strange and multi-strange particle production in p+p at √s= 200 gev in star

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Strange and multi-strange particle production in p+p

at √s= 200 GeV in STAR

Mark HeinzMark Heinz

for the STAR Collaborationfor the STAR Collaboration

University of Bern, SwitzerlandUniversity of Bern, Switzerland

XXXXth Rencontres de Moriond 12-19 March 2005La Thuile, Italie

Mark Heinz 40th Rencontres de Moriond March 12-19, 2005

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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


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3. High-P3. High-PTT strange particles correlated strange particles correlated

with hadrons in jets with hadrons in jets

→ → study azimuthal study azimuthal correlations and correlations and

medium modification/quenchingmedium modification/quenching

→→ flavour dependence of the strong flavour dependence of the strong

interaction and the fragmentation interaction and the fragmentation

processprocess

Motivation

1. QGP signature: Strangeness 1. QGP signature: Strangeness

enhancement. enhancement. →→Measurement of Measurement of

strange particles in p+p used as a strange particles in p+p used as a

baselinebaseline to compare to Au+Au to compare to Au+Au

hadrons

parton

parton

leading particle → Flavour dependence of jets and associated particle yield

2. High-P2. High-PTT strange particles strange particles

high-Qhigh-Q22 pQCD processes pQCD processes production of mini-jetsproduction of mini-jets multiplicity dependence in p+pmultiplicity dependence in p+p

STAR preliminary √s=200 GeV


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STAR Experimental Setup

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)

Year 2000

Magnet

Coils

Central TriggerBarrel (CTB)

Time Projection Chamber(TPC)

Zero Degree calorimeter

(ZDC)


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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% K0

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


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Transverse momentum spectra

K0short K+ Λ

STAR dN/dy

0.128 ± 5%

0.129 ± 2%

0.066 ± 6%

0.0036 ± 6%

UA5 dN/dy

0.150 ± 20% 0.080 ± 25%

0.0070 ± 80%

STAR

<pt>

0.60 ± 1%

0.60 ± 1%

0.76 ± 3%

0.96 ± 5%

UA5

<pt>

0.53 ± 15% 0.80 ± 25%

0.80 ± 50%

K0s

+ -+ +

K+-

STAR measures the strange particles with a great improvement in Statistical errors over previous p +p experiments.

STAR PreliminarySTAR Preliminary


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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 kT of partons (to account for initial state gluon radiation)

STAR

Eskola et al, NPA 713(2003)

K0s + -+ +

K-factor =3

STAR preliminarySTAR 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


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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/0305070)

Special thanks to Werner Vogelsang for computation (Riken/BNL)

FF = KKP

Kniehl et al, hep-ph/0502188

UA1 K0s @ √s=630GeV

STAR K0s @ √s=200GeV

FF = Vogelsang et al.

XiSigma

LambdaProton

Van Leeuwen, nucl-ex/0412023


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Anti-Particle/Particle Ratios

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


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


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<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 ?

<pT> in p+p collisions for most massive particles is approaching the value in Au+Au Collisions !


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Wang et al, Phys Rev D 45 (1992)

<pT> vs charged multiplicity (Nch)

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

E735:Phys Lett B 282 (1992)

Tevatron √s=1800 GeV

π

K-

p

+K0s

+K0s

Evidence for stronger contribution of fragmenting mini-jetsto heavier strange hadrons ?


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Azimuthal correlations with high-pt strange particles (Y.Guo/J.Bielcikova)

p+p/d+Au

A+Aflow

+bkg

near-side away-side

B )2σ

π)(Δ(- expA )

2σ

Δexp(-A )C(Δ

2π

2

π20

2

0

trigger particle: charged particle (TPC) V0 – Λ, Λ, K0s

associated particle: charged tracks from TPC ( 1GeV/c <pTassociated<pTtrigger)

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 • Λ from q-jet,Λ from g-jet ?

STAR, PRL 91 (2003) 072304


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Preliminary results from azimuthal correlations using strange particles

h-Λ



Trigger PTrigger PTT >3.0 GeV/c >3.0 GeV/c

h-Λ K0s-h

h-h


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


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Summary

First high precision measurement of strange particles in p+p collisions First high precision measurement of strange particles in p+p collisions at this energy since ~1985 (UAx SPS) !at this energy since ~1985 (UAx SPS) !

Spectra and multiplicity dependence thereof are measured for Spectra and multiplicity dependence thereof are measured for KK00

ss,K,Kchargecharge Lambda and Xi Lambda and Xi

Current LO pQCD models (eg. PYTHIA) do not describe the STAR Current LO pQCD models (eg. PYTHIA) do not describe the STAR strangeness data without significant tuning of the parameters (K-strangeness data without significant tuning of the parameters (K-factor, intrinsic Kfactor, intrinsic KTT))

NLO pQCD calculations give good description of mesons but fail for NLO pQCD calculations give good description of mesons but fail for strange baryonsstrange baryons

STAR has measured azimuthal correlations with identified strange STAR has measured azimuthal correlations with identified strange trigger particles in p+p, d+Au and Au+Au trigger particles in p+p, d+Au and Au+Au


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The STAR Collaboration

Argonne National Laboratory, Argonne, IllinoisUniversity of Bern, Switzerland

University of Birmingham, Birmingham, United KingdomBrookhaven National Laboratory, Upton, New York

California 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, Russia

University of Frankfurt, Frankfurt, GermanyInsitute of Physics, Bhubaneswar, India

Indian 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, 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 43210Panjab University, Chandigarh 160014, India

Pennsylvania State University, University Park, Pennsylvania

Institute of High Energy Physics, Protvino, RussiaPurdue University, West Lafayette, Indiana 47907

University of Rajasthan, Jaipur 302004, IndiaRice University, Houston, Texas

Universidade de Sao Paulo, Sao Paulo, BrazilUniversity of Science & Technology of China, China

Shanghai Institute of Applied Physics, Shanghai,ChinaSUBATECH, Nantes, France

Texas A&M University, College Station, Texas University of Texas, Austin, Texas

Tsinghua University, Beijing, P.R. ChinaValparaiso University, Valparaiso, Indiana

Variable Energy Cyclotron Centre, Kolkata, IndiaWarsaw University of Technology, Warsaw, Poland

University of Washington, Seattle, WashingtonWayne State University, Detroit, Michigan Institute of Particle Physics, Wuhan, ChinaYale University, New Haven, Connecticut

University of Zagreb, Zagreb, Croatia

52 Institutions , ~530 collaborators


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backups


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Preliminary results from azimuthal correlations using strange particles

p + p


1.5 GeV/c < 1.5 GeV/c < pt(trigger) < 3.0 < 3.0 GeV/cGeV/c1.5 GeV/c < 1.5 GeV/c < pt(assoc) < 3.0 < 3.0 GeV/cGeV/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


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STAR TPC dE/dx Identification


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Identified particles at intermediate to high-pt

Two groups, baryons and mesons, which seem to approach each otheraround 5 GeV/c

Suggesting relevance of constituent quarks for hadron production

Coalescence/recombination provides a description ~1.5 - 5 GeV/c


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K/pi & pbar/pi ratio vs mult

d+Au

Pbar/Pi-

K-/Pi-

dN/d

STAR preliminary

Par

ticl

e ra

tios

(%

)

dN/d

p+p


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<pt> vs Centrality in Au+Au 200


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Non-strange particles with tuned Pythia


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<kT>=4 GeV


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Gamma_s in AuAu

,K,p

,K,p,

STAR Preliminary

Au-Au √s=200 GeV

strange and multi-strange particle production in p+p at √s= 200 gev in star

Documents

p p collisions

p pcomparison

flowp p

au collisions

au of identified particles

p pstar preliminary

massive particles

jets multiplicity dependence