Alexander Milov ICHEP06: Global observables at RHIC July 27, Global Observables at RHIC Alexander Milov ICHEP Moscow July 27, 2006

Alexander Milov ICHEP06: Global observables at RHIC July 27, RHIC capabilities.

Alexander Milov ICHEP06: Global observables at RHIC July 27, % Where do the particles go? y = 0.5ln(E+p z )/(E-p z ) y beam = ln(√s/m p ) sinh(η) = m T /p T sinh(y) Only 22% of all emitted particles have p T > p L But they carry information about the most densest region in the collision B.Back for Lake Louise Workshop 2006

Alexander Milov ICHEP06: Global observables at RHIC July 27, Charged particle distribution: the shape. PHOBOS BRAHMS PHOBOS & BRAHMS can measure a very wide rapidity range dN ch /dη has a trapezoidal shape: almost flat top 4/5 y beam f.w.h.m. ~ 1½ y beam very few particles with |η| > y beam P. QM05 PHOBOS PRL 91,52303 (2003)

Alexander Milov ICHEP06: Global observables at RHIC July 27, Shape: The Tail High η tail has an “inversed” behavior: particle production drops in the more central collisions. PHOBOS PRL 91,52303 (2003)

Alexander Milov ICHEP06: Global observables at RHIC July 27, Shape: Limiting Fragmentation Region PHOBOS PRL 91, (2003) / NPA757, 28 (2005) Limiting fragmentation. In the rest frame of the nuclei the longitudinal scaling appears to be independent of the colliding nuclei over a very large range of |η|-y beam R.Noucier for PHOBOS PANIC05

Alexander Milov ICHEP06: Global observables at RHIC July 27, UA5, Z.Phys.C33, 1 (1986) P.Steinberg JoP c.s. 9(2005) and ref. therein Limiting Fragmentation Region Other systems A-A e+e-e+e- p+p R.Noucier for PHOBOS PANIC05 Limiting fragmentation behavior is a universal phenomenon: It is seen not only in the A+A systems, but in many other symmetric collision systems.

Alexander Milov ICHEP06: Global observables at RHIC July 27, Shape: The Flat Top. Width & Shape follow the characteristic parameter: y beam =ln(√s/m p ) ~ ln(√s) Height and the integral also increases with the beam energy: How fast? PHOBOS PRL 91,52303 (2003)

Alexander Milov ICHEP06: Global observables at RHIC July 27, Energy dependence. QM01 Nucl. Phys. A698, 171 (2002). dN ch /dη ~ ln(√s) PHENIX PRC 71, (2005) dN ch /dη = (½N part ·A)ln(√s NN /√s 0 ) A = 0.74±0.01 √s 0 = 1.48±0.02 GeV LHC prediction based on data trend for 350 participants: dN ch η=0: 1100 Total N ch :13000 PHOBOS PRL 91,52303 (2003)

Alexander Milov ICHEP06: Global observables at RHIC July 27, Finding number of participant. Glauber inspired Monte-Carlo number of participants. (Wounded Nuclear Model). Adding statistics (neg. binominal) for particle production one can reliably reproduce limiting fragmentation region Activity in limiting fragmentation region And measure trigger inefficiency to compare it to other calculation and p+p limit… But most importantly it allows to reproduce the distribution of particles across ~6 units of rapidity which can only be related through the initial assumption of the Glauber model.

Alexander Milov ICHEP06: Global observables at RHIC July 27, Size of a system or type of species? From the N part point of view Cu+Cu is the same as in the first 1/3 of Au+Au. A long standing question: Is N part a valid characteristics? B.Back for Lake Louise Workshop 2006

Alexander Milov ICHEP06: Global observables at RHIC July 27, Au+Au:35-40% N part = 98 Cu+Cu:3-6%, N part = 96 Au+Au:45-50% N part = 62 Cu+Cu:15-25%, N part = 60 Cu+Cu Preliminary at 62.5 GeV Au+Au:35-40% N part = 99 Cu+Cu:3-6%, N part = 100 Au+Au:45-55% N part = 56 Cu+Cu:15-25%, N part = 61 Cu+Cu Preliminary at 200 GeV Size of a system or type of species? Au+Au & Cu+Cu look very similar as soon as N part are the same G. Roland for QM05

Alexander Milov ICHEP06: Global observables at RHIC July 27, RHIC (SPS+AGS) results together Spectacular agreement between 4 RHIC experiments. All measurements are absolutely independent besides similar approach of using Glauber model. BRAHMS:Si + Scintillators PHENIX: PC at 2.5m and 5m, no field PHOBOS: Si detectors STAR:Tracking in the field Plots from PHENIX PRC 71, (2005)

Alexander Milov ICHEP06: Global observables at RHIC July 27, Averaged SPS data at 17.2 GeV is in good agreement to averaged RHIC data at 19.6 GeV (expected difference ~4%) RHIC / SPS / AGS altogether. There is a continuous set of measurements from AGS to RHIC data. The centrality shape at η=0 scales with √s NN Total particle yields are flat in centrality. p+p is ~30%-40% lower PHOBOS nucl-ex/

Alexander Milov ICHEP06: Global observables at RHIC July 27, Centrality profile  Centrality shape scales with incident beam energy  Both show steady rise from peripheral to central  Consistent behavior for E T and N ch PHOBOS nucl-ex/ PHENIX PRC 71, (2005)

Alexander Milov ICHEP06: Global observables at RHIC July 27, ε BJ =(Sτ) -1 dE T /dy  √s NN = 200GeV (0%-5%) & τ =1fm/c5.4 ± 0.6GeV/(fm 2 c) What about “τ”?  Limiting: τ = 1/(2Rγ) 0.15 fm/c  Formation: τ = h/m T ≈ 0.6E T /N ch 0.3 fm/c Bjorken Energy Density estimate PHENIX PRC 71, (2005)

Alexander Milov ICHEP06: Global observables at RHIC July 27, Results: Ratios /.  Ratio / increases by ~20% from 19.6 GeV to 200 GeV and stays the same between 200 GeV and 130 GeV  Consistent with the average particle momentum increase between those two energies.  Ratio / is independent of centrality  Still a puzzle.  Same freeze-out conditions?  Since trigger and centrality related uncertainties cancel out, the flatness of the curves is a very precise statement. PHENIX PRC 71, (2005)

Alexander Milov ICHEP06: Global observables at RHIC July 27, p+p/p+p are lower above √s~10 GeV. What happens below that? √s NN dependence. Au+Au : PRL 91, (2003) PRC: nucl-ex/ Cu+Cu:QM2005: nucl-ex/ PHENIX PRC 71, (2005) dN ch /dη = (½N part ·A)ln(√s NN /√s 0 ) Extrapolation to lowest energy for E T : √s 0 = 2.35 ± 0.2 GeV for N ch : √s 0 = 1.48 ± 0.02 GeV

Alexander Milov ICHEP06: Global observables at RHIC July 27, That’s what we see ln(√s NN ) 2a.m.u. N ch ETET -0.5 GeV +0.5 GeV FOPI Energy conservation law. What do √s o NN mean? FOPI at <0.1 GeV E kinetic ! Lower energy: √s o NN  /  Higher energy: / ~ constant √s o NN  N ch Low √s NN story PHENIX PRC 71, (2005)

Alexander Milov ICHEP06: Global observables at RHIC July 27, What happens to ?  At low √s NN :  E T is “produced” energy only.  N ch can benefit from pre-existing particles (baryons).  At higher √s NN :  Critical temperature T c =0.17GeV.  Assuming: =3/2T c ≈ 0.26 GeV ≈ 0.25 GeV = + ≈ 0.51 GeV / ≈ 1.6 ≈ 0.82 GeV  We measure 0.88 GeV (with flow)  Prediction for LHC: 0.93±0.04 GeV H. Satz, Rep. Prog. Phys. 63, 1511 (2000)

Alexander Milov ICHEP06: Global observables at RHIC July 27, Measured by Basile et al ( ) pQCD e+e- calculation A. Mueller 1983 A+A, p+p and e + e - systems Total multiplicity shown. √s pp = ½√s ee to account for a leading particle effect. Different systems converge at RHIC energy Universality of N ch ?

Alexander Milov ICHEP06: Global observables at RHIC July 27, “Early RHIC” Model Survey Lots of data available: A.M. for PHENIX nucl-ex/ PHENIX PRC 71, (2005) Reproduce most of data: A.M.P.T., K.L.N., Mini-jet

Alexander Milov ICHEP06: Global observables at RHIC July 27, STAR nucl-ex/ Based on: S.Eremin S.Voloshin PRC67, (2003) Other Glauber Models. Glauber model remains a weak point. STAR demonstrates that the data may be consistent with the Saturation EKRT model. What if the real participants are not nucleons but quarks? q-q scenario is as good as N-N because it reproduces the data Too soon to relax. Centrality (N part N coll ) is too important to ignore

Alexander Milov ICHEP06: Global observables at RHIC July 27, Summary  Data !!!  Vast amount of information available from RHIC  All experiments demonstrate consistent results  Quality of the data is very high.  Scalings:  Limiting Fragmentation is universal for different √s NN and collision systems.  Centrality shape scales with energy, the ratios are flat.  Most central events follows ln(√s NN ) over a factor of 100 in √s NN  N part is the ruling parameter  Still unclear:  Why / vs. centrality is flat, although p T changes?  Why / (T f-o ) vs. √s NN has two distinct regions?  What do √s 0 NN mean?  Does MC-Glauber model need to be improved?  LHC predictions are on the desk. Let’s see what is different. My work is supported by the Goldhaber fellowship at BNL

Alexander Milov ICHEP06: Global observables at RHIC July 27, BACKUPS

Alexander Milov ICHEP06: Global observables at RHIC July 27, Low N part problem: Different systems cover different N part. d+Au is tricky, because it is not symmetric Shall we believe that Cu+Cu does that? d+Au p+p Cu+Cu Au+Au We need seamless and overlapping connection between different N part regions Low high N part High low N part Limiting factor: N part CuCu < 126 N part AuAu < 394 The same factor N part A A > 2 Can be used, but still based on the Glauber model. Plots: Phys. Rev. C70, (R) (2004), nucl-ex/ , G. Roland for QM05