Straw Chamber Efficiency

Giuseppe RuggieroCERNStraw Chamber WG meeting07/02/2011Spectrometer Reconstruction: Pattern recognition and Efficiency07/02/20111G.Ruggiero - Spectrometer Efficiency IntroductionSpectrometer Layout (MC)ReconstructionL-R ambiguity resolutionPattern Recognition algorithm

Straw tubes performances vs 1 track reconstructionFull set-upMinimal set-up (2012)

Conclusions07/02/20112G.Ruggiero - Spectrometer Efficiency Full Spectrometer SimulationLayout:4 Chambers4 Views / Chamber (UVXY)4 Single tube planes / View Geometry from TDChamber and tube positions from Beatch file 11/06/2010.

Physical/instrumental effect:d rays, effective radius, uniform inefficiency, gaussian smearing of R measurement, p hadronic interactions, p decays.

Reconstruction algorithm built using p+p+p- events.Analysis performed using a sample of pnn eventsGenerated between 104000 and 170000 m07/02/20113G.Ruggiero - Spectrometer Efficiency Spectrometer ReconstructionRequiremets:High resolution (against backgrounds constrained by kinematics) also in case of multi-track eventsHigh efficiency (signal acceptance and rejection of multi-track background ++-, Ke4) also in case of multi-track eventsAs much as possible independent from the sources of inefficiency of the straws (effective radius, smooth inefficiency)07/02/20114G.Ruggiero - Spectrometer Efficiency Why multi-track environment ?s(t) straw 7 nsDt 3s(t) 20 nsRate per chamber 10 MHzProb(> 1 hit/view) 0.18 Prob(> 1 track) L R ambiguity resolution4 hit fired: not allowed by geometry.3 hits fired: 1 tube hit close to the wire, the other 2 tubes are hit close to the edges. LR solution always possible.2 hits fired: both tubes are hit in the central part. LR solution always possible. 1 hit fired: only close to the beam hole and in case of straw tube inefficiency. LR solution never possible.

Steps:Look for contiguous tubes fired.Sum or subtract the measured R in one tube to the position of the tube according to the pattern of contiguous tubes.07/02/20115G.Ruggiero - Spectrometer Efficiency

Hits and ClustersDefinitionsHit: one straw tube fired. Measured infos:1-D coordinate of the impact point of the track on the tube (or the position of the tube if the LR ambiguity is not solved).Time (Not used in the present work).

Cluster: group of Hits in one view used to solve their LR ambiguity.Types: 1-Hit, 2-Hits, 3-Hits according to the impact point of the track on the view planes.Measured infos (extracted by linear interpolation of the hits forming the cluster):1-D coordinate of the impact point of the track extrapolated at an average ZSlope of the track.07/02/20116G.Ruggiero - Spectrometer Efficiency Each cluster is defined by a coordinate AND by a slope (track slope)Single hit reconstruction07/02/2011G.Ruggiero - Spectrometer Efficiency 7Effective radius 5 mmNo d rays pileupNo smooth inefficiencyNo R smearingp hadronic interactionsp decays

Effective radius 4.7 mmd rays pileup allowed3% smooth inefficiencyR smearing (40-200 mm)p hadronic interactionsp decays

Ideal configurationReal configurationSingle hit reconstruction (contd)07/02/2011G.Ruggiero - Spectrometer Efficiency 8

100 mm17mmIdeal configurationReal configuration1 hit clusters regions07/02/2011G.Ruggiero - Spectrometer Efficiency 9

Ideal configurationReal configuration1999545 morePattern recognition algorithmKalman filter approach starting to the last chamber and adding the clusters down to the first chamber:Initialization step profits from the a-priori knowledge of the track slope.Complications: at least 2 views needed for the initialization of the X-Y angle of the track. The number of the views fired in one chamber depends on the track impact point on the chambers.Momentum initialization possible at the level of the second chamber only.Step 0: all the possible cluster combinations in chambers 4 are considered. And each combination is propagated back in chamber 3 down to a view with at least 1 cluster.Step 1: A cluster in this view is chosen according to the difference between the measured position and the position expected on the basis of the estimated track parameters, divided by the corresponding errors. Step 2: a good cluster is added, the track parameters recomputed, some model of MS added to the correlation matrix of the track parameters and track propagated back again (step 1).Process ends when no more views with clusters are found07/02/201110G.Ruggiero - Spectrometer Efficiency INITFILTERIdentification of the clusters in the different views and chambers belonging to the same trackPattern recognition algorithmFurther complications (short examples): One track with a cluster in only 1 view in chamber 4. A not parallael view in chamber 3 needed for a suitable initialization.No clusters in chamber 4. Clusters in chamber 3 used for initialization. One track with clusters in chamber 4 and another track without chamber 4 No cluster in chamber 2, or 1 cluster in chamber 2 in Y direction. A cluster in chamber 1 is needed to initialize the track momentum.Output: sets of combinations.Track candidates chosen among the combinations on the basis of a suitable 2.Added features: track candidates are indetified also in case of clusters in 3 chambers only (the case of any chamber missing is addressed).

Algorithm tuned using p+p+p- events.07/02/201111G.Ruggiero - Spectrometer Efficiency 1-track event resultsResults presented as a function of the effective radiusReal Configuration07/02/201112G.Ruggiero - Spectrometer Efficiency

Clusters per track vs effective radiushit per clusters per track vs effective radius1-track event results07/02/201113G.Ruggiero - Spectrometer Efficiency

1 hit cluster3 hits cluster2 hits clusterReal configurationSpectrometer efficiency (1-track)

07/02/201114G.Ruggiero - Spectrometer Efficiency 3 Chambers4 ChambersTotal: 95%Effect from p hadronic interactions and p decay includedEfficiency vs P (1-track)07/02/201115G.Ruggiero - Spectrometer Efficiency

Effective radius between 5.0 and 4.5 mm: no visible effect vs track momentumGeometrical acceptance (beam hole)Minimal Spectrometer Layout (2012)Layout:4 Chambers2 Views / Chamber : Chamber 12 XY, Chamber 34 UV 4 Single tube planes / View Geometry from TDChamber and tube positions from Beatch file 11/06/2010.

Analysis performed using a sample of pnn eventsGenerated between 104000 and 170000 m

07/02/201116G.Ruggiero - Spectrometer Efficiency Minimal Spectrometer LayoutResults studied as a function of the effective radiusReal Configuration07/02/201117G.Ruggiero - Spectrometer Efficiency

Clusters per track vs effective radius(hit per clusters ) per track vs effective radiusMinimal Spectrometer Layout

07/02/201118G.Ruggiero - Spectrometer Efficiency 3 Chambers4 ChambersTotal: 75%Efficiency vs Effective RadiusMinimal Spectrometer Layout 07/02/201119G.Ruggiero - Spectrometer Efficiency

Efficiency vs PConclusions 07/02/201120G.Ruggiero - Spectrometer Efficiency Time to build a realistic reconstruction of the Spectrometer

L-R resolution algorithm developed: Independent from the geometry of the planesProvide position and first track slope estimation

Pattern recognition algorithm started:Use of a Kalman Filter techniqueMost part of possible cases addressed and solved.Works in multi-track environments (some refinement still needed)

Conclusions (contd)07/02/201121G.Ruggiero - Spectrometer Efficiency Straw performances vs 1 track events:

Reconstruction efficiency almost not dependent on the effective radiusReconstruction quality does depend on the effective radius

Spectrometer efficiency (including geometry, p interactions, p decays, 3% smooth efficiency of the straws, 4.7 mm effective radius):95% (90% for tracks with 4 chambers) full set-up (16 views)75% (70% for tracks with 4 chambers) minimal set-up (8 views).

Reconstruction quality to be addressed. A further step in the reconstruction needed to reach the highest level of resolution (next talk.)