Commissioning of the CMS Detector

Transcription

1 Commissioning of the CMS Detector Marina Giunta INFN Bologna On behalf of the CMS Collaboration XLIVth Rencontres de Moriond on QCD and High Energy Interactions La Thuile,14-21 March 2009

2 2008: very busy year! Muon (DT+RPC) HB HE HF Tracker First LHC Beams Few hours between 10 th -19 th Sep CRUZETs (Cosmics RUn at Zero Tesla) Between May and Aug 2008 CRAFT (Cosmics Run at Four Tesla) Oct-Nov 2008 Weekly Global Runs ECAL Common data taking, with all available subdetectors All Available Weeks until Christmas Break! DT: Drift Tubes Chambers CSC: Cathode Strips Chambers RPC: Resistive Plate Chambers ECAL: Electromagnetic Calorimeter HB: Barrel Hadronic Calorimeter HE: Endcap Hadronic Calorimeter HF: Forward Hadronic Calorimeter M.Giunta 2

3 CMS % CMS Progress Chart Subdetectors joining GLOBAL data taking With exception of some parts of RPC, all CMS detector and trigger system ready for LHC ALL CMS with exception of ½ RPCE CRUZET 1 First cosmic muon triggers underground M.Giunta 3

4 Cosmics Events Collected in M events ALL CMS except ½ RPCE Ran 4 weeks continuously 19 days with B=3.8T Some >15hr long runs 370M events collected in total 290M events w B=3.8T (194M with all components in) M.Giunta 4

5 Different event topologies Analyzed events spanning 5 orders of magnitude in muon multiplicity! Illustrates versatility and robustness of detector and software Muon track reconstructed in the various subsystems Segments reconstructed in the Muon system Hits recorded in Muon System and Calorimeters Muon System ECAL Tracker Tracking systems OFF HCAL Cosmic / Beam Halo O(1) muon Cosmic Shower O(10-100) muons Beam splash event O(10 5 ) muons M.Giunta 5

6 Cosmic Event Example HCAL Tracker ECAL DT CSC µ + bending in 3.8T Magnetic Field M.Giunta 6

7 Sector Cosmics Events: Efficiencies MB4 MB3 MB2 MB1 DT Muon Chambers Tracker (TIB and TOB) Track hit finding efficiency of TIB and TOB layers (modules not in operation excluded) 100% in almost all Superlayers few (temporary) disconnected channels M.Giunta 7

8 Wheel -2 Sector 4 Cosmics Events : Muon Barrel Resolution Residuals = x Track x RecHit Data MC Resolution σ~ μm B field degrades MB1 in wheels +/-2 MB4 σ=210µm MB3 σ=225µm MB2 σ=237µm Reasonable agreement between data and MC MB1 σ=258µm M.Giunta 8

9 Tracker Alignment with Cosmics Track-based Alignment Algorithms (including survey constraints) χ 2 Minimize function that depends on the residuals HIP (Hits and Impact Point): local iterative method MillePede: global method, accounting for global correlations Mean of residual distributions Sensitive to module displacements PIXEL TIB RMS=47mm TOB RMS=26mm RMS=28mm M.Giunta 9

10 Cosmics Events: Calorimeters ECAL Stopping power data total stopping power in PbWO4 collision loss bremsstrahlung p measured in the tracker de/ρdx energy deposit matched to the track corrected for muon path length - statistical error shown correct tracker momentum scale correct energy scale in ECAL - calibrated with electron at test beams HCAL Energy (200K events) (15K events) good agreement with MC good agreement with test beam results - p =150 Gev, HBE = 2.8 GeV M.Giunta 10

11 Cosmics Events: B Effect Example: Drift Velocity V drift in Muon DT Chambers Due to B field, particles travel longer paths Consequence is a smaller effective v drift Innermost stations (MB1) on outer wheels have largest radial field M.Giunta 11

12 Physics Results: Angular Distribution ξζ-plane: normalized to unity p projection Reconstructed angles of cosmic rays indicate increased acceptance through the access shafts of CMS M.Giunta 12

13 Beam-Halo LHC Beam: Event Types Beam protons interacting with Beam Gas µ passing throuh both CSC endcaps and hadron calorimeter Beam-Splash Beam protons interacting with LHC collimators Hundreds of thousands of µ passing through CMS Energy deposits in HCAL shown debris ~2x10 9 protons on collimator ~150 m upstream of CMS M.Giunta 13

14 Beam Halo Hit Distribution in CSCs YE- (Negative Yoke Endcap) ME 1 ME 2 ME 3 ME 4 CSC Sectors LHC Beam2 passes through CMS from negative to positive z M.Giunta 14

15 LHC Beam captured LHC Beam captured LHC Beam-Halo Events (I) Endcap Muon Chambers (CSCs) Halo Trigger Rate in YE- vs time rate jumps preceding capture due to earlier capture attempts Beam-Halo µ Angles of reconstructed muon tracks Cosmic µ Arbitrary normalization of blue and black histograms (meant to guide the eye) M.Giunta 15

16 Energy LHC Beam-Halo Events (II) Endcap Hadron Calorimeter (HE) BEFORE AFTER HCAL Endcap Energy BEFORE the RF capture, energy deposits due to not-focalized beam AFTER the RF capture, the beam is quite clean Forward Hadron Calorimeter (HF) Events triggered by the HF from LHC Beam 2 Peak in energy deposition towards positive pseudorapidity is a signature of beam-gas interactions near or within the detector η M.Giunta 16

17 LHC Beam-Splash Events Recunstructed energies up to 170 TeV! Hundreds of thousands of muons through the detector! HCAL E vs ECAL E DT MB3 Hits vs ECAL E Linear Correlation between reconstructed energies in HB and EB Muon Chambers or calorimeter? M.Giunta 17

18 Conclusions And Future Plans CMS is ready for LHC Collisions! Several tests (CRUZET, CRAFT, LHC Beam) confirm our subdetectors work as expected! More runs (a long one with field ON) during the summer CMS Commissioning 2009 The new schedule foresees first beams in the LHC at the end of September this year, with collisions following in late October. A short technical stop has also been foreseen over the Christmas period. The LHC will then run through to autumn next year, ensuring that the experiments have adequate data to carry out their first new physics analyses and have results to announce in 2010 Mar Apr May Jun Jul Aug Sep Oct Weekly Global Runs CRUZET5 CRAFT09 CMS Ready For Beam M.Giunta 18

19 Backup Slides M.Giunta 19

20 Cosmic Shower Events 0.02% rate of events with >100 segments in ~10M cosmic events at 0T Event-by-event spread in phi compatible with multiple scattering all events compatible with ~parallel muon shower M.Giunta 20

21 CRAFT Data Acquisition & Distribution Trigger DAQ Level-1 triggers from all muon detectors (DT, CSC, RPC) and calorimeters (ECAL, HCAL), Hz cosmics rate Calibration/test triggers at ~100Hz (in abort-gap), mixed-in Deployed HLT (High-Level Trigger) filtering, streaming, test of startup trigger menu, timing High-rate tests: 60kHz random triggers to stress-test the readout Data Flow Real-life data flow to the CAF (CMS Analysis Facility) and Tier-0,1,2 s From T0 T1:average ~240MB/s transfer rate Data Quality Monitoring & prompt reconstruction at Tier-0 on ALL data M.Giunta 21

22 Data Handling Tests (Simulated Data) Full scope of data handling and analysis activities successfully tested Detector Commissioning Feb Mar Computing & Software DAQ CERN CRUZET1 CRUZET2 CRUZET3 CRUZET4 LHC Beam CRAFT Apr May Jun Jul Aug Sep Oct Nov CCRC/iCSA08 CCRC08A (Common Computing Readiness Challenge of 2008) LHC-wide computing scale test of the Tier-0/Tier-1/Tier-2 infrastructure Workflows closely resembled those needed for actual data taking CSA08 (Computing Software and Analysis challenge of 2008) Complete & deploy physics analysis tools, calibration & alignment World All the major objectives achieved within the pre-defined 4 week schedule M.Giunta 22

23 CSC Alignment with Beam-Halo Muons Select tracks that pass through overlap of two chambers Determine relative position by requiring consistency between track segments rφ position φ z : rotation in layer s plane φ y : rotation around alignment pin axis Solve system for all chambers in a ring (must be consistent with a circle) Cross-check against Photogrammetry (210 μm rφ, 0.23mrad φ z ) Chamber-by-chamber difference w.r.t. PG before and after alignment with tracks Track based alignment accuracy: 270μm rφ, 0.35mrad φ z achieved with 9 min of LHC beam! (33k ev in one YE- overlap regions) M.Giunta 23

24 Some consequences if LHC s=10tev Higgs search (WW* and ZZ* combined) σ Bkgd decreases less than σ Higgs loss of a factor of a factor 2 in luminosity with roughly ~200 pb -1, reach sensitivity for a SM Higgs with m H ~ GeV (comparable to the current Tevatron sensitivity) Discovery potential for new resonances (Z,W,...) M z (TeV) s(14 TeV) / s(10tev) pb -1 : good chances to discover Z bosons at M Z = 1 TeV Integrated luminosity needed to reach 5σ significance M.Giunta 24

25 Momentum Resolution Muon System contribution becomes important for µ with p T > 200GeV M.Giunta 25

26 Energy Resolutions ECAL Energy Resolution Jet E T Resolution Stochastic Noise Constant Test Beam Result Jets reconstructed with cone algorithm (R=0.5) M.Giunta 26