RCNP workshop Oct 27th, Osaka, Japan Tatsuya Chujo 1 Hadron Production at RHIC - Proving Hot and Dense Matter - Tatsuya Chujo (RIKEN) for the PHENIX Collaboration

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 2 Heavy-Ion Program at RHIC Lattice QCD predicts transition to deconfinement sate of quarks and gluons occurs at: –T c ~ 170 ± 10 MeV (10 12 ° K) and  c ≈ 1 GeV/fm 3. –As existed ~ 1 micro sec after the Big Bang. RHIC is designed to create very high temperature and density matter in the laboratory. QGP phase

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 3 First three years of RHIC run High quality hadron data from RHIC experiments! –Hadron Measurements Particle ratio, yield,. p T distribution (soft and hard process). HBT correlations. Event anisotropy (v 2 ). Jet physics. etc …  ,  , K , K *0,K s 0, p, d,  0, ,  ,  , K , K *0,K s 0, p, d,  0, , ,  (+ anti-particles) ,  (+ anti-particles) … 2000 summer (Run-01): Au+Au 130 GeV 2001/2002 (Run-02): Au+Au 200 GeV p+p 200 GeV 2002/2003 (Run-03): d+Au 200 GeV p+p 200 GeV

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 4 PHENIX Experiment Maximal Set of Observables –Photons, Electrons, Muons, ID- hadrons Highly Selective Triggering –High Rate Capability. –Rare Processes. I’m here

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 5 PHENIX Collaboration

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 6 Run Year Species s 1/2 [GeV ]  Ldt N tot p-p Equivalent Data Size Au-Au  b -1 10M 0.04 pb -1 3 TB /2002 Au-Au  b M 1.0 pb TB p-p pb G 0.15 pb TB /2003 d-Au nb G 1.1 pb TB p-p pb G 0.35 pb TB Run-1 Run-2 Run-3 PHENIX Run History

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 7 PHENIX Goals and Achievements Goal: To measures all possible signatures at once for proving QGP. –Hadrons, leptons and photon. Accomplished baseline measurements by 3 RHIC runs. –22 publications (including e- print, as of Oct ) –Much remains Truly rare probes in Au- Au, Species & energy scans.              Conceptual Design Report (29-Jan-1993 )

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 8 Outline of this talk We present the results on hadron production (mainly from PHENIX experiment) and overview the current understanding of hot and dense matter produced at RHIC from hadron production viewpoint. - Physics Topics (in different p T regions) -  Low p T (< 2 GeV/c) –Bulk properties : Energy density and charged multiplicity. –Hydrodynamical behavior and chemical properties in AuAu. –Space-time evolution of the system (HBT correlation). –Event anisotropy (elliptic flow v 2 ).  High p T (5 > GeV/c) –Jet quenching in Au+Au – d+Au experiment  Intermediate p T (2 - 5 GeV/c) –Scaling behavior of baryon and particle compositions.

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 9 PHENIX Event Characterization Centrality selection : Used charge sum of Beam-Beam Counter (BBC, |  |=3~4) and energy of Zero-degree calorimeter (ZDC) in minimum bias events (92% of total inelastic cross sections). Extracted N coll and N part based on Glauber model. Peripheral Central

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 10 PHENIX Hadron PID Charged PID by TOF (DCH+PC1+TOF+BBC)  /K < 2 GeV/c, K/p < 4 GeV/c  =  /8  0 PID by EMCal via  0   (1<p T <10GeV/c) 6 lead- Scintillator (PbSc) sectors 2 lead- glass (PbGl) sectors  =   = 

(1) Particle Production at low p T - Soft Physics - pQCD probes Bulk system ~ 99% of produced particles Bulk Effects Equilibration Equation of State Spatial and Temporal extents

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 12 Energy Density High Enough?   4.6 GeV/fm 3 (130 GeV Au+Au) 5.5 GeV/fm 3 (200 GeV Au+Au) Well above predicted transition! PRL87, (2001) *  0 : Effective thermalization time ( fm/c) Bjorken Formula:

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 13 Charged Particle Multiplicity In initial volume ~ V nucleus Rescattering should be important! N tot = 5000 (Au+Au 130 GeV, central) N tot = 6200 (Au+Au 200 GeV, central)

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 14 PID p T Spectra Central  low p T slopes increase with particle mass  proton and anti- proton yields equal the pion yield at high p T. Peripheral  mass dependence is less pronounced  similar to pp PHENIX: PRC accepted, nucl-ex/

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 15 m T - m 0 Spectra Mid-central (40-50%) Central (0-5%) Peripheral (60-92%) Clear mass and centrality dep. in slope parameter T. Consistent with collective flow picture. PHENIX: PRC accepted, nucl-ex/

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 16 Blast-wave fit and kinetic freeze-out E. Schnedermann, J. Sollfrank, and U. Heinz, Phys. Rev. C 48, 2462 (1993) PHENIX Preliminary QM02 talk, J. Burward-Hoy Freeze-out Temperature T fo = 110  23 MeV Transverse flow velocity  T = 0.7  0.2  T  = 0.47) Au+Au 200 GeV (central)

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 17 p T Spectra for All 4 Experiments and Hydrodynamical Model Data: PHENIX: NPA715(03)151; STAR: NPA715(03)458; PHOBOS: NPA715(03)510; BRAHMS: NPA715(03)478 Hydro-calculations including chemical potentials: P.Kolb and R. Rapp, Phys. Rev. C 67 (03) Hydrodynamics describes all p T spectra up to 2 GeV/c. Calculations  too long a system lifetime Enormous initial pressure, but decouples quickly (~10 fm/c) * Note: all data points are preliminary results (QM02).

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 18 Evidence for equilibrated final state Almost complete reconstruction of hadronic state when system decouples by the statistical thermal model. Fit yields vs. mass (grand canonical ensemble)  T ch = 177 MeV,  B = GeV central AuAu.

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 19 T ch vs.  B from thermal model Statistical thermal model PBM, J. Stachel, nucl-th/ , J. Phys. G28, 1971 (2002) RHIC and SPS points are very close to the phase boundary of lattice QCD.

Elliptic flow is expected to be sensitive to the early stage of the collision. v 2 : 2nd harmonic coefficient of a Fourier expansion in 

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 21  s dependence of integrated v 2 RHIC SPS AGS Smooth increase from AGS-SPS-RHIC. Highest v RHIC: qualitative agreement with hydro model. C. Alt et al., PRC 68, (2003)

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 22 p T dependence of v 2 PHENIX: nucl-ex/ Au+Au 200 GeV Good agreement with QGP type EOS at low p T. Start to deviate from hydro calc. at p T > 2 GeV/c.  Data shows a different p T dependence between meson and baryon! STAR: PRL 87, (2001) Au+Au 130 GeV

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 23 Universality of v 2 (p T ) ? The complicated observed flow pattern in v 2 (p T ) is predicted to be simple at the quark level under p T → p T / n, v 2 → v 2 / n, n = 2,3 for meson,baryon if the flow pattern is established at the quark level Compilation courtesy of H. Huang “RHIC Physics is simple !” (B. Muller, CIPANP2003)

Proving the spatial and temporal extents of source: HBT correlation. Bertsch-Pratt parameterization

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 25 K T dependence of R Au+Au central 0-30% Applied the standard full Coulomb correction. All R parameters decrease as a function of k T  consistent with collective expansion picture (x-p correlation with collective flow). k T : average momentum of pair QM02 talk, A. Enokizono However…

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 26 Comparison with hydrodynamic model Hydrodynamic calculation by U.Heinz and P. F. Kolb (hep-ph/ ) Hydro w/o FS Hydro at e crit Assuming freeze out directly at the hadronization point. (e dec = e crit ) Standard initialization and freeze out which reproduce single particle spectra. Au+Au central 0-30%

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 27 R out /R side vs. K T Data shows R out /R side ≤ 1, and constant with k T. Hydro calculation predicts R out /R side ~ 1.5. * Note: data from 130 GeV Hirano & Tsuda, PRC, (2002). QM02 talk, A. Enokizono * Standard full Coulomb correction “HBT puzzle”

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 28 Revisit Coulomb Corrections! A.Enokizono, JPS 2003 Sep. R out /R side (full coulomb) < R out /R side (partial coulomb) Work in progress on pair efficiency correction. Final results will appear soon! Taking into account the contribution from the long-lived resonance.  “Core-Halo” source picture (“Sinyukov’s fit”).  Fraction of coulomb corr. can be determined by data (  +  - correlation).

(2) High p T Particle Production - Hard Process - pQCD probes Bulk system Jet quenching effect. Control experiment: d+Au

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 30 Hard Scattered Partons Used “calibrated” probe (p+p data). Hard scatterings in nucleon collisions produce jets of particles. –hadron structure function –hard scattering parton (pQCD) –fragmentation of partons In the presence of a color-deconfined medium, the partons lose their energy (~GeV/fm) via gluon bremsstrahlung. –“Jet Quenching”  Color Charge Density “gluonometer” hadrons q q leading particle leading particle schematic view of jet production

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 31 How Quantify the Nuclear Modification Scenario 1 : R AA =1 : Scale with # of binary collisions (N coll ). Scenario 2 : R AA >1 : Cronin effect (observed in ISR and SPS). Scenario 3 : R AA <1 : Suppression. Any departures from the expected binary collision scaling (N coll ) behavior provide the information on the strong interacting medium in AA collisions. Nuclear Modification Factor /  inel p+p NN cross section AA

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 32  0 spectra 200 GeV : Baseline p-p Good agreement with NLO pQCD 00  0 measurement in same experiment allows us the study of nuclear effect with less systematic uncertainties. Good agreement with NLO pQCD Reference for Au+Au spectra PHENIX (p+p) PRL accepted, hep-ex/

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 33  0 and h spectra 200 GeV PHENIX AuAu 200 GeV  0 data: PRL 91, (2003), nucl-ex/ charged hadron: submitted PRC, nucl-ex/ 00 (h + +h - )/2

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 34 R AA for  0 and charged hadron PHENIX AuAu 200 GeV  0 data: PRL 91, (2003), nucl-ex/ charged hadron: submitted PRC, nucl-ex/ R AA is well below 1 for both charged hadrons and neutral pions. The neutral pions fall below the charged hadrons since they do not contain contributions from protons and kaons (will be discussed later). Strong Suppression!

Initial state effect or Final state effect? - d+Au Experiment -

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 36 d+Au: Control Experiment The “Color Glass Condensate” model predicts the suppression in both Au+Au and d+Au (due to the initial state effect). d+Au experiment can tell us whether the observed hadron suppression at high p T central Au+A is the final state effect or initial state effect. Au+Au d+Au = cold medium = hot and dense medium Initial State Effects Only Initial + Final State Effects

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 37 d+Au Spectra Final spectra for charged hadrons and identified pions. Data span 7 orders of magnitude. PHENIX: PRL 91, (2003), nucl-ex/

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 38 R AA vs. R dA for charged hadrons and  0 No Suppression in d+Au, instead small enhancement observed (Cronin effect)!! d-Au results rule out CGC as the explanation for high p T Suppression of hadrons in AuAu central. Initial State Effects Only Initial + Final State Effects d+Au Au+Au PHENIX: PRL 91, (2003), nucl-ex/

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 39 Centrality Dependence Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control. High p T hadron suppression in AuAu is clearly a final state effect. “PHENIX Preliminary” results, consistent with PHOBOS data in submitted paper Au + Au Experimentd + Au Control Experiment

(3) Intermediate p T region pQCD probes Bulk system Interplay between Hard and Soft ( 2 < p T < 5 GeV/c)

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 41 Proton and anti-proton spectra in AuAu at 200 GeV Corrected for weak decay feed-down effect (~40% at 0.6 GeV/c, ~25% at 4 GeV/c). Strong centrality dependence in spectra shape at low p T (< 1.5 GeV/c). PHENIX: PRC accepted, nucl-ex/

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 42 N coll scaled p T spectra for p and pbar Radial Flow Effect Ncoll scaling (p T > 1.5 GeV) for all centrality bins PHENIX: PRL 91, (2003), nucl-ex/

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 43 p T spectra (p vs.  ) in 200 GeV Clearly seen p-  merging at p T ~ 2 GeV/c in central. No p-  merging in peripheral. Suggested significant fraction of p, pbar at pt = GeV/c in central.

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 44 Central-to-Peripheral Ratio (R CP ) vs. p T PHENIX: PRL 91, (2003), nucl-ex/ ≈ R AA N part scaling N coll scaling p : No suppression, N coll scaling at 1.5 GeV GeV  0 : Suppression (central > peripheral) * Shaded boxes : N part, N coll determination errors.

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 45 p/  ratio vs. p T and centrality Both p/  and pbar/  ratios are enhanced compared to peripheral Au+Au, p+p and e + e - at p T = 1.5 ~ 4.5 GeV/c. Consistent with gluon/quark jet fragmentation in peripheral AuAu (> 3 GeV/c). Peripheral Central PHENIX: PRL 91, (2003), nucl-ex/

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 46 Particle composition beyond 5 GeV … Deduced particle compositions at high p T from h/  0 ratio. Peripheral data is consistent with p+p data. Suggested p and pbar contributions in central are limited up to p T ~ 5 GeV/c. Central 0-10% Peripheral 60-92% ~1.6 (p+p data at  s NN = 53 GeV) common for both centralities relative error between central-peripheral PHENIX: PRL 91, (2003), nucl-ex/

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 47 STAR Results STAR: nucl-ex/ Similar behavior has been observed in . Limited behavior of baryon enhancement (< ~4 GeV/c).

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 48 Recombination/Fragmentation Model Quarks and anti-quarks recombine into hadrons locally “at an instant” –qq-bar  Meson –qqq  Baryon Thermal part (quark only) and power law tail (quarks and gluons) from pQCD. Modification of fragmentation function “ D i  h (z)” by energy loss of partons. Competition between recombination and fragmentations mechanism. Quark degrees of freedom play an important role. Lepez, Parikh, Siemens, PRL 53 (1984) 1216 Fragmentation/Recombination model Fries, Muller, Nonaka, Bass, nucl-th/

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 49 Another Approach (Hydro + Jet Model) Hydro+Jet Model: Hirano, Nara, nucl-th/ Explicit 3D Hydrodynamical calculations (including QGP in EOS). Tuned jet quenching effect to reproduce the suppression factor in  0 data. Hydrodynamics can describe p T spectra up to ~ 2 GeV/c. Well described dN/d  distributions and v 2 vs. p T at RHIC. Jet contributions from 2 GeV/c. PID limit (PHENIX)

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 50 Model Comparison (1) - R CP - Hirano, Nara (Hydro+Jet model) nucl-th/ Fries, Muller, Nonaka, Bass (Fragmentation/Recombination model) nucl-th/ Recombination model, Hydro-jet model  Predicted baryon enhancement is limited up to ~ 4-5 GeV/c. Qualitative agreement with data for both models.

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 51 Model Comparison (2) - p/  vs. p T - Fries, Mueller, Nonaka,Bass nucl-th/ Both Parton Recombination and Hydro+Jet models reproduce p/  ratio (p T and centrality dep.) qualitatively. Both models predict p/  enhancement is limited < 5 GeV/c. Another scenarios: Different formation time between baryons and mesons ? or Baryon Junction Mechanism ? ( Vitev, Gyulassy PRC 65, , 2002) Hirano, Nara nucl-th/ Parton recombination/fragmentationHydro+Jet

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 52 Summary (1) E T, N ch Above the critical density of deconfined state predicted by the LQCD. PID spectra Well described by hydrodynamic model up to 2 GeV/c in p T. Particle Yield Well reproduced by the statistical thermal model. (T ch,  B ): close to the phase boundary of QGP predicted by LQCD. Pion HBT R vs. K T : consistent with hydro, but large discrepancy in magnitudes. Suggests the importance of partial Coulomb correction. Elliptic flow Good agreement with hydrodynamics up to 2 GeV/c. Observed Complicated v 2 (p T ) pattern (might be explained by the partonic flow picture).

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 53 Summary (2) High p T Spectra (Au+Au) Both neutral and inclusive charged hadrons are largely suppressed in AuAu central collisions. High p T Spectra (d+Au) Suppressions are not observed in d+Au, instead there is a small enhancement, which suggests the suppression in AuAu is the final state effect. Intermediate p T in Au+Au Proton and anti-proton spectra show the different scaling behavior from pions: NO suppression. Strong centrality dependence of p/  ratio. Recombination, Hydro+Jet, (baryon junction) reproduce the data qualitatively.

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 54 What’s Next We must investigate other probes that look deeply into the medium to characterize it. The Rare Processes Probe the Medium: –Heavy Quark States Dissolution of J/  &  ’, the bound states of charm-anticharm quarks probes quark deconfinement. –Electromagnetic Probes (no strong interaction) Lack of strong interaction allows them to penetrate the black medium and see through the hadronic veil Direct Photons, e + e -,  +  - PHENIX plans to make these measurements in the next high luminosity Au+Au run. See next talk, K. Shigaki.

Backup Slides

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 56 STAR Blast-wave fit

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 57 R dAu and p/h for , K, p in d+Au (STAR) Small particle species dependence of Cronin effect, compared to lower energies. Same (p+pbar)/h ratio in dAu as p+p. Indicated the Cronin effect alone is not enough to account for the relative baryon enhancement in AuAu central (discussed later). STAR nucl-ex/ inclusive charged (dAu) (Fermi Lab, E735)

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 58 Alternative: Initial Effects Gluon Saturation –(color glass condensate: CGC) Wave function of low x gluons overlap; the self-coupling gluons fuse, saturating the density of gluons in the initial state. (gets N ch right!) hep-ph/ ; D. Kharzeev, E. Levin, M. Nardi Multiple elastic scatterings (Cronin effect) Wang, Kopeliovich, Levai, Accardi Nuclear shadowing r/  gg  g D.Kharzeev et al., PLB 561 (2003) 93 Broaden p T

Tatsuya ChujoRCNP workshop Oct 27th, Osaka, Japan 59 R vs. N part 1/3 Fit with p0+p1*N part ^1/3 R out weaker increase with Npart Au+Au at sqrt(s NN ) =200GeV