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

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

3. jaroslav.bielcik@fjfi.cvut.cz 3 Heavy quarks as a probe of QGP 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 extract properties of the medium. Dead cone effect. light M.Djordjevic PRL 94 (2004) Radiative energy loss Wicks et al, Nucl. Phys. A784 (2007) 426

4. The STAR Detector V ertex P osition D etector 4 VPD: minimum bias trigger. TPC: PID, tracking. TOF: PID. BEMC: PID, trigger.

5. 5 D 0 and D* p T spectra in p+p collisions D 0 yield scaled by N D0 /N cc = 0.565 D * yield scaled by N D* /N cc = 0.224 FONLL upper band is consistent with charm spectra FONLL: 200 GeV M. Cacciari, PRL 95 (2005) 122001 500 GeV Ramona Vogt µ F = µ R = mc, |y| < 1. STAR Preliminary 200GeV: Phys. Rev. D 86 (2012) 72013

6. 6 D 0 spectra in Au+Au 200 GeV Suppression at high p T in central and mid-central collisions. Suppression at high p T in central collisions similar to light hadrons. Enhancement at intermediate p T ~ models suggest radial flow of light quarks coalescence with charm. P. Gossiaux: arXiv: 1207.5445

7. Strong suppression at high p T 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. 7 Non-photonic Electron R AA in Au+Au 200 GeV Non-photonic Electrons are from semileptonic c and b decays

8. 8 Quarkonia states in A+A Charmonia: J/ ,  ’,  c Bottomonia:  (1S),  (2S),  (3S) Key Idea: Quarkonia melt in the QG plasma due to color screening of potential between heavy quarks Suppression of states is determined by T C and their binding energy Lattice QCD: Evaluation of spectral functions  T melting Sequential disappearance of states:  Color screening  Deconfinement  QCD thermometer  Properties of QGP H. Satz, HP2006 When do states really melt? T diss (  ’)  T diss (  c )< T diss (  (3S)) < T diss (J/  )  T diss (  (2S)) < T diss (  (1S))

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

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

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

12. Dilepton Physics Chronological division: High Mass Range (HMR) M ee > 3 GeV/c 2 –primordial emission, Drell-Yan –J/Ψ and ϒ suppression Intermediate Mass Range (IMR) 1.1 < M ee < 3 GeV/c 2 –QGP thermal radiation –heavy-flavor modification Low Mass Range (LMR) M ee < 1.1 GeV/c 2 –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 12

13. Production in p+p at 200 GeV 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 Phys. Rev. C 86, 024906 (2012) 13

14. Production in Au+Au 200 GeV 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? 14 difficult to disentangle (modified) charm from thermal QGP contributions  future detector upgrades required HFT+MTD STAR Preliminary

15. 15 Beam Energy Scan Dielectrons 2010 – 2011: Au+Au at 62.4, 39, and 19.6 GeV STAR data samples: 55M, 99M, and 34M min-bias events Dielectron Production at lower √s NN

16. Compare to Theory: in-medium ρ 16 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 STAR Preliminary

17. Summary and Outlook jaroslav.bielcik@fjfi.cvut.cz 17 Large suppression of heavy quark production at high-p T in D 0 and 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 p . Increasing of ϒ suppression vs. centrality. R AA consistent 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.

18. 18 Heavy Flavor Tracker TPC Volume Outer Field Cage Inner Field Cage SSD IST PXL FGT HFT Detector Radius (cm) Hit Resolution R/  - Z (  m -  m) Radiation length SSD2220 / 7401% X 0 IST14170 / 1800<1.5% X 0 PIXEL 812 / 12~0.4% X 0 2.512 / 12~0.4% X 0

19. 19 Physics projections – punchline for Y13,14 R CP =a*N10%/N(60- 80)% Assuming D 0 v 2 distribution from quark coalescence. 500M Au+Au m.b. events at 200 GeV. - Charm v 2 Medium thermalization degree Drag coefficients! Assuming D 0 R cp distribution as charged hadron. 500M Au+Au m.b. events at 200 GeV. - Charm R AA Energy loss mechanism! Color charge effect! Interaction with QCD matter!

20. Future: ϒ via STAR MTD 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  +  - 20 MTD (MRPC)

21. STAR Dileptons: Present & Future 2009 – 2011 –TPC + TOF + EMC dielectron continuum dielectron spectra, and v 2 (p T ) –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 v 2 –LMR: vector meson in-medium modifications –IMR: measure thermal QGP radiation 21

22. 22 D 0 and D* p T spectra in p+p 200 GeV Fixed-Order Next-to-Leading Logarithm: M. Cacciari, PRL 95 (2005) 122001. The charm cross section at mid-rapidity: Phys. Rev. D 86 (2012) 072013. Upper limit of FONLL describes the data well

23. D 0 and D* p T spectra in p+p collisions [1] C. Amsler et al. (Particle Data Group), PLB 667 (2008) 1. [2] FONLL calculation: Ramona Vogt µ F = µ R = m c, |y| < 1 STAR preliminary D 0 yield scaled by N D0 /N cc = 0.565 [1] D * yield scaled by N D* /N cc = 0.224 [1] 23 FONLL upper band consistent with 500GeV (200GeV) charm spectra.

24.  in Au+Au 200 GeV, Centrality 14/Nov/12 Manuel Calderón de la Barca Sánchez 24 Peripheral Central STAR Preliminary

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

26. Dileptons Au+Au theory comparison STAR central 200 GeV Au+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 26 Rapp, Wambach, van Hees arXiv:0901.3289  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