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Identified Hadrons and Their Role at RHIC

Identified Hadrons and Their Role at RHIC. Camelia Mironov Kent State University. Action: w here w hy w hat .bnl.gov. R elativistic H eavy I ons C ollider. Where? USA - Long Island – Brookhaven - RHIC. WHAT? COLLISIONS!. different energy: vary energy density

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Identified Hadrons and Their Role at RHIC

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

  2. Action: wherewhywhat.bnl.gov

  3. Relativistic Heavy Ions Collider Where? USA - Long Island – Brookhaven - RHIC

  4. WHAT? COLLISIONS! • different energy: vary energy density • different A : vary the size of the system • have the p+p baseline

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

  6. Collisions Central ----------------- peripheral Binary Collisions Npart, Nbinary Participants Participants b (fm) Geometry of the collision Nbin(Ncoll): number of inelastic nucleon - nucleon collisions (# binary collisions) b Impact Parameter Npartnumber of nucleons in the overlap region

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

  8. pQCD particle production: p+p (pT>2GeV/c) Parton Distribution Functions hadrons Hard-scattering cross-section Fragmentation Function hadrons leading particle Initial Final c p p a b d

  9. pQCD particle production: Au+Au (pT>2GeV/c) Parton Distribution Functions Intrinsic kT PDF modification (shadowing) Hard-scattering cross-section Fragmentation Function Partonic Energy Loss c a b d hadrons Initial Final leading particle suppressed

  10. 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. pQCD particle production: d+Au (pT>2GeV/c) c a b d hadrons Initial Final Parton Distribution Functions Intrinsic kT PDF Modification (shadowing) Fragmentation Function

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

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

  14. Information via RXX  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. Nuclear modification factors for h+-

  16. RAA/RCP: h± RAA & RdA RCP dAu dAu AuAu AuAu • Charged Hadrons: • Au + Au : RCP and RAA ~ suppression • d + Au : RCP and RdA ~ enhancement (Cronin effect – experimental observation and not the explanation)

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

  18. Phenomenological (Hadronization) scale 0 1 2 3 4 5 6 7 8 9 10 11 12 GeV/c soft pQCD (string fragmentation) Conclusions from h+- • RAA, RdA and RCP give same information  pp and peripheral dAu/ AuAu are “the same” !! h+- dominated by mesons (pions)

  19. Identified hadrons … K(us) 494(MeV/c2) Λ(uds) 1116 (MeV/c2) • p + p d + Au Au + Au (dss) 1321 (MeV/c2) K0s(ds) 498(MeV/c2) Do all these particles have anything extra to add to what unidentified charged hadrons revealed already? (sss) 1673(MeV/c2) (ss) 1020(MeV/c2)

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

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

  22. Au+Au RCP Experiment • Baryons suppressed~ 2.5GeV/c • Mesonssuppressed ~ 1.5GeV/c

  23. Au+Au RAuAu Experiment • Mesons suppressed • Baryons enhanced AND maxRAAp(uud)<maxRAAΛ(uds)<maxRAAΞ(dss)

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

  25. Au+Au RAuAuTheory … Topor-Pop (private comunication and nucl-th/0407095)  Experimental pattern reproduced

  26. [Tounsi & Redlich: hep-ph/0111159] Canonical suppression of yield in pp compared to AA!! My educated guess on this  … RCP 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!

  27. RdA d+Au RCP and RdAu RCP • both ratio present enhancement compared to binary scaling • similar to AA, there seem to be a difference between mesons and baryons • also RdA (baryons) > RCP (baryons) (error bars)

  28. RAB 1.1-1.5 1 A ~2-4 GeV/c pT p 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 pT spectrum 1.Hwa, Yangnucl-th/0404066 Recombination model (Oregon) FINAL STATE recombination of partons determine the enhancement of the nuclear modification factor

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

  30. MHO on this final vs initial issue … Fermilab 772 experiment p+Fe/H2 Drell-Yan production – no final partons to recombine! 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 ! DIS experiments at DESY e+ + N/Kr/Cu Hadron production in eA compared to eD  no initial rescatteings

  31. New phenomenological scale 0 1 2 3 4 5 6 7 8 9 10 11 12 GeV/c soft Intermediate Hard Conclusions from identified hadrons • RAB/RCP HAS TO BE TREATED SEPARATELLY (at least until an explanation/scaling for the RAB 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

  32. TriggerParticle Back side Sameside Associated Particles 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

  33. TriggerParticle Back side Sameside Associated Particles 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  Present results in heavy ions for h-h, baryon-h, meson-h correlations

  34. Trigger Particle Associated Particles Two particle correlations:Hwa, Yangnucl-th/0407081 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. hadrons hadrons Rapidity difference between identified hadron pairs 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

  36. K+(us) <-> K-(su) Λ(uds) <-> K+(su) Λ(uds) <-> K-(su) “Braveheart”: Strange-Strange correlations

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

  38. Final conclusion … Much to learn, you still have!

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