2000/9/23 JPS meeting in Niigata 1

Measurement of single gamma and 0 with PHENIX EMCal (I)

H.Torii Kyoto Univ./RIKEN for the PHENIX Collaboration.

Sep/23/2000, JPS meeting in Niigata

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Physics Motivation

• Quark Gluon Plasma(QGP) search– One of the hard probe for

QGP is “Jet Quenching”– Jet Quenching.

• Quark energy loss in the QGP matter by gluon bremsstrahlung.

• Energy loss can be observed by measuring fragmented pi0

Xin-Nian WangPhys.Rev.C58 2321(1998)Au+Au s=200GeV (dE/dx=1GeV/c)

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PbSc: Shish-Kebab sampling calorimeter

PHENIX EM Calorimeter- PbSc (lead scintillator) and PbGl (lead glass) -

PbSc PbGlSize(cm x cm) 5.52 x 5.52 4.0 x 4.0

Depth(cm) 37.5 40Number of towers 15552 9216Sampling fraction ~ 20% 100%

cov. 0.7 0.7 cov. 90+45deg 45deg/ mod 0.011 0.008 / mod 0.011 0.008

X0 18 14.4Molière Radius ~ 3cm 3.68cm

Only Sector W0/W1 areused in this analysis.

W1

W0

~5m

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Data Set & Event Selection• Analyze Au+Au 130AGeV data sets

– Only for PbSc parts. Sector W0/W1– Aug/6 to Aug/18

• Event Selection– [1126k events]

BBC Z vertex < 40cm– [419k events]

-2.5nsec<(ZDC T0 – BBC T0 – [ZDC T0-BBC T0]) < 4.5nsec

BBC T0 < 13nsec– [371k events]

cm

Vertex Distribution

Time 0 Distribution

nsec

RMS 3nsec

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Geometrical Acceptance & Quality Assurance Check

• Geometrical Acceptance– Bottom 5 rows of W0

Sector are disabled• -0.376< <0.376• -0.636< <-0.213 (W0)• -0.190< <0.190 (W1)

• Quality Assurance Check– Disabled region

• 1.9 %

Normal Position Acceptance

W1

W0

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TOF PID cut

• TOF width 1.4nsec– Still dominated by tower by tower

calibration– Photon efficiency100%(>1GeV)– Background contamination 50%-0%

(Still large uncertainty in background contamination)

Background contaminationPhoton efficiency

Less background high E

Large deviation from simulation at slower TOF.

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Energy Calibration w/MIP• First energy scale is calibrated by cosmic

muon. 38MeV during construction• Measured MIP energy in W0/W1 sectors.

– June-July• W0: 266.11.3MeV• W1: 276.71.2MeV

– Aug• W0: 266.30.03MeV• W1: 257.10.02MeV

• Gain shift during between June/July and Aug.

– W0: 0.10.4%– W1: -7.00.4%

• Laser monitoring will be used soon in the analysis.

Au+Au 130AGeV PHENIX Preliminary

(Run 8713-10767)

Cosmic Muon

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Energy Calibration w/0 • Energy Correction

– Measured by PHENIX clustering algorithm• PHENIX clustering algorithm is energy sum of a

few core towers by considering shower profile. It’s to suppress overlapping effect

• Average energy obtained by PHENIX clustering algorithm is 93% of total shower.

– Energy correction of MIP into 280MeV• Correction is made for every 144 towers.• Path length by geometrical effect is already

accounted. 0 peak

(Asymmetry<0.8 , Pt>2.5GeV , TOF cut<2)– Before correction

• 123.5 1.9MeV =13.72.3MeV

– After correction• 135.91.8MeV

=12.42.1MeV

Absolute energy scale is roughly correctin 2%

Invariant Mass after correction

Invariant Mass before correction

GeV

GeV

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Table of Calibration• Energy

– Relative energy(every 144 towers) 2% (after <6% correction) – Absolute energy 2% (cosmic/hadron mip and pi0)

– Time dependence Studying by laser monitoring data • TOF

– Width 1.4nsec (mainly tower-by-tower calibration)

• Yield of photon– Geometrical acceptance -0.376< <0.376

-0.636< <-0.213 (W1) -0.190< <0.190 (W0)– Quality assurance check 1.9% disabled– TOF PID photon efficiency/background contamination

efficiency> 100%, Background 50-0%(Still large uncertainty in background contamination)

– Overlapping effect Studying

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EM Shower Energy Distribution• Different total energy

– TOF<2– Normalized at 0.5GeV– No efficiency correction

• No TOF efficiency nor background contamination correction

• No shower overlapping effect correction

– 4 slopes seem to be similar– Is there any centrality

dependence?Still Working on TOF

efficiency/background contamination and overlapping effect

Au+Au 130AGeVNo efficiency corr.PHENIX Preliminary

EM Shower Energy(GeV)A

rbitr

ary

GeV

Total Energy

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Summary• PHENIX successfully completed first physics run from June to early-

September in 2000.• PHENIX EM calorimeter works and has measured signals.• EM calorimeter calibration

– Energy, TOF are calibrated by laser, MIP peak of cosmic /charged hadron, an 0 mass

• Physics analysis is in progress.– EM shower energy distribution with different total energy.

• No Efficiency correction– TOF efficiency , background contamination are not corrected.– Shower overlapping effect is not corrected

• Slopes seem to be similar• We still working on TOF efficiency/background contamination and overlapping effects.

• We will investigate centrality dependence