobayashi-Maskawa (CKM) matrix element vertical bar V-cs vertical bar from a global fit and the Lambda(c) lifetime from experiments, this translates to branching fractions of B(Lambda(c) -> Lambda e(e)(+nu)) = 0.0380(19)(LQCD)(11)(tau Lambda c) and B(Lambda(c) -> Lambda mu(+)nu(mu)) 0.0369(19)(LQCD)(11)(tau Lambda c). These results are consistent with, and two times more precise than, the measurements performed recently by the BESIII Collaboration. Using instead the measured branching fractions together with the lattice calculation to determine the CKM matrix element gives vertical bar V-cs vertical bar = 0.949(24)(LQCD)(14)(tau)Lambda c (49)(B).
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Dinh, Nguyen Dinh. "Probing the Possible TeV Scale See-saw Origin of Neutrino Masses with Charged Lepton Flavour Violation Processes and Neutrino Mass Spectroscopy Using Atoms." Doctoral thesis, SISSA, 2013. http://hdl.handle.net/20.500.11767/4727.
Full textAbstract:
In the first part of this thesis, we perform a detailed analysis of lepton flavour violation (LFV) within
minimal see-saw type extensions of the Standard Model (SM), which give a viable mechanism of neutrino mass
generation and provide new particle content at the electroweak scale. We focus, mainly, on predictions
and constraints set on each scenario from muon and tau decays ($\mu\to e \gamma$, $\mu\to 3e$, $\tau\to (\mu,e) \gamma$ and $\tau\to 3\mu$)
and $\mu-e$ conversion in the nuclei. In particular, we show that in some regions of the parameters space of type I and type II see-saw models, the
Dirac and Majorana phases of the neutrino mixing matrix, the ordering and hierarchy of the light neutrino mass
spectrum as well as the value of the reactor mixing angle $\theta_{13}$ may considerably affect the size of the
LFV observables. Besides, the possibilities to observe the LFV processes in the present and future experiments
are also considered. The analytic results of the LFV rates might help to discriminate between the three types of neutrino mass
generation models considered.
In the second part of the thesis, we study a process of collective de-excitation of atoms in a metastable level
into emission mode of a single photon plus a neutrino pair, called radiative emission of neutrino pair (RENP). This process
is sensitive to the absolute neutrino mass scale, to the neutrino mass hierarchy and to the nature (Dirac or Majorana)
of massive neutrinos. We investigate how the indicated neutrino mass and mixing observables can be determined
from the measurement of the corresponding continuous photon spectrum on the example of a transition between
specific levels of the Yb atom. The possibility of determining the nature of massive neutrinos and, if neutrinos
are Majorana fermions, of obtaining information about the Majorana phases in the neutrino mixing matrix, is
analyzed in the cases of normal hierarchical, inverted hierarchical and quasi-degenerate types of neutrino mass spectrum. We find, in particular, that the sensitivity to
the nature of massive neutrinos depends critically on the atomic level energy difference relevant in the RENP.
\vspace{1cm}
The content of this thesis is based on the following works:
\begin{itemize}
\item[ I, ]
D.~N.~Dinh, A.~Ibarra, E.~Molinaro and S.~T.~Petcov, \\
\textit{The $\mu\to e$ Conversion in Nuclei, $\mu\rightarrow e +\gamma$, $\mu\rightarrow 3e$ Decays and TeV Scale
See-Saw Scenarios of Neutrino Mass Generation},\\
JHEP {\bf 1208} (2012) 125, Erratum-ibid. 1309 (2013) 023 [arXiv:hep-ph/1205.4671v4].
%%%
\item[ II, ]
D.~N.~Dinh and S.~T.~Petcov,\\
\textit{Lepton Flavor Violating $\tau$ Decays in TeV Scale Type I See-saw and Higgs Triplet Models},\\
JHEP {\bf 09} (2013) 086 [arXiv:hep-ph/1308.4311].
%%%
\item[ III, ]
D.~N.~Dinh, S.~T.~Petcov, N.~Sasao, M.~Tanaka and M.~Yoshimura,\\
\textit{Observables in Neutrino Mass Spectroscopy Using Atoms},\\
Phys.\ Lett.\ B {\bf 719} (2013) 154 [arXiv:hep-ph/1209.4808].
\end{itemize}
Other papers of the same author, which are not discussed in the thesis:
\begin{itemize}
\item[ I, ]
D.~N.~Dinh and S.~T.~Petcov,\\
\textit{Sterile Neutrino Determination Using Radiative
Emission of Neutrino Pair},\\
Work in progress.
%%%
\item[ II, ]
D.~N.~Dinh, N.~A.~Ky, N.~T.~H.~Van and P.~Q.~Van,\\
\textit{Model of neutrino effective masses},\\
Phys.\ Rev.\ D {\bf 74} (2006) 077701.
\end{itemize}
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Balli, Fabrice. "Calibration de l'échelle d'énergie des jets et mesure de la masse du quark top dans le canal semi-leptonique dans l'expérience ATLAS." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01059762.
Full textAbstract:
L'objectif principal de cette thèse est de fournir une mesure aussi précise que possible de la masse du quark top dans son canal de désintégration semi-leptonique. Cette mesure expérimentale est réalisée à l'aide du détecteur ATLAS, installé auprès du LHC, un collisionneur proton-proton. Les motivations principales à cette mesure de précision sont les contraintes qu'elle apporte aux modèles de physique. Par ailleurs, la masse du quark top est un paramètre permettant d'estimer l'état de stabilité du vide dans le cadre du Modèle Standard, à l'échelle de Planck. Les jets sont des objets dont l'étalonnage en énergie est cruciale pour la mesure. Une étude détaillée de cette calibration est présentée, et notamment l'impact des conditions réelles de prises de données sur la performance de ces objets. La mesure de masse utilisant les données prises en 2011 à une énergie dans le centre de masse de 7 TeV est détaillée. Cette mesure utilise une méthode d'analyse particulière, appelée méthode des templates tridimensionnels. La masse du quark top mesurée est: mtop = 172.01 ± 0.92 (stat) ± 1.17 (syst) GeV. Les données prises en 2012 à une énergie dans le centre de masse de 8 TeV sont aussi analysées, et une mesure préliminaire de la masse du quark top est fournie: mtop = 172.82 ± 0.39 (stat) ± 1.12 (syst) GeV, la combinaison des deux mesures donnant le résultat le plus précis de cette thèse: mtop = 172.64 ± 0.37 (stat) ± 1.10 (syst) GeV.
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Bender, Michael [Verfasser], and Otmar [Akademischer Betreuer] Biebel. "Measurement of the top quark mass using lepton transverse momenta with the ATLAS detector at √s = 8 TeV / Michael Bender ; Betreuer: Otmar Biebel." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/112910527X/34.
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Rasmussen, Rasmus Westphal [Verfasser], Walter [Gutachter] Winter, Christophe [Gutachter] Grojean, and Werner [Gutachter] Rodejohann. "Implications of physics beyond the Standard Model in the quark and lepton sectors / Rasmus Westphal Rasmussen ; Gutachter: Walter Winter, Christophe Grojean, Werner Rodejohann." Berlin : Humboldt-Universität zu Berlin, 2018. http://d-nb.info/1185667652/34.
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Rasmussen, Rasmus W. [Verfasser], Walter [Gutachter] Winter, Christophe [Gutachter] Grojean, and Werner [Gutachter] Rodejohann. "Implications of physics beyond the Standard Model in the quark and lepton sectors / Rasmus Westphal Rasmussen ; Gutachter: Walter Winter, Christophe Grojean, Werner Rodejohann." Berlin : Humboldt-Universität zu Berlin, 2018. http://nbn-resolving.de/urn:nbn:de:kobv:11-110-18452/19925-5.
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Agaras, Merve Nazlim. "Searches for associated Higgs Boson production with top quark pair and Higgs pair production in multi lepton final states with the ATLAS detector." Thesis, Université Clermont Auvergne (2017-2020), 2020. http://www.theses.fr/2020CLFAC023.
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Depuis la découverte du boson de Higgs à une masse d'environ 125 GeV par les deux collaborations ATLAS et CMS en juillet 2012, il est devenu crucial de mesurer ses propriétés, telles que ses couplages avec d'autres particules, et de rechercher tout écart par rapport aux prévisions du Modèle Standard (SM). Le couplage Yukawa du quark top est proche de l'unité et est le plus fort dans le secteur fermionique. Par conséquent, ce couplage joue un rôle crucial dans la théorie. La détermination de la production de boson de Higgs avec une paire de quarks top (ttH) offre un accès a l'ordre dominant pour mesurer ce couplage. L'analyse de la production de ttH dans le cadre de l'expérience ATLAS exploite plusieurs canaux de désintégration du Higgs, ainsi que différents modes de désintégration des quarks top. Dans cette thèse, l'étude du processus ttH (H → Multi lepton) est présentée dans la topologie où le Higgs se désintègre en WW,ZZ ou tautau, en utilisant un ensemble de données correspondant à une luminosité intégrée de 79,8fb^-1 à √s = 13 TeV, recueillies avec le détecteur ATLAS entre 2015 et 2017. L'amélioration des connaissances sur la modélisation des bruits de fond et un modèle d'ajustement complexe est utilisée avec de nombreux degrés de liberté. Des ajustements particulièrement différents sont présentés afin de comprendre la modélisation du principal bruit de fond irréductible, ttW. En outre, une recherche sur la production de paires de bosons de Higgs dans les états finaux multi leptoniques est présentée. La recherche utilise 139fb^-1 de données issues de collisions proton-proton à une énergie de centre de masse de 13 TeV fournies par le Grand collisionneur de hadrons (LHC) et enregistrées par l'expérience ATLAS entre 2015 et 2018. Les premières études du canal 2 leptons de même signe sont réalisées afin d'optimiser le point de fonctionnement des leptons et d'estimer les contributions des bruits de fond. La méthode d'ajustement du modèle est appliquée pour estimer les bruits de fond réductibles et calculer la limite supérieure préliminaire prévueSince the discovery of the Higgs boson at a mass around 125 GeV by both ATLAS and CMS collaborations in July 2012, it became crucial to measure its properties, such as its couplings to other particles, and search for any deviations from the Standard Model (SM) predictions. The top quark Yukawa coupling is close to unity and the strongest in the fermionic sector. Therefore, this coupling plays a crucial role in the theory. Determination of the associated production of The Higgs boson production with a pair of top quarks (ttH) offers a tree-level access to measuring this coupling. The analysis of ttH production at ATLAS experiment exploits several Higgs decay channel, together with different top quark decay modes. In this thesis, the study of the ttH (H → Multi lepton) process is presented in the topology where the Higgs decays to WW,ZZ or tautau, using a dataset corresponding to an integrated luminosity of 79.8fb^-1 at √s = 13 TeV, collected with the ATLAS detector between 2015-2017. Improved knowledge on the background modelling and the complex fit model is used with many degrees of freedoms. Particularly different fit setups are presented in order to understand the modelling of the major irreducible background, ttW. Furthermore, a search for the SM Higgs boson pair production in the multi lepton final states is presented. The search uses 139fb^-1 of proton-proton collisions data at a centre-of-mass energy of 13 TeV provided by the Large Hadron Collider (LHC) and recorded by the ATLAS experiment in 2015 and 2018. The first studies in two lepton same-sign channel is performed for lepton working point optimisation and estimation of background contributions. Template fit method is applied to estimated the reducible backgrounds and preliminary expected upper limit is calculated
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Caldeira, Balkeståhl Li. "Measurement of the Dalitz Plot Distribution for η→π+π−π0 with KLOE." Doctoral thesis, Uppsala universitet, Kärnfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-266871.
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The mechanism of the isospin violating η→π+π−π0 decay is studied in a high precision experiment using a Dalitz plot analysis. The process is sensitive to the difference between up and down quark masses. The measurement provides an important input for the determination of the light quark masses and for the theoretical description of the low energy strong interactions. The measurement was carried out between 2004 and 2005 using the KLOE detector at the DAΦNE e+e− collider located in Frascati, Italy. The data was collected at a center of mass energy corresponding to the φ-meson peak (1019.5 MeV) with an integrated luminosity of 1.6 fb−1. The source of the η-mesons is the radiative decay of the φ-meson: e+e−→φ→ηγ, resulting in the world’s largest data sample of about 4.7·106 η→π+π−π0 decay events. In this thesis, the KLOE Monte Carlo simulation and reconstruction programs are used to optimize the background rejection cuts and to evaluate the signal efficiency. The background contamination in the final data sample is below 1%. The data sample is used to construct the Dalitz plot distribution in the normalized dimensionless variables X and Y. The distribution is parametrized by determining the coefficients of the third order polynomial in the X and Y variables (so called Dalitz plot parameters). The statistical accuracy of the extracted parameters is two times better than any of the previous measurements. In particular the contribution of the X2Y term is found to be different from zero with a significance of approximately 3σ. The systematic effects are studied and found to be of the same size as the statistical uncertainty. The contribution of the terms related to charge conjugation violation (odd powers of the X variable) and the measured charge asymmetries are consistent with zero. The background subtracted and acceptance corrected bin contents of the Dalitz plot distribution are provided to facilitate direct comparison with other experiments and with theoretical calculations.
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Mergelmeyer, Sebastian [Verfasser]. "Measurement of the Associated Production of a Single Top Quark and a W Boson in Single-Lepton Events with the ATLAS Detector / Sebastian Mergelmeyer." Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/110718455X/34.
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Gilles, Geoffrey. "Recherche de résonances W' → tb dans le canal lepton plus jets avec le détecteur ATLAS au LHC." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22576/document.
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Le travail de recherche réalisé au cours de cette thèse s’inscrit dans le contexte de l’expérience ATLAS, l’une des quatre grandes expériences auprès du collisionneur LHC. Il fut principalement dédié à la recherche de nouveaux bosons de jauge lourds chargés, appelé W' et prédits par de nombreuses extensions du Modèle Standard de la physique des particules. Ce manuscrit présente une recherche du boson W' se désintégrant en un quark top et un quark beau à travers une approche de couplage effectif, dans des états finals de désintégrations leptoniques du quark top. Cette recherche fut réalisée avec 20.3 fb−1 de données de collision proton-proton, produits par le LHC à une énergie dans le centre de masse de 8 TeV et collectées par le détecteur ATLAS en 2012. Plusieurs scénarios d’études sont envisagés où le boson W' se couple soit à des fermions de chiralité gauche (W'L) soit de chiralité droite (W'R). Une technique d’analyse multivariée utilisant des arbres de décision boostés (BDT) est utilisée afin de mettre évidence un excès de processus de signal dans les données enregistrées. Aucun excès n’est observé au-delà des incertitudes expérimentales pour la statistique de données analysées jusque-là. Une analyse statistique est réalisée afin d’extraire des limites d’exclusion sur la masse et la section efficace de production de la particule. Des masses inférieures à 1.92, 1.80 et 1.70 TeV furent exclues respectivement pour des bosons W'R et W'L, en tenant compte ou non d’effets d’interférence. Les limites d’exclusion sur les sections efficaces de production sont réinterprétées en matière de limite d’exclusion sur le couplage effectif g'/g de la particule. Les limites d’exclusion les plus basses observées sur le rapport g'/g, respectivement de 0.20 et 0.16 pour les recherches de bosons W'R et W'L, furent obtenues pour une masse de boson W'R/L de 0.75 TeV. Une recherche de bosons de Higgs chargés se désintégrant en un quark top et un quark beau est également présentée dans ce manuscrit. Cette dernière repose sur une approche de couplage effectif décrivant un modèle à deux doublets de Higgs de type II. Cette analyse réutilise l’infrastructure développée pour la recherche du boson W' est complétée d’études phénoménologiques liées au calcul de la section efficace de ce processus ainsi que sur la caractérisation des effets de largeur de la résonance recherchée. Les premiers résultats obtenus sur la limite d’exclusion sur la section efficace de production pp → H+→ tb montrent toutefois que cette analyse ne semble pas être en mesure d’exclure un signal de boson H+ pour l’ensemble des scénarios théoriques considérés, compte tenu des faibles sections efficaces de production prédites. En parallèle de ces activités, des développements ont été réalisés pour la simulation rapide du système de calorimétrie FastCaloSim du détecteur ATLAS afin de pallier ses limitations. En particulier, un nouveau modèle de paramétrisation et de simulation rapide de la réponse en énergie du système de calorimétrie est présenté dans ce manuscrit. Ce modèle, toujours en développement, montre des résultats très encourageant pour la simulation d’événements à pion unique et permet de réduire considérablement l’empreinte mémoire de la paramétrisation en comparaison avec des versions précédentes de FastCaloSim, tout en permettant aux futures reparamétrisations d’être plus rapides et automatiséesThe research work carried out during this Ph.D thesis has been performed in the context of the ATLAS experiment, one of the four major LHC experiments, and was primarily dedicated to the search for a new chaged heavy gauge boson, called W' and predicted by many extensions of the Standard Model of particle physics. This manuscript presents a search for W' boson decaying into a top and a bottom quark through an effective coupling approach, in the lepton plus jets final states. This search is performed with 20.3 fb−1 of proton-proton collision data, produced by the LHC with a center-of-mass energy of 8 TeV and collected by the ATLAS detector in 2012. Several scenarios are considered where the W boson can couple to left-handed (W'L) or right-handed (W'R) fermions. A multivariate techniques based on boosted decision trees is used to search for an excess of W signal process in the recorded data. No excess is observed beyond the experimental uncertainties for the data analysed so far. A statistical analysis is performed in order to extract exclusion limits on the mass and the production cross section of the particle. Masses below 1.92, 1.80 and 1.70 TeV are excluded, respectively for W'R and W'L bosons taking into account or not interference effects. These exclusion limits on the production cross section are also reinterpreted in terms of exclusion limits on the effective coupling g'/g of the particle. The lowest exclusion limits observed on the ratio g'/g are equal to 0.20 and 0.16, respectively, for W'R and W'L searches, and are obtained for a W'R/L mass of 0.75 TeV. A search for charged Higgs boson decaying into a top and a bottom quark is presented in this manuscript. This search is based on an effective coupling approach describing a type II Two Doublet Higgs Model. It reuses the analysis infrastructure developed for the W' search and is completed by phenomenological studies related to the production cross section calculation for the process and the characterisation of the resonance width effects affecting the analysis. Preliminary results on the excluded cross section limits pp → H+→ tb show that the analysis is not able to exclude a signal a H+ boson for all theoretical scenarios considered, due to low production cross sections predicted. In parallel of these activities, several developments have been performed on the fast simulation of the ATLAS calorimeter system in order to overcome its limitations. In particular, a new parametrisation and fast simulation model for the energy response of the calorimeter is presented in this manuscript. This model, still under development, shows encouraging results for simulated single pion event and allows to reduce considerably the memory footprint of the parametrisation compared to previous versions of FastCaloSim, while enabling future reparametrisations to be faster and automated
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Adlarson, Patrik. "Studies of the Decay η→π+π-π0 with WASA-at-COSY." Doctoral thesis, Uppsala universitet, Kärnfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-181236.
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In 2008 a large statistics sample of approximately 1·107 η-decays has been collected with the WASA detector at COSY using the pd→3Heη reaction at the beam kinetic energy of 1 GeV. These data are being used to study the not so rare η decays involving charged pions, like η→π+π-π0. This decay proceeds mainly via a strong isospin violating contribution, where the decay width is proportional to the light quark mass difference squared, (md-mu)2. In addition this decay can be used to search for C-violating effects. The analysis is presented and the Dalitz plot parameters with statistical and systematical uncertainties are determined from a sample of 1.33·105 η→π+π-π0 events in the Dalitz plot. The asymmetry parameters with statistical uncertainties are presented which show no evidence of C-violation.WASA-at-COSY
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Sperlich, Dennis. "Search for the production of a single excited b quark in the Wt final state with a single lepton in pp collisions at sqrt s = 13 TeV with the ATLAS detector." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://edoc.hu-berlin.de/18452/24063.
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In dieser Dissertation wird eine Suche nach einem angeregten $b$ Quark, $b^*$, durchgeführt. Für diese $b^*$ wird eine anomale Kopplung an Bosonen aus dem Standard Modell vorhergesagt. Diese Kopplung führt zu der Produktion in hochenergetischen Proton-Proton Kollisionen. In der Suche zielen wir auf Ereignisse, bei denen eines der zwei $W$ Bosonen in ein Elektron oder Muon zerfällt und das andere in ein Hadronenpaar. Da es nur ein Neutrino in diesem Prozess gibt, kann das ganze Ereigniss kinematisch rekonstruiert werden. Damit ist es möglich, die Masse des $b^*$ als diskriminierende Variable zu verwenden.
Als Datenquelle dienen die Daten, die der ATLAS Detektor in den Jahren 2015 und 2016 bei Proton-Proton Kollisionen mit einer Schwerpunksenergie von $\sqrt s = \SI{13}{\tera\electronvolt}$ aufgezeichnet hat. Dabei entspricht diese Datenmenge einer integrierten Luminosität von $\L_{int} = \SI{36.1}{\femto\barn^{-1}}$. Da die Analyse auf hochmassige $b^*$ abziehlt, kann man davon ausgehen, dass das Hadronenpaar aus dem $W$ Zerfall in einen Jet mit großen Radius passt.
Es wurde kein signifikanter Überschuss über den Untergrund gefunden. Damit können nur obere Ausschlussgrenzen bezüglich der Wirkungsquerschnitte in dem entsprechenden Zerfallskanal abgeleitet werden. Unter Annahme von einer Kopplungskonstanten von 1, sind Zerfälle von $b^*\to Wt$ bis zu einer Masse $m_{b^*,\mathrm{obs}}= \SI{2.5}{\tera\electronvolt}$ ausgeschlossen, wobei erwartet wurde, dass die Ausschlussmasse bei $m_{b^*,\mathrm{exp}}= \SI{2.4}{\tera\electronvolt}$ liegen würde.A search for an excited $b$ quark, $b^*$, in events containing a top quark and a $W$ boson is investigated. These $b^*$ are predicted to have some anomalous couplings to Standard Model bosons aiding the production in high energy proton-proton collisions. The search is aiming for events, where one of the two $W$ bosons decays into an electron or muon, while the other decays hadronically. With only one neutrino, the event can be kinematically fully reconstructed. This enables the use of the mass of the $b^*$ as the discriminant variable. The data source under investigation is the data taken by the ATLAS detector at the LHC accelerator in the years 2015 and 2016 at a center-of-mass energy of $\sqrt s = \SI{13}{\tera\electronvolt}$. The combined dataset corresponds to an integrated luminosity of $\L_{int} = \SI{36.1}{\femto\barn^{-1}}$. The analysis targets high mass excited $b^*$ quarks, where the products of the hadronically decaying $W$ are contained within a large-radius jet. No significant excess over the expected background is observed and upper limits on the cross-section times branching ratio and coupling limits are derived. Assuming unit coupling, $b^*$ decaying into $Wt$ are excluded up to $m_{b^*,\mathrm{obs}}= \SI{2.5}{\tera\electronvolt}$, with an expected exclusion limit of $m_{b^*,\mathrm{exp}}= \SI{2.4}{\tera\electronvolt}$.
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Göttfert, Tobias. "Background suppression for a top quark mass measurement in the lepton+jets tt decay channel and alignment of the ATLAS silicon detectors with cosmic rays." kostenfrei, 2010. https://mediatum2.ub.tum.de/node?id=956486.
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Smith, Geoffrey N. "A Search For the Standard Model Higgs Boson Produced in Association with Top Quarks in the Lepton + Jets Channel at CMS." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397747965.
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Vasquez, Carmona Juan Carlos. "Phenomenology of the right-handed lepton mixings at the LHC in LR symmetric theory and the Time-Reversal symmetry violation in the µ --> eϒ decay and µ --> e conversion process." Doctoral thesis, SISSA, 2016. http://hdl.handle.net/20.500.11767/4913.
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We study how the elements of the leptonic right-handed mixing matrix can be determined at the LHC in the minimal Left-Right symmetric extension of the standard model. We do it by explicitly relating them with physical quantities of the Keung-Senjanovi\'c process and the lepton number violating decays of the right doubly charged scalar. We also point out that the left and right doubly charged scalars can be distinguished at the LHC, without measuring the polarization of the final state leptons coming from their decays.
Then we study time reversal symmetry violation in the $\mu\rightarrow e\gamma $ decay and the $\mu\rightarrow e$ conversion process and compute a T-odd triple vector correlation for the
$\mu\rightarrow e\gamma $ decay and the $\mu\rightarrow e$ conversion process,
finding simple results in terms of the CP violating phases of the effective
Hamiltonians. Finally we focus on the minimal Left-Right symmetric extension of
the
Standard Model, which is a complete model of neutrino masses that can lead to an appreciable correlation. We show that under
rather general assumptions, this correlation can be used to discriminate between
Parity or Charge-conjugation as the discrete Left-Right
symmetry.
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Staśto, Anna. "QCD analysis of deep inelastic lepton-hadron scattering in the region of small values of the Bjorken parameter x." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4515/.
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We present the new framework based on BFKL and DGLAP evolution equations in which the leading in(Q(_2)) and in(l/x) terms are treated on equal footing. We introduce a pair of coupled integro-difFerential equations for the quark singlet and the unintegrated gluon distribution. The observable structure functions are calculated using high energy factorisation approach. We also include the sub-leading in (l/x) effects via consistency constraint. We argue that the use of this constraint leads to more stable solution to the Pomeron intercept than that based on the NLO calculation of the BFKL equation alone and generates resummation to all orders of the major part of the subleading in (l/x) effects. The global fit to all available deep inelastic data is performed using a simple parametrisation of the non-perturbative region. We also present the results for the longitudinal structure function and the charm component of the F(_2) structure function. Next; we extend this approach to the low Q(^2) domain. At small distances we use the perturbative approach based on the unified BFKL/DGLAP equations and for large distances we use Vector Meson Dominance Model and, for the higher mass qq states, the additive quark approach. We show the results for the total cross section and for the ratio of the longitudinal and transverse structure functions. Finally, we calculate the dijet production and consider the decorrelation effects in the azimuthal distributions caused by the diffusion in the transverse momentum k(_r) of the exchanged gluon. Using the gluon distribution which is fixed by the fit to the DIS data we are able to make absolute predictions. We show the results for the dF(_r)/dɸ, the total cross section and also the distributions in Q(^2) as well as in the longitudinal momentum fraction of the gluon. Our theoretical predictions are confronted with the measurements made using ZEUS detector at HERA.