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Jaroslav Biel čí k for STAR collaboration Czech Technical University in Prague

Heavy flavor and dilepton production in STAR experiment. Jaroslav Biel čí k for STAR collaboration Czech Technical University in Prague. Rencontres de Moriond QCD and High Energy Interactions La Thuile , March 9-16, 2013. Outline. Motivation.

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Jaroslav Biel čí k for STAR collaboration Czech Technical University in Prague

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  1. Heavy flavor and dilepton production in STAR experiment Jaroslav Bielčík for STAR collaboration Czech Technical University in Prague Rencontresde Moriond QCD and High Energy Interactions La Thuile, March 9-16, 2013

  2. Outline • Motivation. • Open heavy flavor. • J/y and Upsilon measurements. • Dilepton production. • Summary.

  3. light Heavy quarks as a probe of QGP Radiative energy loss • p+p data:  baseline of heavy ion measurements.  test of pQCD calculations. • Due to their large mass heavy quarks are primarily produced by gluon fusion in early stage of collision.  production rates calculable by pQCD.M. Gyulassy and Z. Lin, PRC 51, 2177 (1995) • heavy ion data: • Studying energy loss of heavy quarks.  independent way to extractproperties of the medium. • Dead cone effect. M.Djordjevic PRL 94 (2004) Wicks et al, Nucl. Phys. A784 (2007) 426 jaroslav.bielcik@fjfi.cvut.cz

  4. The STAR Detector • VPD: minimum bias trigger. • TPC: PID, tracking. • TOF: PID. • BEMC: PID, trigger. VertexPositionDetector

  5. D0 and D* pT spectra in p+pcollisions D0 yield scaled by ND0/Ncc= 0.565 D* yield scaled by ND*/Ncc= 0.224 • FONLL upper band is • consistent with charm • spectra STAR Preliminary 200GeV: Phys. Rev. D 86 (2012) 72013 FONLL: 200 GeV M. Cacciari, PRL 95 (2005) 122001 500 GeVRamona Vogt µF= µR = mc, |y| < 1 . 5

  6. D0 spectra in Au+Au 200 GeV • Suppression at high pT in central and mid-central collisions. • Suppression at high pTin central collisions similar to light hadrons. • Enhancement at intermediate pT ~ models suggest radial flow of light quarks coalescence with charm. P. Gossiaux: arXiv: 1207.5445 6

  7. Non-photonic Electron RAA in Au+Au 200 GeV • Strong suppression at high pT in central collisions • D0, NPE results seems to be consistent  kinematics smearing & charm/bottom mixing • Uncertainty dominated by p+p result. • High quality p+p data from Run09 and Run12 are on disk. Non-photonicElectrons are from semileptonic c and b decays

  8. Quarkonia states in A+A Charmonia: J/y, Y’, ccBottomonia: (1S), (2S), (3S) Key Idea:Quarkonia meltin the QG plasma due to color screening of potential between heavy quarks • Suppression of states is determined by TC and their binding energy • Lattice QCD: Evaluation of spectral functions  Tmelting • Sequential disappearance of states: •  Color screening  Deconfinement •  QCD thermometer  Properties of QGP When do states really melt? Tdiss(y’)  Tdiss(cc)< Tdiss((3S)) < Tdiss(J/y)  Tdiss((2S)) < Tdiss((1S)) H. Satz, HP2006

  9. J/y in Au+Au collisions STAR high-pT : arxiv:1208.2736 Liu et al., PLB 678:72 (2009) and privatecomminication Zhaoet al., PRC 82,064905(2010) and privatecommunication • J/ψ suppression increases with collision centrality and decreases with pT • Low-pT data agrees with two models including color screening and regeneration ef. • At high pT Liu et al. model describes data reasonable well, jaroslav.bielcik@fjfi.cvut.cz

  10. Nuclear modification factor of Upsilon Models from M. Strickland and D. Bazow, arXiv:1112.2761v4 • Indications of suppression of (1S+2S+3S) getting stronger with centrality.

  11. ϒ RAA Comparison to models • Incorporating lattice-based potentials, including real and imaginary parts • A: Free energy • Disfavored. • B: Internal energy • Consistent with data vs. Npart • Includes sequential melting and feed-down contributions • ~50% feed-down from cb. M. Strickland, PRL 107, 132301 (2011).

  12. Dilepton Physics Chronological division: • High Mass Range (HMR) Mee > 3 GeV/c2 • primordial emission, Drell-Yan • J/Ψ and ϒ suppression • Intermediate Mass Range (IMR) 1.1 < Mee< 3 GeV/c2 • QGP thermal radiation • heavy-flavor modification • Low Mass Range (LMR) Mee< 1.1 GeV/c2 • in-medium modification of vector mesons • possible link to chiral symmetry restoration Dileptons are excellent penetrating probes • very low cross-section with QCD medium • created throughout evolution of system

  13. Production in p+p at 200 GeV Phys. Rev. C 86, 024906 (2012) • Understand the p+p reference Cocktail simulation consistent with data L. Ruan (STAR), Nucl. Phys. A855 (2011) 269 Charm contribution dominates IMR • consistent with STAR charm cross-section Adams et al (STAR), Phys. Rev. Lett. 94 (2005) 062301 Uncertainties: • vertical bars: statistical • boxes: systematic • grey band: cocktail simulation systematic • not shown: 11% normalization

  14. Production in Au+Au 200 GeV STAR Preliminary Low Mass: • enhancement when compared to cocktail (w/o ρ meson) little centrality dependence Intermediate Mass: cocktail “overshoots” data in central collisions but, consistent within errors modification of charm? STAR Preliminary • difficult to disentangle (modified) charm from thermal QGP contributions • future detector upgrades required HFT+MTD

  15. Dielectron Production at lower √sNN Beam Energy Scan Dielectrons2010 – 2011: Au+Au at 62.4, 39, and 19.6 GeV STAR data samples: 55M, 99M, and 34M min-bias events

  16. Compare to Theory: in-medium ρ STAR Preliminary • Robust theoretical description top RHIC down to SPS energies • calculations by Ralf Rapp (priv. comm.) • black curve: cocktail + in-medium ρ • Measurements consistent with in-medium ρ broadening • expected to depend on total baryon density • tool to look for chiral symmetry restoration

  17. Summary and Outlook • Large suppression of heavy quark production at high-pTin D0and • non-photonic electrons measurements in 200 GeV central Au+Au collisions. • Similar to light quarks. • J/ψ suppression increases with collision centrality and decreases with pT. • Increasing of ϒ suppression vs. centrality. • RAAconsistent with suppression of feed down from excited states only (~50%). • Dielectron measurement in p+p 200 GeV. • Cocktail describes the data well. • Dielectron measurement in Au+Au 19.6 – 200 GeV. • Low mass enhancement down to low (SPS) energies observed. • Consistent with in-­medium ρ broadening. • Heavy flavor tracker and Muon telescope detector upgrades. • Significant improvement of heavy flavor, quarkonium and dilepton measurements. jaroslav.bielcik@fjfi.cvut.cz

  18. Heavy Flavor Tracker HFT SSD IST PXL Inner Field Cage FGT Outer Field Cage TPC Volume Solenoid EAST WEST 18

  19. Physics projections – punchline for Y13,14 RCP=a*N10%/N(60-80)% • Assuming D0Rcp distribution as charged hadron. • 500M Au+Aum.b. events at 200 GeV. • Charm RAA • Energy loss mechanism! • Color charge effect! • Interaction with QCD matter! Assuming D0 v2 distribution from quark coalescence. 500M Au+Aum.b. events at 200 GeV. - Charm v2 Medium thermalization degree Drag coefficients! 19

  20. Future: ϒ via STAR MTD MTD (MRPC) • A detector with long-MRPCs • Covers the whole iron bars and leave the gaps in between uncovered. • Acceptance: 45% at ||<0.5 • 118 modules, 1416 readout strips, 2832 readout channels • Long-MRPC detector technology, electronics same as used in STAR-TOF • Run 2012 -- 10%; 2013 – 60%+; 2014 – 100%: ϒ via m+m-

  21. STAR Dileptons: Present & Future • 2009 – 2011 • TPC + TOF + EMC • dielectron continuum • dielectron spectra, and v2 (pT) • vector meson in-medium modifications • LMR enhancement • modification in IMR? • 2012-2013 • TPC + TOF + EMC + MTD (partial) • e-μ measurements • IMR: Improve our understanding of thermal QGP radiation • LMR: vector meson in-medium modifications • 2014 and beyond • TPC + TOF + EMC + MTD + HFT • dimuon continuum • e-μ spectra and v2 • LMR: vector meson in-medium modifications • IMR: measure thermal QGP radiation

  22. D0 and D* pT spectra in p+p 200 GeV Phys. Rev. D 86 (2012) 072013. • The charm cross section • at mid-rapidity: • Upper limit of FONLL • describes the data well Fixed-Order Next-to-Leading Logarithm: M. Cacciari, PRL 95 (2005) 122001. 22

  23. STAR preliminary D0 and D* pTspectra in p+pcollisions D0 yield scaled by ND0/Ncc= 0.565[1] D* yield scaled by ND*/Ncc= 0.224[1] [1] C. Amsler et al. (Particle Data Group), PLB 667 (2008) 1. [2] FONLL calculation: Ramona Vogt µF = µR = mc, |y| < 1 FONLL upper band consistent with 500GeV (200GeV) charm spectra. 23

  24.  in Au+Au 200 GeV, Centrality STAR Preliminary STAR Preliminary STAR Preliminary Peripheral Central Manuel Calderón de la Barca Sánchez

  25.  in Au+Au 200 GeV • Advantage:  hasnegligible recombination; smaller co-mover absorption • Raw yield ofe+e-with |y|<0.5 = 197 ± 36 ∫Ldt ≈ 1400 µb-1

  26. DileptonsAu+Au theory comparison • STAR central 200 GeVAu+Au • hadronic cocktail (STAR) Ralf Rapp (priv. comm.) R. Rapp, Phys.Rev. C 63 (2001) 054907 R. Rapp & J. Wambach, EPJ A 6 (1999) 415 Complete evolution (QGP+HG) cocktail + HG + QGP: • Agreement w/in uncertainties • hadronic phase: ρ “melts” when extrapolated close to phase transition boundary • total baryon density plays the essential role • top-down extrapolated QGP rate closely coincides with bottom-up extrapolated hadronic rates Rapp, Wambach, van Hees arXiv:0901.3289

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