Strategy for Physics with Cosmic Muons

• Detector involved

• Trigger

• Events with different trigger

• Topics

Detection of Atmospheric Muons

Muons are generated in the atmosphere Reach the : SURFACECross the : ROCKArrive in : ALICE

30 meters of rock

SurfaceMuons

ALICE Detectors for Cosmic Ray Physics

ACORDE

TPC

SPD

TOF

MAGNET

TRIGGER

• SPD atm. muons low multiplicity mu interaction in magnet iron (0.1 Hz)

• TOF atmospheric muons mu intercation in magnet iron (very flexible)

• ACORDE atmospheric muons (100 Hz)

SPD Trigger : Typical Event

2 Tracks1 Muon

SPD Trigger : Typical Events

8 Tracks1 Muon

The Analysis Cuts

• Select tracks with > 20 clusters in TPC• Loop on tracks and : 1 track && TPC cls > 70 → 1 μ• 2 tracks:

– if (θ and φ match) || (either track has TPC cls > 70) → 1 μ

• 3 to 6 tracks:– count matching tracks (see next slide)

• > 6 tracks: save event, visual scan

• θ and φ matching means

– θ1 + θ2 = π ± 0.1

– | φ1 - φ2 | = π ± 0.2

– tracker make tracks start from central region and go opposite• for 3 to 6 tracks

– loop on tracks, search for a couple inside ITS match θ and φ as above spatial matching: | Xv1 -Xv2 | < 1.0 && | Yv1 - Yv2 | < 1.0 && |

Zv1 - Zv2 | < 20.0

– if match: Nμ++ , take them away from the list, save θ and φ

– loop on remaining tracks if two match and have same θ, φ as ITS track: Nμ++ and take them

out if a track doesn't match with any other but has θ,φ : if outside ITS (|

Xv | > XITS && | Zv | > ZITS) Nμ++ and take it away from the list

The Track Matching

SPD Trigger : Muon Multiplicity

2.9 %

0.9 ‰

SPD Trigger : High Multiplicity

141 tracks

RUN : 60824

SPD TRIGGER RUN : 60824

707 tracks

Cosmic events with SPD trigger

• Analysis of high multiplicity events • Run :

– 60281 8h 6m 9 events > 6 tracks– 60305 2h 02m 3 events > 6 tracks– 60824 8h 12m 210 events > 6 tracks and

20 events > 20 tracks

SPD trigger 7-8 events per minute

We can estimate 1-2 events per hour with high multiplicity Probably muon intercation in iron

Trigger with TOF

• TOF works well in ALICE low background 0.2 Hz/cm2

• Good stability

• Very flexible

– Allow to decide the trigger topology (vertical muons for example) and the rate

Flexibility (example) : Trigger TOF for TRD

Rate Stability : Trigger TOF for TRD (Side C only)

Run 37562 Ev 27 ( Trigger: TOF )

TPC hitsTRD hitsTOF hits

Example of real event : Particle interacting in the iron of the magnet

Trigger with ACORDE

60 modules on the three upper octants of the L3 magnet :

Each module = 20 cm x 190 cm

Area 1 scintillator = 0.38 m2

Total Area = 23 m2

ACORDE Hit Multiplicity

Mario RodriguezAnalysis Run 62107Magnetic Field ON8.5 hours data

TPC track multiplicity

RUN 62107

Number of events

N. TPC tracks vs ACORDE modules

RUN 62107

ACORDE Trigger

14% of the triggershave at least one track in the TPC

ACORDE Trigger Multimuons

High multiplicity in ACORDE

File:/Volumes/MRC/RunsAliEn/Run62107/08000062107000.140/AliESDs.root, N. of Event:2402, ACORDE Multiplicity:7, No. of ESD's tracks:1

High multiplicity in ACORDE

File:/Volumes/MRC/RunsAliEn/Run62107/08000062107000.30/AliESDs.root, N. of Event:14692, ACORDE Multiplicity:5, No. of ESD's tracks:1

High multiplicity in ACORDE and TPC

File:/Volumes/MRC/RunsAliEn/Run62107/08000062107000.460/AliESDs.root, N. of Event:8560, ACORDE Multiplicity:35, No. of ESD's tracks:148

Cosmic Ray Physics with ALICE

• Trigger SPD : High Multiplicity Events– 200 hours of data taking with B=ON– Study mu interaction in iron

• Trigger TOF : Topology and Rate Flexible– Atmospheric muons and mu int. in iron

• Trigger ACORDE : – Atmospheric muons– At least 30 days of data taking better with B=ON

Physics Topics

• Atmospheric muons– Multi-muon Distribution– Correlations between Muon Multiplicity and

Muon Energy– Measurements on Single Muon (Momentum

Distribution, Ratio mu+/mu-)– Event coincidence with other LHC experiment

• Muon interaction in iron (muon photonuclear)– Rate of such process– Hadron identifications and energy distributions