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High P T Identified Particles at STAR

High P T Identified Particles at STAR. Hard Processes at RHIC STAR Measurements Detectors Methods Physics Implication Some Results and Beyond… at STAR. B. Lasiuk (YALE) for the STAR collaboration. Hard Process Observables. Jets are the Most Direct Observable

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High P T Identified Particles at STAR

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  1. High PT Identified Particles at STAR • Hard Processes at RHIC • STAR Measurements • Detectors • Methods • Physics Implication • Some Results and Beyond… at STAR... B. Lasiuk (YALE) for the STAR collaboration High PT Phenomena at RHIC

  2. 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 High PT Phenomena at RHIC

  3. 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 PT Anisotropy • Sensitive to Propagation Through Matter High PT Phenomena at RHIC

  4. Charged Multiplicity M. Gyulassy, I. Vitev, X.N. Wang PRL 86 (2001) 2537 • Spectrum Softens with • Energy Loss • Increasing Multiplicity • Gluon Density • Onset of Hard Scattering Where Does it Affect “MEASURED” Spectrum? High PT Phenomena at RHIC

  5. Magnet Time Projection Chamber ZDC ZDC Central Trigger Barrel RICH STAR Detector • Hadronic Observables: • PID by Several Detectors • Focus on Central Region • Year 1 Detectors Shown • TPC • RICH • Extensions in Year 2… • Calorimeter High PT Phenomena at RHIC

  6. 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 STAR TPC From Embedding “Primaries” Fractional Momentum Resolution PT (GeV/c) High PT Phenomena at RHIC

  7. Identification of Particles • Specific Ionization • Secondary Vertices (Topology) • Ko Lo X W po • RICH • TOF and Calorimetry … High PT Phenomena at RHIC

  8. 80 mm STAR-RICH Detector STAR-RICH Collaboration Headed by F. Piuz, E. Nappi, G. Paic, G.J. Kunde Developed by CERN RD-26 in ALICE framework • Radiator • C6F14 Liquid • Photo Converter • CsI • l < 210 (nm) • Ionization Detector • MWPC pad chamber • CH4 Gas High PT Phenomena at RHIC

  9. Direct Ray Tracing Hough Transform D. Elia et al., NIM A433 (1999) 262. Identification with RICH • Momentum Range 1 < p< 3 p K 2 < p < 5 p High PT Phenomena at RHIC

  10. Geometrical Patterns Statistical Basis p K p Dp p Ring Identification with RICH g Counts High PT Phenomena at RHIC

  11. 15% Central 5% central ZDC ZDC Au Au Triggering Capabilities • Symmetric Zero Degree Calorimeters • Central Trigger Barrel High PT Phenomena at RHIC

  12. X-N Wang STAR preliminary Indications from Inclusive Spectra... Turn over at PT > 2 GeV/c Large Systematic  ~30% Double the PT Reach this Year • Indication of: • JET QUENCHING? High PT Phenomena at RHIC

  13. RICH Range X.N.Wang, Phys.Rev.C 58 (1998) 2321 Identified Particle Yields • Most Striking for Protons • ~30% for STAR-RICH Range • effect slight for p, 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 Ratio High PT Phenomena at RHIC

  14. Protons in the Central Region • Constant Yields with PT • Slight Difference in Centrality • NO DECREASE with PT • Compared to Inclusive Spectra • Compared to v2…??? • Significant in Comparison with Other Observables? • Extend Reach with 2001 Data • Normalized Spectra High PT Phenomena at RHIC

  15. Other Hadrons in Central Region • Less Sensitivity to Energy Loss than Protons • Constant Ratio with PT • More Statistics in 2001… • Normalized Spectra High PT Phenomena at RHIC

  16. Photon Momentum Vector e+ p = pe- + pe+ e- qp Fit Mass ~ 131 MeV/ c2 FWHM ~ 20 MeV/c2 200 Photon Conversion Vector r (cm) qv 100 TPC Primary Vertex Minv (GeV/c2) 0 200 100 0 100 200 z (cm) po Spectra High PT Phenomena at RHIC

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

  18. Azimuthal Anisotropy f path length  • Anisotropy in geometry: • Anisotropy in jet quenching: • hydro valid up to some pt • without dE/dx v2  0 • with finite dE/dx anisotropy in geometry  v2 > 0 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 High PT Phenomena at RHIC

  19. Elliptic Flow…What is it? Origin: Spatial Anisotropy is created in Non-Central Collisions. Subsequent Rescattering in Evolving System Translates to Dynamics spatial anisotropy  momentum anisotropy v2: 2nd Harmonic Fourier Coefficient in Azimuthal Distribution of Particles with Respect to the Impact Parameter Vector High PT Phenomena at RHIC

  20. Physics From Anisotropy • Sensitive to Energy Loss • Saturation at PT=2 GeV/c Gyulassy, Vitev and Wang, Phys. Rev. Lett. 86, 2537(2001). High PT Phenomena at RHIC

  21. STAR Preliminary Calculations: P. Huovinen, P. Kolb and U. Heinz Mass Dependence of v2 • Minimum Bias Comparison • K0S K±consistent • L and K0S increase to PT =1.5 GeV/c • “Saturation” of v2 independent of mass • Low PT Follow Hydro Predictions • High PT Region Access: • L and K0S • RICH in Future High PT Phenomena at RHIC

  22. Conclusions • STAR Capabilities to Measure Complimentary Observables • v2 Measured for Kos and Lo • Saturation of v2 Appears Independent of Particle Type • Hydrodynamics Does NOT Describe v2 at PT > 2 GeV/c • Possibility of Jet Quenching at PT > 2 GeV/c? BUT... • = 0.6 to PT 2.5 GeV/c • NO FALL OFF with increasing PT • Why is Ratio NOT Decreasing if Partonic dE/dx Present? • Flow Effects Strongly Affecting Central Baryons? • Information Regarding Fragmentation Functions? High PT Phenomena at RHIC

  23. The Collaboration STAR The STAR Collaboration > 400 collaborators 34 institutions 8 countries Brazil: Sao Paolo China: IHEP - Beijing, IPP - Wuhan England: Birmingham France: 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 High PT Phenomena at RHIC

  24. STAR-RICH Collaboration(Baria-CERNb-Yalec) Y. Andresa, A. Braemb, D. Cozzaa. M. Davenportb, G. De Cataldoa, L. Dell Oliaa, D. DiBaria, A. DiMaurob, J.C. Dunlopc, E. Finchc, D.Fraissardb, A. Francoa, J. Gansc, B. Ghidinia, J.W Harrisc, M. Horsleyc, G.J. Kundec, B. Lasiukc, Y. Lesenechalb, R.D. Majkac, P. Martinengob, A. Morschb, E. Nappia, G. Paicb, F. Piuzb, B. Posaa, J.Raynaudb, S. Salurc, J. Sandweissc, J.C. Santinardb, J. Satinoverc, E.Schynsb, N. Smirnovc, J. Van Beelenb, T.D Williamsb, Z. Xuc High PT Phenomena at RHIC

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