1. STAR Nov 1-2, 2001High P T Phenomena at RHIC1 High P T Identified Particles at STAR B. Lasiuk (YALE) for the STAR collaboration Hard Processes at RHIC STAR Measurements –Detectors –Methods –Physics Implication Some Results and Beyond… at STAR...

2. STAR Nov 1-2, 2001High P T Phenomena at RHIC2 Hard Process Observables Jets are the Most Direct Observable –30% of particle production at RHIC energies –In pp, e + e -, light ions Event Backgrounds Favorable Difficult in Au+Au What Can We See in Au+Au? –Leading Particles –Azimuthal Correlations –High Mass Objects OPAL qq jet

3. STAR Nov 1-2, 2001High P T Phenomena at RHIC3 Models and Physics Implications Parton Propagation Affects Spectral Shape –dE/dx  softens spectra –color screening (high density) –Where does the onset occur? Identified Particle Production Rates –Medium Effects on Fragmentation Functions –Asymmetries in Coupling Between Quarks and Gluons Measured P T Anisotropy –Sensitive to Propagation Through Matter

4. STAR Nov 1-2, 2001High P T Phenomena at RHIC4 Charged Multiplicity Spectrum Softens with –Energy Loss –Increasing Multiplicity –Gluon Density Onset of Hard Scattering M. Gyulassy, I. Vitev, X.N. Wang PRL 86 (2001) 2537 Where Does it Affect “MEASURED” Spectrum?

5. STAR Nov 1-2, 2001High P T Phenomena at RHIC5 STAR Detector Year 1 Detectors Shown –TPC –RICH Extensions in Year 2… –Calorimeter ZDC Magnet ZDC Central Trigger Barrel Time Projection Chamber RICH Hadronic Observables: PID by Several Detectors Focus on Central Region

6. STAR Nov 1-2, 2001High P T Phenomena at RHIC6 STAR TPC Large Acceptance –|y|<1.6 High Efficiency Tracking Azimuthally Symmetric B Field = 2.5 kG –Limits Momentum Resolution –For 2001: 5.0 kG PID via Ionization –Below 1 GeV/c –Other Detectors Augment Capabilities P T (GeV/c) Fractional Momentum Resolution From Embedding “Primaries”

7. STAR Nov 1-2, 2001High P T Phenomena at RHIC7 Identification of Particles Specific Ionization Secondary Vertices (Topology) K o     RICH TOF and Calorimetry …

8. STAR Nov 1-2, 2001High P T Phenomena at RHIC8 STAR-RICH Detector Radiator –C 6 F 14 Liquid Photo Converter –CsI – < 210 (nm) Ionization Detector –MWPC pad chamber –CH 4 Gas 80 mm STAR-RICH Collaboration Headed by F. Piuz, E. Nappi, G. Paic, G.J. Kunde Developed by CERN RD-26 in ALICE framework

9. STAR Nov 1-2, 2001High P T Phenomena at RHIC9 Identification with RICH Direct Ray Tracing –Hough Transform –D. Elia et al., NIM A433 (1999) 262. Momentum Range 1 < p < 3  2 < p < 5 p

10. STAR Nov 1-2, 2001High P T Phenomena at RHIC10 Identification with RICH Geometrical Patterns –Statistical Basis DD  p K  Ring  Counts

11. STAR Nov 1-2, 2001High P T Phenomena at RHIC11 15% Central Triggering Capabilities Symmetric Zero Degree Calorimeters Central Trigger Barrel 5% central Au ZDC

12. STAR Nov 1-2, 2001High P T Phenomena at RHIC12 Indications from Inclusive Spectra... Indication of: –JET QUENCHING? STAR preliminary Turn over at P T > 2 GeV/c Large Systematic  ~30% Double the P T Reach this Year X-N Wang

13. STAR Nov 1-2, 2001High P T Phenomena at RHIC13 Identified Particle Yields Most Striking for Protons –~30% for STAR-RICH Range –effect slight for , K… Species/Flavor Dependence –Asymmetry of Leading Particle –Propagation in Medium –Coupling to Medium Not Restricted to Protons… Reference Spectra Importance –Need for PID at RHIC X.N.Wang, Phys.Rev.C 58 (1998) 2321 RICH Range Ratio

14. STAR Nov 1-2, 2001High P T Phenomena at RHIC14 Constant Yields with P T *Slight Difference in Centrality NO DECREASE with P T –Compared to Inclusive Spectra –Compared to v 2 …??? –Significant in Comparison with Other Observables? Extend Reach with 2001 Data –Normalized Spectra Protons in the Central Region

15. STAR Nov 1-2, 2001High P T Phenomena at RHIC15 Other Hadrons in Central Region Less Sensitivity to Energy Loss than Protons Constant Ratio with P T More Statistics in 2001… Normalized Spectra

16. STAR Nov 1-2, 2001High P T Phenomena at RHIC16   Spectra p  = p e - + p e + vv pp Primary Vertex Photon Momentum Vector e+e+ e-e- Photon Conversion Vector z (cm) r (cm) 0100200 100 0 200 TPC Fit Mass ~ 131 MeV/ c 2 FWHM ~ 20 MeV/c 2 M inv (GeV/c 2 )

17. STAR Nov 1-2, 2001High P T Phenomena at RHIC17  o Spectrum Small Reconstruction Efficiency…BUT Continuous Kinematic Range 2nd PHENIX p t range  0 - Top 10% most central  0 – Minimum Bias data  0 – 20% - 50% 1/pt dN/dp t (a.u.) X.N.Wang, Phys.Rev.C 58 (1998) 2321 Consistent with   Central To Min Bias ~2-3 …Still Large Errors… EMC Extension to 6-10 GeV/c...

18. STAR Nov 1-2, 2001High P T Phenomena at RHIC18 Anisotropy in geometry: Anisotropy in jet quenching: –hydro valid up to some p t –without dE/dx v 2  0 –with finite dE/dx anisotropy in geometry  v 2 > 0 Azimuthal Anisotropy  path length  X-N. Wang PRC 63 (2001) 054902 A Pathlength Effect Sensitive to In Medium Effects Energy Loss Increases with Distance Difference in Hydrodynamic and Hard Scattering Evolution

19. STAR Nov 1-2, 2001High P T Phenomena at RHIC19 Elliptic Flow…What is it? v 2 : 2 nd Harmonic Fourier Coefficient in Azimuthal Distribution of Particles with Respect to the Impact Parameter Vector Origin: Spatial Anisotropy is created in Non- Central Collisions. Subsequent Rescattering in Evolving System Translates to Dynamics spatial anisotropy  momentum anisotropy

20. STAR Nov 1-2, 2001High P T Phenomena at RHIC20 Physics From Anisotropy Sensitive to Energy Loss Saturation at P T =2 GeV/c Gyulassy, Vitev and Wang, Phys. Rev. Lett. 86, 2537(2001).

21. STAR Nov 1-2, 2001High P T Phenomena at RHIC21 Mass Dependence of v 2 Low P T Follow Hydro Predictions High P T Region Access: –  and K 0 S –RICH in Future Calculations: P. Huovinen, P. Kolb and U. Heinz STAR Preliminary Minimum Bias Comparison – K 0 S K ± consistent –  and K 0 S increase to P T =1.5 GeV/c “Saturation” of v 2 independent of mass

22. STAR Nov 1-2, 2001High P T Phenomena at RHIC22 Conclusions STAR Capabilities to Measure Complimentary Observables –v 2 Measured for K o s and  o Saturation of v 2 Appears Independent of Particle Type Hydrodynamics Does NOT Describe v 2 at P T > 2 GeV/c –Possibility of Jet Quenching at P T > 2 GeV/c? BUT... – = 0.6 to P T  2.5 GeV/c NO FALL OFF with increasing P T Why is Ratio NOT Decreasing if Partonic dE/dx Present? –Flow Effects Strongly Affecting Central Baryons? –Information Regarding Fragmentation Functions?

23. STAR Nov 1-2, 2001High P T Phenomena at RHIC23 The Collaboration The STAR Collaboration > 400 collaborators 34 institutions 8 countries Brazil: Sao PaoloChina:IHEP - Beijing, IPP - Wuhan England: BirminghamFrance:IReS - Strasbourg, SUBATECH-Nantes Germany: Frankfurt, MPI - Munich Poland:Warsaw University, Warsaw U. of Technology Russia: MEPHI - Moscow, JINR - Dubna, IHEP - Protvino U.S.: Argonne, Berkeley, Brookhaven National Laboratories, UC Berkeley, UC Davis, UCLA, Creighton, Carnegie-Mellon, Indiana, Kent State, MSU, CCNY, Ohio State, Penn State, Purdue, Rice, Texas, Texas A&M, Washington, Wayne, Yale University STAR

24. STAR Nov 1-2, 2001High P T Phenomena at RHIC24 STAR-RICH Collaboration (Bari a -CERN b -Yale c ) Y. Andres a, A. Braem b, D. Cozza a. M. Davenport b, G. De Cataldo a, L. Dell Olia a, D. DiBari a, A. DiMauro b, J.C. Dunlop c, E. Finch c, D.Fraissard b, A. Franco a, J. Gans c, B. Ghidini a, J.W Harris c, M. Horsley c, G.J. Kunde c, B. Lasiuk c, Y. Lesenechal b, R.D. Majka c, P. Martinengo b, A. Morsch b, E. Nappi a, G. Paic b, F. Piuz b, B. Posa a, J.Raynaud b, S. Salur c, J. Sandweiss c, J.C. Santinard b, J. Satinover c, E.Schyns b, N. Smirnov c, J. Van Beelen b, T.D Williams b, Z. Xu c