2000/9/23 JPS meeting in Niigata1 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

2000/9/23 JPS meeting in Niigata2 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 Wang Phys.Rev.C (1998) Au+Au  s=200GeV (dE/dx=1GeV/c)

2000/9/23 JPS meeting in Niigata3 PbSc: Shish-Kebab sampling calorimeter PHENIX EM Calorimeter - PbSc (lead scintillator) and PbGl (lead glass) - Only Sector W0/W1 are used in this analysis. W1 W0 ~5m

2000/9/23 JPS meeting in Niigata4 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

2000/9/23 JPS meeting in Niigata5 Geometrical Acceptance & Quality Assurance Check Geometrical Acceptance –Bottom 5 rows of W0 Sector are disabled <  < <  < (W0) <  <0.190 (W1) Quality Assurance Check –Disabled region 1.9 % Normal Position Acceptance W1 W0

2000/9/23 JPS meeting in Niigata6 TOF PID cut TOF width  1.4nsec –Still dominated by tower by tower calibration –Photon efficiency  100%(>1GeV) –Background contamination 50%-0% (Still large uncertainty in background contamination) Background contamination Photon efficiency Less background high E Large deviation from simulation at slower TOF.

2000/9/23 JPS meeting in Niigata7 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:  1.3MeV W1:  1.2MeV –Aug W0:  0.03MeV W1:  0.02MeV Gain shift during between June/July and Aug. –W0: 0.1  0.4% –W1: -7.0  0.4% Laser monitoring will be used soon in the analysis. Au+Au 130AGeV PHENIX Preliminary (Run ) Cosmic Muon

2000/9/23 JPS meeting in Niigata8 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 2.5GeV, TOF cut<2  ) –Before correction  1.9MeV –  =13.7  2.3MeV –After correction  1.8MeV –  =12.4  2.1MeV Absolute energy scale is roughly correct in 2% Invariant Mass after correction Invariant Mass before correction GeV

2000/9/23 JPS meeting in Niigata9 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  <  < <  < (W1) <  <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

2000/9/23 JPS meeting in Niigata10 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 130AGeV No efficiency corr. PHENIX Preliminary EM Shower Energy(GeV) Arbitrary GeV Total Energy

2000/9/23 JPS meeting in Niigata11 Summary PHENIX successfully completed first physics run from June to early- September in 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