Samir Guragain , Marcus Hohlmann Florida Institute of Technology, Melbourne, FL
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Samir Guragain , Marcus Hohlmann Florida Institute of Technology, Melbourne, FL Z Z ′ ′ Mass Reach MC Mass Reach MC Analysis Analysis USCMS meeting Brown University May 6 – 8, 2010 Providence, RI Effect of muon misalignments on the Effect of muon misalignments on the muon p muon p T T resolution and on the search resolution and on the search for Z for Z ′→ ′→ μ μ + + μ μ - - in pp collisions at 7 TeV in pp collisions at 7 TeV Mass and Mass and p p T T Resolutions with 3 Misalignment Resolutions with 3 Misalignment Scenarios Scenarios Muon Endcap Alignment Muon Endcap Alignment Systematics Systematics Muon Endcaps Yokes ME+1 ME+2 ME+3 ME+4 +z Muon Endcap stations: ME- Ideal (MC_31X_V5) Startup STARTUP31X_V4 50 pb -1 (50PBMU31X_V1) LHC STARTUP (now) • Up to muon p T = 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 with or without bias on endcap stations Abstract: Using simulated proton-proton (pp) collisions at √s = 7 TeV, we study the expected effect of muon misalignments on the transverse muon momentum (p T ) resolution and on the search for high-mass resonances decaying to dimuons, in particular Z′→ µ + µ − and Drell-Yan events, for the CMS experiment. We present the p T resolutions for muons from Z′ decays at different masses and center-of-mass energies using different muon misalignments. The simulation results show that the p T resolutions in the endcap are about 15% (5%) with the startup (ideal) muon misalignment scenario. The impact of systematic biases in the muon endcap positions and rotations on the p T resolution is also studied and quantified. Using the MC samples, the discovery potential for M Z′ SSM = 1.2 TeV with different muon misalignments and integrated luminosities is evaluated. We find that a better aligned detector requires significantly less data, i.e. ~200 pb -1 of integrated luminosity, to discover a Z′ signal with 5σ significance than the CMS detector with current startup muon alignment. A preliminary analysis of dimuon data from first collisions at √s = 7 TeV is also presented. Startup alignment Startup alignment and normalized to and normalized to 200 pb 200 pb -1 -1 M M Z ′ ′ =1.2 =1.2 TeV TeV Muons from 2 TeV Z′ at s = 7 TeV • Significance Estimator: Shape-based – likelihood ratio of signal + background and background-only fits to data • Misalignment scenarios • Ideal Alignment (MC_31X_V5): Corresponding to ideal geometry of the detector • Startup Alignment (STARTUP31X_V4): Based on CRAFT 2008 and 2009 data analysis and produced by randomly misaligning chambers with an RMS consistent with cross-checks in CRAFT 2008 & 2009 • 50 pb -1 (50PBMU31X_V1) : Assuming alignment with tracks using 50 pb -1 data. Estimated with the Reference-Target algorithm [aligns a Target set of chambers using global muon tracks from a fixed Reference (tracker)] on appropriate MC samples • MC production at 7 TeV (at Fl. Tech.): Signal (Z′ SSM ) and background (Drell-Yan) samples with 3 standard misalignments using CMSSW_3_1_X • Ran Z′→ μ + μ - analysis code in 3_X_Y •Event selection: - Two opposite sign muons with p T > 20 GeV/c - Isolation Σ track p T (ΔR < 0.3 cm) < 10 GeV/c Collision Collision data data Transverse momentum Transverse momentum Pseudorapidity Pseudorapidity Comparisons: 7 TeV Data Comparisons: 7 TeV Data vs. MC vs. MC MC: /MinBias/Spring10-START3X_v26A_356ReReco-v1/GEN-SIM- RECO Data: /MinimumBias/Commissioning10-GOODCOLL-v8/RAW-RECO Ideal alignment Ideal alignment Tracker + Muon Tracker + Muon Ideal alignment + Ideal alignment + 2mm shift of muon endcap 2mm shift of muon endcap Tracker + Muon Tracker + Muon Muon p Muon p T T resolution vs. resolution vs. η η Muon p Muon p T T resolution vs. p resolution vs. p T Muon p Muon p T T resolution vs. p resolution vs. p T Acknowledgments : Jordan Tucker, Jim Pivarski, Piotr Traczyk, Martijn Mulders, the CMS Collaboration, and the US Department of Energy Acknowledgments : Jordan Tucker, Jim Pivarski, Piotr Traczyk, Martijn Mulders, the CMS Collaboration, and the US Department of Energy Method Method : Muon Endcap was misaligned with respect to ideal : Muon Endcap was misaligned with respect to ideal or startup muon geometry. Then, a signal sample (M or startup muon geometry. Then, a signal sample (M Z ′ =1.2TeV or 2.0TeV) was reconstructed and analyzed =1.2TeV or 2.0TeV) was reconstructed and analyzed repeatedly with each studied misalignment. The sample was repeatedly with each studied misalignment. The sample was reconstructed with a customized global tag by inputting a reconstructed with a customized global tag by inputting a modified SQLite file, with a bias for the position(X modified SQLite file, with a bias for the position(X CMS CMS , , Y Y CMS CMS , Z , Z CMS CMS ) up to 2 mm or a bias on rotation ( ) up to 2 mm or a bias on rotation ( φ φ Z CMS CMS ) up to ) up to 0.5 mrad of muon endcap stations together or individual 0.5 mrad of muon endcap stations together or individual ME stations ME stations. . [For comparison: Current startup ME disk misalignments are 0.5 mm in (∆x, ∆y, ∆z) & 0.1 mrad in ∆φ Z CMS ] µ + µ − Resolution Resolution table table Run 133928 Event 2538823 Date: April 25, 2010 cm Z′ + DY DY Dimuon mass [GeV/c 2 ] 50 pb 50 pb -1 -1 alignment alignment and normalized to and normalized to 50 pb 50 pb -1 -1 • Dimuon Mass spectra and Dimuon Mass spectra and fitting: fitting: : : Z′ + DY DY Significance in 1000 pseudo-experiments STARTUP STARTUP alignment alignment scenario scenario 1.2 TeV Z 1.2 TeV Z ′ ′ 50 pb -1 alignment scenario L int = 200 pb - 1 Discovery L int fit For 1.2 TeV Z′ Better alignment equals doubling the data set Better alignment puts us over 5 discovery threshold This result matches well with scaling results from 14 TeV to 7 TeV => 5 discovery possible with 200 pb -1 of data with the estimated 50 pb -1 alignment or better Global muons Data MC Dimuon mass [GeV/c 2 ] Dimuon mass [GeV/c 2 ] Dimuon mass [GeV/c 2 ] Dimuon mass [GeV/c 2 ] Dimuon mass [GeV/c 2 ] 1.2 TeV Z′ + DY Generated dimuon mass Events Events Signal Significance S L Signal Significance S L An Event Display Dimuon Analysis Ideal alignment Ideal alignment Ideal alignment + Ideal alignment + 2mm shift of muon endcap 2mm shift of muon endcap A simulated Z′→ µ + µ − Event L int = 200 pb -1 Data: GOODCOLL-v7- 9 J/ψ Global muons
description
Effect of muon misalignments on the muon p T resolution and on the search for Z ′→ μ + μ - in pp collisions at 7 TeV. ME -. Muon Endcap stations:. ME+2. ME+3. ME+1. ME+4. +z. Muon Endcaps. Yokes. Tracker + Muon. 50 pb -1 (50PBMU31X_V1). Ideal alignment. Better alignment - PowerPoint PPT Presentation
Transcript of Samir Guragain , Marcus Hohlmann Florida Institute of Technology, Melbourne, FL
Samir Guragain, Marcus Hohlmann Florida Institute of Technology, Melbourne, FL
ZZ′′ Mass Reach MC Analysis Mass Reach MC Analysis
USCMS meeting Brown University May 6 – 8, 2010 Providence, RI
Effect of muon misalignments on the Effect of muon misalignments on the muon pmuon pTT resolution and on the search resolution and on the search for Zfor Z′→′→ μ μ+ + μμ-- in pp collisions at 7 TeVin pp collisions at 7 TeV
Mass and Mass and ppT T Resolutions with 3 Misalignment ScenariosResolutions with 3 Misalignment Scenarios
Muon Endcap Alignment SystematicsMuon Endcap Alignment Systematics
Muon EndcapsYokes
ME+1ME+2ME+3
ME+4
+z
Muon Endcap stations: ME-
Ideal(MC_31X_V5)
StartupSTARTUP31X_V4
50 pb -1
(50PBMU31X_V1)
LHC STARTUP (now)
• Up to muon pT = 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 with or without bias on endcap stations
Abstract: Using simulated proton-proton (pp) collisions at √s = 7 TeV, we study the expected effect of muon misalignments on the transverse muon momentum (pT) resolution and on the search for high-mass resonances decaying to dimuons, in particular Z′→ µ+ µ− and Drell-Yan events, for the CMS experiment. We present the pT resolutions for muons from Z′ decays at different masses and center-of-mass energies using different muon misalignments. The simulation results show that the pT resolutions in the endcap are about 15% (5%) with the startup (ideal) muon misalignment scenario. The impact of systematic biases in the muon endcap positions and rotations on the pT resolution is also studied and quantified. Using the MC samples, the discovery potential for MZ′SSM
= 1.2 TeV with different muon misalignments and integrated luminosities is evaluated. We find that a better aligned detector requires significantly less data, i.e. ~200 pb-1 of integrated luminosity, to discover a Z′ signal with 5σ significance than the CMS detector with current startup muon alignment. A preliminary analysis of dimuon data from first collisions at √s = 7 TeV is also presented.
Startup alignment and Startup alignment and normalized to 200 pbnormalized to 200 pb-1-1
MMZZ′ ′ =1.2 TeV=1.2 TeV
Muons from 2 TeV Z′ at s = 7 TeV
• Significance Estimator: Shape-based – likelihood ratio of signal + background and background-only fits to data
• Misalignment scenarios• Ideal Alignment (MC_31X_V5): Corresponding to ideal geometry of the detector• Startup Alignment (STARTUP31X_V4): Based on CRAFT 2008 and 2009 data analysis and produced by randomly misaligning chambers with an RMS consistent with cross-checks in CRAFT 2008 & 2009 • 50 pb-1 (50PBMU31X_V1) : Assuming alignment with tracks using 50 pb-1 data. Estimated with the Reference-Target algorithm [aligns a Target set of chambers using global muon tracks from a fixed Reference (tracker)] on appropriate MC samples
• MC production at 7 TeV (at Fl. Tech.):Signal (Z′SSM) and background (Drell-Yan) samples with 3 standard misalignments using CMSSW_3_1_X
• Ran Z′→ μ+ μ- analysis code in 3_X_Y•Event selection: - Two opposite sign muons with pT > 20 GeV/c
- Isolation Σ track pT (ΔR < 0.3 cm) < 10 GeV/c
Collision data Collision data Transverse momentumTransverse momentum PseudorapidityPseudorapidity
Comparisons: 7 TeV Data vs. MCComparisons: 7 TeV Data vs. MCMC: /MinBias/Spring10-START3X_v26A_356ReReco-v1/GEN-SIM-RECOData: /MinimumBias/Commissioning10-GOODCOLL-v8/RAW-RECO
Ideal alignmentIdeal alignment
Tracker + MuonTracker + Muon
Ideal alignment + Ideal alignment + 2mm shift of muon endcap2mm shift of muon endcap
Tracker + MuonTracker + Muon
Muon pMuon pT T resolution vs. resolution vs. ηη Muon pMuon pT T resolution vs. presolution vs. pTT
Muon pMuon pT T resolution vs. presolution vs. pTT
Acknowledgments : Jordan Tucker, Jim Pivarski, Piotr Traczyk, Martijn Mulders, the CMS Collaboration, and the US Department of Energy Acknowledgments : Jordan Tucker, Jim Pivarski, Piotr Traczyk, Martijn Mulders, the CMS Collaboration, and the US Department of Energy
MethodMethod: Muon Endcap was misaligned with respect to ideal or startup muon : Muon Endcap was misaligned with respect to ideal or startup muon geometry. Then, a signal sample (Mgeometry. Then, a signal sample (MZZ′′=1.2TeV or 2.0TeV) was reconstructed =1.2TeV or 2.0TeV) was reconstructed and analyzed repeatedly with each studied misalignment. The sample was and analyzed repeatedly with each studied misalignment. The sample was reconstructed with a customized global tag by inputting a modified SQLite reconstructed with a customized global tag by inputting a modified SQLite file, with a bias for the position(Xfile, with a bias for the position(XCMSCMS, Y, YCMSCMS, Z, ZCMSCMS) up to 2 mm or a bias on ) up to 2 mm or a bias on rotation (rotation (φφZZCMSCMS
) up to 0.5 mrad of muon endcap stations together or individual ) up to 0.5 mrad of muon endcap stations together or individual
ME stations ME stations. . [For comparison: Current startup ME disk misalignments are 0.5 mm in (∆x, ∆y, ∆z) & 0.1 mrad in ∆φZCMS
]
µ+
µ−
Resolution tableResolution table
Run 133928Event 2538823Date: April 25, 2010
cm
Z′ + DY
DY
Dimuon mass [GeV/c2]
50 pb50 pb-1-1 alignment and alignment and normalized to 50 pbnormalized to 50 pb-1-1
• Dimuon Mass spectra and fitting: Dimuon Mass spectra and fitting: : :
Z′ + DY
DY
Significance in 1000 pseudo-experiments
STARTUP STARTUP alignment scenarioalignment scenario
1.2 TeV Z1.2 TeV Z′′
50 pb-1 alignmentscenario
Lint = 200 pb-1
Discovery
Lint fit
For 1.2 TeV Z′
Better alignmentequals doublingthe data set
Better alignmentputs us over 5 discovery threshold
This result matches well with scaling results from 14 TeV to 7 TeV
=> 5 discovery possible with 200 pb-1 of data with the estimated 50 pb-1 alignment or better
Global muons
DataMC
Dimuon mass [GeV/c2]
Dimuon mass [GeV/c2] Dimuon mass [GeV/c2]
Dimuon mass [GeV/c2] Dimuon mass [GeV/c2]
1.2 TeV Z′ + DY
Generated dimuon mass
Events Events
Signal Significance SL
Signal Significance SL
An Event Display Dimuon Analysis
Ideal alignmentIdeal alignment
Ideal alignment + Ideal alignment + 2mm shift of muon endcap2mm shift of muon endcap
A simulated Z′→ µ+ µ− Event
Lint = 200 pb-1
Data: GOODCOLL-v7-9
J/ψ
Global muons
