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Identified Hadrons and Their Role at RHIC Camelia Mironov Kent State University.

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Presentation on theme: "Identified Hadrons and Their Role at RHIC Camelia Mironov Kent State University."— Presentation transcript:

1 Identified Hadrons and Their Role at RHIC Camelia Mironov Kent State University

2 2 cmironov@bnl.gov Action: wherewhywhat.bnl.gov

3 3 cmironov@bnl.gov Relativistic Heavy Ions Collider Where? USA - Long Island – Brookhaven - RHIC

4 4 cmironov@bnl.gov System  s (GeV) Au + Au20, 62, 130, 200 d + Au200 p + p200 Cu +Cu20,62, 200  different energy: vary energy density  different A : vary the size of the system  have the p+p baseline WHAT? COLLISIONS!

5 Au+Au collisions dense medium hadrons detector  Au+Au, p+p, d+Au  hadronization mechanisms  Theory vs Experiment  Future measurements High p T hadrons  unidentified  identified

6 6 cmironov@bnl.gov Geometry of the collision N part number of nucleons in the overlap region Collisions Participants Binary Collisions Participants b (fm) N part, N binary Central ----------------- peripheral N bin ( N coll ): number of inelastic nucleon - nucleon collisions (# binary collisions) b Im pa ct Pa ra m et er

7 7 cmironov@bnl.gov How A+A differs from a ‘bunch of p+p’? Initial Final p+p A+A

8 8 cmironov@bnl.gov hadrons leading particle a b c d Hard-scattering cross-sectionFragmentation Function pQCD particle production: p+p (pT>2GeV/c) InitialFinal Parton Distribution Functions p p

9 9 cmironov@bnl.gov c d hadrons a b pQCD particle production: Au+Au (pT>2GeV/c) InitialFinal Parton Distribution FunctionsIntrinsic k T PDF modification (shadowing) Hard-scattering cross-sectionFragmentation Function leading particle suppressed Partonic Energy Loss

10 10 cmironov@bnl.gov Au+Au vs. p+p Au+Au : initial +final state effects pp : ‘simple’ We NEED ALSO A collision system to disentangle the initial-final states effects  p (d) + Au – ‘no final state effects’

11 11 cmironov@bnl.gov pQCD particle production: d+Au (pT>2GeV/c) InitialFinal Parton Distribution Functions Intrinsic kT PDF Modification (shadowing) Fragmentation Function c d hadrons a b

12 12 cmironov@bnl.gov Quantify deviations of A+A from p+p ? !!! Simplest: divide AA spectra to pp spectra!!!!  NUCLEAR MODIFICATION FACTORS

13 13 cmironov@bnl.gov Quantify deviations of A+A from p+p NUCLEAR MODIFICATION FACTORS  Need one collision system  systematic errors cancel out ASSUMPTION: both ratios exhibit the same behavior because of the same underlying physics

14 14 cmironov@bnl.gov Information via R XX  R ~1 -- no nuclear effects: A+B = C * (p+p)  deviation from 1 indicate presence of nuclear effects:  R>1  enhancement (usual explanation: soft scatters before hard collision)  R<1  suppression (energy loss in dense medium)

15 15 cmironov@bnl.gov Nuclear modification factors for h+-

16 16 cmironov@bnl.gov R AA /R CP : h ± Charged Hadrons:  Au + Au : R CP and R AA ~ suppression  d + Au : R CP and R dA ~ enhancement (Cronin effect – experimental observation and not the explanation) R AA & R dA R CP dAu AuAu

17 17 cmironov@bnl.gov STAR, nucl-ex/0305015 pQCD + Shadowing + Cronin pQCD + Shadowing + Cronin + Energy Loss factor ~5 suppression pQCD + initial state effects pQCD + initial+final state effects Theory: R AA for h+-  pQCD+final (energy loss) + initial (intrinsic kT+shadowing) describes data  dense medium created in central AuAu !!!!! pQCD+Shadowing+Intrinsic kT+ Energy Loss pQCD+Shadowing+ Intrinsic kT

18 18 cmironov@bnl.gov Conclusions from h+-  R AA, R dA and R CP give same information  pp and peripheral dAu/ AuAu are “the same” !! h+- dominated by mesons (pions) 0 1 2 3 4 5 6 7 8 9 10 11 12 GeV/c pQCD (string fragmentation) soft Phenomenological (Hadronization) scale

19 19 cmironov@bnl.gov Identified hadrons …  (dss) 1321 (MeV/c 2 ) Λ(uds) 1116 (MeV/c 2 )  (sss) 1673(MeV/c 2 ) K(us) 494(MeV/c 2 ) K 0 s (ds) 498(MeV/c 2 )  (ss) 1020(MeV/c 2 )  p + p d + Au Au + Au Do all these particles have anything extra to add to what unidentified charged hadrons revealed already?

20 20 cmironov@bnl.gov Have I wasted my time doing charged kaons identification analysis? Kaons: p T ~700 MeV Traditional: K  μν (63%) K  ππ0 (21%) Charged  charged + neutral K charged daughter K parent KINK Topological reconstruction

21 21 cmironov@bnl.gov Nuclear Modification Factors for K, Φ, π, Λ,Ξ…  Au+Au  d+Au

22 22 cmironov@bnl.gov Au+Au R CP Experiment  Baryons suppressed ~ 2.5GeV/c  Mesons suppressed ~ 1.5GeV/c

23 23 cmironov@bnl.gov Au+Au R AuAu Experiment  Mesons suppressed  Baryons enhanced AND maxR AA p(uud) <maxR AA Λ(uds) <maxR AA Ξ(dss)

24 24 cmironov@bnl.gov Au+Au R CP Theory Topor-Pop et al ( nucl-th/0407095 ) HIJING/BBbar v2 describe data too!! Hijing/BBbar v2 0-10% / 60-90% For K - + K + and Λ+Λbar  additional production mechanism for baryons (junctions) Reco for K0s and Λ+Λbar Central(b=3fm) / Peripheral (b=12fm)  ReCombination - assumes the recombination of two and three low pT partons to form hadrons from an exponential parton pT spectrum. Recombination describes the baryon – mesons differences Fries et al nucl-th/0306027

25 25 cmironov@bnl.gov Au+Au R AuAu Theory … Topor-Pop (private comunication and nucl-th/0407095 )  Experimental pattern reproduced

26 26 cmironov@bnl.gov My educated guess on this … R CP is the SAME for all baryons !  ? same effect is present in both central and peripheral Au+Au  ? it’s not Au+Au it’s p+p It’s more a p+p effect rather than some fancy stuff going on in Au+Au! [Tounsi & Redlich: hep-ph/0111159] Canonical suppression of yield in pp compared to AA!!

27 27 cmironov@bnl.gov d+Au R CP and R dAu  both ratio present enhancement compared to binary scaling  similar to AA, there seem to be a difference between mesons and baryons  also R dA (baryons) > R CP (baryons) (error bars) R CP R dA

28 28 cmironov@bnl.gov d+Au Theory 1. Kopeliovich, Nemchik, Schafer, Tarasov – Phys. Rev. Lett. 88(2002) 232303 2. Vitev, Gyulassy – Phys. Rev. Lett. 89 (2002) 252301 3. X.N. Wang – Phys. Rev. C 61(2000) 064910 4. Accardi, Trelani –Phys. Rev. D 64(2001) 116004 5. Zhang, Fai, Papp, Bernafoldi, Levai – Phys. Rev. C 65(2002) 034903 Rescatterings (projectile hadron or its partons) PRIOR to the hard collision cause a broadening of the p T spectrum pTpT R AB 1 ~2-4 GeV/c 1.1-1.5 A p 1.Hwa, Yang nucl-th/0404066 Recombination model (Oregon) FINAL STATE recombination of partons determine the enhancement of the nuclear modification factor

29 29 cmironov@bnl.gov d+Au Theory 1.Hwa, Yang nucl-th/0404066 Recombination (Oregon)  Final state effect  Initial state elastic scatterings reproduce the general trend of the R dA but NOT the particle species dependence Kopeliovich, Nemchik, Schafer, Tarasov – Phys. Rev. Lett. 88(2002) 232303

30 30 cmironov@bnl.gov MHO on this final vs initial issue … Fermilab 772 experiment p+Fe/H2 Drell-Yan production – no final partons to recombine! DIS experiments at DESY e+ + N/Kr/Cu Hadron production in eA compared to eD  no initial rescatteings If call ‘Cronin’ an experimental observation then easier to accept that the enhancement observed in different collision systems and energies, can have different (and not unique) explanations !

31 31 cmironov@bnl.gov Conclusions from identified hadrons  R AB /R CP HAS TO BE TREATED SEPARATELLY (at least until an explanation/scaling for the R AB strangeness ordering is found)  Au+Au, d+Au: difference between mesons and baryons in the intermediate pT region  same hadronization mechanism ?!  models assuming different hadronization scenarios, qualitatively describe data  need other probes 0 1 2 3 4 5 6 7 8 9 10 11 12 GeV/c Hard Intermediate soft New phenomenological scale

32 32 cmironov@bnl.gov Other probes to answer the questions DO JET ANALYSIS with identified particles  in p+p, d+A and A+A  trigger on mesons and baryons  trigger on strange and non-strange baryons and meson Back side Same side Trigger Particle Associated Particles

33 33 cmironov@bnl.gov Other probes to answer the questions DO JET ANALYSIS with identified particles  in p+p, d+A and A+A  trigger on mesons and baryons  trigger on strange and non-strange baryons and meson Back side Same side Trigger Particle Associated Particles  Present results in heavy ions for h-h, baryon-h, meson-h correlations

34 34 cmironov@bnl.gov Two particle correlations: Hwa, Yang nucl-th/0407081 Trigger Particle AssociatedParticles Jet structure by two-particle correlation within the jet: must consider 4/5 partons to recombine  Trigger on pions and calculate the distribution of the associated particles (AuAu collisions)

35 35 cmironov@bnl.gov Strange-Strange correlations … Hadron production at SLD  short-range, local correlations  short- range compensation of quantum numbers  long-range correlations between opposite charge  leading particle production: ssbar events different from uubar or ddbar events Rapidity difference between identified hadron pairs

36 36 cmironov@bnl.gov “Braveheart”: Strange-Strange correlations K + (us) K - (su) Λ(uds) K + (su) Λ(uds) K - (su)

37 37 cmironov@bnl.gov Not much… Λ trigger: 2<p T <6 (GeV/c) K assoc: 1.5< pT < p T trigger (GeV/c)  Not much, but an interesting analysis to continue with

38 38 cmironov@bnl.gov Final conclusion … Much to learn, you still have!

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