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System size dependence of strange particle correlations in Cu+Cu and Au+Au collisions at sNN = 200 GeV at RHIC Christine Nattrass (Yale University) STAR Collaboration SQM 2007, Levoča, Slovakia Outline Motivation Analysis technique Results Conclusion s STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 2 Intermediate pT baryon/meson enhancement Large enhancement of baryon/meson ratio in central collisions relative to p+p A. Timmins, SQM 2007 nucl-ex/0608017 in both Au+Au and Cu+Cu reaches maximum at pT ~ 2-3 GeV/c not unmodified jet fragmentation Baryon/meson splitting of Rcp strange and non-strange particles show similar suppression A. Timmins, QM 2006 nucl-ex/0608017 STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 3 Motivation – particle identification in jets Particle/antiparticle differences Quark vs gluon jets Meson/baryon differences Parton Coalescence/ recombination mechanisms Consistent with particle ratios Testable with identified Hadrons particle correlations? Hadrons K0S, Parton K0S, STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 4 Strange particle identification Vo Full azimuthal acceptance Reconstruction of decay vertices possible ~95% purity in Cu+Cu high pT K0S STAR Preliminary Ξ- Ξ+ Mass (GeV/c) Mass (GeV/c) STAR Christine Nattrass, Yale University Slovakia STAR Preliminary STAR Preliminary Arbitrary scale STAR Preliminary Arbitrary scale Arbitrary scale STAR 2.0 GeV<pT<2.5 GeV, 0-10% Preliminary Arbitrary scale Arbitrary scale 2.0 GeV<pT<2.5 GeV, 0-10% SQM 2007 Levoča, 5 Motivation - Long-range pseudorapidity correlations nucl-ex/0701074 h-h STAR Christine Nattrass, Yale University Slovakia Long-range pseudorapidity () correlations observed by STAR in Au+Au at intermediate pT Near side jet peak sits on plateau (Ridge) Significant contribution to the near-side yield in central Au+Au Look for particle and system size dependencies which might reveal information about production mechanism SQM 2007 Levoča, 6 6 ΔΦ-Δη Correlations - Ridge previously observed to be flat in To determine relative contributions, find yields for near-side, take projections in Method Au+Au 0-10% STAR preliminary h+h -0.75<<0.75 Jet + Ridge 0.75<||<1.75 Ridge Jet = (Jet+Ridge) – Ridge*.75/1.75 Ridge = yield from -1.75<<1.75 – jet yield Flow contributions to jet nucl-ex/0701074 cancel v2 roughly flat with 3<pt,trigger<4 GeV pt,assoc.>2 GeV STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 7 Is there a Ridge in Cu+Cu? projection flat at large Small and large regions match on away side Small yield above background in large region Jet yield in consistent with Jet in subtracting (Jet+Ridge)-Ridge (Jet+Ridge) Ridge - Ridge*.75 1/Ntrig dN/d The Ridge in Cu+Cu 1/Ntrig d2N/dd trigtrig trig<6.0 3.0 3.0 GeV<p GeV<p GeV, 1.5 1.5 3.0 GeV<p <6.0GeV, GeV, 1.5 T T T<6.0 assoc assoc<p trigtrig trig assoc GeV<p GeV<p GeV<p <p T T T <p T TT h-h, h-h, 0-20% 0-20% Cu+Cu Cu+Cu ss s = =200 =200 200 GeV GeV h-h, 0-20% Cu+Cu GeV NN NN NN ~.19 Jet + Ridge Ridge STAR Preliminary STAR Preliminary STAR Preliminary -1<<1 1/Ntrig dN/d STAR Preliminary ~.13 Ridge 1/Ntrig dN/d 0 STAR Christine Nattrass, Yale University Slovakia Jet+Ridge -.75<<.75 Different flow background parameters .75<||<1.75 scaled by .75 ~.20 SQM 2007 Levoča, 8 Determination of yields and errors 3.0 GeV<pTtrig<6.0 GeV, 1.5 GeV<pTassoc<pTtrig h-h, 0-20% Cu+Cu sNN = 200 GeV reflected Arbitrary units STAR Preliminary Background: trig assoc B(1+2 v2 v2 cos(2ΔΦ)) Different fit methods for determination of B Zero Yield At Minimum (ZYAM) 1 point, 3 points B as Free parameter (used as best guess) v2 error v2 measurements in progress upper bound for v2 measured v2 10-15% depending on pT, centrality fit with ZYAM with 3 points, best v2 fit with ZYAM with 3 points, high v2 fit with ZYAM with 3 points, low v2 fit with ZYAM with 1 point fit with background as free parameter STAR Christine Nattrass, Yale University Slovakia estimate for lower bound, near 0 Λ,Λ,K0S,Ξ-,Ξ+ v2 not measured Assume quark scaling of h v2 in Cu+Cu SQM 2007 Levoča, 9 9 Near-side Yield vs Npart Jet yield flat with Npart within errors no v2 or background error due to method Ridge yield very small flat with Npart within errors No trigger particle type dependence Data points at same Npart offset for visibility Jet yields: 10% error added to V0 and h triggers to account for track merging, 15% to triggers STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 10 Near-side Yield vs Npart Cu+Cu vs Au+Au Jet yield comparabl e in Cu+Cu and Au+Au Ridge yield consistent with Npart in Cu+Cu and Au+Au STAR Preliminary d+Au, Au+Au from nucl-ex/0701047 Data points at same Npart offset for visibility SQM 2007 Levoča, STAR Christine Nattrass, Yale University Slovakia 11 Near-side yield trigger vs pT Jettrigger yield rises with pT in h-h Yield roughly constant with centrality No particle type dependence within error bars Central Au+Au and 060% Cu+Cu jet yields comparable nucl-ex/0701047 STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 12 pT-distribution of associated particles nucl-ex/0701047 Ridge spectra similar to the bulk Cu+Cu measurements probably not possible Jet spectra are slightly harder Cu+Cu T within error of Au+Au Cu+Cu fit only to h-h Trigger particle T(ridge) MeV T (jet) MeV h+/- 438 ± 4 (stat.) 478 ± 8 K0S 406 ± 20 (stat.) 530 ± 61 Λ 416 ± 11 (stat.) 445 ± 49 STAR Christine Nattrass, Yale University Slovakia J. Putschke, QM 06 445 20 MeV Fit to A exp(-pT/T) SQM 2007 Levoča, 13 Conclusions Ridge yields Cu+Cu very small Cu+Cu and Au+Au consistent at the same Npart No trigger particle type dependence within errors including non-strange, and singly and doubly strange triggers Jet yields Cu+Cu and Au+Au consistent at the same Npart increases with pT trigger constant with centrality independent of system STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 14 Future work Systematics Reduce systematic error from v2 Identified particle v2 STAR Preliminary Coming soon Identified associated particles in Cu+Cu triggers Comparisons to Au+Au – See B. Abelev's SQM talk ~1000 triggers in central Cu+Cu with pT>2.5 GeV/c! ~2000 in central Au+Au Away-side yields Energy dependence of Jet and Ridge yields STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 15 STAR Collaboration University of Illinois at Chicago - Argonne National Laboratory Institute of High Energy Physics - University of Birmingham Brookhaven National Laboratory California Institute of Technology - University of California, Berkeley - University of California, Davis - University of California, Los Angeles - Carnegie Mellon University - Creighton University – Nuclear Physics Inst., Academy of Sciences Laboratory of High Energy Physics - Particle Physics Laboratory - University of Frankfurt - Institute of Physics, Bhubaneswar - Indian Institute of Technology, Mumbai - Indiana University Cyclotron Facility - Institut de Recherches Subatomiques de Strasbourg - University of Jammu - Kent State University Institute of Modern Physics - Lawrence Berkeley National Laboratory Massachusetts Institute of Technology - Max-Planck-Institut fuer Physics Michigan State University - Moscow Engineering Physics Institute - City College of New York - NIKHEF and Utrecht University - Ohio State University - Panjab University - Pennsylvania State University - Institute of High Energy Physics Purdue University – Pusan National University - University of Rajasthan - Rice University - Instituto de Fisica da Universidade de Sao Paulo - University of Science and Technology of China - Shanghai Institue of Applied Physics SUBATECH - Texas A&M University - University of Texas, Austin - Tsinghua University - Valparaiso University – Variable Energy Cyclotron Centre, Kolkata Warsaw University of Technology - University of Washington - Wayne State University - Institute of Particle Physics - Yale University - University of Zagreb Thank you! STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 16 Backup slides STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 17 STAR Christine Nattrass, Yale University Slovakia SQM 2007 Levoča, 18 18
