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 March 2005 La Thuile, Italie

Mark Heinz40 th Rencontres de Moriond March 12-19, Outline Physics Motivation STAR Experiment Results from p+p Comparison to models: PYTHIA (LO) NLO calculations Identified particle azimuthal correlations Summary Relativistic Heavy Ion Collider (RHIC) Brookhaven National Laboratory Long Island, New York

Mark Heinz40 th Rencontres de Moriond March 12-19, High-P T strange particles correlated with hadrons in jets → study azimuthal correlations and medium modification/quenching →flavour dependence of the strong interaction and the fragmentation process → flavour dependence of the strong interaction and the fragmentation process Motivation 1. QGP signature: Strangeness enhancement. →Measurement of strange particles in p+p used as a baseline to compare to Au+Au hadrons parton leading particle → Flavour dependence of jets and associated particle yield 2. High-P T strange particles  high-Q 2 pQCD processes  production of mini-jets  multiplicity dependence in p+p STAR preliminary √s=200 GeV

Mark Heinz40 th Rencontres de Moriond March 12-19, STAR Experimental Setup Year 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) Year 2000 Magnet Coils Central Trigger Barrel (CTB) Time Projection Chamber (TPC) Zero Degree calorimeter (ZDC)

Mark Heinz40 th Rencontres de Moriond March 12-19, 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 Particle identification: V0-decay vertices: Λ  p + π - b.r. 64% K 0 s  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 STAR Time Projection Chamber

Mark Heinz40 th Rencontres de Moriond March 12-19, Transverse momentum spectra K 0 short K+Λ  STAR dN/dy ± 5% ± 2% ± 6% ± 6% UA5 dN/dy ± 20%0.080 ± 25% ± 80% STAR 0.60 ± 1% 0.76 ± 3% 0.96 ± 5% UA ± 15%0.80 ± 25% 0.80 ± 50% K0sK0s  +  - +  + K +- STAR measures the strange particles with a great improvement in Statistical errors over previous p +  p experiments. STAR Preliminary

Mark Heinz40 th Rencontres de Moriond March 12-19, Comparison of to LO pQCD (PYTHIA) Starting point: PYTHIA v6.22 (MSEL1 – inelastic) First Tuning attempts: K-factor (to account for higher order processes) Intrinsic k T of partons (to account for initial state gluon radiation) STAR Eskola et al, NPA 713(2003) K0sK0s  +  - +  + K-factor =3 STAR preliminary 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

Mark Heinz40 th Rencontres de Moriond March 12-19, Comparison to NLO pQCD calculations 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/ ) Special thanks to Werner Vogelsang for computation (Riken/BNL) FF = KKP Kniehl et al, hep-ph/ UA1 √s=630GeV STAR √s=200GeV FF = Vogelsang et al. XiSigma LambdaProton Van Leeuwen, nucl-ex/

Mark Heinz40 th Rencontres de Moriond March 12-19, Anti-Particle/Particle Ratios Is there a hint of a sloping  /  - ratio vs p T ? HIJING predicts that an effect from gluon vs. quark jets should be seen at higher p T STAR preliminary XN. Wang, PRC58 (1998) pQCD Hijing Prediction Au+Au / p+p (no Energy loss) Au+Au, with Energy loss 1 GeV/fm 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

Mark Heinz40 th Rencontres de Moriond March 12-19, systematics in p+p and Au+Au of identified Particles have been measured in p+p and Au+Au over large mass range STAR preliminary Au+Au: mass-dependant contribution to from flow p+p: mass dependence, but not from flow → mass dependence of minijet fragmentation ? in p+p collisions for most massive particles is approaching the value in Au+Au Collisions !

Mark Heinz40 th Rencontres de Moriond March 12-19, Wang et al, Phys Rev D 45 (1992) vs charged multiplicity (N ch ) STAR has measured vs charged multiplicity in p+p for several strange baryons and mesons Increase of is evidence of more contribution from mini-jets fragmenting into strange particles in high multiplicity events E735:Phys Lett B 282 (1992) Tevatron √s=1800 GeV π K- pp  +  K0sK0s K0sK0s Evidence for stronger contribution of fragmenting mini-jets to heavier strange hadrons ?

Mark Heinz40 th Rencontres de Moriond March 12-19, Azimuthal correlations with high-pt strange particles (Y.Guo/J.Bielcikova) p+p/d+Au A+A flow+ bkg near-sideaway-side trigger particle: charged particle (TPC) V0 – Λ, Λ, K 0s associated particle: charged tracks from TPC ( 1GeV/c <p Tassociated <p Ttrigger ) Identified correlations at high-p T can provide additional information: jet quenching (Au+Au) particle production mechanisms recombination models (modified) fragmentation p T dependence of trigger particle species Λ from q-jet,  Λ from g-jet ? STAR, PRL 91 (2003)

Mark Heinz40 th Rencontres de Moriond March 12-19, Preliminary results from azimuthal correlations using strange particles STAR preliminary Trigger P T >3.0 GeV/c K 0 s -h h-h STAR preliminary 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 d+Au 200 GeV Au+Au 200 GeV

Mark Heinz40 th Rencontres de Moriond March 12-19, Summary First high precision measurement of strange particles in p+p collisions at this energy since ~1985 (UAx SPS) ! 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 K 0 s,K charge Lambda and Xi Spectra and multiplicity dependence thereof are measured for K 0 s,K charge 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 K T ) Current LO pQCD models (eg. PYTHIA) do not describe the STAR strangeness data without significant tuning of the parameters (K- factor, intrinsic K T ) NLO pQCD calculations give good description of mesons but fail for strange baryons 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 STAR has measured azimuthal correlations with identified strange trigger particles in p+p, d+Au and Au+Au

Mark Heinz40 th Rencontres de Moriond March 12-19, The STAR Collaboration Argonne National Laboratory, Argonne, Illinois University of Bern, Switzerland University of Birmingham, Birmingham, United Kingdom Brookhaven National Laboratory, Upton, New York California Institute of Technology, Pasadena, California University 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 Republic Laboratory for High Energy (JINR), Dubna, Russia Particle Physics Laboratory (JINR), Dubna, Russia University of Frankfurt, Frankfurt, Germany Insitute of Physics, Bhubaneswar, India Indian Institute of Technology, Mumbai, India Indiana University, Bloomington, Indiana Institut de Recherches Subatomiques, Strasbourg, France University of Jammu, Jammu, India Kent State University, Kent, Ohio Lawrence Berkeley National Laboratory, Berkeley, California Massachusetts Institute of Technology, Cambridge Max-Planck-Institut fur Physik, Munich, Germany Michigan 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 Netherlands Ohio State University, Columbus, Ohio Panjab University, Chandigarh , India Pennsylvania State University, University Park, Pennsylvania Institute of High Energy Physics, Protvino, Russia Purdue University, West Lafayette, Indiana University of Rajasthan, Jaipur , India Rice University, Houston, Texas Universidade de Sao Paulo, Sao Paulo, Brazil University of Science & Technology of China, China Shanghai Institute of Applied Physics, Shanghai,China SUBATECH, Nantes, France Texas A&M University, College Station, Texas University of Texas, Austin, Texas Tsinghua University, Beijing, P.R. China Valparaiso University, Valparaiso, Indiana Variable Energy Cyclotron Centre, Kolkata, India Warsaw University of Technology, Warsaw, Poland University of Washington, Seattle, Washington Wayne State University, Detroit, Michigan Institute of Particle Physics, Wuhan, China Yale University, New Haven, Connecticut University of Zagreb, Zagreb, Croatia 52 Institutions, ~530 collaborators

Mark Heinz40 th Rencontres de Moriond March 12-19, backups

Mark Heinz40 th Rencontres de Moriond March 12-19, Preliminary results from azimuthal correlations using strange particles p + p STAR preliminary 1.5 GeV/c < < 3.0 GeV/c 1.5 GeV/c < p t (trigger) < 3.0 GeV/c 1.5 GeV/c < < 3.0 GeV/c 1.5 GeV/c < p t (assoc) < 3.0 GeV/c Collision centrality 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

Mark Heinz40 th Rencontres de Moriond March 12-19, STAR TPC dE/dx Identification

Mark Heinz40 th Rencontres de Moriond March 12-19, Identified particles at intermediate to high-p t 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 ~ GeV/c

Mark Heinz40 th Rencontres de Moriond March 12-19, K/pi & pbar/pi ratio vs mult d+Au Pbar/Pi- K-/Pi- dN/d  STAR preliminary Particle ratios (%) dN/d  p+p

Mark Heinz40 th Rencontres de Moriond March 12-19, vs Centrality in Au+Au 200

Mark Heinz40 th Rencontres de Moriond March 12-19, Non-strange particles with tuned Pythia

Mark Heinz40 th Rencontres de Moriond March 12-19, =4 GeV

Mark Heinz40 th Rencontres de Moriond March 12-19, Gamma_s in AuAu ,K,p ,K,p,  STAR Preliminary Au-Au √s=200 GeV