Motivation for Studying Heavy Quarks Heavy quark mass

Motivation for Studying Heavy Quarks • Heavy quark mass are external parameter to QCD. • Sensitive to initial gluon density and gluon distribution. K • energy loss feature different from light quarks. Its suppression and the flow capability provide key information on the hot/dense medium properties. • Suppression or enhancement pattern of heavy quarkonium production reveal critical features of the medium. + e-/ - l K - D 0 e+/ + l Open heavy flavor e-/ - • Cold Nuclear effect (CNM): e+/ + – Different scaling properties in central and forward rapidity region CGC. – Gluon shadowing, etc Heavy quarkonia

How the Measurements is done at RHIC Meson J/ψ e e D 0 --> K p D --> e +X D --> +X PHENIX

How the Measurement is done at RHIC Meson J/ψ STAR J/ψ e e D 0 --> K p D --> e +X D --> +X 0 -80% Au+Au STAR Preliminary

Heavy Quark Energy Loss in the Medium Hot/Dense Medium c quark K+ u e-/ - c l D 0 radiative energy loss (D. kharzeev, M. Djordjevic et al. ) Hot/Dense Medium c quark K+ u e-/ - c l D 0 collision energy loss (Teany, Ralf, Denes et al. ) K+ Hot/Dense Medium c quark u c e-/ - D 0 meson energy loss Ivan, et al D 0 l “dead cone effect”: light gluon radiation suppressed at q < m. Q/EQ

Variables to quantify the medium effect RAA ( or Rd. A) “no effect” No medium effect 5 N-N collisions Heavy quarks are from Hard collision: • Each collision is separated clearly. • In the absence of any nuclear effect, Yield(A+A) = yield(p+p)*N(collisions), i. e. scale with number of collisions (Ncoll) The larger the energy loss The smaller the RAA

How Measurements has been done K+ e-/ - l K - D 0 l Open heavy flavor e+/ + PHENIX Measurement • Little material to produce background. • different methods K+ D 0 p STAR Measurement K- • different measurements p • lots of material to produce background. Open heavy flavor

Measurements on RAA in Au+Au collisions STAR hadrons p. T> 6 Ge. V/c • large suppression of charm quark production is observed • D meson probably less suppressed than light hadrons. • Where the bottom show up in the spectrum?

Do we Understand the Result? • Radiative Energy Loss with reasonable gluon densities do not explain the observed suppression – Djordjevic, Phys. Lett. B 632 81 (2006) – Armesto, Phys. Lett. B 637 362 (2006) • Collisional EL may be significant for heavy quarks – Wicks, nucl-th/0512076 – van Hess, Phys. Rev. C 73 034913 (2006) • heavy quarks fragment inside the medium and are suppressed by dissociation? – Adil and Vitev, hepph/0611109 – Similar suppression for B and D at high-p. T PHENIX nucl-ex/0611018 STAR nucl-ex/0607012

Energy Loss and Flow are Closely connected z y x Charm was NOT expected to flow with the medium since it’s too heavy !

Flow of electrons from Charm and Bottom meson decay [Phys. Lett. B 595 202 -208 ] [PRB 637, 362] [PRC 72, 024906] [PRC 73, 034913] n Strong elliptic flow for non-photonic electron n Main source is D meson -> indicate non-zero D v 2 n Charm v 2 also non-zero ? n Bottom sneak in here?

Quarkonia Suppression: “smoking gun” for QGP Physics Letter B Vol. 178, no. 4 1986 c • Low temperature c • Vacuum J/ • High temperature d d • High density (screening effect take place) D+ D- The melting sequence: cc -> Y’ -> J/y -> Upsilon

The life of J/ in the medium is very complicated • Observed J/y is a mixture of direct production+feeddown. – All J/y ~ 0. 6 J/y(Direct) + ~0. 3 cc + ~0. 1 y’ • Important to disentangle different component (through upgrade) • Suppression and enhancement in the “cold” nuclear medium – Nuclear Absorption, Gluon shadowing, initial state energy loss, Cronin effect and gluon saturation (CGC) c J/ c • Hot/dense medium effect – J/y dissociation, i. e. suppression – Recombination from uncorrelated charm pairs – Survival (or not) in the hot/dense medium from lattice calculation c D+

Measurements J/ (in medium) in the world • FNAL: – E 772/789/866: p+A – Sqrt(s) = 38. 8 Ge. V • HERA-B: – p+A – Sqrt(s) ~42 Ge. V • SPS: – NA 3, NA 38/50/60: p+p, p+A, A+A – Sqrt(s) = 18, 20, 28, 30 Ge. V • RHIC: – PHENIX/STAR: p+p, p+A, A+A – Sqrt(s) =20, 62, 130, 200 Ge. V

Comparing RHIC to SPS Suppression results NA 50 at at SPSSPS (0<y<1) NA 50 (0<y<1) PHENIX at RHIC (|y|<0. 35) NA 50 SPS (0<y<1) PHENIX atat RHIC (|y|<0. 35) PHENIX at RHIC (1. 2<|y|<2. 2) NA 50(0<y<1) NA 50 at SPS (0<y<1) PHENIX at RHIC (|y|<0. 35) PHENIX at RHIC (1. 2<|y|<2. 2) One of the key observations for CERN to declare QGP discovery. Bar: uncorrelated error Bar: uncorrelated Normalized by error NA 51 Bracket : correlated error p+p data Bracket : correlated error Global error = 12%based and with correction on Globalerror==7% 12% isnot notshown Global are Eur. Phys. J. C 39 (2005) : 355 • Suppression pattern similar in RHIC and SPS. • After removing the CNM effect, differences start to show-up. • CNM effect not removed yet. • suppression at SPS consistent with the melting of psi’ and chi_c.

Golden Comparisons • Charm flows. If recombination is correct, J/Psi should also flow. Single electron from open charm meson • PHENIX expect to accomplish in run 7 with higher luminosity (x 3) and better (~sqrt(3. 5)) reaction plane resolution. • Charm suppression increase at higher p. T. If recombination is correct, J/Psi suppression should quadratically increased at higher p. T. • Not yet observed in PHENIX up to 5 Ge. V. Single electron from open charm meson • What the minimum p. T to see the pattern? J/ Yan, Zhuang, Xu nucl-th/0608010

A Direct Way to Measure Heavy Flavor (near future)

Heavy Flavor Silicon Tracker Upgrade: the core of RHIC-II heavy flavor program Purdue High Energy Physics P 3 MD lab