Performance of the PHENIX Muon Identifier

• Introduction • Calibration with cosmic rays• Performance in Au+Au collisions• Summary

Hiroki Sato, Kyoto Universityfor the PHENIX Collaboration

Outline

First Joint Meeting of the NuclearPhysics Divisions of APS and JPS October 17, 2001 Wailea, Maui, Hawaii

Physics with the PHENIX Muon Arms

• QGP signals in Au+Au collisions– J/ suppression mass shift – Charm enhancement ← , e

• Proton spin structure with polarized p+p collisions– Double-longitudinal spin asymmetry for

J/ and open heavy flavor production → G(x)

– Parity violating spin asymmetry for W boson production → q(x)

-

←

The PHENIX Muon Arms

Muon Tracker (MuTr)

• Cathode-readout strip chambers at three stations

• x ~ 100m →Δp/p~3%@3~10GeV/c

Muon Identifier (MuID)

• 5 layers of chambers (Iarocci tubes) sandwiched in steel

• misidentification probability ~ 310-4

• used as a trigger counter

Acceptance: 1.2 < || < 2.4

Total absorber ~ 10λint

Minimum Momentum ~ 2GeV/c

2001 South Muon Arm operation started2002~ Both Arms operation

Muon Identifier

Muon Tracker

Muon Magnet

South Muon Arm North Muon Arm

MuID Structure

• 4 large panels and 2 small panels in one layer (gap)

• In a panel, Iarocci tubes with 2.5~5.6m length and 8.4cm width run both horizontally and vertically

• 6340 tubes ( 3170 channels ) / Arm

South Muon Arm

North Arm

• One channel consists of two staggered tubes for better efficiency and faster drift time• Those two layers are in different HV and gas chains to minimize dead channels

Large panel Small panel

Cosmic rays are found!

• Both hardware and software (road-finder, event display, …) are confirmed to be working well.

• Roads matches clusters in MuTr.• Useful for calibration of both MuID and MuTr.

Used MuID NIM-logic trigger→ talked by Ken Read (next speaker)

Reconstructed road (track in MuID)

MuID panel

Hit tubes

MuTr clusters

Hit tube cross points

HV/threshold Scan for Efficiency

• ~95% tube efficiency is achieved

threshold = 90mV HV = 4300V

No threshold dependence→set to 90mVNoise is serious < 60mV

Nice plateau for 4300~4500V→ Operation Voltage is set

Threshold = 90mV

Geometry check

Geometry is confirmed to be OK

Num

ber

of p

anel

s

x (cm)

Num

ber

of p

anel

s

reconstructedroad

Fired tube (2-pack)

x.

Num

ber

of r

oads

(hit

s)

12/)h2pack widt(cm9.8

Mean Distribution RMS Distribution

cm cm

Roads Found in Au+Au Collisions!

• The entire South MuID is being operated in Au+Au collisions ar sNN = 200GeV

• Road-finder is working well in Au+Au collision

MuID road

Au+Au collisionsNN = 200GeV

MuTr clusters

MuID hit tubes

MuID Road

Correlation with Beam-Beam

Counter

• Total number of hits in the South MuID is clearly correlated with the charge sum in the Beam-Beam Counter(3.1<||<4)

• Confirms MuID is observing collisions

Total number of hits in MuID

Cha

rge

Sum

of

Bea

m-B

eam

Cou

nter

Tube Hit Rates

• Hit rates agree with simulation well

Tube y position(cm)

Gap3 (4th gap), Panel0, Horizontal

Num

ber

of h

its/

even

t Gap 3, Panel0, Vertical

Tube x position(cm)

Num

ber

of h

its/

even

tPanel 0

Viewed From IP

Red: Data

Blue: HIJING simulation

Red: Data

Blue: HIJING simulation

Road Density

• Road position distribution agrees with simulation

Num

ber

of R

oads

/eve

nt/b

in

Gap 0 Position(cm)

Red: DataBlue: HIJING simulation

Event vertex

Road efficiency in Au+Au collisions

• Single muons ( Pz = 5GeV/c and = 20deg. ) mixed with HIJING events

• ‘Good’ road means 2/3 of hits of a road comes from the signal muon.

• ~70% of ‘good’ road efficiency will be achieved at most central events

simulation

Single (Pz = 5GeV/c, = 20deg)+ HIJING Au+Au s=200GeV95% tube efficiency

Most Peripheral

Most Central

Summary

• Both hardware and software are confirmed to be working fine with cosmic ray data and chamber efficiency was found to be about 95%.

• The entire South MuID is successfully being operated in Au+Au collisions.

• Hit rates and road density agree with simulation well.

• Road-finder works even at most central Au+Au events.

Top view

Side view

Front view

Geometry check

Geometry is confirmed to be OK

Num

ber

of p

anel

s

x (cm)

Num

ber

of p

anel

s

reconstructedroad

Fired tube (2-pack)

x.

Num

ber

of r

oads

(hit

s)

12/)h2pack widt(cm9.8