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RHIC-PHENIX 実験における 単電子の測定

RHIC-PHENIX 実験における 単電子の測定. T. Hachiya (hachiya@hepl.hiroshima-u.ac.jp) Hiroshima University For the PHENIX collaboration. Motivation. Charm is produced mainly through gluon-gluon fusion in heavy ion collisions Sensitive to gluon density in initial stage of the collisions

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RHIC-PHENIX 実験における 単電子の測定

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  1. RHIC-PHENIX実験における単電子の測定 T. Hachiya (hachiya@hepl.hiroshima-u.ac.jp) Hiroshima University For the PHENIX collaboration

  2. Motivation • Charm is produced mainly through gluon-gluon fusion • in heavy ion collisions • Sensitive to gluon density in initial stage of the collisions • Charm propagates through hot and dense medium created • in the collisions • Energy loss of charms can be tested. • (PHENIX observed high pT suppression in hadron measurements) • PHENIXobserved single electron insNN=130GeV Au+Au collisions. • Consistent with PYTHIA charm assuming binary scaling. • Charm measurements provide an important baseline of J/ • measurement • Charm Measurement • Measure electronsfrom • semi-leptonic decay of • charm and beauty.

  3. PC3 PC2 RICH PC1 DC Mirror e+ X EMCalorimeter Cherenkov light in RICH Electron measurement at PHENIX • Electrons are measured by • DC→PC1→RICH→EMCal • Electron Identification : • Cherenkov light in RICH • Number of Hit PMT • Ring shape • Energy – Momentum matching e±candidates. Net e± BG E/p

  4. Photon conversions : • Dalitz decays of p0,h,h’,w,f (p0eeg, heeg, etc) • Kaon decays • Conversion of direct photons • Di-electron decays of r,w,f • Thermal di-leptons Most background isPHOTONIC • Charm decays • Beauty decays Non-PHOTONIC Signal p0  g g e+e- Background Sources of electrons

  5. e+ γ e- Converter Au Au Photon converter method Photon Converter • 1.7 % radiation length (brass) • The converter increase the yield of electrons from photonic sources by a fixed factor • By comparing the data with and without the converter, electrons from non-photonic and photonic sources can be separated. Non-photonic electrons can be extracted from data itself. Reality pT[GeV/c]

  6. Inclusive e/photonic e Mininum Bias Au+Au in sNN=200GeV Ne 1.7% 1.1% 0.8% With converter Conversion in converter W/O converter Conversion from detector Dalitz : 0.8% X0 equivalent Non-photonic 0 0 Signal Extraction • R(inclusive/photonic) : Non-photonic signal appears above 1.0. • Non-photonic signal is 50 %at pT = 1.0[GeV/c] • compared tophotonic electrons • Backgrounds (K->eX and r,w,f->ee) are still included.

  7. Non-photonic electrons at sNN=200GeV Au+Au collisions PHENIX(Run 2 final result) Min. bias at Au+Au sNN=200GeV (e++e–)/2 sys. error • Fully corrected spectrum • Acceptance & eID efficiencies • 2.5M and 2.2M events analyzed with and without the converter • Backgrounds from KeX (less than 5%) and , , ee (1%) decays subtracted • Systematic error is 13% at high pT

  8. PHENIX PRELIMINARY PHENIX PRELIMINARY Non-photonic electron in pp • Single electron at sNN=200GeV pp collisions is measured by cocktail method. • Reference for Au+Au data • Data is compared with a PYTHIA charm + beauty. • PYTHIA parameter is tuned by low energy data • Spectrum is harder than PYTHIA calculation at higher pT • Cross section is measured. • Data at lower pT is described by PYTHIA • Changing normalizations of PYTHIA charm and beauty to fit spectral shape

  9. PHENIX PHENIX PHENIX PHENIX PHENIX Comparison with pp • Au+Au data is scaled by TAA and compared with pp data. • Au+Au data at lower pT are consistent with p+p data for all centralities • Need more statistics to study higher pT range •  50 times larger statistics in run4

  10. (dN/dy) / Ncoll vs. Ncoll PHENIX • Green and red points shows the (dN/dy) / Ncoll for min. bias and each centrality. • Yellow band shows 90% CL of • Data is consistent with number of binary collision scaling.

  11. Summary • Invariant pT distributions of non-photonic electrons are measured in Au+Au collisions at sNN= 200GeV. • Conversion subtraction method is refined • Systematic error is much reduced. • Non-photonic electron spectra are consistent with pp data assuming binary collision scaling (TAA scaling) • The measured yield of non-photonic electrons is consistent with binary scaling. Indicating no strong enhancement or suppression of the total charm yield. • Statistics is too small to limit the energy loss of charm in high pT (pT > 2 [GeV/c]) (RUN4 data) • Run2 data analysis is completed. To be published soon.

  12. gconversion p0 gee h gee, 3p0 w ee, p0ee f ee, hee r ee h’  gee Cocktail Calculation • pT distribution of 0 are constrained with PHENIX 0 and  measurement • pT spectra of , ’  and  are • estimated with mT scaling • pT = sqrt(pT2 + Mhad2 – M2) • Hadrons are relatively normalized by • 0 at high pT from the other • measurement at SPS, FNAL, ISR, RHIC • Material in acceptance are studied for • photon conversion • Signal above cocktail calculation can be seen at high pT

  13. Centrality dependence PHENIX PHENIX PHENIX (e++e–)/2 0-10% central (e++e–)/2 10-20% central (e++e–)/2 20-40% central PHENIX PHENIX (e++e–)/2 40-60% central (e++e–)/2 60-92% central

  14. Uncertainty on Rsim • amount of Material (4.4%) • diff of acceptance between the converter and the no-converter run (4%) • Eta/pi0 ratio (50%  6% on Rsim) pT[GeV/c] • BG subtraction (KeX, VM  ee) pT[GeV/c] Systematic uncertainty List of Systematic error • eID and acceptance calculation Total systematic error pT[GeV/c]

  15. Ratio of pT in Real Data to Simulation pT[GeV/c] Comparison of electron yields with and without converter in Data and Simulation • If there is no non-photonic source, real data should agree with simulation. • Ratio in simulation increases slightly with pT. • Data shows opposite trend. • Presence of Non-PHOTONIC source in data Photonic simulation R(conv/noconv) data Real data Sim. Sim. at higher limit Sim. at lower limit Higher and lower limit is determined by changing 50% of /0 ratio and amount of material between data and simulation

  16. Raw pT distribution Inclusive(noconv) Photonic Non-photonic # of electrons in the converter run # of electrons in the non-converter run # of photonic electrons # of non-photonic electrons Ratio of photonic electrons in the converter run and the no converter run Extraction of non-photonic electrons Raw pT distribution without Noconv. with Conv. Entries/Nevt Entries/Nevt pT[GeV/c] pT[GeV/c] • The method can separate non-photonic electrons and photonic electrons. • e from Kaon and ee from VM is still remaining in non-photonic electrons

  17. Mee in conv. Run Mee in no-conv. run Mee in real data Mee [GeV] NConverter : Mee: 60-100[MeV] NInner : Mee: 0-40[MeV] Mee in simulation Mee [GeV] Comparison of amount of material in 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( RM ) of Mee(inner) and Mee(converter) • Then, compare RM in real data and simulation. • Difference between real data and simulation is 0.1%4.4%. Conclusion:

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