28/2/2006S. Rosati - MC Workshop1 Muon Identification and Reconstruction Stefano Rosati INFN – Roma 1

28/2/2006S. Rosati - MC Workshop2 Muon Detectors for LHC Aspects of central relevance: Trigger: reduce the event rate from the initial 40 MHz to the ~200 Hz affordable by the event storage system –Organized over more levels, the first one has to operate a fast (<10 ns) choice and identification of the Region of Interest –Following levels process a limited subset of data (only from the RoI) with higher resolution and detail –Final level very close to offline reconstruction, running online on RoI data. Offline reconstruction: provide optimal muon identification and momentum resolution over the p T range GeV –Standalone reconstruction can exploit the cleaner environment of the muon system –Combination with inner tracking detectors to improve resolution

28/2/2006S. Rosati - MC Workshop3 ATLAS and CMS Experiements ATLAS: –3 Air-core Toroids (one barrel, two endcaps), mean field 0.6 T with excellent standalone capabilities – complemented by a 2T Central Solenoid) –Different bending planes for Inner Detector and Muon Spectrometer (  and  ) –Stringent requirements on tracking detectors resolution, calibration and alignment –Combined reconstruction gives optimal resolution in a certain momentum range CMS: –Muon Detectors in the return yoke of the 4 T inner solenoidal field –Resolution dominated by Multiple Scattering up to ~200 GeV p T –Combined reconstruction needed to achieve optimal resolution –Less stringent requirements on muon tracking detectors resolution, and on their calibration and alignment Two approaches for the two experiments:

28/2/2006S. Rosati - MC Workshop4 ATLAS Muon Trigger – LVL1 Uses dedicated detector system based on RPCs and TGCs Selection of events with muons above a given pT threshold (up to six programmable thresholds) Coincidence of hits in space (both  and  ) and time within geometrical windows in different trigger detector layers Barrel Trigger

28/2/2006S. Rosati - MC Workshop5 ATLAS – Level 1 Trigger Endcap Efficiency vs pT Threshold – acceptance up to |  |<2.4 Example trigger menus and final rates, after also LVL2 and Event Filter (for L= cm -2 s -1 ): 1  20 GeV, 2  10 GeV (40 Hz) 2  6 GeV (25 Hz) Valid for both Barrel and Endcap

28/2/2006S. Rosati - MC Workshop6 3 points angle-point Ribs sometimes angle-angle Ribs B~0 B B Initial layout angle-angle Muon Reconstruction in ATLAS

28/2/2006S. Rosati - MC Workshop7 ATLAS - Combined Reconstruction Tracks are back-extrapolated to the IP Parameters corrected for energy losses and multiple scattering Energy loss ~3 GeV at  =0 Look for match with tracks reconstructed in the ID Combined refit of the two tracks or: statistical combination of track parameters Inner Detector in a Solenoidal Field of 2 T. Detector acceptance Initial layout Combined reco efficiency

28/2/2006S. Rosati - MC Workshop8 ATLAS – p T Resolution  -Spectrometer Standalone: ~10%*p T  2 to 3% (p T in TeV) 150 X0 Calo Material: non-gaussian tails when back-extrapolated Inner Detector Standalone: ~40%*p T  1.5 % (|  |<1.9) ~200%*p T  3% (|  |=2.5) (p T in TeV) Combination dominated by the Inner Detector below the cross-over point ~40 to 80 GeV (20 GeV in forward region) Resolution vs p T

28/2/2006S. Rosati - MC Workshop9 ATLAS – p T Resolution Muon Standalone reconstruction in brief: - 10% resolution up to 1 TeV requires 50  m sagitta resolution - Single point resolution ~80  m (MDT tracker – r-t calibration needed) - ~25 measurement points over the 3 stations Alignment and calibration contribution becomes relevant above ~200 GeV Alignment through optical system + alignment with tracks (e.g. data with field off/on) required ~20  m alignment precision obtained during TB of a full-scale slice Contributions to the standalone resolution

28/2/2006S. Rosati - MC Workshop10 Low p T Muon Reconstruction Low pT muons (pT  5 GeV) do not reach the outer muon stations Extrapolate ID tracks and match with patterns of hits in the muon chambers p T (MeV)  =40 MeV Efficiency

28/2/2006S. Rosati - MC Workshop11 GeV ATLAS - Muon Isolation GeV H  ZZ*  4l Zbb tt Calorimeter Isolation - transverse energy ID Isolation,  pT Isolation energies in a  R = 0.2 cone Correlation between Inner Detector and Calo isolation ID vs Calo isolation

28/2/2006S. Rosati - MC Workshop12 ATLAS - Muon Isolation Mean value of the transverse EM energy vs cone size Low and High Luminosity Pileup

28/2/2006S. Rosati - MC Workshop13 Impact Parameter Signal Zbb tt Highest significance 2 nd Highest d0 significance in H  ZZ*  4l event selection Reject Zbb and tt backgrounds d0 w.r.t. primary interaction vertex fitted s=13  m Example:

28/2/2006S. Rosati - MC Workshop14 ATLAS - Cavern Background High background level expected in the ATLAS experimental hall Background particles originating from p+p  hadrons + interactions in: ATLAS shielding, forward detectors, machine elements Relevant for trigger (fake coincidences), reconstruction (pattern recognition), detectors ageing (~0.7 C/cm after 10 years LHC on MDT wires) neutrons53.94% photons43.15% electrons1.88% protons0.54% positrons0.21% anti-neutrons0.17% muons (+-)0.06% Cavern background composition Rates

28/2/2006S. Rosati - MC Workshop15 Cavern Background 10 keV Energy distribution Tracking detectors sensitivities to neutral particles - photons ~1% - neutrons ~0.1% Safety factors included in simulations to account for model uncertainties High rates of uncorrelated hits: e.g. at L=10 34 cm -2 s -1, safety factor 5, 30K hits in MDT chambers (~10% occupancy) Forward processes critical for the correct estimation of background production Propagation of low-energy  and n

28/2/2006S. Rosati - MC Workshop16 ATLAS - Performance H  ZZ*  4  (M=130 GeV)  =1.9 GeV Z   Muon Standalone  =3.0 GeV Z   Muon Combined  =2.5 GeV Mass resolutions for benchmark physics processes Z   fundamental to determine the detector mass scale with the first data, MS and MS-ID data Muon Combined

28/2/2006S. Rosati - MC Workshop17 CMS Muon System 4 measurement stations interleaved with the iron yoke slabs 4T field in the Solenoid Drift Tubes and RPC in the Barrel CSC and RPC in endcap, RPC coverage up to |  |=1.6

28/2/2006S. Rosati - MC Workshop18 CMS LVL1 Trigger Two independent and redundant systems DT+CSC or RPC, can be combined, together with calorimeters in a global trigger (GMT) Trigger coverage for single muons up to |  |=2.1 RPC Trigger will cover up to |  |=1.6 at the startup

28/2/2006S. Rosati - MC Workshop19 CMS Muon Reconstruction Tracks are reconstructed in the muon spectrometer and back-extrapolated to the inner silicon tracker GEANE package for the propagation through calo and coil material Combined refit with vertex constraint

28/2/2006S. Rosati - MC Workshop20 CMS Muon Identification Muon Compatibility Values for two algs: matching tracks with deposits in outer hadron calo matching tracks with patterns in the inner muon chambers, not used for a standalone track fit Cuts on discriminating values tunable for efficiency/purity Calorimeter MatchMuon Detectors Match

28/2/2006S. Rosati - MC Workshop21 CMS Muon Identification Reconstruction+identification efficiency for muons in b-jets (p T >5 GeV) Outside-in approach Inside-out approach (track in Inner Detector matched with muon hits)

28/2/2006S. Rosati - MC Workshop22 CMS - p T Resolution  q/p T ) for various momenta Standalone reconstruction Combined reconstruction

28/2/2006S. Rosati - MC Workshop23 CMS p T Resolution  p/p resolution in barrel and endcap

28/2/2006S. Rosati - MC Workshop24 CMS Muon Isolation b-jet muon rejection vs efficiency for W   identification Three independent isolation criteria: - Energy deposits in calorimeters - Hits in pixel detector - Tracks reconstructed in inner tracker

28/2/2006S. Rosati - MC Workshop25 CMS - Performance

28/2/2006S. Rosati - MC Workshop26 CMS - Performance Z  , reconstructed mass - 1 day of data taking at L= cm -2 s -1 - QCD background and pileup included Z’(1 TeV)   in three scenarios: - Ideal geometry - First data misalignment - Long term misalignment Alignment exploiting inclusive single muons with pT>40 GeV and Z  

28/2/2006S. Rosati - MC Workshop27 In conclusione: competenze italiane ATLAS-Muon (Bologna, Cosenza, Frascati, Lecce, Napoli, Pavia, Roma 1, Roma 2, Roma 3) –Trigger (Livello 1 barrel, Livello 2, Event Filter) –Calibrazione ed allineamento MDT –Simulazione del rivelatore, studi sul fondo di caverna –Ricostruzione standalone e combinata, online e offline, Analysis Software Framework –Analisi (Z+jets, H  ZZ*  4l, A/h   Susy searches ) CMS-Muon (Bari, Bologna, Napoli, Padova, Torino) –Trigger di Livello 1 con I DT –Simulazione/digitizzazione, trigger RPC –Ricostruzione, High Level Trigger, Analysis Software Framework –Analisi (H  WW  2  2, H  ZZ  2e2 , h  , WW scattering) Grazie a Ugo Gasparini per tutta la documentazione su CMS