Betty Abelev UIC University of Illinois at Chicago 1.Motivation 2.Method 3.What we know 4.What we’re investigating 5.Outlook Strange Particle Correlations in STAR

SQM07 Levoča, Slovakia Betty I. Abelev 2 Baryon/Meson ratio increasing w/centrality Hadronization at mid-p T : Interplay between coalescence and fragmentation How does the jet observed in p+p interact with the bulk of central Au+Au? Three data sets: d+Au, Cu+Cu, (s NN ) ½ =200 GeV K 0 S (ds), Λ(uds), Ξ(dss), Ω(sss) Particle production at intermediate p T

SQM07 Levoča, Slovakia Betty I. Abelev Recombination and Fragmentation [GeV/c] dN/p T dp T dy Exponential (thermal) parton spectrum qualitatively explains baryon excess at mid p T mesonsbaryons TTTTT SSSSS TSTSS STT Recombination: – Shower (S) – Thermal (T) S & T can mix – Particle spectra are a sum of various components 3 GeV/c hadron can be  Produced via fragmentation  If meson: coalescence of GeV/c partons  If baryon: 3 1 GeV/c partons (more abundant!) R.Hwa et al, Phys.Rev.C70 (024904) ReCo cartoon 3 pTpT

SQM07 Levoča, Slovakia Betty I. Abelev 4 Strangeness via fragmentation: inaccessible? R.C Hwa & C.B. Yang nucl-th/  Shower s-quarks are suppressed w.r.t u & d quarks -- Ω : sss ( φ ss) at intermediate p T come mostly from TTT (TT)!  Differ significantly from K and Λ, which include non- strange quarks  No Ω baryons in jets?  (STAR)  (STAR)

SQM07 Levoča, Slovakia Betty I. Abelev Correlation Method Calculate  & plot  a doubly-peaked correlation function –Normalize by N triggers p+p and d+Au: 2 Gaussians + flat background Au+Au: 2 Gaussians +flat background+ flow same-side away-side 5 Access fragmentation statistically via azimuthal (φ) and pseudo-rapidity (η) 2-particle correlations

SQM07 Levoča, Slovakia Betty I. Abelev 6 Λ, Ξ, and Ω Δφ correlations! Observe same side peak using singly, doubly and triply strange baryons as triggers The strength of yield per trigger seems independent of s-content An Ω same-side peak clearly present

SQM07 Levoča, Slovakia Betty I. Abelev 7 Strangeness content as a function of p T -trigger No species dependence seen Normalized by N trigger – try other normalizations? Systematic error due to v 2 subtraction is large…

SQM07 Levoča, Slovakia Betty I. Abelev 8   ridge jet Separating Jet from Ridge Divide the  space into jet+ridge and ridge-only slices Subtract ridge from jet+ridge region  get Jet Subtract BG & v 2 from ridge only region  get Ridge      jet+ridge ridge only jet ridge

SQM07 Levoča, Slovakia Betty I. Abelev 9 ∆  projection “The Dip”: a detector effect ∆  projection ∆  projection 5 dips, 4 due to a two-track helicity combination (1,-1), (-1,1); 1 to genuine track merging Corrected by (1) correlating pairs of given helicity only and (2) replacing the dip regions by mirror images, where the dip is gone, and (3) an anti-merging cut M. Bombara, SQM07 A dip at Δη=Δφ ~0 due to track merging at the detector pad crossings

SQM07 Levoča, Slovakia Betty I. Abelev 10 Cu+Cu near-side yields Look at system- size dependence Three centralities Trend is similar to Au+Au No centrality or species dependence observed C. Nattrass, SQM07

SQM07 Levoča, Slovakia Betty I. Abelev 11 Jet vs. Ridge: – p T -trigger dependence near-side yield is ridge-dominated at intermediate p T jet yield: - increases steeply with p T -trig jet/ridge ratio increases with p T -trig Jet+Ridge Jet Ridge

SQM07 Levoča, Slovakia Betty I. Abelev 12 jana Ridge increases with centrality Jet yields stay constant Jet+Ridge Ridge Jet Jet vs. Ridge: – centrality dependence

SQM07 Levoča, Slovakia Betty I. Abelev 13 Jet yields appear constant with centrality Ridge yields are small, consistent with Au+Au Fit well with Au+Au results Investigate in more detail: add Cu+Cu C. Nattrass, SQM07 STAR Preliminary

SQM07 Levoča, Slovakia Betty I. Abelev 14 Associated hadrons in Jets and the Ridge jana Trigger particle T(ridge) MeVT (jet) MeV h +/- 438 ± 4 (stat.)478 ± 8 K0SK0S 406 ± 20 (stat.)530 ± 61 Λ 416 ± 11 (stat.)445 ± 49 STAR preliminary jet slope ridge slope inclusive slope h-h correlations p T associated >2GeV/c Ridge spectra similar to bulk particles Jet spectra are harder (T increases steeply with p T trig )

SQM07 Levoča, Slovakia Betty I. Abelev 15 Δη h, K 0 S, and Λ projections p Ttrigger h-h  -h  -h K 0 -h M. Bombara, SQM GeV/c GeV/c GeV/c GeV/c GeV/c First correction for the “dip”…. All available V0 statistics used

SQM07 Levoča, Slovakia Betty I. Abelev 16 Peak width studies: Δφ vs. Δη Δη peaks narrow with higher p T Δφ peaks: Λ & h yields: perhaps slight narrowing with p T; K 0 S yields ~ constant M. Bombara, SQM % Central 200 GeV AuAu p T associated > 1.5 GeV/c Jet Δφ : |  |<1.0

SQM07 Levoča, Slovakia Betty I. Abelev 17 2D Ξ-h correlations Observe the Δη broadening Cannot separate ridge from jet-only: Not enough statistics or the signal is too broad? Uncorrected for lost pairs at Δη~Δφ~0 STAR Preliminary

SQM07 Levoča, Slovakia Betty I. Abelev <|  η|<.1.4 STAR Preliminary |  η|<0.7 STAR Preliminary Strange associated particles: Jet & Ridge  /K 0 S ratio: in the ridge: ~ 1.0  similar to that from inclusive p T spectra in the jet: ~ 0.5  consistent with p+p

SQM07 Levoča, Slovakia Betty I. Abelev 19 Strange associated particles: B/M ratio –Trigger: High p T charged hadron p T = [3-6] GeV/c –Associate: K 0 S, , or   with p T = [1-4] GeV/c –  range:|  |<1 B/M RatioNear-SideAway-Side (Λ+Λ)/K s ±0.120 (Stat.) ±0.175 (Sys.)1.71 ±0.321 (Stat.) ± (Sys.) Near-Side Away-Side 10%-40% 200 GeV Au+Au 1/N tr dN tr /dΔφ J. Zuo, SQM07 Same-side: p+p-like (jet?) Away-side: Au+Au like (bulk?) STAR Preliminary

SQM07 Levoča, Slovakia Betty I. Abelev 20 No observable differences Particle Ratio Near- Side Away- Side Λ/ΛΛ/Λ ± (Stat.), ±0.200 (Sys.) ± (Stat.) ± (Sys.) Near-Side Away-Side 10%-40% 200 GeV AuAu Strange associated: particle/anti- particle ratio J. Zuo, SQM07

SQM07 Levoča, Slovakia Betty I. Abelev 21 The origin of the ridge? So far explain the ridge qualitatively Can’t distinguish between the models yet So far explain the ridge qualitatively Can’t distinguish between the models yet Armesto et al : expanding medium broadens the jet in η (hep-ph/ ) Hwa et al : ReCo jets (nucl-th/ ) Multi-strange phantom jets? Voloshin et al : radial flow on the same-side (PLB 632 (2006) 490) Majumder et al : gluon field fluctuations (hep- ph/ )

SQM07 Levoča, Slovakia Betty I. Abelev 22 We detect no species dependence as a function of s- quark content Same-side yield increase as a function of collision centrality and system size (due to increase in ridge) “Jet-only” component is independent of centrality Ridge seems to be a part of the bulk, but associated with jet production! Ridge: same or T as the bulk Meson-baryon ratio similar to that of the bulk and to the away side jet-medium coupling? Δη appears to be the same for singly-strange mesons & baryons Multi-strange baryon same-side very broad in Δη Due to s-quark content? Urgently need calculations and predictions for the ridge  that we can test! Summary

SQM07 Levoča, Slovakia Betty I. Abelev 23 The 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 -UNICAMP