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Strange and multi-strange particle production in p+p at √s= 200 GeV in STAR

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  1. Strange and multi-strange particle production in p+p at √s= 200 GeV in STAR Mark Heinz for the STAR Collaboration University of Bern, Switzerland XXXXth Rencontres de Moriond 12-19 March 2005 La Thuile, Italie

  2. Outline Relativistic Heavy Ion Collider (RHIC) Brookhaven National Laboratory Long Island, New York • Physics Motivation • STAR Experiment • Results from p+p • Comparison to models: • PYTHIA (LO) • NLO calculations • Identified particle azimuthal correlations • Summary 40th Rencontres de Moriond March 12-19, 2005

  3. parton parton hadrons leading particle → Flavour dependence of jets and associated particle yield Motivation 1. QGP signature: Strangeness enhancement. →Measurement of strange particles in p+p used as a baseline to compare to Au+Au STAR preliminary √s=200 GeV • 2. High-PT strange particles • high-Q2 pQCD processes • production of mini-jets • multiplicity dependence in p+p 3. High-PTstrange particles correlated with hadrons in jets → study azimuthal correlations and medium modification/quenching →flavour dependence of the strong interaction and the fragmentation process 40th Rencontres de Moriond March 12-19, 2005

  4. STAR Experimental Setup Year 2000 Magnet Coils Central Trigger Barrel (CTB) Time Projection Chamber (TPC) Zero Degree calorimeter (ZDC) Year 2001-2005 • Silicon Vertex Tracker (SVT) • Forward TPC (FTPC) • Barrel EM Cal (BEMC) • Endcap EMCal (EEMC) • Forward Pion Detector (FPD) • Time of Flight (TOF) • Ring Imaging Cherenkov (RICH) • Silicon Strip Detector (SSD) 40th Rencontres de Moriond March 12-19, 2005

  5. Strange particles in p+p collisions at √s= 200 GeV • Event sample • Run 2: 11.5 mio minbias events • Beam-Beam Counters (BBC) • Non-singly-diffractive x-section ~30±3.5 mb • Event-level Corrections • Pile-Up correction • Primary vertex inefficiency STAR Time Projection Chamber • Particle identification: • V0-decay vertices: • Λ p + π- b.r. 64% • K0s  π+ + π- b.r. 68% • -  π- + Λ b.r. 99% • - K- + Λ b.r. 68% • Cuts on dE/dx of charged daughter particles • Topological cuts 40th Rencontres de Moriond March 12-19, 2005

  6. Transverse momentum spectra STAR measures the strange particles with a great improvement in Statistical errors over previous p +p experiments. K0s K+- STAR Preliminary  + -+ + 40th Rencontres de Moriond March 12-19, 2005

  7. Comparison of to LO pQCD (PYTHIA) K-factor =3 STAR • Default PYTHIA does not describe STAR data well • Tuned PYTHIA (K-factor=3) does a much better job for the kaons but still has problems with the strange baryons Eskola et al, NPA 713(2003) • Starting point: PYTHIA v6.22 (MSEL1 – inelastic) • First Tuning attempts: • K-factor (to account for higher order processes) • Intrinsic kT of partons (to account for initial state gluon radiation) K0s  + -+ + STAR preliminary 40th Rencontres de Moriond March 12-19, 2005

  8. NLO calculations for mesons using Kniehl et al.(KKP) fragmentation function and generally reproduce the RHIC charged hadron data very well. For K0s the agreement is not as good as for charged hadrons Large discrepancies between NLO and data for strange baryons Octet-baryon fragmentation functions have been calculated by Bourrely & Soffer (hep-ph/0305070) Comparison to NLO pQCD calculations Proton Lambda FF = Vogelsang et al. UA1 K0s @ √s=630GeV STAR K0s @ √s=200GeV Sigma Xi Van Leeuwen, nucl-ex/0412023 Kniehl et al, hep-ph/0502188 FF = KKP Special thanks to Werner Vogelsang for computation (Riken/BNL) 40th Rencontres de Moriond March 12-19, 2005

  9. Anti-Particle/Particle Ratios pQCD Hijing Prediction Au+Au / p+p (no Energy loss) Au+Au, with Energy loss 1 GeV/fm XN. Wang, PRC58 (1998) Is there a hint of a sloping/-ratio vs pT ? HIJING predicts that an effect from gluon vs. quark jets should be seen at higher pT STAR preliminary • These ratios are approaching unity and very similar to the ones measured in Au+Au→ nearly net-baryon free at mid-rapidity at this energy 40th Rencontres de Moriond March 12-19, 2005

  10. <pT> systematics in p+p and Au+Au • <pT> of identified Particles have been measured in p+p and Au+Au over large mass range • Au+Au: mass-dependant contribution to <pT> from flow • p+p: mass dependence, but not from flow → <pT> mass dependence of minijet fragmentation ? STAR preliminary <pT> in p+p collisions for most massive particles is approaching the value in Au+Au Collisions ! 40th Rencontres de Moriond March 12-19, 2005

  11. <pT> vs charged multiplicity (Nch) Tevatron √s=1800 GeV  + K0s p K- π K0s  + Evidence for stronger contribution of fragmenting mini-jets to heavier strange hadrons ? • STAR has measured <pT> vs charged multiplicity in p+p for several strange baryons and mesons • Increase of <pT> is evidence of more contribution from mini-jets fragmenting into strange particles in high multiplicity events Wang et al, Phys Rev D 45 (1992) E735:Phys Lett B 282 (1992) 40th Rencontres de Moriond March 12-19, 2005

  12. Azimuthal correlations with high-pt strange particles (Y.Guo/J.Bielcikova) near-side away-side A+A flow+bkg p+p/d+Au • Identified correlations at high-pT • can provide additional information: • jet quenching (Au+Au) • particle production mechanisms • recombination models • (modified) fragmentation • pT dependence of trigger particle species • Λfrom q-jet,Λ from g-jet ? STAR, PRL 91 (2003) 072304 trigger particle: charged particle (TPC) V0 – Λ, Λ, K0s associated particle: charged tracks from TPC ( 1GeV/c <pTassociated<pTtrigger) 40th Rencontres de Moriond March 12-19, 2005

  13. Preliminary results from azimuthal correlations using strange particles h-h K0s-h d+Au 200 GeV STAR preliminary Trigger PT >3.0 GeV/c Au+Au 200 GeV Systematic Errors: • Uncorrelated background - 8~10% • Flow – 2.1~2.6% • Fitting method – 3% • misidentified V0s < 1% • trigger bias <1.5% • Marginal statistics in p+p/d+Au (no final state effects) • →No significant dependance of associated yield vs trigger species • Central Au+Au • → First hint of difference between +h and h+h STAR preliminary STAR preliminary 40th Rencontres de Moriond March 12-19, 2005

  14. Summary • First high precision measurement of strange particles in p+p collisions at this energy since ~1985 (UAx SPS) ! • Spectra and multiplicity dependence thereof are measured for K0s,Kcharge Lambda and Xi • Current LO pQCD models (eg. PYTHIA) do not describe the STAR strangeness data without significant tuning of the parameters (K-factor, intrinsic KT) • NLO pQCD calculations give good description of mesons but fail for strange baryons • STAR has measured azimuthal correlations with identified strange trigger particles in p+p, d+Au and Au+Au 40th Rencontres de Moriond March 12-19, 2005

  15. The STAR Collaboration 52 Institutions , ~530 collaborators Argonne National Laboratory, Argonne, IllinoisUniversity of Bern, Switzerland University of Birmingham, Birmingham, United KingdomBrookhaven National Laboratory, Upton, New YorkCalifornia Institute of Technology, Pasadena, CaliforniaUniversity of California, Berkeley, California University of California, Davis, California University of California, Los Angeles, California Carnegie Mellon University, Pittsburgh, Pennsylvania Creighton University, Omaha, Nebraska Nuclear Physics Institute AS CR,Prague, Czech RepublicLaboratory for High Energy (JINR), Dubna, RussiaParticle Physics Laboratory (JINR), Dubna, RussiaUniversity of Frankfurt, Frankfurt, GermanyInsitute of Physics, Bhubaneswar, IndiaIndian Institute of Technology, Mumbai, IndiaIndiana University, Bloomington, Indiana Institut de Recherches Subatomiques, Strasbourg, FranceUniversity of Jammu, Jammu, IndiaKent State University, Kent, Ohio Lawrence Berkeley National Laboratory, Berkeley, CaliforniaMassachusetts Institute of Technology, CambridgeMax-Planck-Institut fur Physik, Munich, GermanyMichigan State University, East Lansing, Michigan Moscow Engineering Physics Institute, Moscow Russia City College of New York, New York City, New York (26)NIKHEF, Amsterdam, The NetherlandsOhio State University, Columbus, Ohio 43210Panjab University, Chandigarh 160014, IndiaPennsylvania State University, University Park, PennsylvaniaInstitute of High Energy Physics, Protvino, RussiaPurdue University, West Lafayette, Indiana 47907University of Rajasthan, Jaipur 302004, IndiaRice University, Houston, TexasUniversidade de Sao Paulo, Sao Paulo, BrazilUniversity of Science & Technology of China, ChinaShanghai Institute of Applied Physics, Shanghai,ChinaSUBATECH, Nantes, FranceTexas A&M University, College Station, Texas University of Texas, Austin, TexasTsinghua University, Beijing, P.R. ChinaValparaiso University, Valparaiso, IndianaVariable Energy Cyclotron Centre, Kolkata, IndiaWarsaw University of Technology, Warsaw, PolandUniversity of Washington, Seattle, WashingtonWayne State University, Detroit, Michigan Institute of Particle Physics, Wuhan, ChinaYale University, New Haven, Connecticut University of Zagreb, Zagreb, Croatia 40th Rencontres de Moriond March 12-19, 2005

  16. backups 40th Rencontres de Moriond March 12-19, 2005

  17. Preliminary results from azimuthal correlations using strange particles Collision centrality STAR preliminary p + p Can STAR measure the leading particle flavor dependence via the associated particle yield ? → Marginal statistics in p+p/d+Au →No flavour dependance seen in pp/d+Au → Central Au+Au → First hint of difference between +h and h+h →gluon/quark jet interact differently in the medium 1.5 GeV/c < pt(trigger) < 3.0 GeV/c 1.5 GeV/c < pt(assoc) < 3.0 GeV/c 40th Rencontres de Moriond March 12-19, 2005

  18. STAR TPC dE/dx Identification 40th Rencontres de Moriond March 12-19, 2005

  19. Identified particles at intermediate to high-pt • Two groups, baryons and mesons, which seem to approach each other around 5 GeV/c • Suggesting relevance of constituent quarks for hadron production • Coalescence/recombination provides a description ~1.5 - 5 GeV/c 40th Rencontres de Moriond March 12-19, 2005

  20. K/pi & pbar/pi ratio vs mult p+p d+Au K-/Pi- Particle ratios (%) Pbar/Pi- STAR preliminary dN/d dN/d 40th Rencontres de Moriond March 12-19, 2005

  21. <pt> vs Centrality in Au+Au 200 40th Rencontres de Moriond March 12-19, 2005

  22. Non-strange particles with tuned Pythia 40th Rencontres de Moriond March 12-19, 2005

  23. <kT>=4 GeV 40th Rencontres de Moriond March 12-19, 2005

  24. Gamma_s in AuAu STAR Preliminary Au-Au √s=200 GeV p,K,p p,K,p,L,X 40th Rencontres de Moriond March 12-19, 2005