The Performance of the ALICE experiment for cosmic ray physics

B. Alessandro, V. Canoa, A. Fernández, M. Rodríguez, M. Subieta

for the

ALICE Collaboration

ALICE Experiment at LHC

ALICE located 40 m. underground30 m of rock (molasse)10 m of air

Threshold Muon Energy ~ 15 GeV

ALICE Experiment during assembly

Detectors used for cosmics in the central region :Trigger : ACORDE, TOF, SPD Tracking : TPC

Detectors used for horizontal muons :Trigger Muon Chambers Tracking Muon Chambers

Study of the cosmic runs taken during Summer 2009 and February 2010

Data Summer 2009 -Muons with central detectors

Triggers: SPD, TOF, ACORDE Tracking : TPC Muon multiplicity distribution Angular distribution Momentum and Ratio +/- (vertical muons 0o-20o)

- Muons with forward muon spectrometer • Trigger and Tracking• Type of events and selections• Momentum and Ratio +/- (horizontal muons 70o-80o)

Data February 2010 Muon Multiplicity Distribution High Multiplicity events

Trigger DetectorsACORDE : 60 scintillatorsTrigger coincidence of twoscintillators : AMU

TOF cylinder of MRPC surrounding the TPC two types of trigger :1 pad up 1 pad down +- 3 pads : TOF Single (OB3)4 pads everywhere : TOF Cosmic (OCP)

SPD small detector trigger whenmuon cross two layers : SCO

Tracking Detector and type of events

Muon Interaction Event

Standard Muon Event (multimuon)

TIME PROJECTION CHAMBER (TPC) :ALICE TPC Collaboration, J. Alme et al., "The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events.", Physics. Ins-Det/10011950 (2010).

Single muon A muon is reconstructed by the TPC as two tracks : up , down

up up

down down

A matching algorithm connects track up with down to count one muon The momentum is given for the two tracks : Pup and Pdown

Algorithm for matching TPC tracks• Find parallel tracks, match the TPC

tracks, count the muons (single TPC track, matched TPC tracks)– N. TCP clusters > 30 (matched tracks)– N. TPC clusters > 50 (single tracks)– P > 0.5 GeV– Cos(DeltaDirection) > 0.990– |Z-Zo| < 250 cm |X-Xo| < 250 cm – DeltaDist < 2 cm for matching

• Tested with real multimuon events (up to ~ 200 muons)

Reconstruction of CR - events with ACORDE , SPD + TPC

Run: 109547 (Feb. 2010)Event: 3723# of TPC tracks: 182# of muons: 89Some TPC tracks fail the N.of cluster cut

DATA TAKING: SUMMER 2009 # Run Time

[h]# Events

OB3OCPAMU

# Events Mu > 0

OB3 OCPAMU

Purity Rate OB3 [Hz]

Purity Rate OCP [Hz]

Purity Rate AMU [Hz]

# Interaction

Events

# Multi- Mu Events

83811 9.48 3422599 719832 20 1 0.03 152 152

83775 1.27 580925 148666 30.1 1.8 0.05 29 19

83802 1.05 382985 81830 20.5 1.1 0.03 18 15

84148 6.4 2720090 682773 28 1.6 0.04 103 98

84205 4.5 1681171 424331 24.7 1.4 0.04 84 76

84254 7 2330994 587554 22 1.3 0.03 99 81

84389 2.23 599723 151642 17.8 1 0.03 33 34

84420 5.12 1958776 495292 25.4 1.4 0.04 80 92

84455 4.43 1883982 478493 28.3 1.6 0.04 98 82

84479 1 377985 96761 25.4 1.5 0.04 19 18

84993 1.52 460389 120291 20.7 1.2 0.03 17 24

85024 1.35 493870 128554 24.9 1.4 0.04 18 18

85031 0.51 304872 79945 41 2.4 0.06 9 10

85032 0.43 14388 3759 2.3 0.13 0.004 1 0

85034 11 3906585 1023590 24.4 1.4 0.04 197 161

Total 57.29 5223313 957 880

Trigger Type Distribution

Muon Multiplicity Distribution for the 4 Triggers

Muon Multiplicity Distribution : Data and Simulation

Real data 2.5 days live time Estimation 30 days live time

C Side

A Side

Zenith & Azimuth Angles for Cosmics

x

Angular Distributions

Azimuth Angle

C SideA Side

Zenith Angley

z

muon

Z

Y

X

A SIDE

C SIDE

SHAFT

SHAFT

Zenith Angle y

x

z

Azimuth Angle

C Side

A Side

Uncorrected Muon Momentum Distribution with Pcov

Vertical muons0o< Teta<20°No shaft effect

Estimated error around 25% at P=100 GeV/cusing Pcov

Pcov : Momentum obtained fitting the whole track length of the muon (up and down as one track)

Ratio +/- (vertical muons)

World Ratio ~ 1.28 P<100 GeV/c

Alice Uncorr. Ratio ~ 1.31 P<100 GeV/c

Study of Horizontal Muons with Forward Muon Spectrometer

y negativey positive

Muon momentum threshold ~ 40GeV/c (due to the rock)

Detector length ~ 17 m (from the interaction point)

Detector length ~ 13 m (from first tracking station)

Data Sample

Runs of August and September 2009Total time ~ 216 h → 9 days Magnetic field → 0.7 TN. Total Events → 200372N. Events with at least one muon →

8194 N. Good events (selected) → 5876

C Side

x

Variables for Horizontal Muons

ThetaX

C SideA Side

y

z

muon

A Side

Z

Y

X

ThetaYThetaY > 0

z z

y y

ThetaY < 0

ThetaY = arctg(Py/Pz)Zenith Cosmic = 90o - |ThetaY|

ThetaX = arctg(Px/Pz)

Selection of good events

Cut to select “good events” :ThetaY > 0 5876 events

Angular Distributions and Selection of the events

70o< Zenith < 80o

85o< Azimuth < 95o 5876 events after these cuts 2862 events

Energy loss from Surface to ALICE

Simulation to obtain the energy loss by + and - crossing the rock from Surface to ALICE experiment at different Zenith Angles

Uncorrected Muon Momentum Distribution (700-800)

ALICE LEVEL

SURFACE LEVEL

Uncorrected Ratio +/- at Surface level (700-800)

DATA TAKING: FEBRUARY 2010

Trigger : ACORDE and SPDTime : 2.2 effective daysTwo events with high muon multiplicity

High Muon Multiplicity Events

Time : 2.2 effective days89 muons182 muons

SimulationTime : 30 effective days

Main Characteristics : Event with 182

Mean Zenith Angle : 40°Mean Azimuth Angle : 212°Density of muons : 12 /m2

Mean Momentum : 123 GeV/c

Main Characteristics : Event with 89

Mean Zenith Angle : 41°Mean Azimuth Angle : 69°Density of muons : 6 /m2

Mean Momentum : 189 GeV/c

Muon Density and Primary Energy Estimate (Simulation)

A density of 6/m2 at ALICE level is obtained with :•Primary with 1016 eV•In the core of the shower

89 muons : 6 /m2 Eprimary >= 1016eV 182 muons : 12/m2 Eprimary > 1016 eV

Final Remarks• ALICE can study atmospheric muons with central

detectors (vertical muons) measuring : Num. of muons, Momentum, Charge, Direction.

• In the future analysis of the correlations of these quantities for composition studies ????

• Measurement of the Ratio +/- for vertical muons with the central detectors (00-200) and for horizontal muons with muon spectrometer (700-800) in progress.

• Study and search of events of very high muon multiplicity can be a test for hadron interaction models