1. Marcello Bindi, on behalf of ATLAS Collaboration KRUGER 2010 : Workshop on Discovery Physics at the LHC 06/12/20101

2. 2 Marcello Bindi - University and INFN of Bologna - Kruger2010 25 meter of diameter, 44 meter length including also the End-caps Three large super- conducting air-core toroidal magnets (2~6 T· m) Weight : 7000 tons x y z 06/12/2010

3. Muon : promising probe for new physics - clean signature of final states with muons over largest possible solid angle is crucial for physics at LHC - H  ZZ*  μμ ll, A  μμ, Z’  μμ … - required mass resolution: Δ m/m < few % Marcello Bindi - University and INFN of Bologna - Kruger2010 3 H  ZZ*  μ + μ − μ + μ − Challenging issues for Muon Spectrometer  Trigger Selectivity : – select muons (p T > 6 GeV) from interaction point – identify interesting events with 25 ns accuracy  P T resolution: 3~4% up to p T = 100 GeV, 10% for p T ~ TeV.  Charge identification for p T ~ TeV. 06/12/2010

4. Marcello Bindi - University and INFN of Bologna - Kruger20104 ~ ~ p p p p 06/12/2010

5. 5 Monitored drift tubes MDT (barrel + end-cap) | η | < 2.7, 370k ch, 6 multi layer Thin Gap Chambers TGC (end-cap) 1.1 < | η | < 2.4, 440k ch, 7 layers Cathodes Strip Chambers CSC (forward) Resistive Plate Chambers RPC (barrel) | η | < 1.1, 360k ch, 6 layers Precise spatial measurements Trigger and Readout 2.0 < | η | < 2.7, 31k ch, 4 layers Marcello Bindi - University and INFN of Bologna - Kruger2010 06/12/2010

6. 6 Marcello Bindi - University and INFN of Bologna - Kruger2010 Fast trigger chambers: RPC(barrel) TGC (end-cap) Precision chambers: MDT (barrel and end-cap) CSC (forward region) Toroidal magnetic field of 0.5 T: barrel and two end-cap toroids complex field ATLAS 06/12/2010

7. 7 Marcello Bindi - University and INFN of Bologna - Kruger2010 Trigger: RPC + TGC  Bunch crossing period: 25 ns @ LHC  Trigger chamber time resolution < 10 ns  p T is estimated by on-detector electronics, according to Δ R w.r.t infinite momentum line.  p T thresholds cab be adjusted: from 6 to ~ 40 GeV Precise P T measurement (MDT+CSC)  Measure magnetic deflection by toroidal field  3 planes of precision chambers: Barrel: 3 point sagitta measurement Endcap: point-angle measurement  p T = 1 TeV ; 500 μ m sagitta  50 μ m point resolution needed 06/12/2010

8. 8 Marcello Bindi - University and INFN of Bologna - Kruger2010 99.7% of channels working during pp data taking (out of 341K tubes) 0.2% lost forever (i.e. broken wire or not accessible anymore) 0.1% to be fixed in X-mas 2011 or later shutdowns Detector coverage : 100% 06/12/2010 Drift time spectrum in the ATLAS MDT chambers. Space time relationship of the ATLAS MDT chambers.

9. 9 Marcello Bindi - University and INFN of Bologna - Kruger2010  Status of non active Gas Gaps unchanged since several months:  1% (out of 3592) disconnected from HV due to broken gas inlets; not accessible anymore  0.6 % disconnected from HV due to excessive gap currents; recoverable during winter shutdown  HV connectors: About 1 failure/10 days (quickly replaced) ; anyway no holes thanks to trigger redundancy  replacement of all connectors already planned Trigger coverage : 99.7 %  1 trigger tower (out of 404) 06/12/2010 The plots show the Eta and Phi view coincidence of Low/High Pt RPC trigger hits.

10. 10 Marcello Bindi - University and INFN of Bologna - Kruger2010  Detector : 98.4% fully operational   50KHz max Level1 (L1) trigger rate (100KHz after Dec.)  HV Trips when Luminosity steps up (most recovered within 24h)  Maintenance foreseen during next winter shutdown. TGC, timing optimization Trigger coverage : 100.0 % 06/12/2010

11.  Detector operational the entire year at 98.5%  Maximum output rate sustainable ~ 70 kHz  1% data loss due to errors (it will be fixed in December) Marcello Bindi - University and INFN of Bologna - Kruger20101106/12/2010

12. 12 Marcello Bindi - University and INFN of Bologna - Kruger2010  Stable running conditions during 2010:  Muon detectors “running efficiency” almost 100% during STABLE beam periods with DAQ running.  Very good working fractions.  Operational developments: 4 sub-detectors have unified their procedures, user interfaces and shifters since the begin of September the HV operations related to LHC beam conditions (injection …) are automatic.  From February one single shifter will supervise the 4 sub-detectors. 06/12/2010

13. Marcello Bindi - University and INFN of Bologna - Kruger20101306/12/2010

14.  L1 custom hardware  Require coincidence in eta phi view.  P T estimation based on geometrical roads.  Road definition and time alignment commissioned.  HLT software  L2: Pattern recognition  EF: Full muon reconstruction available  L1, L2 and EF commissioned and used for active rejection. 14 RPC TGC Marcello Bindi - University and INFN of Bologna - Kruger201006/12/2010

15.  Efficiency determined by looking at  Inclusive muons relative to offline.  Tag & Probe method on J/Psi and Z events.  Trigger Efficiencies at L1  barrel 75%  end-cap 95%  Rel. Trigger efficiencies at HLT  L2 >98%  EF >98% 15 L1 efficiency, T&P with J/Psi Barrel + End-capsL1 efficiency, inclusive muon BarrelEF efficiency, inclusive muon Barrel + End-caps Marcello Bindi - University and INFN of Bologna - Kruger2010 p T > 4 GeV 06/12/2010

16.  Measured L1 trigger rates as a function of the instantaneous luminosity for different L1 thresholds.  Extrapolation to higher luminosity based on rates measured with data  fundamental for the trigger strategy.  The steps are due to different filling schemes changing the contribution of cosmic radiation to the trigger rate. 16 Marcello Bindi - University and INFN of Bologna - Kruger2010 Allocated rate 06/12/2010

17. 17 Marcello Bindi - University and INFN of Bologna - Kruger201006/12/2010

18. Objective: Muon identification in a wide momentum range from GeV to TeV. Make use of all detector components and use different strategies:  Muon Spectrometer Standalone (MS) reconstruction  MS and Inner Detector (ID) combined fit  Outside-in  Inside-out  Statistical combination  Taggers  ID track is matched to MS segments  ID track is matched to a MIP in calorimeter 18 Marcello Bindi - University and INFN of Bologna - Kruger201006/12/2010

19. 19 Marcello Bindi - University and INFN of Bologna - Kruger2010 Di-muon invariant mass spectrum for 2010 full data, from fully combined opposite sign muons. Event Filter applies a p T cut at ~15 GeV, which for consistency is reconfirmed offline for one of the two inner detector-muon spectrometer combined tracks (the other one is required to pass a p T threshold of 2.5 GeV). 06/12/2010

20.  Select events with ID tracks traversing MS barrel.  Look for MS track in  top hemisphere (p ID > 5 GeV)  bottom hemisphere (p ID > 9 GeV)  Measures reconstruction efficiency of MS conditional to a L1 trigger. 20 Turn on curve: Good agreement between Data and MC Average efficiency: 97.4 ±0.1 % 95.2 ±0.1 % ATLAS Preliminary 2009 Cosmic Data ATLAS Preliminary 2009 Cosmic Data Marcello Bindi - University and INFN of Bologna - Kruger201006/12/2010

21. 21 Marcello Bindi - University and INFN of Bologna - Kruger2010 06/12/2010  Use independent algorithms to assess reconstruction efficiency.  Tag and Probe studies are under preparation with J/Psi and Z.  First results from Z will be available soon.

22. Muons from light hadrons (“non-prompt”)  Decay within the ID volume  Hadron and the secondary muon are reconstructed as one track  momentum mismatch of ID and MS P T Muons from heavy flavour (“prompt”)  Secondary muon produced close to IP  ID and MS measure the muon track. Discriminate by “loss momentum” fraction between MS and ID p T measurement: Use templates derived from MC to determine fractions of “prompt” and “non-prompt” secondary muons. 22 K 0 s ->     J/  ->     ID barrel 06/12/2010 Marcello Bindi - University and INFN of Bologna - Kruger2010

23.  Fraction of prompt muons determined in bins of p T and eta.  MC and data agree within uncertainties  Dominant systematic uncertainties:  template shape at low p T  MC flavor content at high p T 23 ID barrel ID end-cap 06/12/2010 Marcello Bindi - University and INFN of Bologna - Kruger2010

24. 24 Marcello Bindi - University and INFN of Bologna - Kruger201006/12/2010

25. 25 Marcello Bindi - University and INFN of Bologna - Kruger2010 Muons from Barrel Region 06/12/2010

26. Marcello Bindi - University and INFN of Bologna - Kruger2010 26  Calibration  Precise r-t relations  Precise t0 values  B field corrections to r-t relations  Objective to reach a MDT hit resolution < 100 μ m  Alignment  Improved alignment in few chamber (End-cap)  Use of Toroid off data  Cross checks using high P T tracks  Magnetic Field - Use of Asymmetric B field map  Results analyses from J/ ψ, W and Z 06/12/2010

27. Marcello Bindi - University and INFN of Bologna - Kruger2010 27 barrel alignment ±50  m (large sectors) ±100  m (small sectors) end-cap alignment ±45  m Goal of the alignment: 300 GeV  Optical alignment system Barrel: relative End-caps: absolute  Data with toroidal B-field off. Momentum from inner detector  Measure alignment with straight tracks. 06/12/2010

28. Z  µµ in the Barrel region Using the Muon Spectrometer and Inner detector Fit using the following function: Z Breit-Wigner with γ - interference convoluted with one single gaussian resolution function with σ Z 28 Marcello Bindi - University and INFN of Bologna - Kruger201006/12/2010

29. 29 Marcello Bindi - University and INFN of Bologna - Kruger2010  Oppositely charged Muon pairs with p T >20 GeV  Track isolation cut: Σ (p Ttracks ) in a cone ( η, Ф ) of radius < 0.4 is < 0.2 p T µ  | η 1, η 2 |<1.05.  EF triggers used: 10 GeV threshold and 13 GeV for higher luminosity.  Monte Carlo prediction using Pythia-generated Z->µµ events. 06/12/2010

30. Marcello Bindi - University and INFN of Bologna - Kruger20103006/12/2010

31.  Muon detectors have been very stable and fully operational during the whole 2010 data taking.  Performance of detector, trigger and reconstruction have been studied with first data and cosmic events.  Overall performance very close to detector design!  Good agreement between data and MC. Some improvements will be following soon, specially in resolution studies.  Many more results soon to come with the full amount of available data set.  Big expectations from 2011 data taking with higher luminosity! 31 Marcello Bindi - University and INFN of Bologna - Kruger201006/12/2010

32. 32 Marcello Bindi - University and INFN of Bologna - Kruger201006/12/2010

33. Marcello Bindi - University and INFN of Bologna - Kruger20103306/12/2010

34.  Trigger efficiency of L1 muon for the lowest threshold MU0 as a function of the offline muon p T obtained with a tag and probe method on Jpsi candidates using combined muons for both the tag and probe tracks. Events are required to have passed the L1 MinBias trigger and a muon EventFilter confirmation. A reconstructed primary vertex with at least 3 Inner Detector (ID) track is required in each event. Muon combined tracks in the eta range [- 2.4,2.4] are required to match with a reconstructed primary vertex with z < 10 mm. Only muons associated with ID tracks that have at least one hit in the pixels and six in the SCT are accepted.MinBiasEventFilter  The Jpsi candidates have been selected asking for two opposite sign muons and with angular distance 0.4<DR<2.0 and with an invariant mass window between 2860 MeV and 3340 MeV. The tag and probe method has been applied matching the combined muons to muon trigger RoIs using the geometrical criteria DR<0.4. L1 triggers found within +- 3 BCs are included in the efficiency calculation as the RPC L1 timing is not yet fully commissioned. The used data sample corresponds to an integrated luminosity of about 210 nb -1.MeV RoIs Marcello Bindi - University and INFN of Bologna - Kruger20103406/12/2010

35. Marcello Bindi - University and INFN of Bologna - Kruger201035 Efficiency of the L2 muon trigger combining muon spectrometer and inner detector information wrt to the L1 muon trigger as a function of the transverse momentum pT from offline reconstructed combined muons. A cut at L2 is applied to retain muons with pt>4GeV. 06/12/2010

36. Marcello Bindi - University and INFN of Bologna - Kruger201036 Big improvement with first few pb-1 in RPC timing RPC is now close to have 100% events in right BC on both, Low and High pT trigger. TGC almost there since the beginning of 2010 data taking.