Strange Particle Ratios on the Near- & Away-Sides of Jets at RHIC

1. SQM 2007, Levoča, Slovakia Strange Particle Ratios on the Near- & Away-Sides of Jets at RHIC Jiaxu Zuo Shanghai Institute of Applied Physics & BNL (For STAR Collaboration)

2. Outline • Motivation • Analysis Method • Results & Discussions • Summary • STAR Au+Au 200GeV Year 2004 Running Data • ~13M Events

3. pT,trig>2.5 GeV/c pT,ass>1.0 GeV/c 0.6 0.4 0.2 0.0 STAR preliminary Di-hadron correlations pT,trig>4 GeV/c pT,ass>2 GeV/c For high pT: away-side correlation is gone! back-to-back jets are quenched At lower pT: away-side correlations return but they are highly modified with a double bump!? We will try to understand what causes this behavior

4. Centrality dependence M. Horner, QM06 pT,trig>2.5 GeV/c pT,ass>1.0 GeV/c Singly-peaked -> broadened -> becomes doubly bump What’s the baryon/meson ratio in the near- and away-side peak? What are the anti-baryon-to-baryon ratios? We will measure the ratios to try to understand the source of the correlations in different centralities.

5. B/M Ratio Intermediate pT STAR preliminary large enhancement of baryon/meson ratio in central Au+Au relative to p+p reaches maximum at pT~3 GeV/c Perhaps related to faster increase with centrality of baryon production from recombination Intermediate pT, Baryon & Meson: Grouping of RCP and v2 ----recombination pictures Can recombination explain particle ratios in the jet cones?

6. Anti-B/B Ratio Intermediate pT STAR preliminary We can also learn about gluons vs quarks from B/B ratios with the jet correlation. For example: anti-baryons  dominated by gluon jets baryons  mixture of quark and gluon

7. STAR preliminary Anti-Baryon Density H.D.Liu QM06 • Collisions which containggg, qbar+g or qqbar+gprocesses have higher anti-baryon phase space density • Anti-baryon phase space density from collisions involving a gluon is much higher than those without a gluon H. Liu, Z. Xu nucl-ex/0610035 • From B/B ratios in the correlation • Baryon & Anti-baryon production with Jets • Gluon vs. Quarks with Jets

8. away-side associated Λ, Λ, K0S parton parton near-side associated trigger hadron Λ, Λ, K0S Trigger-associate correlations • Identified particles correlations & B/M , B/B ratio can provide additional information on: • jet quenching • baryon/meson enhancement at STAR • particle production mechanisms • Di-hadron correlation Away-side shape • We’ll study identified associate particles using • Trigger: Charged hadron, pT>3.0 GeV/c • Associate:KS0, , or (i.e. V0 decay), pT>1.0 GeV/c

9. Analysis method Step 1:3-D histogram with , , and minv (Trigger-V0 pair) Step 2:Project over a given  range in this talk I show results for -1<<1: (combine jets & some ridge) Step 3: Plot minvvs. Fit the minv distribution  yield dN/d( KS0, , or ) minv    minv • Step 4: Repeat 1 to 3 with mixed events • Step 5: Scale the mixed event background with measured v2 • Subtract off the background • ZYAM (zero-yield at the minimum) • ZYA1 (zero-yield at one)

10. Hadron_Ks & L+L Correlation 3<pT,trig<6 GeV/c; 1<pT,ass<4 GeV/c • Centrality Dependence • Double bump -> Broadened -> Singly-peaked • The shape consistent with di-hadron correlation central peripheral

11. Hadron_Ks & L+L Correlation 3<pT,trig<6 GeV/c 1<pT,ass<4 GeV/c • Centrality bin: 10-40% • The yellow band : systematic error • From the line: Left part: near-side Right part: away-side Near-Side Away-Side

12. STAR Preliminary Baryon to Meson Ratio with Jets • Lambda to Ks Ratio : Away-Side > Near-Side • Anti-Proton to p-Ratio : Away-Side > Near-Side (PHENIX) Both STAR and PHENIX results consistent with larger B/M ratio on the Away-Side than Near-Side.

13. pT,trig>2.5 GeV/c pT,ass>1.0 GeV/c near 0.6 0.4 0.2 Medium away mach cone 0.0 STAR preliminary near Medium away deflected jets The shape of the ratio • Mach Cone Concept/Calculations • Stoecker, Casalderry-Solana et al; Muller et al.; Ruppert et al., … • Cherenkov RadiationMajumder, Koch, & Wang; Vitev • Jet Deflection (Flow) • Fries; Armesto et al.; Hwa M. Horner, QM06 • Can we learn something about the shape on the away-side? • Sound wave excitation particles maybe slower than the speed of sound (vs=c/3) • For our pT range slower particles would have to be heavy • For production from sound wave excitation the bumps should have mostly heavy particles (+)/KS0 would get large in the bump region

14. near Medium mach cone away Δ = p/2 Trigger Associate Δ=p Medium B/M Ratio in DFDistribution • A slope at Away-Side? L Slow particle  Double bump KS0 Fast particle  Double bump ?? • B/M ratio: Away-Side seems to increase in the "cone" region - as it maybe for sound wave excitation. • Increased B/M ratio may also be consistent with recombination in high density region of the shock-wave • Error bars too large to get strong conclusions • The same shape in the away-side using v2 background from three different methods • The shape of Baryon to Meson ratio on the away-side seems to be independent of v2 background and background subtraction method. • Perhaps a slope , but error bars are still too large to draw conclusions. L+L/KS0 ???

15. (B/M)A to (B/M)N double ratio central • (B/M)A to (B/M)N double ratio from central to peripheral • 00-10% &10-40% • Maybe a slope here • 40-80% • Difficult to describe • In the correlation function, • 00-10% &10-40% • There is a double bump and broadened away-side. • 40-80% • There seems to be a single peak. peripheral

16. Hadron_L &L Correlation 3<pT,trig<6 GeV/c; 1<pT,ass<4 GeV/c • Centrality Dependence • Double bump, Broadened & Singly-peaked • The shape consistent with di-hadron correlation peripheral central

17. Hadron_L &L Correlation 3<pT,trig<6 GeV/c 1<pT,ass<4 GeV/c Centrality bin: 10-40% • The yellow band: Systematic error. • From the line: Left part: near-side Right part: away-side Near-Side Away-Side

18. (B/B)A to (B/B)N ratio central • (B/B)A to (B/B)N ratio from central to peripheral • The ratio is around one • Maybe a slope at here, but error bars are still too large to conclude. Why is it a slope?? • Independent of v2 and background subtraction method peripheral

19. Summary • Measured the Conditional Yields of identified associate particles on the near- and away-side of jets • From central to peripheral : Double bump -> Broadened -> Singly-peaked • Extracted particle ratios on the near and away-side • Systematic errors from v2 and background normalization are large • errors can be reduced with more data (to reduce error on the level of the background) • and better understanding of v2 (to reduce uncertainty on the shape of the background) • Both STAR and PHENIX results consistent with larger B/M ratio on the away-side than near-side • Shape of away-side has been studied • some indication of a slope for B/M and L/L on the away-side (mach-cone? gluon vs. quark? Or others?) • slope of B/M and L/L on the away-side seems to be independent of v2 and background subtraction method Acknowledgments: STAR Collaboration Dr. Paul Sorensen Thanks!!

20. The Collaboration Shanghai Institue of Applied Physics - 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 - University of Illinois at Chicago - 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 - 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

21. Backup

22. V0 reconstruction V0s from UCLA/LBL picoDsts

23. Fragmentation and energy loss - near-side after v2 subtraction jet+ridge Dj  trigger  jet ridge  ridge Di-hadron correlations pTtrig=3-6 GeV/c, 1.5 GeV/c <pTassoc< pTtrig h-h jet ridge a.u.  Dh Df v2 + away-side peak Au+Au central @ 200 GeV Au+Au: long-range Dh correlations at near side (“the ridge”) Lesson: The near-side jet does interact with the medium

24. Weight average flow: Ks, L & Hadron v2 • Final results background: Average v2 • Ks and L: v2{EP} & v2{LYZ} • Charged Hadron: v2{EP} & v2{4} • A part of systematic errors will be calculated by the v2{EP} & v2{LYZ}, v2{4} • Background:V0 & Hadron v2 • Background function:B()=b0(1+2<v2A*v2B>cos(2)) • V0 LYZ v2:pt [1,4] • Hadron v2{4}:pt [3.2,6.5] v2{4} & v2{EP} Phys. Rev. C 72 (2005) 014904 v2{LYZ} paper in preparation

25. all events First minimum of |G|2 determines r0 average over  Lee-Yang Zeroes method • Lee-Yang Zeroes method is less biased by non-flow correlation. Nucl. Phy. A 727 (2003) 373-426 • Sum generating function: • Flow vector projection into arbitrary angel . • Generating function for a given . • Integrated flow: • From the first minimum r0 • Differential flow all particles in all events average over  removes acceptance effects

26. Same Event & v2 Background STAR preliminary for these plots, efficiency correction not applied

27. Ratio vs.Df • B/B Ratio at Near-Side • B/B Ratio vs.Df at Away-Side • B/M Ratio at Near-Side • B/M Ratio vs.Df at Away-Side