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Near-side  correlations of high-p t hadrons from STAR Jörn Putschke for the STAR collaboration

Near-side  correlations of high-p t hadrons from STAR Jörn Putschke for the STAR collaboration Lawrence Berkeley National Laboratory. “Ridge” observation. d+Au, 40-100%.

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Near-side  correlations of high-p t hadrons from STAR Jörn Putschke for the STAR collaboration

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  1. Near-side  correlations of high-pt hadrons from STAR Jörn Putschke for the STAR collaboration Lawrence Berkeley National Laboratory

  2. “Ridge” observation d+Au, 40-100% Additional near-side long range corrl. in  (“ridge like” corrl.) observed. Dan Magestro, Hard Probes 2004, STAR, nucl-ex/0509030 and P. Jacobs, nucl-ex/0503022 Au+Au, 0-5% 3 < pT(trig) < 6 GeV2 < pT(assoc) < pT(trig)

  3. Outline Au+Au 0-10% preliminary 2-particle  correlations: • How to extract the “ridge” yield ? (additional near-side long range corrl. in ) • Quantify ridge properties in Au+Au (Cu+Cu)200 GeV collisions • Summary & discussion 3<pt,trigger<4 GeV pt,assoc.>2 GeV

  4. Components of  correlations Au+Au 20-30% a b b c c Au+Au 0-10% preliminary Near-side jet-like corrl.+ ridge-like corrl. + v2 modulated bkg. Ridge-like corrl. + v2 modulated bkg. Away-side corrl.+ v2 modulated bkg. Strategy: Subtract  from  projection to isolate the ridge-like correlation

  5. Extracting near-side “jet-like” yields J = near-side jet-like corrl. R = “ridge”-like corrl. 2 (J) ||<0.7 (J) ||<0.7 1 2 const bkg. subtracted const bkg. subtracted  (J+R) - (R) (J) flow (v2) corrected (J+R) ||<1.7 (J+R) ||<1.7 no bkg. subtraction v2 modulated bkg. subtracted Au+Au 20-30%

  6. Jet and Jet+Ridge yields & widths central periph. Correlate Jet ((J)) and Jet+Ridge ((J+R)) widths & yields via centrality pt,assoc. > 2 GeV pt,assoc. > 2 GeV Yield Width preliminary preliminary Jet+Ridge yield () Jet+Ridge width () central periph. preliminary Jet yield () Jet width () • Jet+Ridge yield increasing with centrality • Jet+Ridge shape asymmetric in and

  7. Jet yields & widths:  vs.  periph. central Correlate Jet ((J)) and Jet ((J)) widths and yields via centrality pt,assoc. > 2 GeV pt,assoc. > 2 GeV Yield Jet yield () Jet width () Width preliminary preliminary Jet yield () Jet width () • Jet yield ~ symmetric in  • Jet shape ~ symmetric in  for pt,trig > 4 GeV(asymmetric in  for pt,trig < 4 GeV)

  8. Extracting the ridge yield     3 < pt,trigger < 4 GeV and pt,assoc. > 2 GeV Jet+Ridge () Jet () Jet) preliminary yield,) Npart • Definition of “ridge yield”: i) ridge yield := Jet+Ridge(  Jet() ii) relative ridge yield := ridge yield / Jet()

  9. Ridge shape measurement in central Au+Au Au+Au 0-10% pt,assoc. > 2 GeV ridge yield preliminary  • ridge yield as function of  saturates at high  • non-uniform ridge shape in  • ridge more collimated in  for higher trigger pt

  10. Ridge yield in Au+Au pt,assoc. > 2 GeV preliminary Ridge yield slightly decreasing (~ constant) as function of trigger pt

  11. “Jet yield” vs. pt,assoc. in central Au+Au preliminary Jet yield inclusive “Jet spectrum” much harder than inclusive h and increasing with pt,trigger

  12. Ridge yield vs. pt,assoc. in central Au+Au preliminary inclusive “Ridge spectrum” slightly harder than inclusive h and ~ independent of pt,trigger

  13. “Jet”/ridge yield vs. pt,assoc. in central Au+Au “jet” slope ridge slope inclusive slope preliminary Ridge Jet preliminary preliminary Au+Au 0-10% preliminary Ridge / Jet yield

  14. Pion vs. Proton ridge yield pt,assoc. > 2 GeV preliminary Au+Au 0-10% Assoc. Protons Assoc. Pions Assoc. h Proton content of ridge larger than of jet part (more from strange assoc. particles in Janas talk)

  15. Ridge yield in Au+Au and Cu+Cu pt,assoc. > 2 GeV relative ridge yield relative ridge yield preliminary relative ridge yield relative ridge yield preliminary Relative ridge yield comparable at same Npart in Au+Au and Cu+Cu

  16. Scenarios Armesto et al, nucl-ex/0405301 i) Parton radiates energy before fragmenting and couples to the longitidunal flow • Gluon bremmstrahlung of hard-scattered parton • Parton shifted to lower pt • Radiated gluon contributes to broadening •  contradicts surface bias emission picture ! ii) Parton recombination(Chiu & Hwa Phys. Rev. C72:034903,2005) • Recombination of thermal partons only indirectly affected by hard scattering  not part of the jet • iii) Radial flow + jet-queching(Voloshin nucl-th/0312065)

  17. Discussion ridge/jet yield increasing pt,trig h+,- ridge jet pt,assoc. • ridge spectrum harder than inclusive h+,- (~ 40-50 MeV in slope parameter)  consistent with parton recombination (T~15 MeV) ? • agreement with radial flow + jet quenching ? • ridge spectrum qualitatively in agreement with parton energy loss and coupling to longitudinal flow • quantitative calculation for comparison needed

  18. Outlook y [fm] y [fm] 13 very preliminary ! Part/Col Au+Au 30-40% Part/Col Cu+Cu 0-10% Part ~ energy density Coll ~ parton origin 12 x [fm] x [fm] • Study geometry effects in more detail:  Look at near-side modifications in Au+Au with respect to the reaction plane • PID ridge yield study with pions, protons and strange particles (see Janas talk) • 3-particle  near-side correlations

  19. Backup slides

  20. Analysis methods cont. QM05 preliminary v2 subtraction and systematic error estimation Au+Au: Used v2 values = mean between v2 RP and v2{4} measurements Systematic errors mainly due to uncertainties in v2;use v2 RP and v2{4} as upper and lower limit v2 subtraction and systematic error estimation Cu+Cu: Used v2 values = v2{CuCu-pp} Systematic errors mainly due to uncertainties in v2;use v2 RP and no flow as upper and lower limit • Use event-mixing to account for pair acceptance & use eff. correction for ass. particles • Background: • Subtract constant backgroundfor (J) method • Subtract v2 modulated background for (J+R) method • Assume Gaussian correlation shape:yield() = gaus integral / bin counting () = gaus width

  21. Au+Au near-side (J) (J+R) yields & widths II pt,assoc. > 3 GeV pt,assoc. > 3 GeV (J+R) yield(J+R)) preliminary preliminary yield(J)) (J) Correlate (J) and (J+R) widths & yields via centrality • (J) yield ~ J+R)yield • J) and J+R)widths ~ constant

  22. Relative ridge yield in Au+Au pt,assoc. > 2 GeV preliminary relative ridge yield Relative ridge yield strong increasing with centrality for lower trigger pt

  23. Summary • Ridge shape non-uniform in  in central Au+Aucollisions • Ridge yield slightly decreasing (~ constant) as function of pt,trigger • Ridge spectrum independent of pt,trigger and slightly harder than inclusive charged hadron spectrum (~40-50 MeV in slope parameter) • Relative ridge yield for identified assoc. pions suppressed with respectto charged hadrons (identified assoc. protons enhanced) • At the same Npart the relative ridge yield seems to be comparable in periph. Au+Au (30-40%) and in central Cu+Cu (0-10%) collisions

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