Reconstruction status Content Particle tracking Track finding and reconstruction Primary vertex reconstruction Secondary vertex finding Pile-up removal with HLT Charged particle identification TPC dE/dx measurement ITS particle identification TOF particle identification HMPID particle identification 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status Tracking Status Development since last year We finish Kalman filter (version 2) of the tracker through ITS Reverse propagation - smoothing Tracking in TRD in the same way Connection to other outer detectors (TOF, HMPID, PHOS) General tracking strategy Track seeding starts in TPC outer pad rows uses rough (3cm) vertex constraint !(?) Kalman filter in TPC Kalman filter in ITS (use particle type hypothesis) two passes, with and without ‘real’ (50-100mm) vertex constraint Reverse filter go back through ITS and TPC (out-layers, smoothing) Bridge filter to TRD Extrapolation to other detectors 12 June 2002 Karel Safarik: Reconstruction Status

Tracking efficiencies TPC tracking efficiency (100% event size means dN/dy=8000) 12 June 2002 Karel Safarik: Reconstruction Status

Tracking efficiencies TPC+ITS tracking efficiency at dN/dy 8000 standard definition of good vs. fake tracks requires all 6 ITS hits to be correct most of ‘incorrect’ tracks just has one bad point when this definition is relaxed to 5 out of 6 hits the efficiency is better by 7 - 10 % (fake track probability correspondingly lower) 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status Tracking precision Momentum resolution dependence on magnetic field (high density) Including TRD the estimated improvement in Dp/p at high momenta will be 30 - 40% Dependence on particle density up to dN/dy = 4000 independent on density and corresponds to simple estimates above deteriorates - by factor 1.5 at the density dN/dy = 8000 TPC 2.4 1.2 8.5 5.8 TPC+ITS 1.6 0.7 3.4 1.4 magnetic field (T) 0.2 0.5 0.2 0.5 < pt > pt = 5 GeV/c Dp/p (%) 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status Tracking precision Momentum resolution estimate (at high density) TPC+ITS TPC+ITS+TRD Today the whole tracking chain TPC – ITS – TPC – TRD working 12 June 2002 Karel Safarik: Reconstruction Status

Electrons in Kalman Filter Bremsstrahlung recovery a la Delphi D.Stampfer at al. Comput. Phys. Comm. 79 (1994) 157 Later maybe to change likelihood function maximize the likelihood (the prediction end measurement are not correlated) L  exp [0.5 (An-1-A*n-1)T(V’n-1)-1(An-1-A*n-1)] x x exp [0.5 (M(An-1)-Mn-1)T(Cn-1)-1(M(An-1)-Mn-1)] 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status Primary vertex Correlation of two innermost pixel layers (without tracking) At beam axis sx = 15 mm sy = 15 mm sz = 5 mm 1cm off beam axis sx = 25 mm sy = 25 mm 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status Secondary vertices For the moment restricted inside the beam pipe Fiducial volume R < 2.5cm Tracks found during 2nd ITS pass (without vertex constraint) are prolonged inside beam pipe and opposite charged pairs are combined in attempt to find secondary vertices K0s and L added to full multiplicity events Results at B = 0.2T Position Mass Momentum Efficiency resolution resolution resolution K0s 200-300mm 6-8 MeV 1.5-1.8% 21-25% L 500mm 3-4 MeV 1.3% 15% Low efficiency mainly due to low reconstruction efficiency for secondary tracks, the loss due to vertexing itself only 1% 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status Secondary vertices K0s L 12 June 2002 Karel Safarik: Reconstruction Status

V0 and cascade production Clear signal at highest particle densities fiducial volume until now restricted to R<2.5cm statistics per event (until now)  7 K0s (however, for dN/dy=4000 will be the same)  1 L K0s L X- 12 June 2002 Karel Safarik: Reconstruction Status

Tracking – missing parts As of today seeding still use an approximate vertex constraint sigma is set to the size of beam pipe (3cm) Consequently we are tracking well primary tracks secondary tracks – but only ‘close’ secondaries In order to get better yields for strange particle decays and mainly charged kaons we need to change seeding strategy on top of that we have improve also seeding performance (CPU) Standalone ITS tracking for high momentum tracks (above 1 GeV)  on the way low momentum tracks (below 100 MeV)  much more difficult And to write it ! 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status Muon tracking New cluster finder Development of Kalman filter underway Writing  as previous (However, they already requested the sample files…  so is underway) 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status HLT filtering we have first draft of pile-up removal for pp running timing study  looks very good we need detail efficiency study as a function of pt as function of background we need implement beam-gas background muons almost parallel to beam axis 12 June 2002 Karel Safarik: Reconstruction Status

Charged particle identification ALICE has several PID systems for charged particle dE/dx done by ITS, TPC and TRD Time-of-Flight by multi-layer RPC Higher momentum particles by RICH detector Electron identification by Transition Radiation Detector Muon identification by Forward Muon Detector Underway the combining of PID significances together however, allowed contamination level depends on the physics question under study therefore also momentum range for particle separation is not uniquely defined 12 June 2002 Karel Safarik: Reconstruction Status

TPC particle identification At dN/dy = 8000 At dN/dy = 4000 s dE/dx = 10 % s dE/dx = 7 % electrons electrons 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status TPC dE/dx measurement Results for dN/dy = 4300 Energy loss for 300<p<350 Mev Today even better results: for low multiplicities dE/dx just above 5% 12 June 2002 Karel Safarik: Reconstruction Status

4 ITS layers (silicon drift and strip) capable to measure dE/dx ITS dE/dx 4 ITS layers (silicon drift and strip) capable to measure dE/dx s dE/dx = 10-11 % Separation 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status PID via Time Of Flight Efficiency and contamination at high density (dN/dy = 8000) B = 0.2 T B = 0.4 T 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status TOF for pp environment Efficiency and contamination at low density (pp: dN/dy = 5-7) possibility to detect low momentum electrons 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status RICH PID Efficiency and contamination of RICH PID for different configuration of (passive) material in front of it 12 June 2002 Karel Safarik: Reconstruction Status

Charged PID – missing parts Different detector underway except: TRD (they just finished tracking) Combined PID from different detectors study group started Writing: detector studies on different level ordered list: TOF, HMPID+ITS, TPC TRD  nothing global PID  nothing 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status g and p0 detection Excellent energy resolution: stochastic 2.7%/E1/2 noise 2.5%/E constant 1.3% Fraction of reconstructed energy (simulation 1 - 100 GeV) 12 June 2002 Karel Safarik: Reconstruction Status

Photon identification status Update of the text available including first draft from PMD (without figures !) However, mostly study of standalone detector performance performance study in real environment p0 detection photon detection hard photons still has to be done (in the text is a ‘programme of work’) 12 June 2002 Karel Safarik: Reconstruction Status

Tracking development Strasbourg meeting May 17th – 18th we had a two-days meeting in IReS, Strasbourg First day – tracking itself M.Ivanov: Progress on parallel tracking M.Masera (J.Chudoba): TPC tracking – efficiencies using merged events S.Radomski: Status on TPC tracking code S.Sedykh: TRD tracking status R.Schiker: TRD tracking with tilted pads A.Pulverenti: Neural and combined tracking in ITS 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status Parallel tracking For a long time we plan to develop parallel Kalman filter improvement in cluster deconvolution in TPC improvement in ITS tracking, especially strip layers First thing: we have to change seeding in fact we have only work-around Now the structure of parallel tracking is working in TPC the study for deconvolution started expect improvement in dE/dx (golden clusters) 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status Merged events Gives results well comparable to our standard chain however much faster  partial TPC reconstruction Technical provision for comparison: track reference information at the moment we had for TPC a work-around: special hit Now we have first implementation of track reference (similar structure to hits, one by M.Ivanov) Technical discussion about structure of tracking code static utility classes multi-event per file processing 12 June 2002 Karel Safarik: Reconstruction Status

Standalone ITS tracking TRD tracking Ready for deployment use the same structure as TPC and ITS reconstruction version 2 in this version the non-tilted pad geometry is implemented seeding with TRD itself  slow and not optimized Discussion on tilted pads simple estimates gives expected improvement in z resolution however, problems with ‘real’ implementation implication for online triggering easy to recover Standalone ITS tracking Neural network algorithm with pre-filtering work well above 1 GeV 12 June 2002 Karel Safarik: Reconstruction Status

Karel Safarik: Reconstruction Status Second day Long discussion about V0 vertexing: Strasbourg group presented reconstruction of Omegas background estimates not far from expected has to be study using event merging already developed for TPC and now under development for ITS (Yu.Belikov will tell you more) status of V0 finding with version 1 (Catania group) gives compatible results Status of fast simulation using parameterization of covariance matrix now implemented for different particle types can be used for other physics studies 12 June 2002 Karel Safarik: Reconstruction Status

Method for high statistics study Parameterization of Track parameter covariance matrix after TPC Regularization of pt dependence ‘pulls’ Comparison with full simulation 12 June 2002 Karel Safarik: Reconstruction Status

Impact parameter resolution Basic parameter for charm and beauty study is impact parameter resolution determined by ITS performance and namely pixel detector Full simulation and approximation 12 June 2002 Karel Safarik: Reconstruction Status

Conclusions and outlook Reconstruction development proceed well lower than expected efficiency for secondary tracks outstanding issues improvement in seed finder ‘kink’ finder for charged K decays in TPC V0 finding in larger fiducial volume recovery for electron bremsstrahlung in Kalman filter ( started) need an effort in calibration and alignment software Charged particle identification we have studies of performance on detector levels (ITS, TPC, TOF, HMPID) dependence on particle density ‘correct’ connection with tracking detectors global particle identification performance Photon identification study in the ‘real’ environment 12 June 2002 Karel Safarik: Reconstruction Status