1. RHIC – PHENIX 実験における単電子の測定 Single Electron Measurement at RHIC – PHENIX T. Hachiya Hiroshima Univ. For the PHENIX collaboration

2. 2003/9/11JPS meeting at Miyazaki2 Motivation Charm is produced through mainly gluon-gluon fusion in heavy ion collisions Sensitive to gluon density in initial stage of the collisions Charm propagate through hot and dense medium created in the collisions Energy loss of charms via gluon radiation can be seen. (PHENIX observed high pT suppressions in hadron measurements) Charm measurements bring us an important baseline of J/  measurement Charm Measurement Measure leptons from semi-leptonic decay of charm.

3. 2003/9/11JPS meeting at Miyazaki3 Electron Measurement All charged tracks BG Net e ± e ± real. Electrons are measured by DC → PC1 → RICH → EMCal Electron Identification :  Cherenkov light in RICH Number of Hit PMT Ring shape  Energy – Momentum matching e+ EM Calorimeter PC2 Mirror PC3 RICH PC1 DC X Cherenkov light in RICH

4. 2003/9/11JPS meeting at Miyazaki4 Photon Converter Method Source of Electrons Photonic source Photon conversion, Dalitz decay … Non-photonic source Charm and Beauty decay Photon Converter  1.7 % radiation length (brass)  The converter can increase electrons only from photonic source by a fixed factor  By comparing the data W and W/O the converter, electrons from non- photonic and photonic source can be separated.  Difficulty  Need to adjust acceptance between real data and simulation.  Amount of material in simulation need to be same with that in real data. Photon Converter e+e+ e-e-

5. 2003/9/11JPS meeting at Miyazaki5 Comparison of Conv/No Conv Ratio in Real Data and Simulation If there is no non-photonic source, real data should agree with simulation. The ratio in simulation looks gradually increasing. It is different with that in real data.  Existence of non-photonic source. Different amount of material between real data and simulation is studied. (explained in next page) Real data Sim Sim + ４．３ % Sim – ４．３ % pT of e[GeV/c] Ratio of p T in Real Data and Simulation

6. 2003/9/11JPS meeting at Miyazaki6 Comparison of Amount of Material in Real data and Simulation Assumption : thickness of the converter in simulation is same that in real data. Mee distribution is normalized by Nevent. Calculate the Ratio( R M ) of Mee(inner) and Mee(converter) Then, compare R M in real data and simulation. Difference between real data and simulation is 0.8%  4.3%. N Converter : Mee:60-100[MeV] N Inner : Mee:0-40[MeV] Mee in simulation Mee[GeV] Mee in real data Mee[GeV] Mee in conv. Run Mee in no-conv. run Conclusion:

7. 2003/9/11JPS meeting at Miyazaki7 Separate Non-Photonic and Photonic Electrons Raw pT distribution of both photonic and non-photonic electrons are obtained by following method (converter subtraction). pT[GeV/c ] Raw pT distributions Inclusive e Non-Photonic e Photonic e Ratio of p T in Real Data and Simulation

8. 2003/9/11JPS meeting at Miyazaki8 Corrected Pt spectra of non-photonic electrons Nevents: 2.5M in no conv. Run 2.2M in conv. run Present analysis is consistent with QM02 Preliminary result within errors. Systematic error is much reduced. QM02 : PHENIX PRELIMINALY Current Analysis: Work in Progress Au+Au @  s NN = 200GeV, Min. Bias

9. 2003/9/11JPS meeting at Miyazaki9 10-20% p T [GeV/c] 1/2  p T · dN/dydp T Min. Bias 0-10% 20-40% 40-60% 60-92% 10-20% Centrality Dependence of Non-Photonic Electrons PYTHIA calculation is scaled with number of binary collisions. Well described for all centralities. Work in Progress Data Charm Beauty Combined

10. 2003/9/11JPS meeting at Miyazaki10 Summary Conversion subtraction method is refined Difference of amount of material in real and simulation is 0.8%  4.3% Systematic error is much reduced. Corrected pT spectra of non-photonic electrons are measured in Au+Au collision at  s NN = 200GeV. The Spectra are compared with PYTHIA calculation. Consistent with electrons from charm and beauty decay. Described by binary scaling. Electron measurement by the converter method is very close to final -> Next meeting. Next Step Eta and Kaon should be taken into account. The other method to measure high pT region.