daniele de gruttola (tof group – salerno university and infn ) 2009 cosmic rays data analysis...
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Daniele De Gruttola (TOF group – Salerno University and INFN )
2009 cosmic rays data analysis2009 cosmic rays data analysis
09/Dec/09 ALICE - TOF meeting - CERN
Muons selection with TOFMuons selection with TOF
analysis based on:
• time-of-flight of muons measured
by TOF τ = t – to
• expected time-of-flight assuming
relativistic muons τ exp
= L/c
• TOF hits: tracking system not included
• run 79774 (Aug 2009):
2512944 events - no magnetic field
09/Dec/09 ALICE - TOF meeting - CERN
see R. Preghenella's talk
Full-TOF trigger (back-to-back ±Full-TOF trigger (back-to-back ± 1 1))
09/Dec/09 ALICE - TOF meeting - CERN
simulated trigger: 1 hit in an upper sector and 1 hit in the selected opposite ones
muon selection: purity ~ 95%
09/Dec/09 ALICE - TOF meeting - CERN
Muons selection using tofMuons selection using tof
Muons selection using tofMuons selection using tof
09/Dec/09 ALICE - TOF meeting - CERN
distance between the hit pads on the opposite sectors
vs difference between the hit times
09/Dec/09 ALICE - TOF meeting - CERN
correlation between the time-of-flight and the track length
Muons selection using tofMuons selection using tof
-
09/Dec/09 ALICE - TOF meeting - CERN
after the muon tracks selection on tof – L/c, it's possible to see a peak in the range 105° < < 140 ° (corresponding to ALICE Baby side)
Angular distributionAngular distribution
09/Dec/09 ALICE - TOF meeting - CERN
• peaks related to trigger logic• small peaks around φ = 180° and φ = 350° correspond to quasi horizontal tracks
Angular distributionAngular distribution
vertical tracks
muons coming from the ALICE main shaft
09/Dec/09 ALICE - TOF meeting - CERN
Theta Phi distributionTheta Phi distribution
09/Dec/09 ALICE - TOF meeting - CERN
TOF supermodule
Main shaft to lower detectors in Main shaft to lower detectors in the cavernthe cavern
• the event display shows the larger flow of muons coming from the main shaft
(display over 2000 events for the sake of clarity)
• run 79774: 494527 selected tracks over 2512944 events
• ~ 32 % tracks coming from the shaft , ~ 23 % from opposite side
z
09/Dec/09 ALICE - TOF meeting - CERN
Theta distributionTheta distribution
serviceshaft
ALICEcavern main
shaft
main shaft
ALICEcavern
serviceshaftALICE P2 map
09/Dec/09 ALICE - TOF meeting - CERN
23 m
Tracks surface distributionTracks surface distribution
09/Dec/09 ALICE - TOF meeting - CERN
Full-TOF trigger (back-to-back ±Full-TOF trigger (back-to-back ± 3 3))
1 hit in an upper sector and 1 hit in the selected opposite ones
muons coming from the ALICE main shaft
09/Dec/09 ALICE - TOF meeting - CERN
Theta Phi distributionTheta Phi distribution
09/Dec/09 ALICE - TOF meeting - CERN
Angular distributionAngular distribution
09/Dec/09 ALICE - TOF meeting - CERN
Angular distributions in the two Angular distributions in the two configurationsconfigurations
distribution with peak corresponding to ALICE main shaft? slightly asymmetric φ distribution
09/Dec/09 ALICE - TOF meeting - CERN
sectors with no central modules (PHOS holes)
sectors with no central modules (“simulated” PHOS holes)
PHOS holes are not the cause of the φ distribution asymmetry:Muon Trigger has seen an effect due to Jura (its position corresponds to tracks at 270° < φ < 360°)
φφ distribution asymmetrydistribution asymmetry
back-to-back ± 3
back-to-back ± 1
• good muon selection using only TOF hits
• purity ~ 95%
• reconstructed angular distribution reproducing the real one
• next step: clusterization ready to be applied to the analysis
09/Dec/09 ALICE - TOF meeting - CERN
ConclusionsConclusions
09/Dec/09 ALICE - TOF meeting - CERN
Clusters: Clusters: ΔΔ time vs time vs Δ Δ tottot
• clusters on opposite sectors
• 2-pad clusters