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Thèses sur le sujet « Fisica subnucleare »

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Auteur : Grafiati
Publié le 10 mars 2023
Mis à jour le 11 mars 2023

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1

Bauce, Matteo. « Study of the ZZ diboson production at CDF II ». Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423070.

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The subject of this Thesis is the production of a pair of massive Z vector bosons in the proton antiproton collisions at the Tevatron, at the center-of-mass energy sqrt(s) = 1.96 TeV. We measure the ZZ production cross section in two different leptonic decay modes: into four charged leptons (e or mu) and into two charged leptons plus two neutrinos. The results are based on the whole dataset collected by the Collider Detector at Fermilab (CDF), corresponding to 9.7 fb−1 of data. The combination of the two cross section measurements gives (pp->ZZ) = 1.38+0.28−0.27 pb, and is the most precise ZZ cross section measurement at the Tevatron to date. We further investigate the four lepton final state searching for the production of the scalar Higgs particle in the decay H ->ZZ(*)->lll'l'. No evidence of its production has been seen in the data, hence was set a 95% Confidence Level upper limit on its production cross section as a function of the Higgs particle mass, mH, in the range from 120 to 300 GeV/c2.
In questa Tesi è studiata la produzione di coppie di bosoni vettori massivi Z nelle collisioni protone antiprotone a Tevatron, ad un' energia nel centro di massa di sqrt{s} = 1.96 TeV. La sezione d’urto di produzione di ZZ è misurata in due diversi modi di decadimento leptonici: in quattro leptoni carichi (e o mu) e in due leptoni carichi e due neutrini. I risultati si basano su tutto il campione di dati raccolto dal Collider Detector at Fermilab (CDF), corrispondente a 9.7 fb−1 di dati. La combinazione delle due misure di sezione d’urto da come risultato σ(pp -> ZZ) = 1.38 +0.28−0.27 pb, ed è al momento la misura più precisa di produzione di ZZ al Tevatron. Abbiamo analizzato ulteriormente lo stato finale con quattro leptoni carichi ricercando la produzione della particella scalare di Higgs nel decadimento H -> ZZ -> lll'l'. Non è stata osservata nessuna evidenza della produzione di questa particella nei dati quindi si è ricavato un limite superiore ad un Livello di Confidenza del 95% sulla sezione d’urto di produzione in funzione della massa del bosone di Higgs mH, nell’intervallo compreso tra 120 e 300 GeV/c2.
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2

Noferini, Francesco <1978&gt. « Correlazioni di particelle in collisioni di ioni pesanti per l'esperimento ALICE a LHC ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/182/1/TESIPHDNOFERINI2007.PDF.

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3

Noferini, Francesco <1978&gt. « Correlazioni di particelle in collisioni di ioni pesanti per l'esperimento ALICE a LHC ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/182/.

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4

Giovacchini, Francesca <1978&gt. « Cosmic rays anti-deuteron flux sensitivity of the AMS-02 detector ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/335/1/TESI_DOT.PDF.

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5

Giovacchini, Francesca <1978&gt. « Cosmic rays anti-deuteron flux sensitivity of the AMS-02 detector ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/335/.

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6

Quadrani, Lucio <1973&gt. « Assembly and space qualification of the scintillator detector LTOF for the AMS-02 spectrometer ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/350/1/PhD_thesis_Quadrani_150307.pdf.

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7

Quadrani, Lucio <1973&gt. « Assembly and space qualification of the scintillator detector LTOF for the AMS-02 spectrometer ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/350/.

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8

Veronese, Giulio Paolo <1977&gt. « Carbon nanotubes and nanoporous alumina in the development of a high resolution position detector ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/354/1/PhDThesisVeroneseGP.pdf.

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9

Veronese, Giulio Paolo <1977&gt. « Carbon nanotubes and nanoporous alumina in the development of a high resolution position detector ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/354/.

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10

Balbi, Gabriele <1978&gt. « B mesons proper time measurement with the LHCb experiment : impact on physics parameters and calibration methods ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/504/1/TesiGabrieleBalbi.pdf.

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11

Balbi, Gabriele <1978&gt. « B mesons proper time measurement with the LHCb experiment : impact on physics parameters and calibration methods ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/504/.

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12

Gregori, Daniele <1975&gt. « Sistema di monitor e controllo della farm on-line e studio del decadimento Bºs → J/Ψ Φ a LHCb ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/849/1/Tesi_Gregori_Daniele.pdf.

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13

Gregori, Daniele <1975&gt. « Sistema di monitor e controllo della farm on-line e studio del decadimento Bºs → J/Ψ Φ a LHCb ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/849/.

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14

De, Sanctis Jacopo <1977&gt. « Pattern recognition analysis on heavy ion reaction data ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/851/1/Tesi_DeSanctis_Jacopo.pdf.

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One of the problems in the analysis of nucleus-nucleus collisions is to get information on the value of the impact parameter b. This work consists in the application of pattern recognition techniques aimed at associating values of b to groups of events. To this end, a support vec- tor machine (SVM) classifier is adopted to analyze multifragmentation reactions. This method allows to backtracing the values of b through a particular multidimensional analysis. The SVM classification con- sists of two main phase. In the first one, known as training phase, the classifier learns to discriminate the events that are generated by two different model:Classical Molecular Dynamics (CMD) and Heavy- Ion Phase-Space Exploration (HIPSE) for the reaction: 58Ni +48 Ca at 25 AMeV. To check the classification of events in the second one, known as test phase, what has been learned is tested on new events generated by the same models. These new results have been com- pared to the ones obtained through others techniques of backtracing the impact parameter. Our tests show that, following this approach, the central collisions and peripheral collisions, for the CMD events, are always better classified with respect to the classification by the others techniques of backtracing. We have finally performed the SVM classification on the experimental data measured by NUCL-EX col- laboration with CHIMERA apparatus for the previous reaction.
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15

De, Sanctis Jacopo <1977&gt. « Pattern recognition analysis on heavy ion reaction data ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/851/.

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One of the problems in the analysis of nucleus-nucleus collisions is to get information on the value of the impact parameter b. This work consists in the application of pattern recognition techniques aimed at associating values of b to groups of events. To this end, a support vec- tor machine (SVM) classifier is adopted to analyze multifragmentation reactions. This method allows to backtracing the values of b through a particular multidimensional analysis. The SVM classification con- sists of two main phase. In the first one, known as training phase, the classifier learns to discriminate the events that are generated by two different model:Classical Molecular Dynamics (CMD) and Heavy- Ion Phase-Space Exploration (HIPSE) for the reaction: 58Ni +48 Ca at 25 AMeV. To check the classification of events in the second one, known as test phase, what has been learned is tested on new events generated by the same models. These new results have been com- pared to the ones obtained through others techniques of backtracing the impact parameter. Our tests show that, following this approach, the central collisions and peripheral collisions, for the CMD events, are always better classified with respect to the classification by the others techniques of backtracing. We have finally performed the SVM classification on the experimental data measured by NUCL-EX col- laboration with CHIMERA apparatus for the previous reaction.
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16

Bindi, Marcello <1981&gt. « Measurement of the charm production cross section in DIS events at HERA ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/853/1/Tesi_Bindi_Marcello.pdf.

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17

Bindi, Marcello <1981&gt. « Measurement of the charm production cross section in DIS events at HERA ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/853/.

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18

Preghenella, Roberto <1980&gt. « The Time-Of-Flight detector of ALICE at LHC : construction, test and commissioning with cosmic rays ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1373/1/Preghenella_Roberto_PhDthesis.pdf.

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The Time-Of-Flight (TOF) detector of ALICE is designed to identify charged particles produced in Pb--Pb collisions at the LHC to address the physics of strongly-interacting matter and the Quark-Gluon Plasma (QGP). The detector is based on the Multigap Resistive Plate Chamber (MRPC) technology which guarantees the excellent performance required for a large time-of-flight array. The construction and installation of the apparatus in the experimental site have been completed and the detector is presently fully operative. All the steps which led to the construction of the TOF detector were strictly followed by a set of quality assurance procedures to enable high and uniform performance and eventually the detector has been commissioned with cosmic rays. This work aims at giving a detailed overview of the ALICE TOF detector, also focusing on the tests performed during the construction phase. The first data-taking experience and the first results obtained with cosmic rays during the commissioning phase are presented as well and allow to confirm the readiness state of the TOF detector for LHC collisions.
Il rivelatore Time-Of-Flight (TOF) di ALICE (A Large Ion Collider Experiment) è progettato per l'identificazione delle particelle cariche prodotte nelle collisioni nucleari di LHC (Large Hadron Collider) allo scopo di studiare la fisica della materia fortemente interagente ed il Quark-Gluon Plasma (QGP). Il rivelatore sfrutta la tecnologia innovativa MRPC (Multigap Resistive Plate Chamber) che garantisce le eccellenti prestazioni richieste ad un vasto sistema per la misura del tempo di volo. La costruzione e l'installazione dell'apparato nel sito sperimentale sono state completate ed il rivelatore è attualmente operativo in tutte le sue parti. Tutti i passi necessari per la costruzione del rivelatore finale sono stati accompagnati da una serie di procedure per il controllo della qualità della produzione allo scopo di garantire prestazioni elevate ed uniformi; infine il corretto funzionamento del rivelatore è stato verificato con raggi cosmici. Questo resoconto ha lo scopo di fornire una visione d'insieme dettagliata del rivelatore TOF di ALICE, focalizzando l'attenzione anche sui test effettuati durante le fasi di costruzione. Oltre ad una breve descrizione dell'esperienza acquisita nelle prime fasi di presa dati sono presentati i primi risultati ottenuti con raggi cosmici che confermano promettenti prestazioni del rivelatore TOF per lo studio delle collisioni di LHC.
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19

Preghenella, Roberto <1980&gt. « The Time-Of-Flight detector of ALICE at LHC : construction, test and commissioning with cosmic rays ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1373/.

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The Time-Of-Flight (TOF) detector of ALICE is designed to identify charged particles produced in Pb--Pb collisions at the LHC to address the physics of strongly-interacting matter and the Quark-Gluon Plasma (QGP). The detector is based on the Multigap Resistive Plate Chamber (MRPC) technology which guarantees the excellent performance required for a large time-of-flight array. The construction and installation of the apparatus in the experimental site have been completed and the detector is presently fully operative. All the steps which led to the construction of the TOF detector were strictly followed by a set of quality assurance procedures to enable high and uniform performance and eventually the detector has been commissioned with cosmic rays. This work aims at giving a detailed overview of the ALICE TOF detector, also focusing on the tests performed during the construction phase. The first data-taking experience and the first results obtained with cosmic rays during the commissioning phase are presented as well and allow to confirm the readiness state of the TOF detector for LHC collisions.
Il rivelatore Time-Of-Flight (TOF) di ALICE (A Large Ion Collider Experiment) è progettato per l'identificazione delle particelle cariche prodotte nelle collisioni nucleari di LHC (Large Hadron Collider) allo scopo di studiare la fisica della materia fortemente interagente ed il Quark-Gluon Plasma (QGP). Il rivelatore sfrutta la tecnologia innovativa MRPC (Multigap Resistive Plate Chamber) che garantisce le eccellenti prestazioni richieste ad un vasto sistema per la misura del tempo di volo. La costruzione e l'installazione dell'apparato nel sito sperimentale sono state completate ed il rivelatore è attualmente operativo in tutte le sue parti. Tutti i passi necessari per la costruzione del rivelatore finale sono stati accompagnati da una serie di procedure per il controllo della qualità della produzione allo scopo di garantire prestazioni elevate ed uniformi; infine il corretto funzionamento del rivelatore è stato verificato con raggi cosmici. Questo resoconto ha lo scopo di fornire una visione d'insieme dettagliata del rivelatore TOF di ALICE, focalizzando l'attenzione anche sui test effettuati durante le fasi di costruzione. Oltre ad una breve descrizione dell'esperienza acquisita nelle prime fasi di presa dati sono presentati i primi risultati ottenuti con raggi cosmici che confermano promettenti prestazioni del rivelatore TOF per lo studio delle collisioni di LHC.
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20

Marini, Paola <1981&gt. « Isospin dependence of the Ar+Ni fusion-evaporation cross section ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1532/1/marini_paola_tesi.pdf.

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The fundamental goal of this thesis is the determination of the isospin dependence of the Ar+Ni fusion-evaporation cross section. Three Ar isotope beams, with energies of about 13AMeV, have been accelerated and impinged onto isotopically enriched Ni targets, in order to produce Pd nuclei, with mass number varying from 92 to 104. The measurements have been performed by the high performance 4pi detector INDRA, coupled with the magnetic spectrometer VAMOS. Even if the results are very preliminary, the obtained fusion-evaporation cross sections behaviour gives a hint at the possible isospin dependence of the fusion-evaporation cross sections.
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21

Marini, Paola <1981&gt. « Isospin dependence of the Ar+Ni fusion-evaporation cross section ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1532/.

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The fundamental goal of this thesis is the determination of the isospin dependence of the Ar+Ni fusion-evaporation cross section. Three Ar isotope beams, with energies of about 13AMeV, have been accelerated and impinged onto isotopically enriched Ni targets, in order to produce Pd nuclei, with mass number varying from 92 to 104. The measurements have been performed by the high performance 4pi detector INDRA, coupled with the magnetic spectrometer VAMOS. Even if the results are very preliminary, the obtained fusion-evaporation cross sections behaviour gives a hint at the possible isospin dependence of the fusion-evaporation cross sections.
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22

Antonelli, Stefano <1969&gt. « Study of production of high-PT leptons and limits on single top production at HERA ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2026/1/antonelli_stefano_tesi.pdf.

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23

Antonelli, Stefano <1969&gt. « Study of production of high-PT leptons and limits on single top production at HERA ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2026/.

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24

Massimi, Cristian <1980&gt. « Improved cross-section on n+197Au from high resolution time-of-flight measurements at n_TOF and GELINA : the road to a new standard ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2098/1/cristian_massimi_tesi.pdf.

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25

Massimi, Cristian <1980&gt. « Improved cross-section on n+197Au from high resolution time-of-flight measurements at n_TOF and GELINA : the road to a new standard ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2098/.

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26

Silenzi, Alessandro <1982&gt. « The topological trigger system of the TOF detector for the ALICE experiment at the LHC ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2842/1/silenzi_alessandro_tesi.pdf.

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The ALICE experiment at the LHC has been designed to cope with the experimental conditions and observables of a Quark Gluon Plasma reaction. One of the main assets of the ALICE experiment with respect to the other LHC experiments is the particle identification. The large Time-Of-Flight (TOF) detector is the main particle identification detector of the ALICE experiment. The overall time resolution, better that 80 ps, allows the particle identification over a large momentum range (up to 2.5 GeV/c for pi/K and 4 GeV/c for K/p). The TOF makes use of the Multi-gap Resistive Plate Chamber (MRPC), a detector with high efficiency, fast response and intrinsic time resoltion better than 40 ps. The TOF detector embeds a highly-segmented trigger system that exploits the fast rise time and the relatively low noise of the MRPC strips, in order to identify several event topologies. This work aims to provide detailed description of the TOF trigger system. The results achieved in the 2009 cosmic-ray run at CERN are presented to show the performances and readiness of TOF trigger system. The proposed trigger configuration for the proton-proton and Pb-Pb beams are detailed as well with estimates of the efficiencies and purity samples.
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27

Silenzi, Alessandro <1982&gt. « The topological trigger system of the TOF detector for the ALICE experiment at the LHC ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2842/.

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The ALICE experiment at the LHC has been designed to cope with the experimental conditions and observables of a Quark Gluon Plasma reaction. One of the main assets of the ALICE experiment with respect to the other LHC experiments is the particle identification. The large Time-Of-Flight (TOF) detector is the main particle identification detector of the ALICE experiment. The overall time resolution, better that 80 ps, allows the particle identification over a large momentum range (up to 2.5 GeV/c for pi/K and 4 GeV/c for K/p). The TOF makes use of the Multi-gap Resistive Plate Chamber (MRPC), a detector with high efficiency, fast response and intrinsic time resoltion better than 40 ps. The TOF detector embeds a highly-segmented trigger system that exploits the fast rise time and the relatively low noise of the MRPC strips, in order to identify several event topologies. This work aims to provide detailed description of the TOF trigger system. The results achieved in the 2009 cosmic-ray run at CERN are presented to show the performances and readiness of TOF trigger system. The proposed trigger configuration for the proton-proton and Pb-Pb beams are detailed as well with estimates of the efficiencies and purity samples.
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28

Valentinetti, Sara <1981&gt. « Luminosity measurements with the LUCID detector in the ATLAS experiment ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3486/1/valentinetti_sara_tesi.pdf.

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La misura della luminosità è un obiettivo importante per tutta la fisica del modello standard e per la scoperta di nuova fisica, poiché è legata alla sezione d'urto (σ) e al rate di produzione (R) di un determinato processo dalla relazione L = R*σ. Nell'eserimento ATLAS a LHC è installato un monitor di luminosità dedicato chiamato LUCID (Luminosity measurements Using Cherenkov Integrating Detector). Grazie ai dati acquisiti durante il 2010 la valutazione off-line delle performances del LUCID e l'implementazione di controlli on-line sulla qualità dei dati raccolti è stata possibile. I dati reali sono stati confrontati con i dati Monte Carlo e le simulazioni sono state opportunamente aggiustate per ottimizzare l'accordo tra i due. La calibrazione della luminosità relativa che permette di ottenere una valutazione della luminosità assoluta è stata possibile grazie ai cosiddetti Van der Meer scan, grazie ai quale è stata ottenuta una precisione dell'11%. L'analisi della fisica del decadimento della Z è in tuttora in corso per ottenere tramite il rate a cui avviene il processo una normalizzazione della luminosità con una precisione migliore del 5%.
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29

Valentinetti, Sara <1981&gt. « Luminosity measurements with the LUCID detector in the ATLAS experiment ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3486/.

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La misura della luminosità è un obiettivo importante per tutta la fisica del modello standard e per la scoperta di nuova fisica, poiché è legata alla sezione d'urto (σ) e al rate di produzione (R) di un determinato processo dalla relazione L = R*σ. Nell'eserimento ATLAS a LHC è installato un monitor di luminosità dedicato chiamato LUCID (Luminosity measurements Using Cherenkov Integrating Detector). Grazie ai dati acquisiti durante il 2010 la valutazione off-line delle performances del LUCID e l'implementazione di controlli on-line sulla qualità dei dati raccolti è stata possibile. I dati reali sono stati confrontati con i dati Monte Carlo e le simulazioni sono state opportunamente aggiustate per ottimizzare l'accordo tra i due. La calibrazione della luminosità relativa che permette di ottenere una valutazione della luminosità assoluta è stata possibile grazie ai cosiddetti Van der Meer scan, grazie ai quale è stata ottenuta una precisione dell'11%. L'analisi della fisica del decadimento della Z è in tuttora in corso per ottenere tramite il rate a cui avviene il processo una normalizzazione della luminosità con una precisione migliore del 5%.
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30

Morelli, Luca <1982&gt. « Competition between evaporation and fragmentation in nuclear reactions at 15-20 AMeV beam energy ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3537/1/Morelli_Luca_tesi.pdf.

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The reactions 32S+58,64Ni are studied at 14.5 AMeV. From this energy on, fragmentation begins to be a dominant process, although evaporation and fission are still present. After a selection of the collision mechanism, we show that important even-odd effects are present in the isotopic fragment distributions when the excitation energy is small. The staggering effect appears to be a universal feature of fragment production, slightly enhanced when the emission source is neutron poor. A closer look at the behavior of isotopic chains reveals that odd-even effects cannot be explained by pairing effects in the nuclear mass alone, but depend in a more complex way on the de-excitation chain.
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31

Morelli, Luca <1982&gt. « Competition between evaporation and fragmentation in nuclear reactions at 15-20 AMeV beam energy ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3537/.

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The reactions 32S+58,64Ni are studied at 14.5 AMeV. From this energy on, fragmentation begins to be a dominant process, although evaporation and fission are still present. After a selection of the collision mechanism, we show that important even-odd effects are present in the isotopic fragment distributions when the excitation energy is small. The staggering effect appears to be a universal feature of fragment production, slightly enhanced when the emission source is neutron poor. A closer look at the behavior of isotopic chains reveals that odd-even effects cannot be explained by pairing effects in the nuclear mass alone, but depend in a more complex way on the de-excitation chain.
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32

Mussini, Manuel <1978&gt. « Measurement of low pT D0 meson production cross section at CDF II ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3589/1/Mussini_Manuel_tesi.pdf.

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In this thesis we present a study of the D0 meson (through one of its two-body decay channel, D0 → Kπ) collected by the CDF II experiment at the Tevatron pp ̄ collider at Fermilab. In particular we measured the differential production cross section as a function of the transverse momentum down to pT = 1.5 GeV/c.
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33

Mussini, Manuel <1978&gt. « Measurement of low pT D0 meson production cross section at CDF II ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3589/.

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In this thesis we present a study of the D0 meson (through one of its two-body decay channel, D0 → Kπ) collected by the CDF II experiment at the Tevatron pp ̄ collider at Fermilab. In particular we measured the differential production cross section as a function of the transverse momentum down to pT = 1.5 GeV/c.
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34

Brunetti, Giulia <1981&gt. « Neutrino velocity measurement with the OPERA experiment in the CNGS beam ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3917/1/brunetti_giulia_tesi.pdf.

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In the thesis is presented the measurement of the neutrino velocity with the OPERA experiment in the CNGS beam, a muon neutrino beam produced at CERN. The OPERA detector observes muon neutrinos 730 km away from the source. Previous measurements of the neutrino velocity have been performed by other experiments. Since the OPERA experiment aims the direct observation of muon neutrinos oscillations into tau neutrinos, a higher energy beam is employed. This characteristic together with the higher number of interactions in the detector allows for a measurement with a much smaller statistical uncertainty. Moreover, a much more sophisticated timing system (composed by cesium clocks and GPS receivers operating in “common view mode”), and a Fast Waveform Digitizer (installed at CERN and able to measure the internal time structure of the proton pulses used for the CNGS beam), allows for a new measurement with a smaller systematic error. Theoretical models on Lorentz violating effects can be investigated by neutrino velocity measurements with terrestrial beams. The analysis has been carried out with blind method in order to guarantee the internal consistency and the goodness of each calibration measurement. The performed measurement is the most precise one done with a terrestrial neutrino beam, the statistical accuracy achieved by the OPERA measurement is about 10 ns and the systematic error is about 20 ns.
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35

Brunetti, Giulia <1981&gt. « Neutrino velocity measurement with the OPERA experiment in the CNGS beam ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3917/.

Texte intégral
Résumé :
In the thesis is presented the measurement of the neutrino velocity with the OPERA experiment in the CNGS beam, a muon neutrino beam produced at CERN. The OPERA detector observes muon neutrinos 730 km away from the source. Previous measurements of the neutrino velocity have been performed by other experiments. Since the OPERA experiment aims the direct observation of muon neutrinos oscillations into tau neutrinos, a higher energy beam is employed. This characteristic together with the higher number of interactions in the detector allows for a measurement with a much smaller statistical uncertainty. Moreover, a much more sophisticated timing system (composed by cesium clocks and GPS receivers operating in “common view mode”), and a Fast Waveform Digitizer (installed at CERN and able to measure the internal time structure of the proton pulses used for the CNGS beam), allows for a new measurement with a smaller systematic error. Theoretical models on Lorentz violating effects can be investigated by neutrino velocity measurements with terrestrial beams. The analysis has been carried out with blind method in order to guarantee the internal consistency and the goodness of each calibration measurement. The performed measurement is the most precise one done with a terrestrial neutrino beam, the statistical accuracy achieved by the OPERA measurement is about 10 ns and the systematic error is about 20 ns.
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36

Perazzini, Stefano <1984&gt. « Measurement of branching fractions and CP violation for charmless charged two-body B decays at LHCb ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4292/1/Stefano_Perazzini_tesi.pdf.

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Charmless charged two-body B decays are sensitive probes of the CKM matrix, that parameterize CP violation in the Standard Model (SM), and have the potential to reveal the presence of New Physics. The framework of CP violation within the SM, the role of the CKM matrix, with its basic formalism, and the current experimental status are presented. The theoretical tools commonly used to deal with hadronic B decays and an overview of the phenomenology of charmless two-body B decays are outlined. LHCb is one of the four main experiments operating at the Large Hadron Collider (LHC), devoted to the measurement of CP violation and rare decays of charm and beauty hadrons. The LHCb detector is described, focusing on the technologies adopted for each sub-detector and summarizing their performances. The status-of-the-art of the LHCb measurements with charmless two-body B decays is then presented. Using the 37/pb of integrated luminosity collected at sqrt(s) = 7 TeV by LHCb during 2010, the direct CP asymmetries ACP(B0 -> Kpi) = −0.074 +/- 0.033 +/- 0.008 and ACP(Bs -> piK) = 0.15 +/- 0.19 +/- 0.02 are measured. Using 320/pb of integrated luminosity collected during 2011 these measurements are updated to ACP(B0 -> Kpi) = −0.088 +/- 0.011 +/- 0.008 and ACP(Bs -> piK) = 0.27 +/- 0.08 +/- 0.02. In addition, the branching ratios BR(B0 -> K+K-) = (0.13+0.06-0.05 +/- 0.07) x 10^-6 and BR(Bs -> pi+pi-) = (0.98+0.23-0.19 +/- 0.11) x 10^-6 are measured. Finally, using a sample of 370/pb of integrated luminosity collected during 2011, the relative branching ratios BR(B0 -> pi+pi-)/BR(B0 -> Kpi) = 0.262 +/- 0.009 +/- 0.017, (fs/fd)BR(Bs -> K+K-)/BR(B0 -> Kpi)=0.316 +/- 0.009 +/- 0.019, (fs/fd)BR(Bs -> piK)/BR(B0 -> Kpi) = 0.074 +/- 0.006 +/- 0.006 and BR(Lambda_b -> ppi)/BR(Lambda_b -> pK)=0.86 +/- 0.08 +/- 0.05 are determined.
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37

Perazzini, Stefano <1984&gt. « Measurement of branching fractions and CP violation for charmless charged two-body B decays at LHCb ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4292/.

Texte intégral
Résumé :
Charmless charged two-body B decays are sensitive probes of the CKM matrix, that parameterize CP violation in the Standard Model (SM), and have the potential to reveal the presence of New Physics. The framework of CP violation within the SM, the role of the CKM matrix, with its basic formalism, and the current experimental status are presented. The theoretical tools commonly used to deal with hadronic B decays and an overview of the phenomenology of charmless two-body B decays are outlined. LHCb is one of the four main experiments operating at the Large Hadron Collider (LHC), devoted to the measurement of CP violation and rare decays of charm and beauty hadrons. The LHCb detector is described, focusing on the technologies adopted for each sub-detector and summarizing their performances. The status-of-the-art of the LHCb measurements with charmless two-body B decays is then presented. Using the 37/pb of integrated luminosity collected at sqrt(s) = 7 TeV by LHCb during 2010, the direct CP asymmetries ACP(B0 -> Kpi) = −0.074 +/- 0.033 +/- 0.008 and ACP(Bs -> piK) = 0.15 +/- 0.19 +/- 0.02 are measured. Using 320/pb of integrated luminosity collected during 2011 these measurements are updated to ACP(B0 -> Kpi) = −0.088 +/- 0.011 +/- 0.008 and ACP(Bs -> piK) = 0.27 +/- 0.08 +/- 0.02. In addition, the branching ratios BR(B0 -> K+K-) = (0.13+0.06-0.05 +/- 0.07) x 10^-6 and BR(Bs -> pi+pi-) = (0.98+0.23-0.19 +/- 0.11) x 10^-6 are measured. Finally, using a sample of 370/pb of integrated luminosity collected during 2011, the relative branching ratios BR(B0 -> pi+pi-)/BR(B0 -> Kpi) = 0.262 +/- 0.009 +/- 0.017, (fs/fd)BR(Bs -> K+K-)/BR(B0 -> Kpi)=0.316 +/- 0.009 +/- 0.019, (fs/fd)BR(Bs -> piK)/BR(B0 -> Kpi) = 0.074 +/- 0.006 +/- 0.006 and BR(Lambda_b -> ppi)/BR(Lambda_b -> pK)=0.86 +/- 0.08 +/- 0.05 are determined.
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38

Guerzoni, Barbara <1982&gt. « Identified primary hadron spectra with the TOF detector of the ALICE experiment at LHC ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4293/1/Guerzoni_Barbara_tesi.pdf.

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In this thesis the analysis to reconstruct the transverse momentum p_{t} spectra for pions, kaons and protons identified with the TOF detector of the ALICE experiment in pp Minimum Bias collisions at $\sqrt{s}=7$ TeV was reported. After a detailed description of all the parameters which influence the TOF PID performance (time resolution, calibration, alignment, matching efficiency, time-zero of the event) the method used to identify the particles, the unfolding procedure, was discussed. With this method, thanks also to the excellent TOF performance, the pion and kaon spectra can be reconstructed in the 0.5
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39

Guerzoni, Barbara <1982&gt. « Identified primary hadron spectra with the TOF detector of the ALICE experiment at LHC ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4293/.

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In this thesis the analysis to reconstruct the transverse momentum p_{t} spectra for pions, kaons and protons identified with the TOF detector of the ALICE experiment in pp Minimum Bias collisions at $\sqrt{s}=7$ TeV was reported. After a detailed description of all the parameters which influence the TOF PID performance (time resolution, calibration, alignment, matching efficiency, time-zero of the event) the method used to identify the particles, the unfolding procedure, was discussed. With this method, thanks also to the excellent TOF performance, the pion and kaon spectra can be reconstructed in the 0.5
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40

Baiocco, Giorgio <1984&gt. « Towards a Reconstruction of Thermal Properties of Light Nuclei from Fusion - Evaporation reactions ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4295/1/baiocco_giorgio_tesi.pdf.

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This thesis work has been developed in the framework of a new experimental campaign, proposed by the NUCL-EX Collaboration (INFN III Group), in order to progress in the understanding of the statistical properties of light nuclei, at excitation energies above particle emission threshold, by measuring exclusive data from fusion-evaporation reactions. The determination of the nuclear level density in the A~20 region, the understanding of the statistical behavior of light nuclei with excitation energies ~3 A.MeV, and the measurement of observables linked to the presence of cluster structures of nuclear excited levels are the main physics goals of this work. On the theory side, the contribution to this project given by this work lies in the development of a dedicated Monte-Carlo Hauser-Feshbach code for the evaporation of the compound nucleus. The experimental part of this thesis has consisted in the participation to the measurement 12C+12C at 95 MeV beam energy, at Laboratori Nazionali di Legnaro - INFN, using the GARFIELD+Ring Counter(RCo) set-up, from the beam-time request to the data taking, data reduction, detector calibrations and data analysis. Different results of the data analysis are presented in this thesis, together with a theoretical study of the system, performed with the new statistical decay code. As a result of this work, constraints on the nuclear level density at high excitation energy for light systems ranging from C up to Mg are given. Moreover, pre-equilibrium effects, tentatively interpreted as alpha-clustering effects, are put in evidence, both in the entrance channel of the reaction and in the dissipative dynamics on the path towards thermalisation.
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41

Baiocco, Giorgio <1984&gt. « Towards a Reconstruction of Thermal Properties of Light Nuclei from Fusion - Evaporation reactions ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4295/.

Texte intégral
Résumé :
This thesis work has been developed in the framework of a new experimental campaign, proposed by the NUCL-EX Collaboration (INFN III Group), in order to progress in the understanding of the statistical properties of light nuclei, at excitation energies above particle emission threshold, by measuring exclusive data from fusion-evaporation reactions. The determination of the nuclear level density in the A~20 region, the understanding of the statistical behavior of light nuclei with excitation energies ~3 A.MeV, and the measurement of observables linked to the presence of cluster structures of nuclear excited levels are the main physics goals of this work. On the theory side, the contribution to this project given by this work lies in the development of a dedicated Monte-Carlo Hauser-Feshbach code for the evaporation of the compound nucleus. The experimental part of this thesis has consisted in the participation to the measurement 12C+12C at 95 MeV beam energy, at Laboratori Nazionali di Legnaro - INFN, using the GARFIELD+Ring Counter(RCo) set-up, from the beam-time request to the data taking, data reduction, detector calibrations and data analysis. Different results of the data analysis are presented in this thesis, together with a theoretical study of the system, performed with the new statistical decay code. As a result of this work, constraints on the nuclear level density at high excitation energy for light systems ranging from C up to Mg are given. Moreover, pre-equilibrium effects, tentatively interpreted as alpha-clustering effects, are put in evidence, both in the entrance channel of the reaction and in the dissipative dynamics on the path towards thermalisation.
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42

Fasanella, Daniele <1981&gt. « Study of the X(3872) state with the CMS experiment at LHC ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4300/1/thesis.pdf.

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The surprising discovery of the X(3872) resonance by the Belle experiment in 2003, and subsequent confirmation by BaBar, CDF and D0, opened up a new chapter of QCD studies and puzzles. Since then, detailed experimental and theoretical studies have been performed in attempt to determine and explain the proprieties of this state. Since the end of 2009 the world’s largest and highest-energy particle accelerator, the Large Hadron Collider (LHC), started its operations at the CERN laboratories in Geneva. One of the main experiments at LHC is CMS (Compact Muon Solenoid), a general purpose detector projected to address a wide range of physical phenomena, in particular the search of the Higgs boson, the only still unconfirmed element of the Standard Model (SM) of particle interactions and, new physics beyond the SM itself. Even if CMS has been designed to study high energy events, it’s high resolution central tracker and superior muon spectrometer made it an optimal tool to study the X(3872) state. In this thesis are presented the results of a series of study on the X(3872) state performed with the CMS experiment. Already with the first year worth of data, a clear peak for the X(3872) has been identified, and the measurement of the cross section ratio with respect to the Psi(2S) has been performed. With the increased statistic collected during 2011 it has been possible to study, in bins of transverse momentum, the cross section ratio between X(3872) and Psi(2S) and separate their prompt and non-prompt component.
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43

Fasanella, Daniele <1981&gt. « Study of the X(3872) state with the CMS experiment at LHC ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4300/.

Texte intégral
Résumé :
The surprising discovery of the X(3872) resonance by the Belle experiment in 2003, and subsequent confirmation by BaBar, CDF and D0, opened up a new chapter of QCD studies and puzzles. Since then, detailed experimental and theoretical studies have been performed in attempt to determine and explain the proprieties of this state. Since the end of 2009 the world’s largest and highest-energy particle accelerator, the Large Hadron Collider (LHC), started its operations at the CERN laboratories in Geneva. One of the main experiments at LHC is CMS (Compact Muon Solenoid), a general purpose detector projected to address a wide range of physical phenomena, in particular the search of the Higgs boson, the only still unconfirmed element of the Standard Model (SM) of particle interactions and, new physics beyond the SM itself. Even if CMS has been designed to study high energy events, it’s high resolution central tracker and superior muon spectrometer made it an optimal tool to study the X(3872) state. In this thesis are presented the results of a series of study on the X(3872) state performed with the CMS experiment. Already with the first year worth of data, a clear peak for the X(3872) has been identified, and the measurement of the cross section ratio with respect to the Psi(2S) has been performed. With the increased statistic collected during 2011 it has been possible to study, in bins of transverse momentum, the cross section ratio between X(3872) and Psi(2S) and separate their prompt and non-prompt component.
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44

Masi, Nicolò <1985&gt. « The AMS-02 Experiment and the Dark Matter Search ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5179/1/Masi_Nicolo_tesi.pdf.

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AMS-02 is running after great scientific goals since one year and a half: a final setting up for dark matter searches has been achieved, allowing to study the so important antiparticle to particle ratios, which will probably be the first dark matter signals ever corroborated. Even if primary cosmic rays fluxes are subjected to a lot of uncertainties sources, some statements can be done and have been written down about dark matter properties: DM should be a heavy Majorana fermion or Spin 0 or 1 boson, with a mass from about 1 TeV to 10 TeV - unveiling a new TeV-ish search age - which could be able to originate antiparticle fluxes enhancements at high energies, both for positrons and antiprotons. All the observations, direct and indirect, point to these new paradigms or can be traced back to them quite easily. These enhancements perfectly fall into the research window of AMS-02, allowing the experiment to attack each today credible theory. Also an investigation of the Sommerfeld effect-associated dark boson will be possible, in terms of antiparticle to particle ratios substructures. The first great AMS-02 measurement is the positron fraction: an official paper is going to be submitted in few months, where the correct behavior of the apparatus will be reviewed and the full positron fraction rate will be analyzed up to 200 GeV. In this concern, one of the objectives of this work is to test the AMS-02 capability and versatility in doing these dark matter researches, thanks to an orbital temporal (and geomagnetic) stability. The goal has been accomplished: the experiment is very stable in time, so that the temporal error associated to the positron fraction measurement is compatible with zero, offering a beyond belief opportunity to measure CR antiparticle to particle ratios.
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45

Masi, Nicolò <1985&gt. « The AMS-02 Experiment and the Dark Matter Search ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5179/.

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Résumé :
AMS-02 is running after great scientific goals since one year and a half: a final setting up for dark matter searches has been achieved, allowing to study the so important antiparticle to particle ratios, which will probably be the first dark matter signals ever corroborated. Even if primary cosmic rays fluxes are subjected to a lot of uncertainties sources, some statements can be done and have been written down about dark matter properties: DM should be a heavy Majorana fermion or Spin 0 or 1 boson, with a mass from about 1 TeV to 10 TeV - unveiling a new TeV-ish search age - which could be able to originate antiparticle fluxes enhancements at high energies, both for positrons and antiprotons. All the observations, direct and indirect, point to these new paradigms or can be traced back to them quite easily. These enhancements perfectly fall into the research window of AMS-02, allowing the experiment to attack each today credible theory. Also an investigation of the Sommerfeld effect-associated dark boson will be possible, in terms of antiparticle to particle ratios substructures. The first great AMS-02 measurement is the positron fraction: an official paper is going to be submitted in few months, where the correct behavior of the apparatus will be reviewed and the full positron fraction rate will be analyzed up to 200 GeV. In this concern, one of the objectives of this work is to test the AMS-02 capability and versatility in doing these dark matter researches, thanks to an orbital temporal (and geomagnetic) stability. The goal has been accomplished: the experiment is very stable in time, so that the temporal error associated to the positron fraction measurement is compatible with zero, offering a beyond belief opportunity to measure CR antiparticle to particle ratios.
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46

Monzani, Simone <1981&gt. « Study of the forward photons productions in pp collisions at sqrt{s} = 7 TeV with the ZDC detector of the ATLAS experiment ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5186/1/Monzani_Simone_tesi.pdf.

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The Zero Degree Calorimeter (ZDC) of the ATLAS experiment at CERN is placed in the TAN of the LHC collider, covering the pseudorapidity region higher than 8.3. It is composed by 2 calorimeters, each one longitudinally segmented in 4 modules, located at 140 m from the IP exactly on the beam axis. The ZDC can detect neutral particles during pp collisions and it is a tool for diffractive physics. Here we present results on the forward photon energy distribution obtained using p-p collision data at sqrt{s} = 7 TeV. First the pi0 reconstruction will be used for the detector calibration with photons, then we will show results on the forward photon energy distribution in p-p collisions and the same distribution, but obtained using MC generators. Finally a comparison between data and MC will be shown.
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47

Monzani, Simone <1981&gt. « Study of the forward photons productions in pp collisions at sqrt{s} = 7 TeV with the ZDC detector of the ATLAS experiment ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5186/.

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Résumé :
The Zero Degree Calorimeter (ZDC) of the ATLAS experiment at CERN is placed in the TAN of the LHC collider, covering the pseudorapidity region higher than 8.3. It is composed by 2 calorimeters, each one longitudinally segmented in 4 modules, located at 140 m from the IP exactly on the beam axis. The ZDC can detect neutral particles during pp collisions and it is a tool for diffractive physics. Here we present results on the forward photon energy distribution obtained using p-p collision data at sqrt{s} = 7 TeV. First the pi0 reconstruction will be used for the detector calibration with photons, then we will show results on the forward photon energy distribution in p-p collisions and the same distribution, but obtained using MC generators. Finally a comparison between data and MC will be shown.
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48

Mengarelli, Alberto <1981&gt. « Measurement of the ZZ production cross section and limits on anomalous neutral triple gauge couplings with ATLAS ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5196/1/Mengarelli_Alberto.pdf.

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The main work of this thesis concerns the measurement of the production cross section using LHC 2011 data collected at a center-of-mass energy equal to 7 TeV by the ATLAS detector and resulting in a total integrated luminosity of 4.6 inverse fb. The ZZ total cross section is finally compared with the NLO prediction calculated with modern Monte Carlo generators. In addition, the three differential distributions (∆φ(l,l), ZpT and M4l) are shown unfolded back to the underlying distributions using a Bayesian iterative algorithm. Finally, the transverse momentum of the leading Z is used to provide limits on anoumalus triple gauge couplings forbidden in the Standard Model.
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49

Mengarelli, Alberto <1981&gt. « Measurement of the ZZ production cross section and limits on anomalous neutral triple gauge couplings with ATLAS ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5196/.

Texte intégral
Résumé :
The main work of this thesis concerns the measurement of the production cross section using LHC 2011 data collected at a center-of-mass energy equal to 7 TeV by the ATLAS detector and resulting in a total integrated luminosity of 4.6 inverse fb. The ZZ total cross section is finally compared with the NLO prediction calculated with modern Monte Carlo generators. In addition, the three differential distributions (∆φ(l,l), ZpT and M4l) are shown unfolded back to the underlying distributions using a Bayesian iterative algorithm. Finally, the transverse momentum of the leading Z is used to provide limits on anoumalus triple gauge couplings forbidden in the Standard Model.
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50

Romano, Marino <1985&gt. « Measurement of the differential cross section of tt pairs in pp collision at sqrt(s) = 7TeV with the ATLAS detector at the LHC ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5197/1/TESI.pdf.

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In this thesis three measurements of top-antitop differential cross section at an energy in the center of mass of 7 TeV will be shown, as a function of the transverse momentum, the mass and the rapidity of the top-antitop system. The analysis has been carried over a data sample of about 5/fb recorded with the ATLAS detector. The events have been selected with a cut based approach in the "one lepton plus jets" channel, where the lepton can be either an electron or a muon. The most relevant backgrounds (multi-jet QCD and W+jets) have been extracted using data driven methods; the others (Z+ jets, diboson and single top) have been simulated with Monte Carlo techniques. The final, background-subtracted, distributions have been corrected, using unfolding methods, for the detector and selection effects. At the end, the results have been compared with the theoretical predictions. The measurements are dominated by the systematic uncertainties and show no relevant deviation from the Standard Model predictions.
In questo lavoro verranno presentate tre misure di sezione d'urto differenziale di eventi top-antitop ad un'energia nel centro di massa pari a 7 TeV in funzione dell'impulso trasverso, della massa invariante e della rapidità del sistema. L'analisi è stata effettuata su un campione di dati pari a circa 5/fb raccolti dal rivelatore ATLAS durante il run del 2011 dell'LHC. Gli eventi sono stati selezionati con un approccio basato sui tagli nel canale "leptone più jet", dove il leptone può essere un elettrone o un muone. I principali fondi (QCD multi-jet e W+ jet) sono stati estratti con metodi "data driven", mentre i rimanenti (Z+ jet, WW/ZZ/WZ e top singolo) sono stati simulati con tecniche Monte Carlo. Le distribuzioni finali, dopo la sottrazione del background, sono state corrette, attraverso procedure di unfolding, dagli effetti del rivelatore e della selezione. In questo modo è possibile confrontare i risultati ottenuti con quelli di altri esperimenti. Le misure risultano dominate dalle incertezze sistematiche e non mostrano alcuna deviazione significativa dalle predizioni del Modello Standard.
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