Quarkonia and heavy flavors at RHIC Andry Rakotozafindrabe

Quarkonia (and heavy flavors) at RHIC Andry Rakotozafindrabe LLR – École Polytechnique QGP – France, Étretat 2006 05/07/2006

Physics motivation – the starting point m What are the properties of the hot and dense matter produced in relativistic heavy ion collisions ? m c and b are produced in the initial parton collisions, so they can be used to probe the created medium : l open charm (or beauty) energy loss energy density l l Only a few words here ( from a newbie ☺) , (quarkonia) suppressed by color screening deconfinement l We will focus on quarkonia in this talk, especially on hidden charm. 2 05/07/2006 Andry Rakotozafindrabe – LLR

Heavy quarks 05/07/2006

Heavy quarks dynamic m Measuring non-photonic electrons at RHIC: l RAA l v 2 4 05/07/2006 Andry Rakotozafindrabe – LLR

Heavy quark (radiative? ) energy loss (1 -3) N. Armesto et al. , PRD 71, 054027 (charm contribution only) m m m (1) q_hat = 0 Ge. V 2/fm J. Dunlop, J. Bielcik; QM 05 V. Greene, S. Butsyk; QM 05 (4) M. Djordjevic et al. , PRL 94, 112301 (beauty included) (4) d. Ng / dy = 1000 (2) q_hat = 4 Ge. V 2/fm (3) q_hat = 14 Ge. V 2/fm Agreement between both experiments Significant reduction at high p. T suggests sizeable heavy quark energy loss. Data favors a strong transport coefficient* q_hat ~14 Ge. V²/fm (radiative energy loss only model) large initial gluon density ~ 3500! Too high! Should take into account the collisionnal energy loss? (see M. Djordjevic, nucl -th/0603066) *q_hat density of scattering centers in the medium 5 05/07/2006 Andry Rakotozafindrabe – LLR

Charm flow S. Butsyk QM 05 Greco, Ko, Rapp, PLB 595 (2004) 202 M. Djordjevic et al. , Phys. Lett. B 632 (2006) 81 d. Ng/dy=1000 c and b quark p. T distributions at midrapidity before fragmentation : b contribution is dominant at high p. T m m Significant flow observed for heavy flavor electrons Indication for reduction of v 2 at p. T > 2 Ge. V/c. Due to beauty contribution? 6 05/07/2006 Andry Rakotozafindrabe – LLR

Quarkonia Mostly J/ (mostly PHENIX results) 05/07/2006

Screening the J/ in a QGP m Production l l l m Temperature of dissociation Td l l m ~ 60% direct production J/ ~ 30% via χc J/ + x ~ 10% via ’ J/ + x Sequential dissociation as the temperature (or energy density) increases : Satz, hep-ph/0512217 ’ χc J/ for χc and ’: Td ~ 1. 1 Tc for J/ : T for d ~ 1. 5 to 2 Tc Energy density (τ0 = 1 fm) vs the max. √s for SPS, RHIC and LHC 8 05/07/2006 Andry Rakotozafindrabe – LLR

Physics motivation – a few complications m quarkonia production l m g+g fusion dominant at RHIC energies J/ or Sensitive to: l Initial state l l Modification of the parton distribution functions (shadowing, CGC) p. T broadening (Cronin effect) Parton energy loss in the initial state ? Final state l l l “Normal” nuclear absorption Absorption by (hadronic ? ) comovers ? Color screening ? In-medium formation (recombination) ? Flow ? + feed-down b, , c J/ + x 9 05/07/2006 Andry Rakotozafindrabe – LLR

Production baseline : p+p J/ energy rapidity Phys. Rev. Lett. 96, 012304 Cross section vs : p. T y Total cross section in p+p = 2. 61 0. 20 0. 26 µb in agreement with COM Cross section vs rapidity follow PYTHIA shape Cross section vs p. T <p. T²> = 2. 51 0. 21 (Ge. V/c)² p+p J/ measurement will be used as a reference for A+B J/ : 10 05/07/2006 Andry Rakotozafindrabe – LLR

Phys. Rev. Lett. 96 (2006), 012304 Low x 2 ~ 0. 003 Cold nuclear effects : d+Au J/ (shadowing region) gluons in Pb / gluons in p Shadowing Anti Shadowing x Vogt, PRC 71, 054902 (2005), Kopeliovich, NP A 696, 669 (2001) J/ South y<0 xd x. Au rapidity y m Available d+Au data : J/ North y>0 y < -1. 2 : large x. Au ~ 0. 090 y ~ 0 : intermediate x. Au ~ 0. 020 y > 1. 2 : low x. Au ~ 0. 003 05/07/2006 Nucl. Phys. A 696 (2001) 729 -746 l Weak shadowing (modification of gluon distribution) and weak nuclear absorption (σabs ~ 1 mb favored) 11 Andry Rakotozafindrabe – LLR

RHIC : beyond cold nuclear effects ? m Au+Au data : even compared to the « worst » σabs~ 3 mb case l Factor 2 of suppression beyond cold effects in the most central Au+Au bin σabs =1 =3 mb Suppression Factor ~ 2 Number of participants Cold nuclear matter predictions from Vogt, nuclth/0507027 (shadowing + σabs = 1, 3 mb) 12 05/07/2006 Andry Rakotozafindrabe – LLR

RHIC vs SPS (I) : raw comparison m SPS : l l l m PHENIX : |y|~1. 7 √s ~ 17 Ge. V i. e. a factor 10 below RHIC Cold effect = normal nuclear = absorption σabs = 4. 18 ± 0. 35 mb Maximum ε ~ 3 Ge. V/fm 3 (τ0 = 1) PHENIX cold effect NA 50 cold effect Compare to RHIC : l l Cold effect = shadowing + nuclear = absorption σabs ~ 1 mb (Vogt, nuclth/0507027) Maximum ε ~ 5 Ge. V/fm 3 (τ0 = 1), higher than at SPS, but still, the same pattern of J/ suppression ! PHENIX NA 50 NA 60 Cu+Cu Au+Au Pb+Pb In+In SPS normalized to NA 51 p+p value (NA 60 preliminary points from Arnaldi, QM 05). 13 05/07/2006 Andry Rakotozafindrabe – LLR

RHIC vs SPS (II) : extrapolating suppression models m Suppression models in agreement with NA 50 data overestimate the suppression when extrapolated at RHIC energies : l l quite striking for mid and most central Au+Au bins already the case for Cu+Cu most central bins ? (Hadronic? ) co-mover scattering Direct suppression in a hot medium : Cu+Cu Au+Au 14 05/07/2006 Andry Rakotozafindrabe – LLR

Some recombination effects ? m Adding some regeneration that partially compensates the suppression : there is a better agreement between the model and the data. Grandchamp et al. hep-ph/0306077 Direct suppression in a hot medium : Cu+Cu Au+Au Regeneration : Cu+Cu Au+Au Total : Cu+Cu Au+Au 15 05/07/2006 Andry Rakotozafindrabe – LLR

Recombination predictions for < p. T² > vs Ncoll m m Recombination predicts a narrower p. T distribution with an increasing centrality, thus leading to a lower <p. T²> Within the large error bars : l l <p. T²> seems to be consistent with a flat dependence data falls between the two hypothesis partial recombination ? Thews & Mangano, PRC 73 (2006) 014904 c p+p, d+Au, Cu+Cu, Au+Au ion No nat mbi reco Open markers : |y|<0. 35 Solid markers : |y|~1. 7 n tio a n bi m co e r o N With recombination 16 05/07/2006 Andry Rakotozafindrabe – LLR

Predictions for < p. T² > vs Ncoll : Cronin effect ? m m m Random walk of the initial gluons in the transverse plane : <p. T 2>AA = <p. T 2>pp + 0 g-N p. T 2 LAA Use this linear L dependence to fit the <p. T²> brodening seen in dimuon data from p+p to d+Au at RHIC <p. T²> = 2. 51+0. 32*L Using L↔Ncoll, plot the result vs Ncoll VN Tram, Moriond 2006 & Ph. D thesis p+p d+Au Au+Au Cu+Cu RHIC (y~1. 7) Lower energy survey pp, p. A and AA Open symbol: y ~ 0 Full & curves: y ~ 2 17 05/07/2006 Andry Rakotozafindrabe – LLR

Recombination predictions vs rapidity Thews & Mangano, PRC 73 (2006) 014904 c No recombination All recombination m Recombination predicts a narrower rapidity distribution with an increasing Npart. m Going from Cu+Cu to the most central Au+Au : no significant change seen in the shape of the rapidity distribution. Blue bands: cold nuclear matter prediction from Vogt, nucl-th/0507027 (shadowing + σabs = 0, 3 mb) 18 05/07/2006 Andry Rakotozafindrabe – LLR

Ending where it began: revisiting the sequential dissociation Karsch, Kharzeev & Satz, PLB 637 (2006) 75 m m Data driven parametrization of cold nuclear effect (expected) Sequential melting overall J/ survival probability (measured/expected): S = 0. 6 S direct J/ + 0. 4 S J/ ← ’, χc Excited states melting from ψ’ suppression pattern @ SPS Recent lattice QCD results : direct J/ melting at 10 -30 Ge. V/fm 3 Real Au+Au systematic errors i. e. pt-to-pt and global scale added (small systematic errors associated with NA 50 published data) A. Bickley, Hard Probes 06 SPS and RHIC data seems to be consistent with the sequential melting. m 19 05/07/2006 Andry Rakotozafindrabe – LLR

Summary (I) PHENIX preliminary results on J/ dileptons at forward and mid-rapidity in Cu+Cu and Au+Au : m Suppression pattern l l l m Beyond cold nuclear effects, at least factor 2 of suppression in most central Au+Au events Similar to SPS suppression? despite a higher energy density reached Overestimated by models in agreement with NA 50 data and extrapolated at RHIC energy Understandable as recombinations that partially compensate the J/ suppression ? l Still open question (test vs <p. T²> dependance and rapidity distribution) 20 05/07/2006 Andry Rakotozafindrabe – LLR

Summary (II) m Alternate explanations ? l l m Direct J/ is not melting at present energy densities ? Only the higher mass resonances ’ and χc ? (recent lattice QCD results) J/ transport (with high p. T J/ escaping QGP region) + QGP suppression ? (Zhu, Zhuang, Xu, PLB 607 (2005) 107) QGP suppression ? ( Need to improve knowledge on cold nuclear effects at RHIC 21 05/07/2006 Andry Rakotozafindrabe – LLR

Hint of things to come Improved reference p+p : l l m m m x 10 higher statistics from run 5 x 30 higher statistics from run 6 Future measurements in ’ ? Future measurements in χc Planning d+Au (28 nb-1 vs 2. 7 nb-1 in run 3) and Au+Au (1 nb-1 vs 0. 24 nb-1 in run 4 ) with high luminosity A. Bickley, Hard Probes 06 Run 6 200 Ge. V p+p PHENIX Run 5 200 Ge. V p+p W or pr k u og nd re er ss m ( c - J/ ) Mass (Ge. V/c 2) Invariant Mass (Ge. V/c 2) ( c - J/ ) Mass (Ge. V/c 2) 22 05/07/2006 Andry Rakotozafindrabe – LLR

First upsilon measurement Hie Wei, QM 05 Dimuon mass spectrum for the two muon arms added together. 1 st Upsilons at RHIC from ~3 pb-1 collected during the 2005 run. 23 05/07/2006 Andry Rakotozafindrabe – LLR

STAR results and near future M. Cosentino, QWG 06 STAR Preliminary STAR – J/ Run 4 Au. Au m Dataset Au+Au@200 Ge. V : l l l m No trigger due to high background Just a faint signal For efficient J/ trigger, full barrel To. F is needed (just patch in Run 5) p+p@200 Ge. V (Run 5): l m STAR – J/ Run 5 pp trigger commissioning (~1. 7 M events) Run 6 (this year): expect 500 -1000 (work in progress) 24 05/07/2006 Andry Rakotozafindrabe – LLR

Back-up 25 05/07/2006 Andry Rakotozafindrabe – LLR

Heavy flavour energy loss? average energy loss Casimir coupling factor distance travelled in the medium transport coefficient of the medium R. Baier et al. , Nucl. Phys. B 483 (1997) 291 (“BDMPS”) Energy loss for heavy flavours is expected to be reduced: i) Casimir factor l l light hadrons originate predominantly from gluon jets, heavy flavoured hadrons originate from heavy quark jets CR is 4/3 for quarks, 3 for gluons ii)dead-cone effect l gluon radiation expected to be suppressed for q < MQ/EQ [Dokshitzer & Karzeev, Phys. Lett. B 519 (2001) 199] [Armesto et al. , Phys. Rev. D 69 (2004) 114003] 05/07/2006 Andry Rakotozafindrabe – LLR 26

Charm flow [F. Laue@QM`05] [S. Butsyk@QM`05] m Disagreement between STAR and PHENIX v 2 27 05/07/2006 Andry Rakotozafindrabe – LLR

Alternate model : Hydro + J/ transport One detailed QGP hydro + J/ψ transport (Zhu et al) m g + J/ψ c + c First published without cold nuclear effects, but here : + Nuclear absorption (1 or 3 mb) + Cronin effect from d. Au Zhu, Zhuang, Xu, PLB 607 (2005) 107 + private communication <p. T 2> ok (as on previous slide) m Model should be valid for y=0 l l But match y=1. 7 (and central y=0) Predicted RAA for y=0 28 05/07/2006 Andry Rakotozafindrabe – LLR

Recombination predictions vs rapidity No recombination All recombination m Recombination ( Thews et al. , nucl-th/0505055 ) predicts a narrower rapidity distribution with an increasing Npart. m Going from p+p to the most central Au+Au : no significant change seen in the shape of the rapidity distribution. 29 05/07/2006 Andry Rakotozafindrabe – LLR

J/ production in d+Au vs centrality High x 2 ~ 0. 09 m m Small centrality dependence Model with absorption + shadowing ( black lines* ): l l m m shadowing EKS 98 σabs = 0 to 3 mb σabs = 1 mb good agreement σabs = 3 mb is an upper limit weak shadowing and weak nuclear absorption Low x 2 ~ 0. 003 *Colored lines: FGS shadowing for 3 mb 30 05/07/2006 Andry Rakotozafindrabe – LLR

RHIC vs SPS m PHENIX : |y|~1. 7 Plotted « à la SPS » way i. e. normalize the J/ production with the cold nuclear effects : l l nuclear absorption with σabs = 4. 18 ± 0. 35 mb at SPS Shadowing + nuclear absorption with σabs ~ 1 mb at RHIC (Vogt, nuclth/0507027) PHENIX NA 50 NA 60 Cu+Cu Au+Au Pb+Pb In+In (NA 60 preliminary points from Arnaldi, QM 05). 31 05/07/2006 Andry Rakotozafindrabe – LLR

SPS vs RHIC + private communications d+Au Cu+Cu Au+Au |y|<0. 35 |y|~1. 7 (Arnaldi, QM 05) m SPS : l l l m √s ~ 17 Ge. V Measured/expected measured = J/ / D. Y expected = normal nuclear absorption expected = normal nuclear σ = 4. 18 ± 0. 35 mb NA 50: |y*| = [0, 1] RHIC : l √s = 200 Ge. V l RAA i. e. (J/ in A+A) / (Ncoll * J/ in p+p) l « expected » = = nuclear absorption ( à 3 3 mb mb ) ) + + « expected » absorption (σ ~ 1 à shadowing l |y| = [0, 0. 35] or [1. 2, 2. 2] 32 05/07/2006 Andry Rakotozafindrabe – LLR

PHENIX detector J/ e+e– |y| < 0. 35 Pe > 0. 2 Ge. V/c = • Tracking, momentum measurement with drift chambers, pixel pad chambers • e ID with Em. CAL + RICH J/ µ+µ– 1. 2< |y| < 2. 2 Pµ > 2 Ge. V/c = 2 • Tracking, momentum measurement with cathode strip chambers • µ ID with penetration depth / momentum match 05/07/2006 Centrality measurement, vertex position Beam-beam counters (charged particle production) Zero-degree calorimeters (spectator neutrons) 33 Andry Rakotozafindrabe – LLR

Invariant yield vs p. T at forward rapidities Cu+Cu (|y| [1. 2, 2. 2]) m Au+Au (|y| [1. 2, 2. 2]) we fit the p. T spectrum using to extract <p. T 2> 34 05/07/2006 Andry Rakotozafindrabe – LLR

Invariant yield vs p. T at mid-rapidity Cu+Cu (|y|~0. 35) m Au+Au (|y|~0. 35) we fit the p. T spectrum using to extract <p. T 2> 35 05/07/2006 Andry Rakotozafindrabe – LLR

Computing the J/ yield Invariant yield : i : i-th bin (centrality for e. g. ) : number of ‘s reconstructed : probability for a thrown and embeded into real data to be found (considering reconstruction and trigger efficiency) : total number of events : BBC trigger efficiency for events with a : BBC trigger efficiency for minimum bias events For Au+Au or Cu+Cu collision : ~ 36 05/07/2006 Andry Rakotozafindrabe – LLR

Signal extraction in Cu+Cu – 1. 95 < y < – 1. 70 m Cuts : l Dimuons cuts l l 2. 6 < mass < 3. 6 Ge. V/c² 1. 2 < |rapidity| < 2. 2 Track quality cuts … m Combinatoric background from uncorrelated dimuons : l Nbgd = 2√(N++. N– –) m S i g n a l = n u m b e r o f c o u n t s w i t h i n t h e J / i n v a r i a n t m a s s r e g i o n (2. 6 – 3. 6 Ge. V/c²) after subtracting Nbgd to the distribution of the opposite sign dimuons. m m Systematic errors : ~10% from varying fits of the background subtracted signal. Also account for the physical background that can be included into the previous counting. 37 05/07/2006 Andry Rakotozafindrabe – LLR

Getting acc*eff correction factors in Cu+Cu m m m Using Monte Carlo J/ generated by PYTHIA over 4π embed the J/ within muon arm acceptance into real minimum bias Cu+Cu data Apply to them the same triggers and signal extraction method as the ones applied to the data Acc. eff(i) is the probability that a J/ thrown by PYTHIA in a given bin i to survive the whole process followed by the data Systematic errors : • 5% from track/pair cuts and uncertainities in p. T, y and z-vertex input distribution Acc*eff vs rapidity (statistical errors only) Acc*eff vs p. T (statistical errors only) Acc*eff vs centrality (statistical errors only) 05/07/2006 Andry Rakotozafindrabe – LLR • 8% from run to run variation (mainly due to the varying number of dead channels in Mu. Tr). 38

Collision geometry and centrality (eg : Cu+Cu) Participants (charged particles) Spectators (neutrons) 10 fm 0 0 EZDC For a given b, Glauber model 0 fm (Woods-Saxon function) predicts: 104 ● Npart (No. participants) 198 ● Ncoll (No. binary collisions) b Npart Ncoll BBC charge N+S distribution for min. bias Cu+Cu √s = 200 Ge. V data etc QBBC 70 -80% 80 -88% Monte-Carlo Glauber model Probability for a given Npart Each participant contributes to a Negative Binomial distribution of hits Fit BBC charge distribution 05/07/2006 Andry Rakotozafindrabe – LLR 39

[1] PRL 92 (2004) 051802 [2] PRC 69 (2004) 014901 [3] PRL 96 (2006) 012304 [4] QM 05, nucl-ex/0510051 Run 1 to Run 5 capsule history and J/ in PHENIX Year Ions s. NN Luminosity Status J/ (ee + μμ) 2000 Au-Au 130 Ge. V 1 b-1 Central (electrons) 0 2001 Au-Au 200 Ge. V 24 b-1 Central 13 + 0 [1] 2002 p-p 200 Ge. V 0. 15 pb-1 + 1 muon arm 46 + 66 [2] 2002 d-Au 200 Ge. V 2. 74 nb-1 Central 360 + 1660 [3] 2003 p-p 200 Ge. V 0. 35 pb-1 + 2 muon arms 130 + 450 [3] Au-Au 200 Ge. V 240 b-1 preliminary ~ 1000 + 5000 [4] Au-Au 63 Ge. V 9. 1 b-1 analysis ~ 13 p-p 200 Ge. V 324 nb-1 Cu-Cu 200 Ge. V 4. 8 nb-1 preliminary ~ 1000 + 10000 [4] Cu-Cu 63 Ge. V 190 mb-1 analysis ~ 10 + 200 p-p 200 Ge. V 3. 8 pb-1 p-p 200 Ge. V ~10 pb-1 2004 2005 2006 05/07/2006 ~ 1500 + 10000 Just done… Andry Rakotozafindrabe – LLR ~3000 + 30000 40

Cu+Cu 200 Ge. V data taking: triggers and level 2 filtering Minimum Bias trigger: BBC 173 Tb Level 1 trigger: Mu. ID Deep-Deep 50 Tb New ! Level 2 filtering: Mu. Tr + Mu. ID 2. 5 Tb Reconstruction • reconstruction of 2 D road in Mu. ID used as seed for Mu. Tr track finding • rough track momentum estimate invariant mass cut for tracks pairs at 2 Ge. V/c² Volume o f d a ta 500 Mb • fast online reconstruction of 1 D road in Mu. ID • di-road accepted if last Mu. ID gap reached (with a minimum number of hit gaps) 41 05/07/2006 Andry Rakotozafindrabe – LLR

J/ as a probe of the produced medium (I) m Hard probe l l l m Large charme quark mass (m. J/ ~3. 1 Ge. V/c²) J/ produced at early stages of the collision Size r. J/ ~0. 2 fm < typical hadronique size (~1 fm) Recent lattice QCD result : melting temperature in a deconfined medium is T ~ 1. 5 à 2 T is C Production l g+g fusion PDF ~60% direct production J/ ~30% via χc J/ + x ~10% via ’ J/ + x l PDF l p+p reference for p+A or A+A l m ratios (p+A)/(p+p) or (A+A)/(p+p) Suppression or enhancement of the J/ yield : l Due to nuclear matter or to deconfined medium ? medium 42 05/07/2006 Andry Rakotozafindrabe – LLR

J/ as a probe of the produced medium (II) m Initial state effect l m CGC, shadowing Final state effect l Nuclear ( hadronic ) absorption Projectile PDF J/ L l l PDF l QGP ? l Cronin effect : multiple elastic scattering p. T broadening Cible suppression : « colour screening » or enhancement : recombinaison l From 10 to 20 cc in central Au+Au at RHIC V(r) ’ χc J/ r l Evaluated via p+A ou d+A 05/07/2006 l Accessible via A+A Andry Rakotozafindrabe – LLR 43

Background sources m Physical background: correleted dimuons l Drell-Yan: l Open charm: D, D µ± + … m Combinatoric background: uncorrelated dimuons l , K µ + … (decay before the absorber) 44 05/07/2006 Andry Rakotozafindrabe – LLR

Energy density m Longitudinally expanding plasma : p. R 2 t 0 ~ 1 fm/c l l d. ET/dη measurement at mid-rapidity by PHENIX EMCal Which τ0 ? tcross ~ 0. 13 fm/c 05/07/2006 tsecondaries formation ttherm ~ 0. 35 fm/c ~ 0. 6 - 1 fm/c Andry Rakotozafindrabe – LLR 45

Commonly used variables m Transverse : perpendicular to the beam direction m Transverse momentum : p. T = sqrt( p 2 x + p 2 y ) m Rapidity : y = 1/2 ln (E+pz )/(E-pz) m Pseudorapidity : m Invariant mass of a pair : M 2 inv = (E 1 +E 2) 2 - (p 1+p 2)2 η = 1/2 ln (p+pz )/(p-pz) 46 05/07/2006 Andry Rakotozafindrabe – LLR