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High-p T Identified Hadron Production in Au+Au and Cu+Cu Collisions at RHIC-PHENIX

High-p T Identified Hadron Production in Au+Au and Cu+Cu Collisions at RHIC-PHENIX. Masahiro Konno (Univ. of Tsukuba) for the PHENIX Collaboration. Outline. Physics Motivation Method New Data Set (full statistics now available) : Cu+Cu 200GeV / p+p 200 GeV

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High-p T Identified Hadron Production in Au+Au and Cu+Cu Collisions at RHIC-PHENIX

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  1. High-pT Identified Hadron Production in Au+Au and Cu+Cu Collisions at RHIC-PHENIX Masahiro Konno (Univ. of Tsukuba) for the PHENIX Collaboration

  2. Outline • Physics Motivation • Method • New Data Set (full statistics now available) : • Cu+Cu 200GeV / p+p 200 GeV • Results and Comparisons: • - p/ ratios • - Npart Scaling of p/ in Au+Au, Cu+Cu • - RAA in Au+Au, Cu+Cu • Summary

  3. PRC 74, 024904 (2006) p/ ratio PRL 91, 172301 (2003) • What is the origin of (anti-)proton • enhancement at intermediate pT(2~5 GeV/c) ? • A systematic study at intermediate pT is • necessary over different collisions systems. Physics Motivation - Baryon Enhancement - RAA Au+Au 200 GeV • High-pT suppression due to parton energy loss • in the medium (jet quenching). • The suppression patterns depend on particle type. • Protons are enhanced, while pions and kaons are suppressed.

  4. - - p (p) ID up to 7 GeV/c p (p) ID up to 4 GeV/c PHENIX detector EM Calorimeter (PID) TOF (PID) • - Central Arm Detectors • (magnetic spectrometer) • Event Characterization detectors • PID (particle identification) is • a powerful tool to study hadron • production. Aerogel Cherenkov (PID) Aerogel Cherenkov (ACC) Time of Flight (TOF) Drift Chamber (momentum meas.) p K+ Tracking detectors (PC1,PC2,PC3) π+ Veto for proton ID

  5. Phenix preliminary pT spectra (Cu+Cu √sNN = 200 GeV) (Anti-) protons ACC • pT reach extended for (anti-)protons with fine centrality bins. • <= (1) Aerogel Cherenkov, (2) Enough statistics in Au+Au/Cu+Cu NOTE: No weak decay feed-down correction applied.

  6. TOF Phenix preliminary pT spectra (p+p √s = 200 GeV) • High statistics 200 GeV p+p data. • More than10 times statistics used compared to previous Run3 p+p analysis. • The p+p data provides baseline spectra to heavy ion data, and it is • important to quantify in-medium nuclear effects in heavy ion collisions at RHIC NOTE: No weak decay feed-down correction applied.

  7. p/ p/ vs. pT Au+Au 200 GeV ACC p/ - p/ (pbar/) ratios seem to turn over at intermediate pT, and be close to the value of fragmentation at higher pT. - Clear peak in central events than that in peripheral. - Indicating a transition from soft to hard at intermediate pT. NOTE: - No weak decay feed-down correction applied. - p+p data (PRC 74, 024904 (2006))

  8. p/ Phenix preliminary p/ vs. pT Cu+Cu 200 GeV ACC p/ • Baryon enhancement observed in Cu+Cu at 200 GeV. • - pT dependence in Cu+Cu is similar to that in Au+Au. • => How about the magnitude as a function of centrality? see Next. NOTE: No weak decay feed-down correction applied.

  9. 0.6 - 1.5 GeV/c 2.0 - 3.0 GeV/c 1.0 - 2.0 GeV/c 3.0 - 4.0 GeV/c 4.0 - 5.0 GeV/c pT Phenix preliminary Phenix preliminary pT Cu+Cu 200 GeV vs. Au+Au 200 GeV p/ vs. Npart1/3 Npart dependence in Cu+Cu looks similar to that in Au+Au (Npart scaling !). Slight difference in the magnitude seen. TOF (<3 GeV/c) ACC (>3 GeV/c) NOTE: No weak decay feed-down correction applied.

  10. TOF (Anti-)protons Phenix preliminary Phenix preliminary p/ vs. pT (Low pT) - Radial flow - At low pT, p/ shows weak and decreasing Npart dependence because inverse slope (from mT exponential fitting) also shows it. NOTE: No weak decay feed-down correction applied.

  11. Au+Au 200 GeV Central Peripheral p/ vs. pT(Intermediate pT) TOF, ACC - Radial flow (ex. blast-wave fit) - • Spectra for heavier particles has • a convex shape due to radial flow. • Using Blast-wave fitting, try to • estimate p/ ratio as a function of pT. NOTE: No weak decay feed-down correction applied. (hydro p)/(hydro ) (hydro p)/(real ) • Hydrodynamic contribution for protons is one of • the explanations (baryon enhancement). • - Other contribution is also needed: Recombination, Jet fragmentation

  12. Phenix preliminary p/ TOF ACC Now, we find a similar trend. p/ vs. pT(Intermediate pT) ACC - Quark Recombination - At intermediate pT, recombination of partons may be a more efficient mechanism of hadron production than fragmentation. A number of models predicted a turnover in the B/M ratio at pT just above where the available data finished… Fries, R et al PRC 68 (2003) 044902 Greco, V et al PRL 90 (2003) 202302 Hwa, R et al PRC 70(2004) 024905 etc. NOTE: No weak decay feed-down correction applied.

  13. TOF Phenix preliminary Cu+Cu 62 GeV vs. Au+Au 62 GeV p/ vs. pT - Similar tendencies as at 200 GeV.

  14. p/ vs. Npart1/3 Cu+Cu 62 GeV vs. Au+Au 62 GeV TOF Phenix preliminary • Npart scaling of p/ also at 62 GeV in Au+Au/Cu+Cu. NOTE: No weak decay feed-down correction applied.

  15. Phenix preliminary Phenix preliminary p/ vs. Npart1/3 ,(dET/dy)1/3 Au+Au 200 GeV vs. Au+Au 62 GeV TOF • No Npart scaling of p/ (pbar/) in Au+Au between 62 GeV and 200 GeV. • dET/dy scaling of pbar/ seen. => Proton production (this pT range) • at 62 GeV is partly from baryon transport, not only pair production. NOTE: No weak decay feed-down correction applied.

  16. Similar Npart dependence • for Au+Au / Cu+Cu. • - Cronin effect in peripheral NOTE: Systematic errors (~10%) for overall normalization not shown. RAA vs. pT TOF Phenix preliminary • Proton, antiproton are enhanced at 1.5 - 4 GeV/c • for all centralities. (enhancement > suppression) • - Suppression is seen for pions, kaons. NOTE: No weak decay feed-down correction applied.

  17. Summary • pT reach of PID (especially for p, pbar) extended with: • (1) High statistics Au+Au/Cu+Cu data • (2) New PID detector (Aerogel) • (Anti-)Proton enhancement is observed • in Au+Au/Cu+Cu collisions at 200/62 GeV. • p/ ratios: • (1) Indicating a transition from soft to hard production at intermediate pT. • (2) Npart scaling (dET/dy scaling) over different collision systems. • (3) Recombinatio + radial flow would explain the pT, Npart dependencies. • - Systematic study of PID spectra (and jet correlations) • for different collision systems can provide information • to understand the hadron production mechanisms.

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