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

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 –2 nd journal publication with major Fl. Tech contributions on behalf of CMS collaboration (1 st was CMS detector paper) 18 pp. w/o author list Sept. 8, 20102Ph. D. Thesis Defense, S. Guragain CRAFT = Cosmic Run At Four Tesla

Major achievements (II) Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain3 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 –1 st 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 pages

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 Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain4

Standard model & Elementary particles Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain5 The Standard Model (SM) current knowledge in particle physics. theory of strong interactions and unified theory of weak and electromagnetic interactions Fermions (spin ½, 3/2, 5/2,..): Leptons & Quarks (Spin ½) and Bosons (spin 0,1, 2..): Known Force carriers (Spin 1) 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. Lack of gravitational interactions in the SM

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/c 2 (CDF) LHC is the first opportunity to search for Z' in a high-mass (TeV/c 2 ) 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-p T muons Detector misalignment Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain6

Proposed new particle Z' Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain7 Model: Z SSM within the sequential standard model (SSM), which has the same coupling as the standard model Z. 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. pp → Z' → µ + µ -

Current lower Z′ mass limits for various models Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain8 Z′ Mass limit (TeV) From CDF collaboration, “Search for High-Mass Resonances Decaying to Dimuons at CDF” Phys. Rev. Lett. 102 (2009) Z′ SSM lower mass limit Channel Collaboration TeV in 2009 Dimuon CDF (Tevatron at Fermilab) TeV in 2010 Dielectron D0 (Tevatron at Fermilab) Collider Detector at Fermilab (CDF) result in 2009

LHC at CERN Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain9 LHCb (beauty) ALICE (A large Ion Collider Experiment) Cessy, France Genève, Switzerland LHC detectors and accelerator are the most complex scientific instruments ever built. TOTal Elastic and diffractive cross-section Measurement A Toroidal LHC ApparatuS / LHC forward

Compact Muon Solenoid (CMS) Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain10 Tracker Calorimeters Magnet Muon ME+4 ME -

Particle detection in CMS & muon reconstructions Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain11 Global Muon TrackStandalone Muon Track Muon Hits and Track Segments Muon in Silicon Tracker

Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain12 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!

Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain13 Full reconstruction model R-sensors Z-sensors Note: only small sample of analog sensors shown Clinometers Transfer Plate (TP) DCOPS’s Straight Line Monitors (SLMs) and Transfer lines Lasers The system monitors the positions of CSCs relative to each other and to the central disk. TOTAL: 768 sensors and 60 lasers

Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain14 A part of CMS 2 Crosshair Lasers (adjustable) Ref. DCOPS Chamber DCOPS’s Transfer Line DCOPS Z-tube Z-sensors Transfer Plate 1 Clinometer Mounting Tower ME+2 SLM Back Chamber R-sensor Laser beam Laser on ! Z CMS Rphi CMS

Relative displacements at fields using Z-sensor measurements Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain15

Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain16 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

ME+3 SLM1-4 at 0T using DCOPS & PG measurements Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain17 Reconstructed chamber center position Fit residual ~ 50 µm

Comparison with PG Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain µm

Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain19 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

ME+2,3 CSC displacements using relative shift of TP from 0 to 3.8T Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain20

ME-2,3 CSC displacements using relative shift of TP from 0 to 3.8T Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain21

Bending of YE2 disk due to magnetic field at 3.8T Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain mm YE2 bending towards the interaction point (IP) of CMS

ME Alignment constants Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain23 1/6 of 468 CSCs are monitored and corrected individually. For the remaining unmonitored CSCs, average corrections are applied.

Physics: Z′→  +  - search Unique contributions: –Studied impact of muon misalignment systematics on High-p T Muon p T 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/ contributed presentations at Exotica Muon meetings (since 4/1/09) Taken on responsibility for MC samples in Z ′→  +  - group: Sept. 8, Ph. D. Thesis Defense, S. Guragain

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 (φ x,φ y,φ z ) 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 (φ x,φ y,φ z ) Tracker misalignment scenarios in startup and 50 pb -1 are the same and based on CRAFT 2008 (tag TrackerCRAFTScenario310_mc) Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain25

MC samples and event selection Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain26 MC samples (50K events) Z′ signal samples with full Z′/Z/γ interference for M Z′ SSM =1.0 TeV/c 2, 1.2 TeV/c 2, 1.3 TeV/c 2, and 2.0 TeV/c 2 Drell-Yan samples, one in the mass region (>500 GeV/c 2 ) around the Z′ mass and another at lower mass(>200 GeV/c 2 ) Analysis Code “Zprime2muAnalysis” package in CMSSW Event selection: At least a pair of oppositely charged muons p T of each muon track in a pair > 20 GeV/c Isolated muons: Σ track p T (ΔR < 0.3) < 10 GeV/c

Resolution study for 3 alignment scenarios using 1.2 TeV Z′ MC sample at √s = 7TeV Sept. 8, Ph. D. Thesis Defense, S. Guragain Muon Momentum resolution (endcap) for 3 misalignment scenarios with M Z′ = 1.2 TeV at 7 TeV CM energy Z' SSM → µ + µ - analysis

Summary: resolutions for 3 alignments and different Z′ mass with √s=7TeV & 10TeV Sept. 8, Ph. D. Thesis Defense, S. Guragain 50 pb -1 alignment scenario is validated. GR = Global Reconstruction TK = Tracker only FS = Tracker plus First Muon Station

Systematics study: Muon endcap alignment Method: 1.Muon Endcap was misaligned systematically with respect to ideal or startup muon geometry. 2.A signal sample (M Z′ =1.2TeV/c 2 or 2.0TeV/c 2 ) was fully reconstructed. –The sample was reconstructed with a customized global tag by inputting a modified SQLite file, with a bias for the position(X CMS, Y CMS, Z CMS ) up to 2 mm or a bias on rotation (φ Z CMS ) up to 0.5 mrad of muon endcap stations together or individual ME stations. [For comparison: Current startup ME disk misalignments are mm in (∆x, ∆y, ∆z) & 0.1 mrad in ∆φ Z CMS ] 3. The analysis code was re-run over the resulting biased MC data set for each misalignment. Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain29

p T resolution vs. η Ideal alignement & with 2mm Bias Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain30 2 TeV Z′ Sample No systematic bias applied to the Barrel and Tracker- only Ideal alignment Ideal alignment + 2mm shift of muon endcaps

Comparison: p T resolution Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain31 Up to 200 GeV/c, no significant change due to bias but changes at higher p T Muon alignment becomes prominent at higher p T in all scenarios Demonstrates tracker-only does not change, as expected with or without bias on endcap stations Ideal alignment + 2mm shift of muon endcap LHC startup alignment (now)

Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain32 Alignment Systematics Study: Bias on ideal Endcap positions

Alignment Systematics Study: Bias on startup Endcap positions Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain33 Asymmetric results

MC Mass Spectra Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain34 Ideal alignment (MC_31X_V5) 50 pb -1 alignment (50PBMU31X_V1) Startup alignment (STARTUP31X_V4) Generated and reconstructed dimuon mass with 3 alignment scenarios M Z′ = 1.2 TeV Better aligned detector narrows the signal peak; e.g. from startup to 50 pb -1

Z′ Mass Reach Analysis: Signal and background samples Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain35 Z′ signal sample with full Z′/Z/γ interference, reconstructed with startup alignment ; and the background samples, one in the mass region (> 500 GeV/c 2 ) around the Z′ mass and the other at lower mass (>200 GeV/c 2 ). For the significance calculation, the reconstructed background sample is the weighted sum of these two background datasets.

Reconstructed Mass fits: Significance with 200pb -1 Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain36 Likelihood-ratio estimator has been used to evaluate the significance STARTUP align. M Z′ = 1.2 TeV & 200pb -1 M Z′ = 1.2 TeV & 200pb pb -1 align pseudo-experiments (SL )(SL ) (SL )(SL ) Entries

Signal significance vs. L int Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain37 Variation of signal significance for M Z′ = 1.0 TeV/c 2 and 1.2 TeV/c 2 for different alignments and integrated luminosities. Better alignment equals doubling the data set Better alignment puts us over 5  discovery threshold

Int. luminosity for 5σ Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain38 Estimated data required for the expected Z′ signal with 5σ

Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain39 Negligible effect with the bias on endcaps only Z′ signal significance with misaligned muon endcaps only

7 TeV collision data analysis Datasets: (pre-ICHEP 2010) 1./MinimumBias/Commisioning10-CS_Onia-Jun14thSkim_v1/RAW-RECO – events, Run range , March 30 – April 15, /Mu/Run2010A-CS_Onia-jun14thSkim_v1/RAW-RECO –79833 events, Run range , April 15 – June 10, /Mu/Run2010A-PromptReco-v4/RECO –1M events, Run range (July 19), (Updated with data until September 3, 2010) Event selections: Official good runs & lumisections certified from DQM group (Cert_ _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 p T > 1 GeV/c (Std. 20 GeV/c) Isolation Σ track p T (ΔR < 0.3 ) < 10 GeV/c Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain40

Dimuon mass spectra with data taken through July 19 Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain41 Z J/ψ Events

Up to date high-mass dimuon mass spectrum Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain42 Until September 3, 2010 Z 2.88 pb -1

A CMS collision event display Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain43 µ - η= 0.46, p T =86 GeV µ + η=-0.18, p T =87 GeV M µ+µ- = 181 GeV

Summary (I) 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 z CMS and 200 µrad in φ Z CMS & error < 500 µm Muon endcap alignment constants are delivered to CMS Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain44

Summary (II & III) Samples for M Z′ = 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 (p T ) 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 p T 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 M Z′ 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 (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. Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain45

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 ( nb -1 ) and updated with 2.88 pb -1 Got approval / endorsement of my Ph.D. thesis by CMS on August 3 rd, 2010 Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain46 Contributed presentations =

Acknowledgements Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain47 Thank you ! &

A question! Is there something special about that day? Dr. Oswalt’s question by on input to fix defense date Apparently! Yes Today is Sept. 8, 2010Ph. D. Thesis Defense, S. Guragain48 औसी (New moon) २०६७ भाद्र २३ (2067/5/23) September बुवाको मुख हेर्ने दिन Father’s face see day (Father’s day) This work is dedicated to his memory.