1. The ATLAS Muon Landscape towards a common Muon Reconstruction Rosemarie Aben, Peter Kluit, John Ottersbach, Egge van der Poel, Marcel Raas, Nicole Ruckstuhl, Giuseppe Salamanna*, Antonio Salvucci, Rikard Sandstrom* Atlas NIKHEF Outing Hindeloopen 18 May 2011 1 * left us

2. Overview - Description of Combined Muon algortihms - Towards a common Muon – combined – reconstruction NIKHEF’s contributions Current understanding of the Muon Spectrometer data - Efficiencies - Fake rates -> Nicole - Momentum resolution -> Antonio - Material in MS -> Rosemarie - Magnetic Field Topics J/psi efficiencies, rates, Z efficiencies, momentum Studies, B field, muons for physics and conclusions 2

3. Muon algorithms Muon StandAlone algorithms: Moore output: Muon segments and Muon tracks Muonboy output: same - SA muon == muon extrapolated to IP: MuidSA Muonboy - Combined muon: input ID tracks and Muon tracks Full refit MuidCB and statistical combination Staco - Segment tagged muon: input ID tracks and segments MuTagIMO and MuTag (only I/M no CSC stations) - MuGirl muon: input ID tracks and MS hits MuGirl refitted or tagged muons - Calorimeter tagged muon: input ID tracks and E deposits: CaloTag and CaloLR 3

4. Muon algorithms ◦ Moore/Muid runs in the trigger 4 MuidStaco CombinedMuidCBStacoCB RefitMuGirl TaggedMuTagIMO/MuGirlMuTag SAMuidSA/MooreMuonboy Muon reconstruction task Force lead by David Quarrie - Group that discussed a strategy to combine the two muon reconstruction programs Moore and Muonboy - Produced a document with recommendations and a path - New code has been written for a common C++ programme - Modules will be ported to C++ or wrapped - Current situation is that in release 17 this code will be available and compared to the standard algorithms

5. Towards a common - combined - muon reconstruction 5 It is clear that the combined reconstruction programms need to follow this up: - Discussed in the MCP developers meeting - Foresee extension of the Muon object to hold e.g.: - simultanuous results from a fit and a statistical combination - scattering and curvature significance (pi/K suppression) - Further integration and speed up by running from extrapolated ID tracks NIKHEF’s input into all this: - Historically: provided large part of the code for Moore, muon combined fit (now part of Muid), MuTagIMO and the CaloTag

6. Towards a common - combined - muon reconstruction 6 Proposed NIKHEF’s input into all this: - Validation of the new reconstruction chain based on precise performance measurements Peter - Validation and cross check of the MS material services Rosemarie - Adaptation of the combined algorithms to the new structure: MuTagIMO and calorimeter taggers Antonio, Tatjana - Performance improvements (CPU/fake rate/efficiency) Peter, Tatjana - PhD students work is often for ATLAS qualification - For postdoc/staff we get OTP credits - Still possibilities available for Muon qualification work

7. J/ψ in the 2011 data 7 Using all Muid muons (MuidCB, MuGirl, MuTagIMO) Nice clean J/ψ peak -> dedicated triggers at work

8. J/ψ Efficiency Combined muons in 2010 data using Tag and Probe 8 From John

9. J/ψ Efficiency combined or tagged in 2010 data 9 From John

10. Rates of the Muid algorithms 10 Using all Muid muons (MuidCB, MuGirl, MuTagIMO) MuGirl and MuTagIMO add only little at high pT Convention added rate: MuGirl == what is added to MuidCB etc. etc. Learned: Fake rate mostly from pions/Kaons decaying to muons is small O(1%) at high pT Dominant backgrounds for high pT physics are muons from b/c decays.

11. Z in the 2011 data 11 runNumber 179710 Lumiblocks 584 bcids 236 runNumber 179725 Lumiblocks 213 bcids 219 runNumber 179739 Lumiblocks 144 bcids 220 runNumber 179771 Lumiblocks 92 bcids 323 runNumber 179804 Lumiblocks 396 bcids 336 runNumber 179938 Lumiblocks 99 bcids 326 runNumber 179939 Lumiblocks 301 bcids 331 runNumber 179940 Lumiblocks 19 bcids 322 using two MuidCB or two Staco CB muons Muid10347 Staco 9657 Similar results available from official MCP efficiency 2011 note

12. Z efficiencies T&P latest data runs 179710-940 12 MuidCB

13. Z efficiencies T&P latest data Staco run 179710-940 13 Staco CB

14. Z efficiencies T&P latest data run 179710-940 14 Muid Tight

15. Z efficiencies T&P latest data Staco run 179710-940 15 Staco Tight Why not flatter in barrel?

16. Efficiencies for 2010 Z release 16: MuidCB or MuGirl or MuTagIMO 16 or MuGirl refitted or MuTagIMO

17. Z mass reconstruction run 178044-179940 17 Using only Combined parameters Muid has better momentum resolution normalized to the same # Z events

18. Momentum studies B field 18 Using MuidCB muons dp/p = pID – pMS / pID remove EE SL and BE tracks Runs 178044-109 Symmetric Field Map (15/16) -> Asymmetric Field Map (16.6 all 2011 data)

19. Momentum studies: ID alignment 19 Using MuidCB muons q dp/p = q pID – pMS / pID remove EE SL and BE tracks Runs 178044-109 Misalignments ID: best plot up to now: Still endcap torque can be observed

20. Muons for physics analyses Important to apply ID MCP quality selection to get rid of badly reconstructed tracks and pi/K decays. High efficiency for Muid algorithms For high pT physics tight muons can be used Interesting to add SA muons for |eta|>2.5–2.7 Advantages of Muid over Staco ◦Higher efficiency for Combined muons 3% ◦Higher efficiency for tight muons 1% ◦Better data/MC agreement of efficiency vs eta ◦Better missing Et due to the fact that tight muons are used in MET ◦Better SA and CB momentum resolution for Zs by about 5% NB Staco applies tighter cuts; fake rates are a bit lower; pi/K decays are anyway small…For Muid additional cuts can be applied to get a similar fake rate. 20

21. Conclusions Muid algorithms are in great shape ◦Puzzling why SM group does not use Muid as baseline ◦Further improvements can be made Important steps are made to understand the puzzles in the data ◦Momentum resolution and material ◦Contribution of the magnetic field ◦Momentum resolution (and alignment) at high pT (and high eta) Important that ATLAS wil have a common Muon Reconstruction chain and a follow up of this for the Combined muons Basically ready for the new Physics that might be out there 21