1. Muon Detection at CMS: from Detector and Software Commissioning to SM Physics and Higgs discovery 2° year Ph.D. Seminar, February 2008 Sara Bolognesi - Torino University and INFN

2. Drift Tubes: Hardware and Software Commissioning

3. Outline  Introduction on Muon Detector System in CMS:  Drift Tubes detector at work!  single cell operation principle (calibration procedure)  chamber structure and track segment reconstruction  barrel: Drift Tubes (DT) and Resistive Plate Chambers (RPC)  endcap: Cathode Strip Chambers (CSC) and RPC  DT Commissioning with Cosmic Muons:  …continuous integration/commissioning effort ever since …  Magnet Test and Cosmic Challenge in 2006 Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)3

4. Barrel: 5 wheel (+/-2, +/-1,0) in  4 DT stations (from inner MB1 to outer MB4) 12 sectors in  Magnetic field map B≈4T B≈1.8T 6 RPC stations Endcaps: 4 disks in z 2-3 rings 18-36 trapezoidal CSC in outer rings (  <1.6) 18-36 trapezoidal RPC Muon detectors half PhD seminar (2008 Febr. 22 Torino)Sara Bolognesi4

5. Drift Tubes   ionization (E  <1TeV, ArCO 2 gas) → electron drift→avalanche at wire→signal:  drift velocity calibration:  time synchronization: t meas = t electr + t.o.f. + t prop + t drift e - drift time measured and converted into distance (with L/R ambiguity) TDC spectrum time pedestal (t trig ) v drift = L / (2 × ) resolution = v drift × T max distributions Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)5 time pedestal (t trig )

6. DT chambers  2D segments reconstructed in each SL pattern recognition and linear fit → L/R ambiguity solved  1D hit from drift time measurement: constant v drift or v drift = f(t drift, ,B wire,B norm ).  3D segments reconstr. in each camber conflicts solved and ghosts suppressed (  , n hits ) r-  and r-z segments matched (all combinations)  Resolutions: r-  90  m (7mrad on angle) r-z 120  m (60mrad on angle) only 4 hits bending coordinate → 8 hits (non-Gaussian tails from  -rays) simulation r-  residuals r-z residuals Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)6

7. DT Commissioning with Cosmics  Timing:  Angular distribution: cosmics have random arrival time while CMS trigger designed for bunched muons (40 MHz) with fixed t.o.f. → additional smearing of (25/√12) ns ≈ 400  m CMS (software and hardware) designed for  from IP e.g.: DT trigger < 45°, track reconstruction with vertex constraint  CMS is not designed for cosmics! correct segment (33°) wrong reconstructed segment (65°) real cosmic in CMS visualization: total rate ≈ 30000 Hz (600 Hz in cavern) Distributions on CMS surface (510m on sea level): Sara Bolognesi half PhD seminar (2008 Febr. 22 Torino) 7

8. wheel 2 wheel 1 Magnet Test and Cosmic Challenge  B ramping up and down (0-4T) various times  Detector run in stable mode for more then 2 months → 230 M recorded events  14 DT chambers  21 RPC chambers  3 Barrel sectors + 60° slice of adjacent Endcap: (some tracker modules, ECAL crystals and HCAL sectors also in the DAQ) DAQ & trigger  subset of final readout and trigger electronics, global trigger and DAQ  36 CSC chambers Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)8

9. TDC spectra trigger source: DT Commissioning & Global Runs noise Test pulse signals for a single wire good test pulse signals electronic noise due to enabling/disabling masks  Test of calibration procedures in real life: e.g. integration of different sub-detectors robust software implementation reliable strategy of databases production and storage  The full detector monitored/calibrated run by run: high automation  Monitor of the detector performances: noise, dead wire, interchannel synchronization Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)9

10. My work on DT  I was strongly involved in  software development: calibration, local reconstruction, Data Quality Monitoring  data taking  real and simulated data analysis calibration, residuals, noise/dead channels (DQM responsible at MTCC) (calibration responsible in 2007):  Publications:  Measurement of Drift Velocity in the CMS Barrel Muon Chambers at the CMS Magnet Test Cosmic Challenge  Results of the first integration test of the CMS drift tubes muon trigger  Offline Calibration Procedure of the Drift Tube Detectors  Local Muon Reconstruction in the Drift Tube Detectors  Test of the DT Simulation and Local Reconstruction Algorithms on the 2004 Test-Beam data Nucl.Instrum.Meth.A579:951-960,2007. CMS NOTE-2007/034. CMS NOTE-2008/003. CMS NOTE in publication CMS NOTE in preparation  The CMS Precision Muon Chamber in the Magnet Test Cosmic Challenge (MTCC). CMS NOTE in preparation Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)10

11. Muon momentum scale calibration

12. Outline  Muon reconstruction strategy in CMS  Calibration of muon momentum scale exploiting the Z peak:  likelihood method based on real data and Z mass precise knowledge  effects due to realistic detector behavior (misalignment, B field distortion)  a use-case: evaluation of Z cross section systematics  Z resonance as a tool for “physics commissioning” Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)12  future plans: resolution, low mass resonances, backgrounds

13. Muon Reconstruction  Tracker Muons:good resolution at low p T, high background  StandAlone Muons (DT, CSC, RPC): high purity, good resolution at high p T  Global Muons (matching): p T resolution (barrel) a compromise between multiple scattering and lever arm Resolution results from Sara Bolognesi13 STA purity and Tracker resolution

14. |  | 20 GeV MC  cut: xsec(Z→  ) ≈ 1.8 nb xsec × kin. accept. ≈ 0.8 nb efficiency trigger 98.1% ≈ 8000 Z with 10 pb -1 lumi ≈ 14 pb -1 ; Physics Commissioning: Z→   “Standard candle” to measure detector performance from data and to control uncertainties and systematics: tag&probe method →  trigger and reconstruction efficiency mass peak →  momentum scale calibration and resolution measurement well known xsec → constraint on PDF and luminosity  Z @ LHC Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)14

15. Calibration strategy  The muon p T is modified to force the Z peak in the right position p T corr = k × p T NOT a simple p T shift BUT a correction as a function of muon kinematic: k = a 1 + a 2 p T + a 3 |  | + a 4  2 +  8 correction parameters (a i ) computed maximizing a likelihood: (i=1,2) different for  + and  - + q×a 5,i sin(  +a 6,i ) fit Lorentzian + decr. expo.  M i corr computed event by event using the muon momentum correction With a likelihood you can take into account the full  kinematic for each event without averaging!!  M ref MonteCarlo or PDG value Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)15

16. Generated Z mass  Lorentzian + decr. expo fit: generated Z mass 91.13 GeV ≈ 50 MeV PDF effect generated  mass 90.89 GeV ≈ 250 MeV Final State Radiation  Results from the fit used as reference  and M Z ref value in the likelihood fit Lorentzian + decr. expo. FSR Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)16

17. Reconstr. Z mass Tracks  STA  scale bias > 10%  GLB  and Tracks scale bias 0.5%  bias linear in p T and parabolic in  (no  dependence) Mean 90.89 ± 0.02 Gamma 2.95 ± 0.05 Mean 88.2 ± 0.2 Gamma 17.7 ± 0.4 Mean 89.7 ± 0.1 Gamma 16.4 ± 0.3 Mean 90.89 ± 0.02 Gamma 2.95 ± 0.05 Mean 88.2 ± 0.2 Gamma 17.7 ± 0.4 Mean 89.7 ± 0.1 Gamma 16.4 ± 0.3 STA  Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)17

18. Realistic detector  Scenarios with worsening of the detector behaviour:  Tracker and Muon System misaligned in 10pb -1 scenario:  B field distortion: Tracks: additional  dependence B'=B*1.002 B'=B*1.02 B'=B*1.05 Tracks: new little dependence on  STA  big dependence on  new  dependence additional correction as a function of p T (only 2‰ distortion) (barrel yoke: 2% distortion) (endcap: 5% distortion) (B increased => p T underestimated) GLB  : not sizeable effects Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)18

19. Systematics on Z cross section  Muon momentum scale systematics: GLB  +Track+STA  2.7% GLB  +Track 0.03% Z reconstructed with GLB  +GLB , GLB  +Tracks, GLB  +STA  to maximize efficiency, standard selection cuts applied on pure signal sample  Other systematics:  Tracker misalignment: 3.5% without corrections 0.9% after corrections  B field misknowledge: 1.8% without corrections 0.5% after corrections Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)19  Muon System misalignment: 3.2% without corrections 0.3% after corrections

20. consider background in the likelihood (from sidebands) Future plans  Improve the likelihood convolving resolution function resolution = Gaussianresolution = Crystal Ball  Extract also the muon resolution as a function of muon kinematic  Study low mass resonances (J/ ,  ) to calibrate low p T muons (Gaussian with asymmetric queue) FSR FSR effect well fitted   = 1.2  = 1.15±0.05 GeV   = 3.4  = 1.08±0.05 GeV Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)20

21. Plans for H→ZZ→  H→ZZ→4 , M H = 150 GeV H→ , M H = 100 GeV H→ZZ→4e, M H = 150 GeV

22. excluded by LEP Higgs @ LHC PRODUCTION DECAY Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)22

23. New channel : H→ZZ→   Leptonic final states favored inside the big hadronic background at LHC quite high BR ≈ 10 × BR(4  )  Difficult to work with MET: good detector control needed; high DY background H→ZZ→4l “golden channel” H→WW→lnln most promising @ 160GeV  Not yet considered: H→  for low Higgs mass g g H Z Z     H Z Z V V  ≈ 50 fb  ≈ 9 fb 150 GeV MHMH 200 GeV 500 GeV N ev (1 fb ≈ start-up year) 59 15 30 Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)23

24. H→ZZ→  analysis strategy  Ask for  Main backgrounds: ttbar → bb   ≈ 9.4 pb ZZ →   ≈ 0.10 pb WW →   ≈ 1.3 pb Drell-Yan (+jets) →  jets)   ≈ 65 pb WZ →   ≈ 0.25 pb → irreducible → big  (QCD process) → high  efficiency needed → MET resolution is crucial!!  exactly 2  with high p T (>20 GeV) in barrel region with opposite charge and M(  ) ≈ M Z  high MET = p T Z (big for high M H )  central jet veto b-tagging against ttbar  Analysis cuts as a function of M H → maximum significance for right M H single Z has lower p T, ZZ more soft and less central (same for  from ttbar), WW are back-to-back → lower MET,  kinematical cuts: ATLAS significance (3years low lumi) Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)24

25. Publications on Z and H CMS technical design report, volume II: Physics performance. J.Phys.G34:995-1579,2007. Boson-boson scattering and Higgs production at the LHC from a six fermion point of view: Four jets + l nu processes at O( alpha(em)**6 ). JHEP 0603:093,2006, e-Print: hep-ph/0512219 W and Z bosons physics at LHC at low luminosity. IFAE proceedings: Pavia 2006, High energy physics Workshop on CP Studies and Non-Standard Higgs Physics e-Print: hep-ph/0608079 Les Houches physics at TeV colliders 2005, standard model and Higgs working group: Summary report. e-Print: hep-ph/0604120 HERA and the LHC: A Workshop on the implications of HERA for LHC physics. Proceedings, Part A. HERA and the LHC: A Workshop on the implications of HERA for LHC physics: Proceedings Part B. CERN-2005-014, DESY-PROC-2005-01, e-Print: hep-ph/0601013 + e-Print: hep-ph/0601012 Higgs at CMS with 1, 10, 30 fb -1. 2007 International Linear Collider Workshop proceedings to be published Workshop sui MonteCarlo la Fisica e la Simulazione a LHC. Proceedings in preparation Study of VV-scattering processes as a probe of electroweak symmetry breaking. CMS Analysis Note, CMS-AN 2007/005 Towards a measurement of the inclusive W→  and Z→  cross sections in pp collisions at √s = 14 TeV. CMS Analysis Note, CMS-AN 2007/031 Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)25

26. The end. Thanks! Back-up slides

27. Drift Tube non-linearities test beam (0°) test beam (30°) A parameterization of the cell response can be used: v drift = f(t drift, ,B wire,B norm ).  Angular effects:  Magnetic field effects: simulation (wh+/-2)  reconstr. with constants v drift Residuals TDC spectrum e-e- half cell Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino) 27

28. Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)5 half cell Drift Tubes in real life!  rays: high energy e- knocked out from atoms by the   e-e- after-pulses: primary e - produce  that can extract secondary e - from cell wall shorter drift time   secondary signals after T max Other effects: (a),(f) random electronic noise (b),(e) pile-up hits from muons in other bunches of the beam (d) after-pulses (c) signal region test beam MTCC simulation Residuals TDC spectrum t secondary - t primary e-e- e-e- e-e-

29. W1 10 11 10 11 10 11 W2 W1 W2 W1 W2 MB1MB2MB3MB4 W1W2W1 W2 101114 TOF effect (10 ns) 10 B = 3.8 T (global run) B off (local run)  t trig for two trigger configuration: Shift ~ 28 BX T mean [nsec] MB1MB2MB3MB4  t trig for two MTCC runs: Station & Sector 1-> 12 Technical Trigger Default Cosmic t trig calibration Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)29

30. Meantimer computation  Different formulas for different track patterns T max distributions (“meantimer”) (most simple case)  It’s the average T max mediated on the whole semicell: Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)30

31. B = 3.8 T (global run) B off (local run) ~2% W1 W2 W1 W2 W1 W2 MB1MB2MB3MB4 W1 W2W1 W2 v drift for each SL W1W2W1W2W1W2 MB1MB2MB3MB4 W1W2W1 W2 SL theta SL phi v drift (Boff) - v drift (Bon) v drift (Boff) for each SL 10 11 10 11 10 11 1011 14 10 11 10 11 10 11 1011 14 10 v drift calibration Sara Bolognesi 31

32. hit resolution = v drift ×  meantimer hit resolution distribution for each SL deviation from linearity mean 560  m mean 600  m B = 3.8 T (global run) B off (local run) With B on the resolution become worse because of deviations from linearity W1 W2 W1 W2 W1 W2 MB1 MB2MB3MB4 W1 W2W1 W2 CMS NOTE 2005/018 10 11 10 11 10 11 10 1114 10 Resolution calibration Sara Bolognesihalf PhD seminar (2008 Febr. 22 Torino)32