Rare particle production 1. strangeness 2. open charm 3. quarkonia

Strangeness: Two historic QGP predictions restoration of  symmetry -> increased production of s restoration of  symmetry -> increased production of s  mass of strange quark in QGP expected to go back to current value (m S ~ 150 MeV ~ Tc)  copious production of ss pairs, mostly by gg fusion [Rafelski: Phys. Rep. 88 (1982) 331] [Rafelski-Müller: P. R. Lett. 48 (1982) 1066] deconfinement  stronger effect for multi-strange deconfinement  stronger effect for multi-strange  can be built using uncorrelated s quarks produced in independent microscopic reactions, faster and more copious than in hadronic phase  strangeness enhancement increasing with strangeness content [Koch, Müller & Rafelski: Phys. Rep. 142 (1986) 167] Strangeness production depends strongly on baryon density (i.e. stopping vs. transparency, finite baryo-chemical potential)

Strangeness yields from pp to AA A strong increase of strange baryon production relative to a scaled yield as measured in pp was considered a main signature for the QGP (Rafelski, Mueller (1982)) A strong increase of strange baryon production relative to a scaled yield as measured in pp was considered a main signature for the QGP (Rafelski, Mueller (1982)) The main reason is that in particular multi-strange baryon production in a hadronic medium is a multi-step (and therefore) slow process, i.e. it is suppressed. The main reason is that in particular multi-strange baryon production in a hadronic medium is a multi-step (and therefore) slow process, i.e. it is suppressed. The problem with the simple QGP explanation for an enhanced cross section arises from a statistical consideration called ‘canonical suppression in pp collisions’. The problem with the simple QGP explanation for an enhanced cross section arises from a statistical consideration called ‘canonical suppression in pp collisions’. It simply means that strange baryon production in pp collisions could be suppressed on the basis of the rarity of strange quarks in the correlation volume that has to be considered in pp collisions, i.e. the strange quarks have to be sufficiently abundant in the proper volume in order to form a strange baryon. So strange baryon production might simple seem enhanced in AA collisions, because more strange quarks are produced in the same volume. It simply means that strange baryon production in pp collisions could be suppressed on the basis of the rarity of strange quarks in the correlation volume that has to be considered in pp collisions, i.e. the strange quarks have to be sufficiently abundant in the proper volume in order to form a strange baryon. So strange baryon production might simple seem enhanced in AA collisions, because more strange quarks are produced in the same volume.

Plots of canonical suppression equilibration volume ? Tounsi et al.

Strangeness yields from pp to AA Production not well modeled by N part (correlation volume) Canonical suppression increases with increasing strangeness  and  are not flat

Canonical suppression as function of incident energy Correlation volume: V= A  NN ·V 0 A NN = N part /2 V 0 = 4/3  ·R 0 3 R 0 = 1.1 fm proton radius/ strong interactions T= MeV  = 1 K. Redlich – private communication Particle ratios indicate T= 165 MeV Solid – STAR Open – NA57  1 2/3 1/2  = 2/3 - area drives yields  = 1/2 - best fit

Strangeness enhancement: Wroblewski factor evolution Wroblewski factor dependent on T and  B dominated by Kaons Lines of constant S / = 1 GeV I. Increase in strange/non-strange particle ratios II. Maximum is reached III. Ratios decrease (Strange baryons affected more strongly than strange mesons) Peaks at 30 A GeV in AA collisions due to strong  B dependence mesons baryons hidden strangeness mesons PBM et al., hep-ph/ total

Strangeness enhancement K/  – the benchmark for abundant strangeness production: K/  – the benchmark for abundant strangeness production: K/  K+/K+/ [GeV]

New machines to explore the high density regime new European ‘can-do-all’ facility GSI) A new European heavy-ion machine (FAIR) to be ready in Low energy running at RHIC ( )

Heavy flavor production

Flavor dependence of yield scaling participant scaling for light quark hadrons (soft production) binary scaling for heavy flavor quark hadrons (hard production) strangeness is not well understood (canonical suppression in pp) PHENIX D-mesons up, down strange charm

Charm cross-section measurements in pp collisions in STAR  Charm quarks are believed to be produced at early stage by initial gluon fusions  Charm cross-section should follow number of binary collisions (N bin ) scaling Measurements direct D 0 (event mixing) c→  +X (dE/dx, ToF) c→e+X (ToF) (EMC) p T (GeV/c) 0.1    4.0  1.5 constraint , d  /dp T  d  /dp T

LO / NLO / FONLL? A LO calculation gives you a rough estimate of the cross section A LO calculation gives you a rough estimate of the cross section A NLO calculation gives you a better estimate of the cross section and a rough estimate of the uncertainty A NLO calculation gives you a better estimate of the cross section and a rough estimate of the uncertainty Fixed-Order plus Next-to-Leading-Log (FONLL) Fixed-Order plus Next-to-Leading-Log (FONLL)  Designed to cure large logs in NLO for p T >> m c where mass is not relevant  Calculations depend on quark mass m c, factorization scale  F (typically  F = m c or 2 m c ), renormalization scale  R (typically  R =  F ), parton density functions (PDF)  Hard to obtain large  with  R =  F (which is used in PDF fits) FONLL RHIC (from hep-ph/ ): LO: NLO: CDF Run II c to D data (PRL 91, (2003): The non-perturbative charm fragmentation needed to be tweaked in FONLL to describe charm. FF FONLL is much harder than used before in ‘plain’ NLO  FF FONLL ≠ FF NLO The non-perturbative charm fragmentation needed to be tweaked in FONLL to describe charm. FF FONLL is much harder than used before in ‘plain’ NLO  FF FONLL ≠ FF NLO

RHIC: FONLL versus Data Matteo Cacciari (FONLL): Matteo Cacciari (FONLL): factor 2 is not a problem factor 2 is not a problem factor 5 is !!! factor 5 is !!!  Spectra in pp seem to require a bottom contribution  High precision heavy quark measurements are tough at RHIC energies. Need direct reconstruction instead of semi-leptonic decays. Easy at LHC.  Reach up to 14 GeV/c D-mesons (reconstructed) in pp in first ALICE year. hep-ex/ nucl-ex/

Heavy Flavor in AA collisions Theory: there are two types of e-loss: radiative and collisional, plus dead-cone effect for heavy quarks Flavor dependencies map out the process of in-medium modification

χ 2 minimum result D->e 2σ 4σ 1σ A.) charm flows like light quarks strong elliptic flow of electrons from D meson decays → v 2 D > 0 strong elliptic flow of electrons from D meson decays → v 2 D > 0 v 2 c of charm quarks? v 2 c of charm quarks? recombination Ansatz: (Lin & Molnar, recombination Ansatz: (Lin & Molnar, PRC 68 (2003) ) universal v 2 (p T ) for all quarks universal v 2 (p T ) for all quarks simultaneous fit to , K, e v 2 (p T ) simultaneous fit to , K, e v 2 (p T ) a = 1 b = 0.96  2 /ndf: 22/27

submitted to PRL (nucl-ex/ ) charged hadrons B.) charm quenches like light quarks Describing the suppression is difficult for models

How difficult ? R AA of electrons from heavy flavor decay R AA of electrons from heavy flavor decay radiative energy loss with typical gluon densities is not enough (Djordjevic et al., PLB 632(2006)81)  models involving a very opaque medium agree better (qhat very high !!) (Armesto et al., PLB 637(2006)362)  collisional energy loss / resonant elastic scattering (Wicks et al., nucl-th/ , van Hees & Rapp, PRC 73(2006)034913)  heavy quark fragmentation and dissociation in the medium → strong suppression for charm and bottom (Adil & Vitev, hep-ph/ )

Useful to constrain medium viscosity  /s…. Simultaneous description of Simultaneous description of STAR & PHENIX R(AA) and PHENIX v2for charm. (Rapp & Van Hees, PRC 71, 2005) Ads/CFT ==  /s ~ 1/4  ~ 0.08 Ads/CFT ==  /s ~ 1/4  ~ 0.08 Perturbative calculation of D (2  t) ~6 Perturbative calculation of D (2  t) ~6 (Teaney & Moore, PRC 71, 2005) ==  /s~1 transport models require transport models require  small heavy quark relaxation time  small diffusion coefficient D HQ x (2  T) ~ 4-6  this value constrains the ratio viscosity/entropy ratio viscosity/entropy   /s ~ (1.3 – 2) / 4   within a factor 2 of conjectured lower quantum bound  consistent with light hadron v 2 analysis  electron R AA ~  0 R AA at high p T - is bottom suppressed as well?

cc Cold Matter Path = L c-cbar suppression rr V(r)/  Lattice QCD calculation

PHENIX signals in pp Proton-Proton Data

PHENIX signals in AuAu central J/   ee AuAu 10% Central S/B ~ 0.25 J/    AuAu 20% Central S/B ~ 0.1 Detailed event mixing background subtraction, modified log likelihood fitting, and careful systematic error determination.

nucl-ex/ submitted to PRL The Unadulterated Data!

Still Just the Data! Nuclear Suppression Factor Collision Centrality (  More Central) Ratio Blue / Red

Assume J/  is at rest and a static medium (no time evolution). If local density (dE T /dy or dN  /dy) > threshold then no J/ . Note it does include a Woods-Saxon Density Profile ! Predictions: (1) Much larger J/  suppression at RHIC compared with SPS. (2) Larger J/  suppression at mid-rapidity where local density is highest. Simple Theory J/ 

Statistical and Systematic Comparison PHENIX data at 200 GeV is quite surprisingly compatible with NA50 data at 17.2 GeV ! PHENIX data at forward rapidity shows a significantly stronger suppression.

Similar Trends (?)

Cancelling Effects ? Grandchamp, Rapp, Brown PRL 92, (2004) nucl-ex/ R. Rapp et al. (for y=0) PRL 92, (2004) R. Thews (for y=0) Eur. Phys. J C43, 97 (2005) N. Xu et al. (for y=0) nucl-th/ Bratkovskaya et al. (for y=0) PRC 69, (2004) A. Andronic et al. (for y=0) nucl-th/ And many other calculations…. Original J/  suppressed. Compensated for by recombination of originally uncorrelated c and c.

nucl-ex/ submitted to PRL Open Charm Input Non-photonic electrons (from heavy flavor decay) Any recombination model must also match the charm distribution. Note that J/  get contributions from charm at ½ J/  p T. And charm yields electrons with ~ 0.7 x D meson p T. J/ 

Exciting new results on heavy quarkonia at RHIC are of major import and potentially profound, though not easily digested. On the experiment side, we must have measurements of multiple states (J/ ,  ’,  C,  1s,2s,3s)) ! Theory needs full dynamical evolution matching both open and closed charm in a consistent picture (good progress here). Less drawing lines through points. Exciting future with more results from SPS, RHIC, and LHC! Heavy Outlook