Daniele De Gruttola (TOF group – Salerno University and INFN ) 2009 cosmic rays data analysis...

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

http://aliceinfo.cern.ch/

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


see R. Preghenella's talk


Full-TOF trigger (back-to-back ±Full-TOF trigger (back-to-back ± 1 1))


simulated trigger: 1 hit in an upper sector and 1 hit in the selected opposite ones


muon selection: purity ~ 95%


Muons selection using tofMuons selection using tof


distance between the hit pads on the opposite sectors

vs difference between the hit times


correlation between the time-of-flight and the track length


-



ALICE coordinatesALICE coordinates



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



• peaks related to trigger logic• small peaks around φ = 180° and φ = 350° correspond to quasi horizontal tracks



vertical tracks

muons coming from the ALICE main shaft


Theta Phi distributionTheta Phi distribution



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


Theta distributionTheta distribution


serviceshaft

ALICEcavern main

shaft

main shaft

ALICEcavern

serviceshaftALICE P2 map


23 m

Tracks surface distributionTracks surface distribution



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


Theta Phi distributionTheta Phi distribution



Angular distributions in the two Angular distributions in the two configurationsconfigurations

distribution with peak corresponding to ALICE main shaft? slightly asymmetric φ distribution



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


ConclusionsConclusions


MoreMore



Clusters: Clusters: ΔΔ time vs time vs Δ Δ tottot

• clusters on opposite sectors

• 2-pad clusters


Daniele De Gruttola (TOF group – Salerno University and INFN ) 2009 cosmic rays data analysis...

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