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Dmitri Kotchetkov (University of California at Riverside) for PHENIX Collaboration

Study of Cronin effect and nuclear modification of strange particles in d-Au and Au-Au collisions at 200 GeV in PHENIX. Dmitri Kotchetkov (University of California at Riverside) for PHENIX Collaboration. Quark Matter’04, Oakland, January 16 th , 2004. Strangeness at PHENIX. Motivations:

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Dmitri Kotchetkov (University of California at Riverside) for PHENIX Collaboration

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  1. Study of Cronin effect and nuclearmodification of strange particles in d-Au and Au-Au collisions at 200 GeV in PHENIX Dmitri Kotchetkov (University of California at Riverside) for PHENIX Collaboration Quark Matter’04, Oakland, January 16th, 2004.

  2. Strangeness at PHENIX • Motivations: • Strange particles as a tool to quantify the effects of medium modification • Strangeness observables to look into initial (gluon saturation) or final state (quark recombination, flow) • Effects of strangeness on energy loss • PHENIX ongoing analyses: • single

  3. Nuclear enhancement and suppression Parallel Session talk “p/K/p production and Cronin effect from p-p, d-Au and Au-Au collisions at 200 GeV” by Felix Matathias

  4. Mesons vs. baryons or heavier vs. lighter? In central Au-Au collisions: • No suppression of protons at Pt > 2.0 GeV • Suppression of p0 up to measurement limits (~10 GeV) In central d-Au collisions: • Nuclear enhancement (Cronin) is larger for protons

  5. How strangeness affects nuclear modification? • Effect of strange quarks on Rcp • Strange baryons and antibaryons vs. strange mesons (number of quarks) • Mass dependence of Rcp among strange particles

  6. Detectors West Arm East Arm PbSc Electromagnetic Calorimeter Pad Chambers 450 900 2m 5.1m Drift Chambers Beam-Beam Counters Time of flight Counters Beam direction h = -0.35…+0.35

  7. Hadron’s time of flight In Time of flight Counters (TOF): In Electromagnetic Calorimeter (EMC): p+ p+ K+ P+ P+ K+ charge/momentum (c/GeV) charge/momentum (c/GeV) P- K- P- K- p- p- time of flight (ns) time of flight (ns) time of flight resolution: TOF: 115 ps EMC: 700 ps (average) function of energy of a cluster

  8. L reconstruction • high asymmetry of decay • mean P of p from L decay equals 0.3 GeV • detect protons in high resolution TOF (up to 3 GeV) • reconstruct protons into pairs with any hadron detected either in TOF or EMC • event mixing technique to build a combinatorial background

  9. counts/2.5(MeV/c2) ppinvariant mass from d-Au collisions L: S/B = 1/5 L-bar: S/B = 1/4 L Signal+Background Background counts/2.5(MeV/c2) invariant mass (GeV/c2) L From 63 x 106 minimum bias d-Au collisions: L: Counts = 24395+/-373(stat) L-bar: Counts = 9744+/-229(stat) Signal invariant mass (GeV/c2)

  10. counts /5(MeV/c2) ppinvariant mass from Au-Au collisions L: S/B = 1/33 L-bar: S/B = 1/33 L Signal+Background Background counts /5(MeV/c2) invariant mass (GeV/c2) From 20 x 106 minimum bias Au-Au collisions: L: Counts = 62786+/-1580(stat) L-bar: Counts = 48377+/-1358(stat) L Signal invariant mass (GeV/c2)

  11. Detector acceptance normalization acceptance acceptance K0S Pt (GeV/c) Pt (GeV/c) • Single particle generator (K0S, L, e t.c.) • Simulation of PHENIX detector response • Extract particle yields as for real data

  12. 1/Nevt 1/2p 1/mt dN2/dmtdy (GeV/c)-2 PHENIX Preliminary Pt (GeV/c) Only statistical errors are shown L and L-bar Pt spectra in d-Au Minimum bias collisions at 200 GeV Poster Strangeness 5 Arkadij Taranenko

  13. f reconstruction • f -> K+K- channel • identify kaons either in TOF or EMC • event mixing technique to build a combinatorial background

  14. K+K-invariant mass from Au-Au collisions counts/1(MeV/c2) From 19 x 106 minimum bias Au-Au collisions: f: Counts = 5560+/-240(stat) invariant mass (GeV/c2) S/B = 1/8.5 counts/1(MeV/c2) Posters: Strangeness 14 by Charles Maguire Flow 7 by Debsankar Mukhopadhyay invariant mass (GeV/c2)

  15. f mt spectra in Au-Au collisions at 200 GeV K+K- Minimum bias events dN/dy=1.340.09(stat) 0.20(syst) T=366 11(stat) 18(syst) MeV 0-10% 0-10% on correct scale, others offset by factors of 10 1/2mT dN/dmTdy(GeV/c2)-2 10-40% Parallel Session talk “Light vector mesons (f) in d-Au collisions in PHENIX” by Richard Seto 40-92% PHENIX MT(GeV/c2)

  16. Cronin effect in d-Au collisions

  17. Rcp of identified hadrons (0-20% d-Au central collisions) at 200 GeV Only statistical errors shown for L

  18. Rcp of identified hadrons (20-40% d-Au central collisions) at 200 GeV • ‘s Rcp modification is very similar to one of the proton

  19. Rcp of identified hadrons (40-60% d-Au central collisions) at 200 GeV Mass of L is close to one of a proton

  20. Nuclear modification in Au-Au collisions

  21. Rcp of identified hadrons (0-10% Au-Au central collisions) at 200 GeV nucl-ex/0307022 Rcp (0-10%)/(60-92%) pt (GeV/c)

  22. Rcp of f (0-10% Au-Au central collisions) at 200 GeV Mass of f is close to one of a proton

  23. Summary Are differences in Rcp attributable to mass or quark number? • There is no evidence for mass dependence of Rcp • Strangeness seems to have no effect on Rcp • There is a difference in Rcp for mesons and baryons (see STAR results of L’s Rcp in Au-Au)

  24. Outlook • Rcp results from K0S and from L (Au-Au) • Analysis of multi-strange baryons (X0, X+, X-, W- and others)

  25. Extracted K0S signal counts/2.5(MeV/c2) counts/2.5(MeV/c2) p-p d-Au invariant mass (GeV/c2) invariant mass (GeV/c2) From 48.85 x 106 minimum bias p-p collisions: Counts = 16630+/-605(stat) 62.20 x 106 minimum bias d-Au collisions: Counts = 116397+/-2627(stat)

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