Ralf Averbeck, Stony Brook University XXXX th Rencontres de Moriond La Thuile, Italy, March 12-19, 2005 The Charm (and Beauty) of RHIC l Heavy flavor in nuclear collisions l Open heavy flavor at RHIC: PHENIX & STAR l Selected results l pp: reference l dAu: cold nuclear matter effects l AuAu: probing the hot medium Heavy quarkonia (J/  ) at RHIC: PHENIX l snapshot of current results and future attractions l Summary

R. Averbeck, Stony Brook 2 Moriond 3/18/2005 l production of heavy quark-antiquark pairs: cc (bb) l dominated by gluon-gluon hard scattering –sensitive to initial gluon density (and spin) l additional thermal production  enhancement? –sensitive to initial temperature l propagation through dense medium l energy loss or thermalization  softening of spectra? –sensitive to properties of the produced nuclear medium l does charm flow? –sensitive to collectivity on parton level quarkonia (J  in dense medium l suppression via color screening? l enhancement via coalescence? è heavy quarks = rich probe of the nuclear medium è study of yields & spectra in pp, dAu, and AuAu Why is heavy flavor interesting?

R. Averbeck, Stony Brook 3 Moriond 3/18/2005 l ideal (but very challenging in HI environment) direct reconstruction of charm decays (e.g. ) l STAR experiment (in dAu) much easier if displaced vertex is measured (c  = 123  m) Open heavy-flavor measurements D0  K- +D0  K- + l alternative (but indirect) l contribution of semileptonic decays to lepton spectra (singles & pairs) l PHENIX experiment (in pp, dAu, AuAu) l STAR experiment (pp, dAu) K-K- ++

R. Averbeck, Stony Brook 4 Moriond 3/18/2005 PHENIX & STAR at RHIC 2 forward muon spectrometers: 1.2 < |  | < 2.4 p  2 GeV/c l muons in forward arms l tracking l muon ID: l “absorber” l electrons in central arms l tracking l electron ID: l RICH + EMC 2 central electron/photon/hadron spectrometer arms:  0.35 p  0.2 GeV/c large acceptance  tracking detector: TPC l hadrons: l TPC (dE/dx) l Time-of-Flight detector l electron ID: EMC  <1  in addition

R. Averbeck, Stony Brook 5 Moriond 3/18/2005 √s = 200 GeV l STAR: consistent results (PRL 94, (2005)) l slightly larger cross section l agreement within errors l subtract e ± from background sources (cocktail) from inclusive e ± spectrum  e ± from heavy flavor l comparison with PYTHIA (tuned to available data) l p T < 1.5 GeV/c: reasonable l p T > 1.5 GeV/c: spectra “harder” than PYTHIA –bottom enhancement? –hard fragmentation? l comparison with FONLL l Fixed Order Next-to-Leading Log pQCD calculation (M. Cacciari, P. Nason, R. Vogt hep-ph/ ) l good description of spectral shape l barely in agreement with data (within errors) PHENIX data

R. Averbeck, Stony Brook 6 Moriond 3/18/2005 STAR Preliminary STAR data √s NN = 200 GeV l STAR: 1 st direct reconstruction of charmed hadrons at RHIC (PRL 94, (2005)) l D 0 → K -  + (and charge conjugate) l D ±, D* as well l D spectra confirm failure of tuned PYTHIA l D and e ± measurements are consistent l with each other l with PHENIX e ± data in dAu l medium effects? l R dA is consistent with binary scaling (within errors) l indication for Cronin enhancement l PHENIX observes no significant centrality dependence of e ± spectra STAR Preliminary

R. Averbeck, Stony Brook 7 Moriond 3/18/2005 √s NN = 200 GeV: yields l heavy flavor e ± inv. differential multiplicity as function of collision centrality l insufficient statistics at p T > 1.5 GeV/c to study modification of spectral shape PHENIX: PRL 94, (2005) total yield at p T > 0.8 GeV/c l total charm yield in AuAu agrees with binary scaled pp yield (as expected for point-like pQCD process)!

R. Averbeck, Stony Brook 8 Moriond 3/18/2005 PHENIX Preliminary √s NN = 200 GeV: spectra nuclear modification factor R AA of e ± from heavy flavor is compatible with R AA of  0 l present precision insufficient to examine centrality dependence l strong medium modification of spectral shape is observed! l full statistics cocktail analysis l indication for suppression at high p T (relative to binary scaled pp reference) R AA with yield above 2.5 GeV/c

R. Averbeck, Stony Brook 9 Moriond 3/18/2005 p T [GeV/c] R AA √s NN = 200 GeV: energy loss l comparison of R AA of e ± from heavy flavor for central AuAu collisions with theoretical predictions M. Djordjevic et al., hep-ph/ N. Armesto et al. hep-ph/ l measured suppression pattern at high p T l is in reasonable agreement with theoretical models incorporating heavy quark energy loss l can differentiate between different scenarios l caveat l currently compared to charm calculations only l data contain significant contribution from b decays for p T ≥ 4 GeV/c l heavy quarks DO interact strongly with the medium!

R. Averbeck, Stony Brook 10 Moriond 3/18/2005 PHENIX: nucl-ex/ STAR: Preliminary theory: Greco et al. PL B595(2004) 202 √s NN = 200 GeV: elliptic flow pYpY pXpX Y X Z Reaction plane: Z-X plane High pressure Low pressure pressure gradients (early) l data show v 2 (electron) ≠ 0  v 2 (D meson) ≠ 0 l interaction of heavy quarks with the medium, possibly thermalization l spatial anisotropy in initial stage l momentum anisotropy in final stage l elliptic flow strength

R. Averbeck, Stony Brook 11 Moriond 3/18/2005 J/  : the other heavy flavor probe at RHIC l PHENIX measurements in pp, dAu, AuAu (CuCu currently in progress) at 200 GeV J/  → e + e - at midrapidity J/  →  +  - at forward and backward rapidity l pp reference l total cross section  J/  = 2.69 ± 0.23 ± 0.33  b l consistent with predictions from –Color Octet (COM) and Color Evaporation (CEM) model calculations –using “typical” parton distribution functions (PDF) l consistent with gluon-fusion picture of J/  production

R. Averbeck, Stony Brook 12 Moriond 3/18/2005 Klein,Vogt, PRL 91:142301,2003 Kopeliovich, NP A696:669,2001 PHENIX PRELIMINARY gluons in Pb / gluons in p X Anti Shadowing Eskola, Kolhinen, Vogt, NP A696(2001)729 PHENIX North Muon Arm: y < 0 PHENIX Central Arms: y ≈ 0 PHENIX South Muon Arm: y > 0 J/  in dAu: cold nuclear matter effects l gluon PDF modifications: (anti)shadowing l data indicate weak (anti)shadowing l also observed l weak absorption l p T broadening similar to measurements at lower energy (E866/NuSea)

R. Averbeck, Stony Brook 13 Moriond 3/18/2005 R. L. Thews, M. Schroedter, J. Rafelski, Phys Rev C 63, Plasma Coalescence Model Binary Scaling Stat.Model Andronic et al nucl-th/ Absorption (Nuclear + QGP) + final-state coalescence Absorption (Nuclear + QGP) L. Grandchamp, R. Rapp, Nucl Phys A709, 415; Phys Lett B 523, 60  y = 1.0  y = 4.0 l RHIC Run-4 (analysis in progress) l statistics increased by factor ~50 l better mass resolution l better S/B J/  →  +  - measurement in addition l differentiating between different scenarios should be feasible l RHIC Run-5 (CuCu) l data on A dependence J/  in AuAu: suppressed or enhanced? l RHIC Run GeV) J/  → e + e - only (~12 counts): PRC69, ,2004 l not conclusive J/  →ee

R. Averbeck, Stony Brook 14 Moriond 3/18/2005 Summary & Outlook l Open heavy flavor measurements at RHIC l D mesons and single e ± from heavy flavor decays are measured l reference measurement is available for 200 GeV –spectra are harder than PYTHIA prediction l cold nuclear matter effects (in dAu) are small l heavy flavor in the hot and dense medium (AuAu) –yields are consistent with binary scaling (point like pQCD process) –high p T suppression and elliptic flow indicate significant interaction of heavy quarks with a (colored) medium l near future –increase p T reach: what happens with beauty? –single muon measurement –dileptons from correlated heavy flavor decays J/  at RHIC l pp reference is available l “normal” nuclear matter effects have been studied in dAu l stage is set for nucleus-nucleus collisions l upgrades (vertex spectrometers) will provide new opportunities