1. System size dependence of azimuthal correlations at RHIC Christine Nattrass Yale University Star Collaboration

2. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 2Outline Motivation Motivation Analysis technique Analysis technique Results Results Conclusions Conclusions

3. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 3 Motivation – particle identification in jets Parton Parton Hadrons Hadrons Λ,Λ,K 0 S,Ξ +,Ξ -... Particle/antiparticle differences Particle/antiparticle differences Quark vs gluon jets Quark vs gluon jets Meson/baryon differences Meson/baryon differences Coalescence/ recombination mechanisms Coalescence/ recombination mechanisms Consistent with particle ratios Consistent with particle ratios Testable with identified particle correlations? Testable with identified particle correlations?

4. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 4 Strange particle identification Full azimuthal acceptance Full azimuthal acceptance Reconstruction of decay vertices possible Reconstruction of decay vertices possible ~95% purity in Cu+Cu high p T ~95% purity in Cu+Cu high p T VoVo 

5. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 5 5 Motivation - Long-range pseudorapidity correlations Long-range pseudorapidity ( Δη ) correlations observed by STAR in Au+Au at intermediate p T Long-range pseudorapidity ( Δη ) correlations observed by STAR in Au+Au at intermediate p T Near side jet peak sits on plateau (Ridge)‏ Near side jet peak sits on plateau (Ridge)‏ Significant contribution to the near-side yield in central Au+Au 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 Look for particle and system size dependencies which might reveal information about production mechanism nucl-ex/0701074 h-h

6. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 6 ΔΦ-Δη Correlations - Method Ridge previously observed to be flat in Δη in Au+Au Ridge previously observed to be flat in Δη in Au+Au To determine relative contributions, find yields for near-side, take ΔΦ projections in To determine relative contributions, find yields for near-side, take ΔΦ projections in -0.75<Δη<0.75 Jet + Ridge -0.75<Δη<0.75 Jet + Ridge 0.75<|Δη|<1.75 Ridge 0.75<|Δη|<1.75 Ridge Jet = (Jet+Ridge) – Ridge*.75/1.75 Jet = (Jet+Ridge) – Ridge*.75/1.75 Ridge = yield from -1.75<Δη<1.75 – Jet yield Ridge = yield from -1.75<Δη<1.75 – Jet yield Flow contributions to jet cancel Flow contributions to jet cancel v 2 flat with η for |η|<1 v 2 flat with η for |η|<1 Phys. Rev. C72, 051901(R) (2005), Phys. Rev. Lett. 94, 122303 (2005)‏ Phys. Rev. C72, 051901(R) (2005), Phys. Rev. Lett. 94, 122303 (2005)‏ 3<p t,trigger <4 GeV p t,assoc. >2 GeV Ridge Jet+ Ridge Ridge Au+Au 0-10% STAR preliminary h+h nucl-ex/0701074

7. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 7 7 Determination of yields and errors Determination of yields and errors Background: B(1+2 v 2 trig v 2 assoc cos(2ΔΦ))‏ Background: B(1+2 v 2 trig v 2 assoc cos(2ΔΦ))‏ Different fit methods for determination of B Different fit methods for determination of B Zero Yield At Minimum (ZYAM)‏ Zero Yield At Minimum (ZYAM)‏ 1 point, 3 points 1 point, 3 points B as Free parameter (used as best guess)‏ B as Free parameter (used as best guess)‏ v 2 error v 2 error v 2 measurements in progress v 2 measurements in progress Upper bound for v 2 measured Upper bound for v 2 measured v 2 ≈ 10-15% depending on p T, centrality v 2 ≈ 10-15% depending on p T, centrality Estimate for lower bound, near 0 Estimate for lower bound, near 0 v 2 not measured Λ,Λ, K 0 S, Ξ +, Ξ -... v 2 not measured Assume quark scaling of h v 2 in Cu+Cu Assume quark scaling of h v 2 in Cu+Cu fit with ZYAM with 3 points, high v 2 fit with ZYAM with 1 point fit with ZYAM with 3 points, best v 2 fit with ZYAM with 3 points, low v 2 fit with background as free parameter reflected 3.0 GeV<p T trig <6.0 GeV, 1.5 GeV<p T assoc <p T trig h-h, 0-20% Cu+Cu  s NN = 200 GeV STAR Preliminary Arbitrary units

8. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 8 3.0 GeV/c < p T trigger 6.0 GeV/c; 1.5 GeV/c < p T associated < p T trigger Near-side Yield vs N part Cu+Cu vs Au+Au Identified triggers: Jet yield Jet yield Nearly flat with N part within errors across d+Au, Cu+Cu, Au+Au Nearly flat with N part within errors across d+Au, Cu+Cu, Au+Au No v 2 or background error due to method No v 2 or background error due to method No trigger dependence within errors No trigger dependence within errors Ridge yield Ridge yield No Ridge within errors in d+Au No Ridge within errors in d+Au Rises with N part in Cu+Cu and Au+Au Rises with N part in Cu+Cu and Au+Au No trigger dependence within errors No trigger dependence within errors d+Au, Au+Au from nucl-ex/0701047 Data points at same N part offset for visibility Jet yields: 10% error added to V 0 and h triggers to account for track merging, 15% to  triggers

9. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 9 Jet yieldvs p T trigger Identified triggers: Jet yield rises with p T trigger in h-h Jet yield rises with p T trigger in h-h Yield roughly constant with centrality Yield roughly constant with centrality Central Au+Au and 0-60% Cu+Cu jet yields comparable Central Au+Au and 0-60% Cu+Cu jet yields comparable No particle type dependence within error bars No particle type dependence within error bars nucl-ex/0701047 Cu+Cu Au+Au Data points at same p T trigger offset for visibility Jet yields: 10% error added to V 0 and h triggers to account for track merging, 15% to  triggers

10. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 10 nucl-ex/0701047 Fit to A exp(-p T /T)‏ Au+Au √s NN = 200 GeV Au+Au p T -distribution of associated particles Identified triggers: Ridge spectra similar to the bulk Ridge spectra similar to the bulk Cu+Cu measurements probably not possible Cu+Cu measurements probably not possible Jet spectra are slightly harder Jet spectra are slightly harder Cu+Cu fit only to h-h Cu+Cu fit only to h-h Inverse slope T consistent between Cu+Cu and Au+Au Inverse slope T consistent between Cu+Cu and Au+Au 416 ± 11 (stat.)‏ 406 ± 20 (stat.)‏ 438 ± 4 (stat.)‏ T(ridge) MeV 445 ± 49Λ 530 ± 61K0SK0S 478 ± 8h +/- T (jet) MeVTrigger particle Inclusive slope fit above 2.0 GeV: 355 +/- 6 J. Putschke, QM 06 p T associated > 2.0 GeV open symbols – Jet closed symbols - Ridge Fit to A p T exp(-p T /T)‏ 1/N trigger dN/dp T Fits assuming 1/p T dN/dp T = A p T exp(-p T /T)‏ 445  20 MeV Fit to A exp(-p T /T)‏ Cu+Cu

11. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 11 Identified associated yield vs p T trigger In Au+Au In Au+Au Jet: Λ)/K 0 S ≈1 Jet: ( Λ+Λ)/K 0 S ≈1 similar to vacuum fragmentation similar to vacuum fragmentation Ridge: Λ)/ K 0 S ≈ 2 Ridge: ( Λ+Λ)/ K 0 S ≈ 2 similar to the bulk similar to the bulk In Cu+Cu In Cu+Cu Ridge: data not attainable Ridge: data not attainable Jet: Λ)/ K 0 S ≈ 1 Jet: ( Λ+Λ)/ K 0 S ≈ 1 STAR Preliminary Au+Au Au+Au Cu+Cu

12. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 12Conclusions Identified triggers Identified triggers Ridge yields Ridge yields Cu+Cu very small Cu+Cu very small Cu+Cu and Au+Au consistent at the same N part Cu+Cu and Au+Au consistent at the same N part Jet yields Jet yields d+Au, Cu+Cu,Au+Au nearly consistent at the same N part d+Au, Cu+Cu,Au+Au nearly consistent at the same N part Increases with p T trigger Increases with p T trigger Constant with centrality Constant with centrality Independent of system Independent of system No trigger particle type dependence within errors No trigger particle type dependence within errors Including non-strange, and singly and doubly strange triggers Including non-strange, and singly and doubly strange triggers Identified associated Identified associated Λ)/K 0 S in Ridge similar to inclusive ( Λ+Λ)/K 0 S in Ridge similar to inclusive Λ)/K 0 S in Jet similar to vacuum fragmentation ( Λ+Λ)/K 0 S in Jet similar to vacuum fragmentation In Cu+Cu and Au+Au In Cu+Cu and Au+Au

13. STAR Collaboration Argonne National Laboratory - University of Birmingham - Brookhaven National Laboratory - California Institute of Technology - University of California, Davis - University of California - University of California, Los Angeles - Carnegie Mellon University - University of Illinois at Chicago - Creighton University - Nuclear Physics Institute Prague - Laboratory for High Energy (JINR) - Particle Physics Laboratory (JINR) - University of Frankfurt - Institute of Physics, Bhubaneswar - Indian Institute of Technology, Mumbai - Indiana University, Bloomington - Institut de Recherches Subatomiques - University of Jammu - Kent State University - Institute of Modern Physics, Lanzhou - Lawrence Berkeley National Laboratory - Massachusetts Institute of Technology - Max-Planck-Institut fuer Physik - Michigan State University - Moscow Engineering Physics Institute - City College of New York - NIKHEF and Utrecht University - Ohio State University, Columbus - Panjab University - Pennsylvania State University - Institute of High Energy Physics, Protvino, Russia - Purdue University - Pusan National University, Pusan, Republic of Korea - University of Rajasthan, Jaipur - Rice University - Universidade de Sao Paulo - University of Science & Technology of China - Shanghai Institute of Applied Physics - SUBATECH, Nantes, France - Texas A\&M University - University of Texas - Tsinghua University - Valparaiso University - Variable Energy Cyclotron Centre, Kolkata, India - Warsaw University of Technology - University of Washington - Wayne State University - Institute of Particle Physics, CCNU (HZNU), Wuhan - Yale University - University of Zagreb Argonne National Laboratory - University of Birmingham - Brookhaven National Laboratory - California Institute of Technology - University of California, Davis - University of California - University of California, Los Angeles - Carnegie Mellon University - University of Illinois at Chicago - Creighton University - Nuclear Physics Institute Prague - Laboratory for High Energy (JINR) - Particle Physics Laboratory (JINR) - University of Frankfurt - Institute of Physics, Bhubaneswar - Indian Institute of Technology, Mumbai - Indiana University, Bloomington - Institut de Recherches Subatomiques - University of Jammu - Kent State University - Institute of Modern Physics, Lanzhou - Lawrence Berkeley National Laboratory - Massachusetts Institute of Technology - Max-Planck-Institut fuer Physik - Michigan State University - Moscow Engineering Physics Institute - City College of New York - NIKHEF and Utrecht University - Ohio State University, Columbus - Panjab University - Pennsylvania State University - Institute of High Energy Physics, Protvino, Russia - Purdue University - Pusan National University, Pusan, Republic of Korea - University of Rajasthan, Jaipur - Rice University - Universidade de Sao Paulo - University of Science & Technology of China - Shanghai Institute of Applied Physics - SUBATECH, Nantes, France - Texas A\&M University - University of Texas - Tsinghua University - Valparaiso University - Variable Energy Cyclotron Centre, Kolkata, India - Warsaw University of Technology - University of Washington - Wayne State University - Institute of Particle Physics, CCNU (HZNU), Wuhan - Yale University - University of Zagreb

14. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 14 Backup slides

15. The End

16. Future work Systematics  Reduce systematic error from v 2  Identified particle v 2 Expand identified associated analysis Coming soon  Ω triggers Comparisons to Au+Au – See B. Abelev's SQM talk Away-side yields Energy dependence of Jet and Ridge yields Ω Ω Ω ~1000 Ω triggers in central Cu+Cu with p T >2.5 GeV/c! ~2000 in central Au+Au STAR Preliminary

17. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 17 Intermediate p T baryon/meson enhancement Large enhancement of baryon/meson ratio in central collisions relative to p+p Large enhancement of baryon/meson ratio in central collisions relative to p+p in both Au+Au and Cu+Cu reaches maximum at p T ~ 2- 3 GeV/c reaches maximum at p T ~ 2- 3 GeV/c not unmodified jet fragmentation Baryon/meson splitting of R cp Baryon/meson splitting of R cp strange and non-strange particles show similar suppression nucl-ex/0608017 A. Timmins, SQM 2007 A. Timmins, QM 2006

18. Christine Nattrass (STAR Collaboration), Yale University, DNP 10 October 2007, Newport News, Virginia 18 The Ridge in Cu+Cu Is there a Ridge in Cu+Cu?  projection flat at large   projection flat at large  Small and large  regions match on away side Small and large  regions match on away side Small yield above background in large  region Small yield above background in large  region Jet yield in  consistent with Jet in  subtracting (Jet+Ridge)- Ridge Jet yield in  consistent with Jet in  subtracting (Jet+Ridge)- Ridge 1/N trig d 2 N/d  d  3.0 GeV<p T trig <6.0 GeV, 1.5 GeV<p T assoc <p T trig h-h, 0-20% Cu+Cu  s NN = 200 GeV STAR Preliminary 1/N trig dN/d  0 ~.13 -1<<1 STAR Preliminary 3.0 GeV<p T trig <6.0 GeV, 1.5 GeV<p T assoc <p T trig h-h, 0-20% Cu+Cu  s NN = 200 GeV STAR Preliminary Jet + Ridge Ridge Ridge 1/N trig dN/d  STAR Preliminary Jet+Ridge -.75<  <.75 Ridge.75<|  |<1.75 scaled by.75 ~.20 Different flow background parameters 3.0 GeV<p T trig <6.0 GeV, 1.5 GeV<p T assoc <p T trig h-h, 0-20% Cu+Cu  s NN = 200 GeV 1/N trig dN/d  ~.19 (Jet+Ridge) - Ridge*.75