STAR: recent results and future physics program

1. STAR: recent results and future physics program Olga Barannikova for the STAR Collaboration

2. STAR Preliminary Not in this talk: Overview of strangeness production from STAR • Strangeness production in light vs. heavy systems • Collision geometry effects on strangeness production at RHIC • … • See talk by Anthony Timmins this afternoon… STAR Preliminary Olga Barannikova University of Illinois at Chicago

3. Not in this talk: Recent heavy flavor results from STAR • J/ spectra in 200 GeV ppand Cu+Cu  RAA measurements • Azimuthal correlations for HF • J/  -hadron, e-D0, … •  capabilities in pp and Au+Au • … • See talk by Zhangbu Xu on Tuesday J/-h Olga Barannikova University of Illinois at Chicago

4. In this talk… Outline: • Selected recent STAR results on medium properties • Collectivity and Thermalization • Particle production and Parton propagation • Energy density & Energy loss • Near-term program • Physics plans and goals for upcoming runs • Summary Olga Barannikova University of Illinois at Chicago

5. Thermalization Differential v2 studies • Dense medium flowing with minimal shear viscosity • Sizeable v2 for f mesons, nq scaling  partonic nature • Assuming same parton σ for all hadrons  universal trend toward hydro limit • v2 / e ~ 30% below ideal hydro (even central collisions) • Knudsen number K is not 0 as for ideal hydro Ideal Hydro? Olga Barannikova University of Illinois at Chicago

6. hard soft + + Angular pair correlations Au+Au 200 GeV STAR Preliminary STAR Preliminary STAR Preliminary STAR Preliminary Fit function = Olga Barannikova University of Illinois at Chicago

7. peak amplitude peak η width STAR Preliminary STAR Preliminary 200 GeV 62 GeV 83-94% 55-65% 0-5% 46-55% STAR Preliminary STAR Preliminary STAR Preliminary STAR Preliminary Transverse particle density ηΔ width Low pT ridge Same-side evolution • Sharp transition in both amplitude and width at ρ~ 2.5 • Similar ρ-trends at 62 and 200 GeV Olga Barannikova University of Illinois at Chicago

8. 3 < pt,trig< 4 GeV/c pt,assoc. > 2 GeV/c Au+Au 0-10% STAR preliminary Intermediate pT ridge Production mechanisms Au+Au: 2 < pTtrig < 3 GeV/c Cu+Cu: 3 < pTtrig < 6 GeV/c pTtrig > 4.0 GeV/c 2.0 < pTAssoc< pTtrig p+p / p++p- • Jet+ridge yields follow similar trend in pT for all trigger types • Production mechanisms for jet and ridge are different

9. No acceptance No acceptance Au+Au 0-12% d+Au STAR Preliminary STAR Preliminary Dh-Dh correlations 3<pTTrig<10 GeV/c 1<pTAsso<3 GeV/c • No apparent substructure – no gluon fragments/flow coupling? • No cross-like term – ridge and cone decoupled? Olga Barannikova University of Illinois at Chicago

10. Charge-ordering in Dh-Dh • Charge-ordering in Jet • No ordering in Ridge Ridge (T- A+ ) = Ridge (T+ A+) Ridge (T+ A-) = Ridge (T- A- ) STAR Preliminary Tlike,AAlike : Only ridge Tunlike,AAlike: Jet + Ridge Use charge-ordering for Jet-Ridge separation STAR Preliminary STAR Preliminary Olga Barannikova University of Illinois at Chicago

11. 90º 0º in-plane fS=0 out-of-plane fS=90o Path-length effects 3<pTtrig<4GeV/c 1 < pTasso < 1.5GeV/c STAR Preliminary 20-60% • Jet peak shows little changes from d+Au to central Au+Au collisions • Ridge decreases from in-plane to out-of-plane STAR Preliminary Olga Barannikova University of Illinois at Chicago

12. Direct  0 Associated yield/Ntrig Jet-energy calibration Direct g - hadron correlations STAR Preliminary • p0 -triggers are from higher energy parton, and more surface-biased • Away-side yield results consistent with in-medium parton energy loss scenario Olga Barannikova University of Illinois at Chicago

13. Full jet reconstruction In Au+Au collisions! • Will allow direct measurements of jet spectra and fragmentation functions in AA STAR Preliminary STAR Preliminary • No apparent modification with respect to pp!? • To do: • need to understand trigger bias • ξ not yet corrected for jet energy shift due to quenching STAR Preliminary Olga Barannikova University of Illinois at Chicago

14. The “QCD factory” STAR – new advances in studies of medium properties, new questions Dense QCD medium, strong coupling with parton Eloss Differential qualitative studies of the medium: precise jet FF measurements, energy loss, “ridgeology”, colour-charge effects ? Conventional hydro picture, initial eccentricity ? ? Mechanisms of jet-medium interactions ? RHIC stochastic cooling +STAR detector upgrades: High precision measurements, strong pQCD tests Olga Barannikova University of Illinois at Chicago

15. STAR: the near future • Longitudinal and transverse spin programs - Study proton intrinsic properties • Forward programs - Study low-x properties and search for CGC • Tagged forward protons - Study elastic and inelastic process - Investigate gluonic exchanges and search for gluonic matter • RHIC beam energy scan - Search for critical point - Chiral symmetry restoration Olga Barannikova University of Illinois at Chicago

16. Evolution of the system is attracted to the critical point • Focusing causes broadening of signal region Search for QCD Critical Point Strategy: Search for disappearance of dense medium effects Search for onset of de-confinement Scan plan: Olga Barannikova University of Illinois at Chicago

17. Energy scan test run Au+Au collisionsat 9 GeV: Central Collision Non-central Collision Olga Barannikova University of Illinois at Chicago

18. Key measurements Hadron ratios and fluctuations • STARadvantages: • Large acceptance: full azimuthal coverage and |y|<1.0 • Extended particle identification: (TPC, ToF, EMC) • Same detector – same systematics Olga Barannikova University of Illinois at Chicago

19. The STAR Upgrade MTD EMC barrel MRPC ToF barrel Ready for run 10 EMC End Cap RPSD FMS FPD TPC PMD Complete Ongoing DAQ1000 Ready for run 9 HFT FGT R&D Olga Barannikova University of Illinois at Chicago

20. STAR Highlights on Strangeness Production - Anthony Timmins STAR Highlights on Heavy Quark Production - Zhangbu Xu Parallel Talks: Non-photonic electron yields in p+p Collisions at 200 GeV with reduced detector material in STAR -- Fu Jin First results from Au+Au collisions at 9.2 GeV in STAR -- Lokesh Kumar System size, energy and centrality dependence of strange hadron elliptic flow at STAR -- Hiroshi Masui Anisotropic flow: indications for incomplete thermalization -- Yuting Bai Strange hadron production in 62 GeV collisions at RHIC -- Marcelo Munhoz Thermal production of particles at RHIC–Jun Takahashi For more details: Olga Barannikova University of Illinois at Chicago

21. Back Up Olga Barannikova University of Illinois at Chicago

22. Angular pair correlations Correlation measure: Olga Barannikova University of Illinois at Chicago

23. A2 A1 3-particle correlation in  STAR TPC acceptance for 3-particle correlation in  (||<1 and full azimuth) T : Trigger particle A1: First Associated particle A2: Second Associated particle In medium radiation + Longitudinal flow Jet fragmentation in vacuum N.Armesto et.al Phys.Rev.Lett. 93(2004) 242301 Transverse flow boost Turbulent color field. Momentum Kick C.Y. Wong hep-ph:0712.3282 S.A.Voloshin, Phys.Lett.B. 632(2006)490 E.Shuryak, hep-ph:0706.3531 A.Majumder et.al Phys. Rev. Lett.99(2004)042301 Olga Barannikova University of Illinois at Chicago