1. STAR 1 Strange Particle Ratios on the Near- & Away-Side of Jets at RHIC Jiaxu Zuo BNL/SINAP with Paul Sorensen BNL For STAR Collaboration 23rd Winter Workshop on Nuclear Dynamics

2. STAR 2 Outline Motivation Analysis Method Results & Discussions Summary STAR Au+Au 200GeV run4 Data 13M Events Related STAR analysis presented at WWND07: Near-side correlations of strange baryons and mesons (Jana Bielcikova) Mulit-strange triggers correlations (Betty Abelev)

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

4. STAR 4 Di-hadron correlations 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 0.2 0.6 0.4 0.0 p T,trig >2.5 GeV/c p T,ass >1.0 GeV/c STAR preliminary

5. STAR 5 Intermediate p T particle ratios large enhancement of baryon/meson ratio in central Au+Au relative to p+p reaches maximum at p T ~3 GeV/c Perhaps related to faster increase with centrality of baryon production from recombination

6. STAR 6 Intermediate p T particle recombination pictures of intermediate p T particle production: supported by meson and baryon grouping of R CP and v 2 can recombination explain particle ratios in the jet cones?

7. STAR 7 Intermediate p T particle ratios We can also learn about gluons vs quarks from  B/B ratios for example:anti-baryons  dominated by gluon jets baryons  mixture of quark and gluon STAR preliminary

8. STAR 8 Trigger-associate correlations  identified correlations at high-p T can provide additional information on: jet quenching baryon/meson enhancement at STAR particle production mechanisms  Λ from q-jet and g-jet,  Λ more from g-jet We’ll study identified associate particles using Trigger: High p T charged hadron p T >3.0 GeV/c Associate: K S, , or  (i.e. V 0 decay) with p T >1.0 GeV/c parton trigger hadron Λ, Λ, K 0 S parton near-side associated away-side associated

9. STAR 9 Analysis method Step 1:for each trigger-V 0 pair fill a 3-D histogram with , , and m inv Step 2:I project over a given  range in this talk I show results for -1<  <1: this combine jets & some ridge Step 3:plot m inv vs  fit the m inv distribution to get the yield dN/d  for K S, , or    m inv Step 4:repeat 1 to 3 with mixed events Step 5:scale the mixed event background with measured v 2 subtract off the background assuming zero-yield at the minimum or zero-yield at one (ZYAM or ZYA1) Jana Bielcikova's talk

10. STAR 10 Ks & Lambda Mass Fit Ks and Lambda Invariant Mass distribution in different  bins 10-40%

11. STAR 11 Same Event & v 2 Background STAR preliminary for these plots, efficiency correction not applied

12. STAR 12 Hadron_Ks & + Correlation   distribution of Hadron_Ks &  +  Correlation 10-40% Near-Side: Ks seems higher than Lambda+Anti-Lambda, point by point. Away-Side: It seems that Ks is lower than Lambda+Anti- Lambda. Particle Ratios Near-SideAway-Side (  +  )/Ks 0.765(0.120(Stat.) 0.175(Sys.)) 1.71(0.321(Stat.), 0.589(Sys.)) Near-SideAway-Side 3<p T,trig <6 GeV/c 1<p T,ass <4 GeV/c efficiency corrections now applied

13. STAR 13 Baryon to Meson Ratio with Jets pbar to    Ratio : Away-Side > Near-Side (PHENIX) Lambda to Ks Ratio : Away-Side > Near-Side

14. STAR 14 (B/M) Away /(B/M) Near Double Ratio at PHENIX & STAR Both STAR and PHENIX data are consistent with a larger B/M ratio on the away-side -> more matter seems to yield more baryons (B/M) Away /(B/M) Near Double Ratio 1<p T,assoc <4, 3<p T,trig <6 PHENIX: Meson Trigger PHENIX QM05 Nucl-ex/0510040

15. STAR 15 The shape of the ratio away near Medium mach cone Medium away near deflected jets can we learn something about the shape on the away-side? mach cone particles must be slower than the speed of sound for our p T range they would have to be heavy for mach-cone emission the bumps should have mostly heavy particles  (  +  )/K S would get large in the bump region 0.2 0.6 0.4 0.0 p T,trig >2.5 GeV/c p T,ass >1.0 GeV/c STAR preliminary

16. STAR 16 B/M Ratio in Distribution  Slow particle  Mach ConeA slope at Away-Side?  Slow particle  Mach Cone Ks Fast particle  Mach Cone?? Ks Fast particle  Mach Cone?? B/M ratio: Away-Side seems to increase in the "cone" region - as it should for mach cone emissionB/M ratio: Away-Side seems to increase in the "cone" region - as it should for mach cone emission Error bars are still too large to concludeError bars are still too large to conclude ??? away near Medium mach cone Δ=Δ= Trigger Δ  =  /2 Medium Associate

17. STAR 17 Hadron_ & Correlation   distribution of Hadron_  &  Correlation 10-40% Near-Side: Anti-Lambda and Lambda seems consistent. Away-Side: Seems a little difference between Anti-Lambda and Lambda from correlation function Particle Ratios Near-SideAway-Side // 0.916(0.200(Stat.), 0.200(Sys.)) 0.894(0.173(Stat.), 0.368(Sys.)) Near-SideAway-Side 3<p T,trig <6 GeV/c 1<p T,ass <4 GeV/c

18. STAR 18 The Ratio at Near-Side & Away-Side is consistent with non-trigger Anti-B/B ratio. STAR preliminary Anti-B/B Ratio in Distribution

19. STAR 19 Anti-B/B Ratio in Distribution Anti-B/B Ratio : The same slope at Away-Side?? Why is it a slope?? If it is, Why is it a slope??

20. STAR 20 Summary Measured the Conditional Yields of identified associate particles on the near- and away-side of jets Extracted particle ratios on the near and away-side Systematic errors from v 2 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 v 2 (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  /  on the away-side (mach-cone? gluon vs. quark?) –slope of B/M and  /  on the away-side seems to be independent of v 2 and background subtraction method

21. STAR 21 Backup

22. STAR 22 V0 reconstruction V0s from UCLA/LBL picoDsts

23. STAR 23 Near-Side Away-Side preliminary results B/M Ratio in Distribution

24. STAR 24 Near-SideAway-Side STAR preliminary Anti-B/B Ratio in Distribution

25. STAR 25 Δη correlations - the ridge Au+Au 20-30% a b cc b

26. STAR 26 Ks,  & Hadron v 2 V0 LYZ v 2 : 10-40%, pt [1,4] Ks: =0.104353 (0.000916851)  =0.105984 (0.00108642) Hadron v 2 {4}: 10-40%, pt [3.2,6.5] =0.151251 (0.00175313) Background: V0 & Hadron v 2 Background function: B(  )=b 0 (1+2 cos(2  )) AuAu@200GeV