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Samir Guragain

Ph. D. Thesis Defense. Muon endcap alignment for the CMS experiment and its effect on the search for Z′ bosons in the dimuon channel at LHC. Dissertation Committee Dr. Marcus Hohlmann (Advisor) Dr. Debasis Mitra (Outside member) Dr. László A. Baksay Dr. Terry D. Oswalt Dr. Ming Zhang.

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Samir Guragain

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  1. Ph. D. Thesis Defense Muon endcap alignment for the CMS experiment and its effect on the search for Z′ bosons in the dimuon channel at LHC • Dissertation Committee • Dr. Marcus Hohlmann (Advisor) • Dr. Debasis Mitra (Outside member) • Dr. László A. Baksay • Dr. Terry D. Oswalt • Dr. Ming Zhang Samir Guragain Department of Physics and Space Sciences, Florida Institute of Technology September 8, 2010

  2. Major achievements (I) • Published paper on muon alignment in 2008 CRAFT exercise in J. of Inst. • I am a principal co-author of muon endcap alignment • Presented at Muon alignment meetings during CMS weeks and / or regular, South Eastern Section meeting of American Physical Society (SESAPS) in 2006 and 2007 • 2nd journal publication with major Fl. Tech contributions on behalf of CMS collaboration (1st was CMS detector paper) CRAFT = Cosmic Run At Four Tesla 18 pp. w/o author list Ph. D. Thesis Defense, S. Guragain

  3. Major achievements (II) • Published an analysis note on Z′ search in the dimuon channel with CMS expt. • I am a principal author • Full responsibility of work from the beginning to the final approval and endorsement of the analysis • 1st CMS physics analysis note publication from our research group at Florida Tech • Presented at various CMS meetings (Exotica, EXO-resonances, TeV muon, muon POG, and muon alignment) and US CMS meeting 2010 Ph. D. Thesis Defense, S. Guragain 25 pages

  4. Outline • Motivations • Compact Muon Solenoid (CMS) experiment at LHC and the Muon alignment system • Muon endcap hardware alignment system • Commissioning of the ME system at CERN • Muon endcap alignment constants • Physics analysis: Z′ → + - search • Monte Carlo (MC) simulation • Effect of muon misalignments • CMS collision data analysis Ph. D. Thesis Defense, S. Guragain

  5. Standard model & Elementary particles The Standard Model (SM) current knowledge in particle physics. theory of strong interactions and unified theory of weak and electromagnetic interactions These theories are called gauge theories, meaning that they model the forces between fermions by coupling them to bosons, called gauge bosons. These gauge bosons are force carriers. Fermions (spin ½, 3/2, 5/2, ..): Leptons & Quarks (Spin ½) and Bosons (spin 0,1, 2..): Known Force carriers (Spin 1) Lack of gravitational interactions in the SM Ph. D. Thesis Defense, S. Guragain

  6. Motivations Physics • Many models predict new heavy force carrier particles • An extended gauge model predicts a neutral and heavy gauge boson, Z' • The cleanest signal is decay to opposite-signed muons • Current mass limit is > 1030 GeV/c2 (CDF) • LHC is the first opportunity to search for Z' in a high-mass (TeV/c2) range • Z' → µ+ µ- is one of the most promising channel for its discovery (clear signature, low background) • CMS discovery potential Detector Implications • Good benchmark channel for muon detector • Importance of reconstruction of very-high-pT muons • Detector misalignment Ph. D. Thesis Defense, S. Guragain

  7. Proposed new particle Z' Model: ZSSM within the sequential standard model (SSM), which has the same coupling as the standard model Z. pp → Z' → µ+ µ- Table from H. Lee’s PhD defense talk on May 20, 2005 Muon Tracks in the simulated event of a dimuon decay: pp → Z' → µ+ µ- Z′ is a new (proposed) force carrier with spin 1. Ph. D. Thesis Defense, S. Guragain

  8. Current lower Z′ mass limits for various models Collider Detector at Fermilab (CDF) result in 2009 Z′ Mass limit (TeV) 0.789 0.821 0.861 0.878 0.892 0.904 1.030 Z′SSM lower mass limit Channel Collaboration 1.030 TeV in 2009 Dimuon CDF (Tevatron at Fermilab) 1.023 TeV in 2010 Dielectron D0 (Tevatron at Fermilab) From CDF collaboration, “Search for High-Mass Resonances Decaying to Dimuons at CDF” Phys. Rev. Lett. 102 (2009) 091805 Ph. D. Thesis Defense, S. Guragain

  9. LHC at CERN A Toroidal LHC ApparatuS / LHC forward LHC detectors and accelerator are the most complex scientific instruments ever built. Genève, Switzerland LHCb (beauty) Cessy, France ALICE (A large Ion Collider Experiment) TOTal Elastic and diffractive cross-section Measurement Ph. D. Thesis Defense, S. Guragain

  10. Compact Muon Solenoid (CMS) • Tracker • Calorimeters • Magnet • Muon ME+4 ME - Ph. D. Thesis Defense, S. Guragain

  11. Particle detection in CMS & muon reconstructions Global Muon Track Standalone Muon Track Muon in Silicon Tracker Muon Hits and Track Segments Ph. D. Thesis Defense, S. Guragain

  12. Installation & commissioning of CMS ME system at CERN Cross-hair laser adjustment to pass through four CCDs in Digital CCD based Optical Positioning Sensors (DCOPS) Fully instrumented ME+1 in 2006! Ph. D. Thesis Defense, S. Guragain

  13. Full reconstruction model Z-sensors Clinometers Transfer Plate (TP) Lasers Note: only small sample of analog sensors shown R-sensors DCOPS’s The system monitors the positions of CSCs relative to each other and to the central disk. Lasers Straight Line Monitors (SLMs) and Transfer lines • TOTAL: 768 sensors and 60 lasers Ph. D. Thesis Defense, S. Guragain

  14. A part of CMS Ref. DCOPS 2 Crosshair Lasers (adjustable) Z-sensors Z-tube Back Chamber Chamber DCOPS’s Laser beam Clinometer Transfer Plate 1 Mounting Tower Transfer Line DCOPS R-sensor Laser on ! ZCMS RphiCMS ME+2 SLM Ph. D. Thesis Defense, S. Guragain

  15. Relative displacements at fields using Z-sensor measurements Ph. D. Thesis Defense, S. Guragain

  16. Basic strategy for reconstruction of chamber positions at B=3.8T • Fit DCOPS data at B=0T and reconstruct DCOPS and chamber positions using COCOA(CMS Object-oriented Code for Optical Alignment) • Check B=0T reco results for one SLM against photogrammetry (PG) in full detail and with great care until we can trust the reconstruction • Reconstruct chamber positions using DCOPS data and Z-sensor relative shifts at B=3.8T • Apply lessons learned to reco of other SLMs Ph. D. Thesis Defense, S. Guragain

  17. ME+3 SLM1-4 at 0T using DCOPS & PG measurements Fit residual ~ 50 µm Reconstructed chamber center position Ph. D. Thesis Defense, S. Guragain

  18. Comparison with PG 345 µm Ph. D. Thesis Defense, S. Guragain

  19. ME+3 SLM1-4 at 3.8T using DCOPS & Z sensor measurements TP’s position from PG and relative shift from Z-sensor Disk bending is reconstructed ! Fit residual ~ 50 µm Ph. D. Thesis Defense, S. Guragain

  20. ME+2,3 CSC displacements using relative shift of TP from 0 to 3.8T Ph. D. Thesis Defense, S. Guragain

  21. ME-2,3 CSC displacements using relative shift of TP from 0 to 3.8T Ph. D. Thesis Defense, S. Guragain

  22. Bending of YE2 disk due to magnetic field at 3.8T 10 - 14 mm YE2 bending towards the interaction point (IP) of CMS Ph. D. Thesis Defense, S. Guragain

  23. ME Alignment constants 1/6 of 468 CSCs are monitored and corrected individually. For the remaining unmonitored CSCs, average corrections are applied. Ph. D. Thesis Defense, S. Guragain

  24. Physics: Z′→ +- search • Unique contributions: • Studied impact of muon misalignment systematics on • High-pT Muon pT resolution • Z′ signal significance • Provided first 7 TeV Monte Carlo samples (signal & DY background) for analysis using local CMS Tier-3 cluster • Analyzed these MC samples and updated the CMS discovery potential for Z′SSM at 7 TeV center-of-mass energy pp collision • Analysis note: CMS AN-2010/064 • 14 contributed presentations at Exotica Muon meetings (since 4/1/09) • Taken on responsibility for MC samples in Z′→ +- group: https://twiki.cern.ch/twiki/bin/viewauth/CMS/ExoticaZprimeMumu Ph. D. Thesis Defense, S. Guragain

  25. Alignment scenarios and corresponding global tags • IDEAL (MC_31X_V5) : Ideal geometry of the detector • STARTUP (STARTUP31X_V4): Based on CRAFT 2008 and 2009 data analysis for early phase and produced by randomly misaligning chambers with an RMS consistent with cross-checks Uncertainty in chamber positions: 0.05 cm – 0.60 cm in (x,y,z) & 0.3 mrad – 2.3 mrad in (φx,φy,φz) • 50 pb-1 (50PBMU31X_V1) : Assuming an alignment with tracks using 50 pb-1 data and produced by running the Reference-Target algorithm on MC samples Uncertainty in chambers: 0.05 cm – 0.18 cm (x,y,z) & 0.3 mrad – 0.6 mrad (φx,φy,φz) Tracker misalignment scenarios in startup and 50 pb-1 are the same and based on CRAFT 2008 (tag TrackerCRAFTScenario310_mc) Ph. D. Thesis Defense, S. Guragain

  26. MC samples and event selection MC samples (50K events) • Z′ signal samples with full Z′/Z/γ interference for MZ′SSM=1.0 TeV/c2, 1.2 TeV/c2, 1.3 TeV/c2, and 2.0 TeV/c2 • Drell-Yan samples, one in the mass region (>500 GeV/c2) around the Z′ mass and another at lower mass(>200 GeV/c2) Analysis Code “Zprime2muAnalysis”package in CMSSW Event selection: • At least a pair of oppositely charged muons • pT of each muon track in a pair > 20 GeV/c • Isolated muons: Σ track pT (ΔR < 0.3) < 10 GeV/c Ph. D. Thesis Defense, S. Guragain

  27. Resolution study for 3 alignment scenarios using 1.2 TeV Z′ MC sample at √s = 7TeV Muon Momentum resolution (endcap) for 3 misalignment scenarios with MZ′ = 1.2 TeV at 7 TeV CM energy Z'SSM → µ+ µ- analysis Ph. D. Thesis Defense, S. Guragain

  28. Summary: resolutions for 3 alignmentsand different Z′ mass with √s=7TeV & 10TeV GR = Global Reconstruction TK = Tracker only FS = Tracker plus First Muon Station 50 pb-1 alignment scenario is validated. Ph. D. Thesis Defense, S. Guragain

  29. Systematics study:Muon endcap alignment Method: • Muon Endcap was misaligned systematically with respect to ideal or startup muon geometry. • A signal sample (MZ′=1.2TeV/c2 or 2.0TeV/c2) was fully reconstructed. • The sample was reconstructed with a customized global tag by inputting a modified SQLite file, with a bias for the position(XCMS, YCMS, ZCMS) up to 2 mm or a bias on rotation (φZCMS) up to 0.5 mrad of muon endcap stations together or individual ME stations. [For comparison: Current startup ME disk misalignments are 0.5 - 1.0 mm in (∆x, ∆y, ∆z) & 0.1 mrad in ∆φZCMS] 3. The analysis code was re-run over the resulting biased MC data set for each misalignment. Ph. D. Thesis Defense, S. Guragain

  30. pT resolution vs. ηIdeal alignement & with 2mm Bias Ideal alignment 2 TeV Z′ Sample 2 TeV Z′ Sample No systematic bias applied to the Barrel and Tracker-only Ideal alignment + 2mm shift of muon endcaps Ph. D. Thesis Defense, S. Guragain

  31. Comparison: pT resolution Ideal alignment + 2mm shift of muon endcap • Up to 200 GeV/c, no significant change due to bias but changes at higher pT • Muon alignment becomes prominent at higher pT in all scenarios • Demonstrates tracker-only does not change, as expected with or without bias on endcap stations LHC startup alignment (now) Ph. D. Thesis Defense, S. Guragain

  32. Alignment Systematics Study: Bias on ideal Endcap positions Ph. D. Thesis Defense, S. Guragain

  33. Alignment Systematics Study: Bias on startup Endcap positions Asymmetric results Ph. D. Thesis Defense, S. Guragain

  34. MC Mass Spectra Generated and reconstructed dimuon mass with 3 alignment scenarios Ideal alignment (MC_31X_V5) 50 pb -1 alignment (50PBMU31X_V1) MZ′ = 1.2 TeV Startup alignment (STARTUP31X_V4) Better aligned detector narrows the signal peak; e.g. from startup to 50 pb -1 Ph. D. Thesis Defense, S. Guragain

  35. Z′ Mass Reach Analysis:Signal and background samples Z′ signal sample with full Z′/Z/γ interference, reconstructed with startup alignment ; and the background samples, one in the mass region (> 500 GeV/c2) around the Z′ mass and the other at lower mass (>200 GeV/c2). For the significance calculation, the reconstructed background sample is the weighted sum of these two background datasets. Ph. D. Thesis Defense, S. Guragain

  36. Reconstructed Mass fits: Significance with 200pb-1 Likelihood-ratio estimator has been used to evaluate the significance 1000 pseudo-experiments Entries Entries STARTUP align. 50 pb -1 align. MZ′ = 1.2 TeV & 200pb-1 MZ′ = 1.2 TeV & 200pb-1 (SL) (SL) Ph. D. Thesis Defense, S. Guragain

  37. Signal significance vs. Lint Variation of signal significance for MZ′ = 1.0 TeV/c2 and 1.2 TeV/c2 for different alignments and integrated luminosities. Better alignment puts us over 5 discovery threshold Better alignment equals doubling the data set Ph. D. Thesis Defense, S. Guragain

  38. Int. luminosity for 5σ Estimated data required for the expected Z′ signal with 5σ Ph. D. Thesis Defense, S. Guragain

  39. Z′ signal significance with misaligned muon endcaps only Negligible effect with the bias on endcaps only Ph. D. Thesis Defense, S. Guragain

  40. 7 TeV collision data analysis Datasets: (pre-ICHEP 2010) • /MinimumBias/Commisioning10-CS_Onia-Jun14thSkim_v1/RAW-RECO • 135740 events, Run range 131511-135802, March 30 – April 15, 2010 • /Mu/Run2010A-CS_Onia-jun14thSkim_v1/RAW-RECO • 79833 events, Run range 135821-137436, April 15 – June 10, 2010 • /Mu/Run2010A-PromptReco-v4/RECO • 1M events, Run range 137437-140399 (July 19), (Updated with data until September 3, 2010) Event selections: • Official good runs & lumisections certified from DQM group (Cert_132440-140399_7TeV_StreamExpress_Collisions10_JSON.txt) • Scraping filter to remove beam background rejection requiring ≥ 25% of high purity tracks with more than 10 tracks • Primary vertex (not fake) with at least 4 tracks (ndof ≥ 4) and with the z-coordinate of the point of closest approach to the tracks to the z-axis, i.e. |Z| ≤ 15 cm & position.Rho ≤ 2 cm • Two opposite sign muons with pT > 1 GeV/c (Std. 20 GeV/c) • Isolation Σ track pT (ΔR < 0.3 ) < 10 GeV/c Ph. D. Thesis Defense, S. Guragain

  41. Dimuon mass spectrawith data taken through July 19 J/ψ Events Z Ph. D. Thesis Defense, S. Guragain

  42. Up to date high-massdimuon mass spectrum Z 2.88 pb-1 Until September 3, 2010 Ph. D. Thesis Defense, S. Guragain

  43. A CMS collision event display µ-η= 0.46, pT=86 GeV µ+η=-0.18, pT=87 GeV Mµ+µ-= 181 GeV Ph. D. Thesis Defense, S. Guragain

  44. Summary (I) • CMS muon endcap alignment system is commissioned • Entire muon endcap geometrical model is built and validated with independent survey and photogrammetry measurements using cosmic data at 0 Tesla (T) • CARFT 2008 data are analyzed and CSC positions are reconstructed at 3.8T precisely • Precisions ~300 µm in zCMS and 200 µrad in φZCMS& error < 500 µm • Muon endcap alignment constants are delivered to CMS Ph. D. Thesis Defense, S. Guragain

  45. Summary (II & III) • Samples for MZ′ = 1.0 TeV, 1.2 TeV, 1.3 TeV, & 2 TeV and Drell-Yan at √s=7 TeV with the ideal, startup & 50 pb-1 alignment scenarios are generated, analyzed and published in CMS Database Bookkeeping System [hosted by FLTECH T3]. • The transverse momentum (pT) resolutions and dimuon mass resolutions are studied for various scenarios with the aforementioned samples. Typical dimuon mass resolutions are ~3% for ideal (MC), 6% for 50 pb-1 & 10% for startup. • The muon pT resolution in Endcaps is sensitive to the disk misalignment in position as well as rotation and the resolution is quantified for various misalignment scenarios. • Simulation results for discovery potential for MZ′SSM= 1.0 TeV & 1.2 TeV with different muon alignments and integrated luminosities are studied. • Effect of muon (mis)alignment on mass spectra • Expect to observe the Z′ (M = 1.2 TeV) with 5σ significance at √s=7 TeV and integrated luminosity of 250pb-1 with the 50pb-1 alignment or better • Negligible effect of muon endcap (only) misalignments upto 2 mm in translation or 0.5 mrad in rotation on Z′ signal significance Analyzed 7 TeV collision data up to run 140399 (July 19, 2010) and the dimuon mass spectra are shown and compared with simulated events of Z → µ+ µ- around Z mass region. The dimuon mass spectrum is updated. The search is in progress. Ph. D. Thesis Defense, S. Guragain

  46. Conclusions • Published a paper on muon alignment in CRAFT08 exercise in J. of Inst.(Led, completed, and co-authored Muon Endcap alignment system) • Commissioned CMS ME alignment system at CERN • Delivered muon endcap alignment constants to CMS • Published a CMS physics analysis note on muon misalignment systematics and expected Z′ signal significance using 7 TeV MC samples • Analyzed CMS early collision data taken through July 19 (250-300 nb-1)and updated with 2.88 pb-1 • Got approval / endorsement of my Ph.D. thesis by CMS on August 3rd, 2010 Contributed presentations = 63 + 10 Ph. D. Thesis Defense, S. Guragain

  47. Acknowledgements Thank you ! & Special thanks to my Ph.D. committee members: Drs. Baksay, Hohlmann, Mitra, Oswalt, and Zhang Ph. D. Thesis Defense, S. Guragain

  48. A question! • Is there something special about that day?Dr. Oswalt’s question by email on input to fix defense date Apparently! Yes Today is औसी (New moon)२०६७ भाद्र२३ (2067/5/23) September 82010 बुवाको मुख हेर्ने दिन Father’s face see day (Father’s day) This work is dedicated to his memory. Ph. D. Thesis Defense, S. Guragain

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