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Measurement of Production and Decay Properties of Bs Mesons Decaying Into J/Psi Phi with the CMS Detector at the LHC

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Measurement of Production and Decay Properties of Bs Mesons Decaying Into J/Psi Phi with the CMS Detector at the LHC University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 5-2012 Measurement of Production and Decay Properties of Bs Mesons Decaying into J/Psi Phi with the CMS Detector at the LHC Giordano Cerizza University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Elementary Particles and Fields and String Theory Commons Recommended Citation Cerizza, Giordano, "Measurement of Production and Decay Properties of Bs Mesons Decaying into J/Psi Phi with the CMS Detector at the LHC. " PhD diss., University of Tennessee, 2012. https://trace.tennessee.edu/utk_graddiss/1279 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Giordano Cerizza entitled "Measurement of Production and Decay Properties of Bs Mesons Decaying into J/Psi Phi with the CMS Detector at the LHC." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Physics. Stefan M. Spanier, Major Professor We have read this dissertation and recommend its acceptance: Marianne Breinig, George Siopsis, Robert Hinde Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Measurements of Production and Decay Properties of Bs Mesons Decaying into J/Psi Phi with the CMS Detector at the LHC A Thesis Presented for The Doctor of Philosophy Degree The University of Tennessee, Knoxville Giordano Cerizza May 2012 c by Giordano Cerizza, 2012 All Rights Reserved. ii A mia moglie Joey iii Acknowledgements I would like to thank many people, without whom this work would not have been possible. First, I would like to express my gratitude to Stefan Spanier for giving me the opportunity to do this Ph.D. study and for sharing his great knowledge and experience in particle physics. Throughout the past five years, his expert guidance, motivation, patience, and continuous support have been truly invaluable. The CMS Pixel Online group helped me to understand the nuances of experimental detector design and operations. I would like to especially thank: Anders Ryd (Cornell); Danek Kotlinsky (PSI); Gino Bolla (Purdue); Karl Ecklund (Rice); Will Johns from (Vanderbilt); and all the graduate students and friends associated with CMS with whom I spent most of my time while stranded at CERN: Souvik Das, Ben Kreis, Vincenzo Lombardo, Simone Stracka, Marco Pappagallo, Antonio Petrella, Giacomo Fedi, and the UT colleagues Andrew York, Matt Hollingsworth, and Zongchang Yang. The CMS B-Physics analysis working group helped me publishing the results presented in this dissertation with their careful scrutiny of the analysis. I want to thank: Paula Eerola (Helsinki); Vincenzo Chiochia (Zurich); Carlos Louren¸co (CERN); Jim Olsen (Princeton); Gigi Rolandi (Pisa); Kevin Stenson (Colorado at Boulder); Nuno Leonardo (CERN); Hermine K. W¨ohri(CERN); Alexander Schmidt (Hamburg); and all the other people who sent comments and suggestions during the approval stage of the analysis. iv A special thank you to Laurent Gross from University of Strasbourg for all the time I spent in his office discussing and for his friendship outside the CERN. I really appreciate all the things you helped me with. Alfio Lazzaro, a great friend and colleague from CERN/openlab, who helped me greatly with discussions on the Maximum Likelihood fitting procedures; David Lopes Pegna from Princeton for giving me input on the analysis techniques and for an unforgettable overnight session of work during the conference organized by the University of Michigan; Keith Ulmer from University of Colorado at Boulder for the discussions and cross checks during the period of the analysis approval. To Geri Ragghianti for his friendship and always prompt computing support with the Newton cluster. Your contribution to the final results was fundamental. I would like to thank my fellow graduate student friends at UT for all the time we spent solving homework and having fun during the first two years: Merek Chertkow, Andrew York, Jason Lambert, Andrew Nicholson, Zach Barnett, Chris Smith, and Dwayne John. And, finally, the two Italians at UT: Norman Mannella and Paolo Vilmercati. Great times with great friends. My mother and father, who always stood behind me during this overseas adventure, and my brother, who came to visit me in 2008 during a very hard year for me, deserve thanks as well. Above all, my greatest thanks to my wife Joey, who, for three long years, had to put up with incalculable schedules and indefinite plans. You encouraged me to accomplish this goal. Thank you. v \I don't know anything, but I do know that everything is interesting if you go into it deeply enough." Richard Feynman vi Abstract The production of hadrons containing b-quarks has been measured in proton anti-proton collisions up to center-of-mass energies of 1:96 TeV at the Tevatron. Information at lower energy is provided by electron-positron collision experiments. The underlying theory of hadronic interactions is tuned to those data but cannot reliably predict reaction rates from first principles for higher energies. Therefore, it is important to test the extrapolations and optimize model parameters for the new energy regime at the LHC. The b-hadrons from proton-proton collisions are a major source of background in searches for the Higgs boson and other heavy not- yet-discovered particles. Hence, it is important to quantify their presence in different reactions for the main research program at the LHC. The measurement of the Bs-meson production cross section presented in this dissertation complements the measurements for the B+ and the Bd mesons. The outcome is compared to different models for quark production and hadronization. The three CMS measurement of B-meson production cross sections are used to calculate the Bs to J/psi phi branching fraction. The measurement of the time-dependent decay rate of Bs mesons probes the weak interaction and includes the possibility to observe sizable particle anti-particle asymmetries caused by heavy particles and new forces between them that are not predicted by the Standard Model. In this dissertation the lifetime, lifetime difference, and CP-composition in the decay Bs to J/psi phi have been extracted with a vii Maximum Likelihood fit. The J/psi meson decays into two muons, while the phi meson into two charged kaons. The results are presented for the data recorded during the year 2010 with the Compact Muon Solenoid. It is a general-purpose particle detector centered at one of the interaction points of the Large Hadron Collider, a proton-proton collider located at the particle physics laboratory CERN in Geneva (Switzerland). It is designed to explore a wide range of physics in proton-proton collisions. The investigations presented here assess and benchmark the performance of a variety of detector components including track and muon reconstruction. For reconstruction of long- lived particles, such as the b-hadrons, the silicon pixel detector provides the most significant information. viii Contents Motivations1 1 Introduction on B Physics4 0 1.1 Production and Decay of Bs Mesons..................4 1.2 The Standard Model of Particle Physics................6 1.3 Production Mechanism of B Mesons at the LHC............ 17 1.3.1 Production of bb¯ Quark Pairs.................. 17 1.3.2 Hadronization........................... 22 1.3.3 Monte Carlo Generator Implementation............ 25 1.4 B Decays................................. 29 0 1.4.1 The Bs ! J= φ Decay..................... 29 0 ¯ 0 1.4.2 Bs -Bs Mixing........................... 30 0 1.4.3 CP Violation in the Bs System................. 35 1.4.4 Angular Analysis......................... 37 2 Experimental Setup 45 2.1 The Large Hadron Collider........................ 45 2.1.1 Acceleration............................ 48 2.1.2 Beam Steering and Focus.................... 50 2.1.3 Luminosity............................ 51 2.2 The Compact Muon Solenoid...................... 55 2.2.1 Momentum Measurement of Charged Particles......... 59 ix 2.2.2 The Silicon Tracker........................ 67 2.2.3 The Electromagnetic Calorimeter................ 72 2.2.4 The Hadronic Calorimeter.................... 73 2.2.5 The Muon System........................ 76 2.3 The CMS Trigger............................. 82 2.3.1 Level-1 Trigger.......................... 82 2.3.2 High-Level Trigger........................ 84 2.4 CMS Analysis Software.......................... 85 2.4.1 Event Reconstruction....................... 86 3 The CMS Pixel Detector 89 3.1 Introduction................................ 89 3.2 Pixel Sensors............................... 90 3.3 Pixel Readout System.......................... 99 3.3.1 Detector Commissioning..................... 103 3.4 Online Data Acquisition Software (DAQ) Architecture........ 105 3.4.1 Run Control and Monitor System................ 106 3.4.2 Detector Control System..................... 106 3.4.3 Data Acquisition Components.................. 107
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