A Case For RHICII Heavy Flavor Physics Status

A Case For RHIC-II: Heavy Flavor Physics Status Report of the RHIC-II Heavy Flavor Working Group Thomas Ullrich for the HF Group BNL Program Advisory Committee Meeting November 3, 2005 Heavy Flavor Group Conveners: T. Frawley, R. Vogt, TU Web site: http: //rhicii-science. bnl. gov/heavy/

Why Quarkonia? – What Can We Learn? Charmonia: J/y, Y’, cc u Bottomonia: (1 S), (2 S), (3 S) Key Idea: Melting in the plasma l l Color screening of static potential between heavy quarks: § J/y suppression: Matsui and Satz, Phys. Lett. B 178 (1986) 416 Suppression of states is determined by TC and their binding energy Ebinding (Ge. V) u J/y 0. 64 y’ 0. 05 cc 0. 2 (1 S) 1. 1 (2 S) 0. 54 (3 S) 0. 31 Sequential disappearance of states: Color screening Deconfinement QCD thermometer Properties of QGP 2

Quarkonia – Baseline Theory (pp/d. A) u Need properly “normalized” Quarkonia baseline l l u pp production baseline d+Au cold matter effects (absorption, shadowing) pp l l Color Evaporation Model (CEM) Quarkonium production treated as fraction of all QQ pairs below HH threshold CEM taken to NLO (Gavai et al. , G. Schuler and R. Vogt) Parameters adjusted to existing data Direct production ratio 0. 62 y’ 0. 14 cc 1 0. 60 cc 2 0. 99 (1 S) 0. 52 (2 S) 0. 33 (3 S) 0. 20 J/y + ’+ ’’ hep-ph/0412158 J/y 3

Quarkonia – Baseline Theory (pp/d. A) u p. A l l Nuclear Absorption § Breakup of quarkonia in the final state § Depends if produced as color singlet or octet Shadowing § Modification of PDFs in the nucleus w. r. t. free nucleon § NB: y-distributions more sensitive than p. T R. Vogt, RHIC-II Science Workshop 4

Quarkonia – Lattice QCD (AA) Singlet free energy: F 1 (entropy term? ) l Singlet energy: V 1 l u When do states really melt? Neither F 1 nor V 1 are potentials spectral functions (results consistent with V 1) J/y melts at 1. 5 -2. 5 TC l Tdiss(y’) Tdiss(cc)< Tdiss( (3 S)) < Tdiss(J/y) Tdiss( (2 S)) < Tdiss( (1 S)) l F. Karsch, RHIC-II Science Workshop Recent developments: u Heavy Quark potential? Collision with thermal gluons, p ~ 3 Tc can lead to earlier dissociation: d. NJ/y/dt = -Ng sdis 5

Quarkonia – Effects in AA u Feed down: Large from cc states (30 -40% ? ) l Not well measured in hadronic collisions l Unknown at RHIC energies l u Other sources of quarkonia production Statistical coalescense (thermal production) § too small at RHIC – larger at LHC ? l Dynamic coalescence § coalescence: c+c J/y § recombination: J/y c+c J/y § narrower y and softer p. T distributions l u u Quenching at high-p. T ( discussed later) Comover absorption l J/y + p (r) DD (negligible for ) Many effects that need to be understood to extract pure “suppression” mechanism 6

Open Heavy Flavor – What Can We Learn? Open Heavy Flavor Mesons: D 0, D*, D±, Ds, B u Key Idea: Study interaction with hot and dense media l l l u u u Yields Spectra Correlations High-p. T suppression Density of medium, E-Loss mechanism Low-p. T flow, spectra Thermalization ? Transport properties of the medium Charm-Charm, Charm-Hadron, J/y-Hadron Correlations: l l Low-p. T High-p. T Thermalization ? Tomography of medium Study of heavy flavor Properties of QGP (Density, Thermalization) 7

Open Heavy Flavor – Baseline Theory (pp) Heavy Quark production is a “hard” process perturbative QCD u Calculations on NLO (e. g. R. Vogt et al. hep-ph/0502203) depend on: Quark mass mc, mb l Factorization scale m. F (typically m. F = m. T or 2 m. T) l Renormalization scale m. R (typically m. R = m. F) l Parton density functions (PDF) l Fragmentation functions (FF) – plays important role l Fixed-Order plus Next-to-Leading-Log (FONLL) l designed to cure large logs for p. T >> mq where mass is not relevant M. Cacciari et al. , PRL 95: 122001, 2005 u 8

Open Heavy Flavor – Energy Loss in Medium path length L w k. T u l In vacuum, gluon radiation suppressed at q < m. Q/EQ l l u Various Models to describe E-loss in hot medium: BDMPS, GLV, … Gluon Radiation Probability “dead cone” effect implies lower energy loss (Dokshitzer-Kharzeev, ‘ 01) energy distribution w d. I/dw of radiated gluons suppressed by angle-dependent factor suppress high-w tail Collisional E-loss: Qg Qg, Qq l d. E/dx ln p - considered small (Armesto, Salgado, Wiedemann, PRD 69 (2004) 9

Open Heavy Flavor – Elliptic Flow u Observed large elliptic flow of light/s quark mesons at RHIC l u Strong evidence for thermalization What about charm? Naïve kinematical argument: need mq/T ~ 7 times more collisions to thermalize lv 2 of charm closely related to. Study R Van Hees & Rapp, PRC 034907: resonantinheavy-light Moore & Teeny: diffusion coefficient QGP, AA of 71, l u Examples: quark scattering viacoefficient), scalar, pseudoscalar, vector, model and axial D = T/Mh (h drag using a Langevin vector D-like-mesons 10

RHIC Results – Charm Cross Section u Study of D mesons (Kp combinations/event mixing) and non-photonic single electrons (from semileptonic D decays) l Cross section 2 -4 × larger than predictions from NLO H. Zhang, QM’ 05 u Issues: D mesons: large background l Non-photonic electrons: smeasured/scc ~ 15% l Need direct measurement of D mesons (via K p) 11

RHIC Results – Charm Energy Loss u Study of non-photonic single electrons (from semileptonic D decays) First evidence of strong suppression of charm at high-p. T l Challenge to existing E-loss paradigm (collisional E-loss important? ) l X. Dong, QM’ 05 u Issues: Statistics at high-p. T limited, uncertainties due to photonic background l Cannot deconvolute contributions from charm and bottom l Need direct measurement of high-p. T D mesons (via K p) and B mesons (via J/y) 12

RHIC Results – Charm Flow u Study of non-photonic single electrons (from semileptonic D decays) First hint of strong charm elliptic flow for p<2 Ge. V/c l Measurements from STAR & PHENIX deviate at higher p T l STAR: 30 -40% sys. errors u Issues: l l u Statistics limited Uncertainties due to photonic background Large sys errors Cannot deconvolute contributions from charm and bottom Need direct measurement of D mesons (via K p) v 2 X. Dong, QM’ 05 13

RHIC Results – J/y Suppression u Study of J/y ee and mm in Au+Au and Cu+Cu l l l u V. Ciancolo, PANIC’ 05 l Yield is suppressed compared to that in p+p collisions Suppression is larger for more central collisions. Suppression beyond that of cold nuclear matter for most central collisions even if sabs ~ 3 mb. Cold matter effects underpredict the suppression Issues: Lack of statistics l Only J/y measurement so far l Need more statistics and data on Y’, cc, and states 14

RHIC Results – J/y Suppression T. Gunji, PANIC’ 05 No recombination Recombination predicts narrow p. T and rapidity distribution: u p. T 2 vs. Ncollisions l Predictions of recombination model match better. u RAA vs. Rapidity l No significant change in rapidity shape compared to p+p result. Recombination compensates suppression? u Issues: l Charm rapidity distributions at RHIC are open questions l Require more data on √s, A dependence Need more statistics, J/y v 2 15

Quarkonia – RHIC-II Goals and Requirements Physics Motivation Probes Studies Requirements Baseline J/y, y’, (1 S), (2 S), (3 S) through mm and ee decay channels Rapidity y(x. F) and p. T spectra in AA, pp as a function of A, √s High luminosity and acceptance. High resolution to resolve states Deconfinement & Initial Temperature J/y, y’, (1 S), (2 S), (3 S) Melting patterns of quarkonia states Extract suppression mechanism taking into account: feed down, nuclear absorption, and recombination Properties of the medium High-p. T J/y RAA: Dissociation Quenching High luminosity Thermalization &Transport properties of the Medium J/y flow (v 2) as a function of A, √s Recombination: y and p. T 2 High luminosity to obtain good statistics in short time (A, √s scans) 16

Quarkonia – RHIC-II Goals and Requirements In order to extract the desired suppression signals the following measurements have to be achieved: Topic Studies Requirements Nuclear effects • shadowing • absorption Quarkonia in pp, p. A: • x 2, x. F dependence • A dependence • rapidity distributions over wide range Large y coverage Forward coverage to high x. F Suppression vs. Recombination • charm production ds/dp. Tdy • v 2 of J/y • p. T dependence of suppression High resolution vertex detectors Contribution from feed down Measure cc at least in pp and p. A Photon detection at mid and forward rapidity, high luminosity, good energy & momentum resolution to minimize background Quarkonium production p. A: cc / J/y A-dependence J/y polarization (? ) As above Large acceptance for cos q* 17

Open Heavy Flavor – RHIC-II Goals and Requirements Physics Motivation Probes Studies Requirements Baseline D/B mesons, nonphotonic electrons • Rapidity y(x. F) and p. T spectra in AA, p. A as a function of A, √s High Luminosity High resolution vertex detectors (ct(D) ~ 100300 mm) High-p. T PID (D Kp) Thermalization, Transport properties of the medium D mesons, B? non-photonic electrons (D+B) Elliptic flow v 2 p. T spectra as above Properties of the medium Initial conditions D, B (B J/y + X) mesons, nonphotonic electrons RAA(p. T), RCP of D , B as a function of p. T for various √s as above Properties of the medium Heavy Flavor Production D mesons, nonphotonic electrons Correlations: • charm-charm • charm-hadron • J/y-hadron HIGH luminosity (eff 2 !) Large coverage Trigger ? 18

RHIC-II - Facing the Challenge u Addressing the requirements: l l u STAR: l l l u RHIC-II: increased luminosity (RHIC-II ≈ 40 × RHIC) § Note: collision diamond s = 20 cm at RHIC and s = 10 cm at RHIC II gain in usable luminosity is larger than “nominal” increase PHENIX & STAR: more powerful upgraded detectors crucial to the Heavy Flavor physics program - completed in mid/near term ~5 years. DAQ upgrade increases rate to 1 KHz, triggered data has ~ 0 dead time. Silicon tracking upgrade for heavy flavor, jet physics, spin physics. Barrel TOF for hadron PID, heavy flavor decay electron PID. EMCAL + TOF J/y trigger useful in Au+Au collisions. Forward Meson Detector PHENIX: l l l Silicon tracker for heavy flavor, jet physics, spin physics. Forward muon trigger for high rate pp + improved pattern recognition. Nose cone calorimeter for heavy flavor measurements. Aerogel + new MRP TOF detectors for hadron PID. Hadron-blind detector for light vector meson e+e- measurements. 19

RHIC-II – Open Heavy Flavor u With detector upgrades (both PHENIX and STAR): l l l u Dramatically reduce backgrounds for all open charm, open beauty signals using displaced vertex measurement. Separate open charm and beauty statistically using displaced vertex. Separate B → J/y from prompt J/y using displaced vertex. And with the luminosity upgrade: l l l Extend open charm and beauty RAA measurements to high p. T. What is the energy loss well above thermalization region? Measure D & semileptonic charm and beauty decay v 2 to high p. T. See the transition from thermalization to jet energy loss for charm. Measure open charm correlations with open charm or hadrons. 20

RHIC-II - Quarkonia u With detector upgrades: J/y from B decays with displaced vertex measurement (both). l Reduce J/y →mm background with forward m trigger in PHENIX. l Improve mass resolution for charmonium and resolve family. l See g in forward calorimeter in front of muon arms (PHENIX) and in FMD in STAR l u And with the luminosity upgrade: J/y RAA to high p. T. Does J/y suppression go away at high p. T? l J/y v 2 measurements versus p. T. See evidence of charm recombination? l RAA. Which Upsilons are suppressed at RHIC? l Measure cc → J/y+g RAA. Ratio to J/y? l Measure Y‘ RAA. Ratio to J/y? l Measure B → J/y using displaced vertex - independent B yield measurement, also get background to prompt J/y measurement. l 21

RHIC-II - Heavy Flavor Yields All numbers are first rough estimates (including trigger and reconstruction efficiencies) for 12 weeks physics run (∫Leff dt ~ 18 nb-1) Signal RHIC Exp. Obtained RHIC I (>2008) RHIC II LHC/ALICE+ J/y →e+e. J/y →m+m- PHENIX ~800 ~7000 3, 300 29, 000 45, 000 395, 000 9, 500 740, 000 → e+ e → m+m- STAR PHENIX - 830 80 11, 200 1, 040 2, 600 8, 400 B→J/y→e+e. B→J/y→m+m- PHENIX - 40 420 570 5, 700 N/A cc→e+e- g cc→m+m- g PHENIX - 220 8, 600 2, 900* 117, 000* N/A ~0. 4× 106 (S/B~1/600) 30, 000** 8000 D→Kp STAR T. Frawley, PANIC’ 05, * Large backgrounds, quality uncertain as yet RHIC-II Satellite Meeting ** Running at 100 Hz min bias + 1 month (= year), P. Crochet, EPJdirect A 1, a (2005) and private comm. 22

Summary & Conclusions u Heavy Flavor Physics at RHIC teaches us about: l l l u Heavy Flavor Physics at RHIC is just at the beginning l u Already the first glimpses points to new physics § Charm suppression at high-p. T § J/y: suppression + recombination § Cross sections larger than NLO predictions RHIC-II luminosity & detector upgrades dramatically expand capabilities and thus our understanding l l u Deconfinement Thermalization Transport properties of the medium Study sequential suppression of many quarkonium states Evaluate effects: feed down, absorption, recombination Study D, B production and suppression in the medium Study thermalization via charm and quarkonium flow Still challenging: l Correlation measurements, cb impossible? 23