The CMS Muon system status and plans

1. The CMS Muon system status and plans Armando Lanaro UW-Madison on behalf of Muon DPGs and Operations CMS Week Bodrum

2. outline • Muon System Operation • Calibration • Detector parameters • Timing • Alignment • Data monitoring and run certification • System performances • Chamber level efficiencies • Local reconstruction • Muon simulation • Short term issues • Longer term issues • Summary & outlook Plots, information, comments, feedback were kindly provided by many friends within the Muon community. Thanks! CMS Week Bodrum

3. Muon System Operationsafter 6 months of sustained operation with beam CMS Week Bodrum

4. 3 % 0.6 % RUN impressive achievements RE efficiency before/after HV tuning • Operating status • DT has ~99.8% of system operating • RPC has ~98.5% of system operating • CSC has ~98.6% of system operating • https://twiki.cern.ch/twiki/bin/viewauth/CMS/OnlineWBActiveChannels HV=9.5 kV HV=9.4 kV Masked RPC strips vs Time • RPC - New HV setting in RE (9.5 kV) yield higher efficiency (from 87% to 94%), now comparable to RB • thresholds wrt noise procedure optimized to recover larger fraction of detector • DT - Dominated by cosmics for a along time. Happy to see collision muons with increasing rate as L grows. Able now to perform calibrations using IP muons • CSC - Huge effort to optimize trigger/readout timing and synch. Fine tuning of thresholds to handle increasing size of DAQ readout buffers due to increasing occupancy • Very stable operations performance reached by all subsystems. Not a major contributor to CMS downtime. Detector expert availability guaranteed 24h CMS Week Bodrum

5. impressive achievements cont. • Detector noise • DT - average noise rate ~5Hz (like in CRAFT) from high hit rates in single cell. Automatic resynch enabled to recover from bursts of noise, mainly due to HV discharges in RPC and DT (frequency ~1/day) • RPC - 98% of chambers with less than 1Hz/cm2 average noise rate • CSC – difficult to quantify the noise level when there is no signal (m) because of the pretrigger requirement on the front-end read out. Indications from “single-layer” trigger mode tests show little/no effect • Recently • DT - Trigger instabilities during LHC beam ramp understood and fixed • CSC – LV instabilities in some crates (contacts?) resulted in (TMB) VME communication problems (fixed) – Investigating reason for HV channel trips • DT and RPC running shiftless since early June, CSC maintains owl shifts till mid Sept. Bottom line Low luminosity runs have been a great opportunity to test robustness of several aspects of muon system operation. Still, one shouldn’t believe that the detector commissioning phase is over. There are several issues which are been investigated and not all is DONE as it might sounds! As Luminosity increases we might uncover NEW problems. CMS Week Bodrum

6. LHC tech stop Temporary loss of 18 CSC due to turbine failure muon system operational stability (March-Sept 2010) A. Benvenuti, A. Dimitrov, M. Ignatenko • DT: • >99.5% channels alive • 28 UXC accesses and 18 repairs (~5.2% of detector recovered during TS) • breakdown of failure/repairs • Stable loss of ~0.25% of the detector • RPC: • 98.3-98.7% channels alive • 26 UXC accesses and 17 repairs (~10.8% of detector recovered during TS) [breakdown of failure/repairs in appendix] DT • CSC: • 98.6% channels alive • ~5.6% of detector recovered (includes losses due to infrastructure failures) during TS • failure rate ~0.07%/month (projects to 97.5% by Dec 2011) Message: necessary to maintain present rate of technical stops for system maintenance CSC CMS Week Bodrum

7. calibration CMS Week Bodrum

8. detector parameters DT major step-forward: • new full calibration using ~1/pb available from 38X (supersedes old constants from cosmics) • compute tdrift using the time pedestal (tTrig ) from fitting the time-box rising-edge • Corrections to time pedestal resolution obtained from position residuals • Preliminary agreement on resolution (~350 mm) between sim and data with new constants • RPC • The detector is a digital device not requiring a special calibration tuning • main parameters to monitor are: cluster size, efficiency, dead/masked strips • CSC calibration flow: • Measured front-end parameters (pedestals, cross-talk, gain, noise) are very stable • Still crucial to update status of electronics (dead channels, chambers) in CondDB Chambers and Sectors • MuDPG_skim - Events: DT activity + collision + at least 1 GLB or TRK m in DT CMS Week Bodrum

9. parameter stability • Monitoring of CSC gas gain • Mean of Landau cathode strip signal spectrum (use beam halo data) • gains are stable wrt chamber type. Small HV corrections of <1% to achieve full gain equalization (not yet done) • Must tune simulated digitization (to agree with data) • adjust gains per chamber type • improve strip charge data/MC agreement Cathode strip ADC sum in 3 strips and 3 time bins CMS Week Bodrum

10. - MB1 - MB2 -MB3 - MB4 timing & synchronization • Remarkable achievements from all Muon subsystems • several iterative tunes performed since April • probably not much room left for major improvements • DT • DT Local Trigger well timed in • Tuning (1-2ns level) ongoing to fine-adjust BX assignment on MB1/2/3 (slightly larger corrections needed for MB4) rms <~1ns 0.99915 • RPC hit synchronization • excellent time synchronization achieved (>99% of RB+RE has DBX=0) • Some fine tuning still possible (~1-2 ns) for a fraction of the LB at BX=0 0.00044 0.00025 RPC hit-time relative to L1A CMS Week Bodrum

11. more on timing before • CSC Trigger synchronization • Anode trigger sync. refined using offline analysis; no timing scan needed • Most chambers within ±1ns of best timing position (chamber level corrections available in 3.8.X) • Cathode trigger sync to be further refined very near term (already sufficient for anode-cathode coincidence) after rms=0.9ns /Mu/ dataset global muons average anode time CMS Week Bodrum

12. barrel muon alignment • Barrel:track-based (TB) and hardware (HW) systems are operating and producing constants • Constants are highly correlated, but systematic issues remain(4 mm “twist” discrepancy from one end of the barrel to the other) both methods identify the same large differences with respect to the design geometry (mostly gravitational sag) • Currently used alignment is derived from the hardware measurements CMS Week Bodrum

13. endcap muon alignment • Endcap:track-based and hardware systems are operating and producing constants. The methods are more orthogonal than in the barrel, making direct comparisons more difficult (ongoing study) • Endcap alignment constructed from both sources: transverse degrees of freedom (x, y, rotation around z) from beam-halo tracks, and longitudinal (z, bending of disk in magnetic field) from hardware. Detector position relative to disk from beam halo and SLM. Disk position from cosmics and TL. Photogrammetry provides additional constraints. • Track-based results from 2010 beam-halo agree well (0.6 mm RMS) with 2007 photogrammetry • Example from disk-alignment using cosmic rays: after before cosmics are mostly only on top and bottom; collisions will fill gaps CMS Week Bodrum

14. muon alignment uncertainties • Endcap:largest uncertainty in placement of endcap disks: about 2-3 mm (statistical), mostly vertically • Also leads to a few percent increase in smearing of high-momentum track curvatures (high pTm from Z’) • Barrel:largest uncertainty from TB-HW discrepancy (~0.5mrad twist) • Wrong alignment would introduce ~0.2 c/TeV bias in momentum (vs eta) • 1.1 TeV/c2 Z' mass would be smeared about 40% more than with ideal geometry CMS Week Bodrum

15. data monitoring and validation CMS Week Bodrum

16. data monitoring • Has become one of the main tasks for Muon DPG and detector Operations • Monitoring tools that have been developed and deployed have now to be used and maintained • As instantaneous luminosity grows we learn new features of the Muon system response uniformity/efficiency/asymmetries. Some effects may not be intuitive • Additional ‘features’ depend on the specific data stream and pT selection (strange hit-occupancy patterns observed for streams filtered on muon HLT) • In addition, detectors can unexpectedly experience hw failures (seen as sudden efficiency losses, noise increase, …) which have to be to spotted fast! Any hint of slow degradation of detector specific parameters (gain, noise, resolution, …) has to be identified by performing time-dependent analyses • So far, we have only looked at the detector at a macroscopic level. Now is time to dig into fine details to sharpen our level of knowledge and understanding CMS Week Bodrum

17. monitoring examples (CSC) Cosmics stream Express stream MinBias Onia CMS Week Bodrum

18. organization • Data monitoring shifts are now replacing regular 8h shifts at P5. This activity is complementary to online DQM shifts. Reasons: • Time-scale is different • Faster feedback and response from detector experts • Involve a larger number of physicists in data monitoring • This effort is coordinated jointly by the DPGs and detector Operations to benefit of the experience of those who have built the detector CMS Week Bodrum

19. run certification & validation Goal: to optimize data taking DPGs set a minimal set of requirements to certify a run as “good” for physics analyses as guidance to online DQM shifters • Not yet uniform requirements for muon subsystems. All tend to be rather conservative (lost data are lost forever) while gaining experience. Need feedback: • from physics analyses • from analysis of BAD runs • criteria are common but not yet consistently adopted The hope: • The Muon system has enough redundancy to assume that bad information from a fraction of the system would hardly affect the quality of the reconstructed muon. Subtle failures can however induce operational problems, e.g. at HLT level. Present thresholds on ‘good’ data certification: • DT: detector ON [based on HV and readout status; will reconsider once all relevant parameters are fully understood/stable (depends on calibration, statistics, experience)] • CSC: >75% of detector channels sending data • RPC: >95% of detector channels live guidelines @ https://twiki.cern.ch/twiki/bin/view/CMS/RFMCertRequirements History: of 343 collision runs in 2010: all certified GOOD by CSC and DT, 6 certified BAD by RPC (wrong config status in early March) CMS Week Bodrum

20. monitoring & certification issues • This activity will likely continue through the lifetime of CMS and might impinge on the DPG resources significantly • More quantitative than qualitative investigations will be needed in order to match the certification requirements to the evolving physics analyses needs. • resources are thin and will probably not increase much in the future • may be worthwhile to invest soon in a more automated workflow (CSC is already working on implementing an Expert System) strategy • A coordinated effort from all Muon DPGs • Failure criteria should be uniformed across all detectors (a nice attempt being proposed by TRK DPG) • Operation, DPG, and POG should perform regular reviews of the data certification criteria for physics analyses (establish coherent criteria between detector/data validation and validation of reconstructed objects) CMS Week Bodrum

21. system performances (at chamber level) This is where one starts putting together a coherent picture of the system behavior Some performance parameters are easily ‘monitorable’, others require complex analyses CMS Week Bodrum

22. chamber hit residuals and efficiency before <mean>=-0.004 after <mean>=0.05 DT - Distribution of hit-segment residuals before and after the correction to tTrig is applied RPC –high rechit efficiency (~94%) for all chambers in both barrel and endcap RPC barrel ~94.2% RPC endcap ~93.6% CMS Week Bodrum

23. Data Mu PD MC ppMuX Data Mu PD MC ppMuX pT>3 GeV pT GeV/c h chamber segment efficiency • CSC • T&P using single-m • High quality GM with pT>10GeV • use non m-triggered data sets • Interpolation from a shadowing chamber enabling the m-ID of the GM • Longer term: T&P from Zmm ring gaps • Ex: ME1 reco-segment efficiency using extrapolated TTwith a matched segment in ME2 (tag) is well above ~95% CMS Week Bodrum

24. - MB1 - MB2 -MB3 - MB4 One TP matched to a reco segment at same BX Two TP matched to a reco Global m at same BX trigger primitives efficiency Enters all muon trigger efficiency calculations: L1 = TP + Track Finder DT • TP eff. wrt reco segment ~95% (better than in TDR) • MB4 will improve after deployment of new timing constants • DTLT eff. wrt Global m ~92% (input to DTTF). • Comparison to MC underway (new MC sample with proper DTLT emulator) minimum pT requirement to reach MB2 CSC • readout requires Pretrigger (complicates measuring TP efficiency in unbiased way) • Select TT, tag a segment in ME2, interpolate and require a matched TP (LCT) in ME1 waiting for plots CMS Week Bodrum

25. local reconstruction The ‘building block’ of offline and HLT m-reconstruction CMS Week Bodrum

26. rms=2.2ns muon time at vertex [ns] rms=2.9ns DT Onia skim old constants new constants pT > 10 GeV/c c2/dof muon time at vertex [ns] local reconstruction Local reconstruction algorithms for rec-hit and segment building have been quite stable. Nevertheless, there is scope for improvements (both in offline and HLT). Refinement and development must be maintained as critical DPG tasks in addition to standard code maintenance and release validation. • We have already seen the beneficial effects of the newest calibration on the quality of the reconstruction • CSC • Rechit Timing alignment is corrected offline with conditions data (from 3.8.X) • Track resolution for global muons (pT>7.5 GeV/c) using only CSC hits is ~2.2 ns • DT • Effects of new calibration constants on standalone muon reconstruction (from 3.8.X) CSC MinBias PD CMS Week Bodrum

27. local reconstruction cont. Additional activities are underway: CSC • First data uncovered a number of problems related to the ganging of strips in ME1/1a, which have been fixed. • Rechit errors have been re-tuned based on real data • Rechit building currently does not make use of strip noise correlation matrix (obtained from CSC electronics calibration procedures) • Include Anode timing in hit reconstruction (already very useful for trigger synch). • Recent issues: • Special Triggers (activity triggers) for both operations tests and performance studies have proven to be very useful. Need to discuss further needs • Nice proposal to skim “golden muons” off Z and W decays (preserving the raw information) for testing new reconstruction algorithms and/or validate sw developments (strongly encouraged by Muon DPGs) CMS Week Bodrum

28. muon performance plots • Many excellent results from analyses of collision runs and comparison to simulation have been presented and are available for public use. • Should plan to report the recent progress in a series of specific notes (DPS), and aim at producing one note summarizing the Muon system performance (CSC, DT and RPC combined) • A public page exists where all approved results (including Muons) are kept for general use (see ‘overview’ of the plots in the appendix) https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResults CMS Week Bodrum

29. muon simulation CMS Week Bodrum

30. RelValSingeMuPt10 3_8_1 RelValSingeMuPt10 3_8_2 Standalone muons simulation status and plans Several performance plots are confirming the good low-level (hits, segments) agreement between reconstructed data and simulation (some plots in appendix) • There is an effort to produce a more realistic MC with time-dependent detector conditions • DT - Startup MC constants were based on the knowledge of performance from cosmics data (smeared vDrift and tTrig). It turned out that the assumption was too pessimistic (~600mm)! • From 3.8.X a constant vDrift (like on data) and a smeared tTrig are used • CSC - Already uses realistic calibration constants and ‘bad channels’ information in order to properly simulate digis, but pick ‘typical’ sets for a given simulation production, rather than being able to match time-dependent variation • CMSSW does not yet have the infrastructure to allow use of IOV-dependent conditions data, appropriately weighted by luminosity, etc • Muon DPGs agrees with the proposal from DPG coord. to adopt run-by-run conditions data to follow the detector status (discussion just started!) CMS Week Bodrum

31. other simulation achievements and plans CSC • Pretrigger readout condition has been implemented in simulation (in DigiToRaw) • Work is underway to cross-check timing from simulated collision at t=0 to simulated electronic pulses on strips and wires. Electronics pulse-shaping and amplification are modelled quite well. But full cable length delays are not simulated, therefore offsets are required to match real data. • Geometry description is being reviewed after some minor inconsistencies between software description and reality have been noticed. (e.g. ME2/2 active gas volume for simhit generation is about 0.4% too small) RPC • RPC efficiency and cluster size are estimated from data using DT/CSC segment extrapolation or reconstructed muons • Dead and masked strips are monitored run by run but still not in DB. All the software infrastructure is ready to handle them. • Data collected are now enough to produce efficiency table chamber-by-chamber and new condition DB tags should be available soon • Cluster size is at the moment modeled as a function of the local impact point on the strip. Present data will be used to model it as function of slope as well CMS Week Bodrum

32. short term issues CMS Week Bodrum

33. muon system readiness for HI • CMS muon acceptance complementary to ALICE  unique data • Expect muon rates not substantially higher than in 7 TeV pp collisions • Truly high multiplicity events should be ~1% of all HI collisions (head-on b=0) • DT, CSC, RPC checked for • Multiplicity (x4 increase in CSC) and occupancy (mostly fw and in ME1/1) • Readout volumes for an interaction rate of ~400Hz CSC CSC • Current progress: • Cross check HI simulations • CSCTF limit in heavy ion? but current plan is to use MinBias trigger • HI physics reach (in mm): • ~50 Z0 (S/B=20): first measurement in HI ever, fast, insight on PDF modifications • ~150 U (S/B=0.1): CMS resolution should allow S-state separation for the first time in HI • ~1500 J/Y (S/B=1): investigate suppression/regeneration in HI ? • Muon contacts : [dilepton]/DT Catherine Silvestre, CSC Jorge Robles, RPC Hyunchul Kim CMS Week Bodrum

34. CSCTF performance in HI run CSCTF emulator CMS Week Bodrum

35. Longer term issues CMS Week Bodrum

36. neutron background • Long-lived neutrons created, diffuse around collision hall • They get captured by nuclei, emitting a photon • Compton scattering or photoelectric effect makes MeV electrons, which cause hits in muon chambers CMS Week Bodrum

37. simulation of neutron bck in muon system QGSP_BERT_EMLSN 37 • Hard to simulate but well advanced • Live up to 1sec before making a signal; simulation is slow • Can’t be treated like ordinary MinBias PU because many BXs in the past can contribute • Solution for neutron hits in muon systems: • Reset n-hits time into a BX-wide interval, preserving hit time ordering • Sample: add n-bck to signal + MinBias PU • Should get the correct BX occupancy, assuming steady-state running • Looked at different GEANT simulation models • Predicted n-hit production rates vary by up to x4 in some CSC stations • More validation and understanding is needed • Some observations: • Good agreement with TDR n-hits fluxes predictions in CSC for QGSP_BERT_EMLSN • CSC and DT have many low energy hits from secondary interactions; RPC are less sensitive • YE4 shielding: reduces n-hit occupancies in ME4/2 by more then x4 CMS Week Bodrum

38. MinBias neutrons something to worry about? @ L=10E34 • Rates in barrel ~10 times lower than in endcaps • Neutrons leave hits in 1-2 layers most of the time. Multi-layer systems (CSC, RPC) are protected by design. • Need to check RPC rates with proper (double-gap) geometry • May affect rate of CSC pretrigger requirement (>=3 layers) and marginally the LCT (>=4 layers) and CSCTF rates Plans • Trigger study: special run with 1-layer (instead of 4 out of 6) CSC L1 trigger. Measure ‘prompt’ and ‘non-prompt’ n-components. Expected single rate ~600kHz! • Then offline study rates at DIGI level, Trigger Primitives and GMT • Extend the configuration for HI sim TDR geometry with YE4 CMS Week Bodrum

39. Summary and outlook • The Muon DPGs and the Operation teams have been very effective in delivering high-quality data during the startup phase. This has been possible thanks to meticulous commissioning, efficient operation and systematic optimization of the system. • The next step is to aim at a gradual improvement of the performances through a deeper, more quantitative and systematic investigation of all aspects of the system response. This will require a revived effort and improved integration of the Muon communities. The Muon DPG is an appropriate forum. • It also require a more efficient vertical coordination with POG, TPG and PAGs. • We begin to lack manpower due to increased focus on physics, which certainly provides enormous motivation and visibility (see ICHEP), at the expense of decreased interest in DPG-level detector studies and detector operation and monitoring. • The highest priority is to reach and maintain excellent detector performances and deliver the best data, not just for 1 or 2 years but for the next 20 years or so. This will be challenging and will require considering such type of aspects, including revisiting the specific charges of the DPGs. CMS Week Bodrum

40. appendix CMS Week Bodrum

41. RPC InterventionsDuring Technical Access • CMS UXC announced as conventional zone on 20.Nov.2009. 49 CMS Accesses ever since • RPC has used 26 of them or 53% of CMS TA • RPC has requested 36 WP in those 26 TA • 17 crucial WP with effect on the RPC performance • 19 WP with no impact on the RPC performance • No CMS downtime due to RPC hardware failure • No special/urgent call for access due to RPC hardware failure • 10.76% of total detector channels would have been lost if CMS UXC access has not taken place CMS Week Bodrum

42. Work Packages by EMDb system CMS Week Bodrum

43. CMS Week Bodrum

44. CSC Segment efficiency using MinBias MC MinBias pT spectrum of TR-muons in IhI>0.9 Single muons no tag Single muons with ME2 tag CSCreconstructed segment efficiency from TM to segment matching CMS Week Bodrum

45. CSC approved plots • Good agreement between Minbias data and Minbias simulation • Excellent timing results CMS Week Bodrum

46. DT approved plots BX distribution for best TP Average of BX distribution for best TP CMS Week Bodrum

47. RPC approved plots CMS Week Bodrum

48. CMS Week Bodrum

49. r-z neutron hits heatmap Endcap in currentgeometry TDR geometry with YE4 49 CMS Week Bodrum

50. PU in CSC system • Expect irrelevant rate of pile-up given that CSC is a “sparse” detector (negligible fraction of events overlap) • CSC uses “dynamic” pedestals for the cathode readout (at high rate pedestal are expected to float) – with some penalty price on the chamber resolution (larger error in measured charge due to larger electronic noise contribution) CMS Week Bodrum