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

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

3 STAR 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 p T,trig >2.5 GeV/c p T,ass >1.0 GeV/c STAR preliminary

4 STAR Centrality dependence 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. p T,trig >2.5 GeV/c p T,ass >1.0 GeV/c M. Horner, QM06

5 STAR STAR preliminary B/M Ratio Intermediate p T 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 Intermediate p T, Baryon & Meson: Grouping of R CP and v recombination pictures Can recombination explain particle ratios in the jet cones?

6 STAR Anti-B/B Ratio Intermediate p T 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 STAR preliminary

7 STAR Anti-Baryon Density Collisions which contain ggg, qbar+g or qqbar+g processes 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 STAR preliminary H.D.Liu QM06 From  B/B ratios in the correlation Baryon & Anti-baryon production with Jets Gluon vs. Quarks with Jets H. Liu, Z. Xu nucl-ex/

8 STAR 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, p T >3.0 GeV/c Associate: K S 0, , or  (i.e. V 0 decay), p T >1.0 GeV/c parton trigger hadron Λ, Λ, K 0 S parton near-side associated away-side associated

9 STAR Analysis method Step 1:3-D histogram with , , and m inv (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 m inv vs.  Fit the m inv distribution  yield dN/d  ( K S 0, , 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 ZYAM (zero-yield at the minimum) ZYA1 (zero-yield at one )

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

11 STAR Hadron_Ks & + Correlation Centrality bin: 10-40% The yellow band : systematic error From the line: Left part: near-side Right part: away-side Particle Ratios Near-SideAway-Side (  +  )/Ks0.77  0.12 (stat) 0.18 (sys)1.7  0.3 (stat) 0.6 (sys) Near-SideAway-Side 3<p T,trig <6 GeV/c 1<p T,ass <4 GeV/c

12 STAR STAR Preliminary Baryon to Meson Ratio with Jets Lambda to Ks Ratio : Away-Side > Near-Side Anti-Proton to    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 STAR 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? Sound wave excitation particles maybe slower than the speed of sound (v s =c/3) For our p T range slower particles would have to be heavy For production from sound wave excitation the bumps should have mostly heavy particles  (  +  )/K S 0 would get large in the bump region p T,trig >2.5 GeV/c p T,ass >1.0 GeV/c STAR preliminary Mach Cone Concept/Calculations Stoecker, Casalderry-Solana et al; Muller et al.; Ruppert et al., … Cherenkov Radiation Majumder, Koch, & Wang; Vitev Jet Deflection (Flow) Fries; Armesto et al.; Hwa M. Horner, QM06

14 STAR B/M Ratio in Distribution ??? away near Medium mach cone Δ=Δ= Trigger Δ  =  /2 Medium Associate A slope at Away-Side?  Slow particle  Double bumpA slope at Away-Side?  Slow particle  Double bump K S 0 Fast particle  Double bump ?? K S 0 Fast particle  Double bump ?? B/M ratio: Away-Side seems to increase in the "cone" region - as it maybe for sound wave excitation.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-waveIncreased B/M ratio may also be consistent with recombination in high density region of the shock-wave Error bars too large to get strong conclusionsError bars too large to get strong conclusions The same shape in the away-side using v 2 background from three different methods The shape of Baryon to Meson ratio on the away-side seems to be independent of v 2 background and background subtraction method. Perhaps a slope, but error bars are still too large to draw conclusions.  +  K S 0

15 STAR (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. (B/M) A to (B/M) N double ratio peripheral central

16 STAR Centrality Dependence –Double bump, Broadened & Singly-peaked –The shape consistent with di-hadron correlation Hadron_ & Correlation peripheral 3<p T,trig <6 GeV/c; 1<p T,ass <4 GeV/c central

17 STAR Hadron_ & Correlation Centrality bin: 10-40% The yellow band: Systematic error. From the line: Left part: near-side Right part: away-side Particle Ratios Near-SideAway-Sidep T =1.5GeV/c // 0.92  0.20 (stat) 0.20 (sys)0.89  0.17 (stat) 0.37 (sys)0.76  Near-SideAway-Side 3<p T,trig <6 GeV/c 1<p T,ass <4 GeV/c

18 STAR (  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 v 2 and background subtraction method (  B/B) A to (  B/B) N ratio peripheral central

19 STAR 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 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? Or others?) –slope of B/M and  /  on the away-side seems to be independent of v 2 and background subtraction method Thanks!! Acknowledgments: STAR Collaboration Dr. Paul Sorensen

20 STAR 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 STAR Backup

22 STAR V0 reconstruction V0s from UCLA/LBL picoDsts

23 STAR   a.u. p T trig =3-6 GeV/c, 1.5 GeV/c <p T assoc < p T trig Au+Au 200 GeV  ridge    ridge jet jet+ridge after v 2 subtraction jet ridge v 2 + away-side peak h-h Au+Au: long-range  correlations at near side (“the ridge”) Lesson: The near-side jet does interact with the medium Fragmentation and energy loss - near-side Di-hadron correlations  trigger

24 STAR Ks,  & Hadron v 2 Background: V0 & Hadron v 2 Background function: B(  )=b 0 (1+2 cos(2  )) Final results background: Average v 2 –Ks and  v 2 {EP} & v 2 {LYZ} –Charged Hadron: v 2 {EP} & v 2 {4} A part of systematic errors will be calculated by the v 2 {EP} & v 2 {LYZ}, v 2 {4} Weight average flow: v2v2 HadronKsLambda V0 LYZ v 2 : pt [1,4] Hadron v 2 {4}: pt [3.2,6.5] v2{4} & v2{EP} Phys. Rev. C 72 (2005) v2{LYZ} paper in preparation

25 STAR Lee-Yang Zeroes method is less biased by non-flow correlation. Nucl. Phy. A 727 (2003) Sum generating function: –Flow vector projection into arbitrary angel . –Generating function for a given . Integrated flow: –From the first minimum r 0  Differential flow Lee-Yang Zeroes method First minimum of |G| 2 determines r 0  all events average over  all particles in all events average over  removes acceptance effects

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

27 STAR Ratio vs.  B/M Ratio at Near-Side B/M Ratio vs.  at Away-Side  B/B Ratio at Near-Side  B/B Ratio vs.  at Away-Side