May 23, 2003 Ivan Vitev 1 Au+Au and d+Au Reactions at RHIC: Theory on a Positive Note Ivan Vitev Iowa State University, Ames, IA CIPANP-2003 Conference, May 19-24, 2003 New York, NY

May 23, 2003 Ivan Vitev 1 Approximations to QCD tested in Au+Au and d+Au F. Karsch et al. Deconfinement phase transition Chiral symmetry restoration Thermal equilibration of the partonic medium AGS, SPS, RHIC, LHC t Lattice QCD Perturbative QCD & QCD in nuclear matter Supershadowed classical QCD Collective limits, EOS, cascades RHIC A note on “first principles scales” QCD has no scale in itself, e.g. What QCD computes is evolution RHIC

May 23, 2003 Ivan Vitev 1 High-p T Hadron Production from LO pQCD Parton distribution functions Fragmentation functions xbxb XaXa Q2Q2 A B  zczc IS nuclear broadening IS energy loss FS energy loss S. Kretzer et al. P. Levai et al.

May 23, 2003 Ivan Vitev 1 The Reaction Operator Approach to Multiple Elastic and Inelastic Scatterings Reaction Operator = all possible on-shell cuts through a new Double Born interaction with the propagating system + + For the elastic scattering case illustrated here : + + M.Gyulassy, P.Levai, I.V., Nucl.Phys. B594, (2001); Phys.Rev.Lett. 85, (2000). For the inelastic scattering case:

May 23, 2003 Ivan Vitev 1 The Center of Mass Energy Systematics of Mono-jet Tomography I.V. and M.Gyulassy, Phys.Rev.Lett. 89 (2002) 1. At SPS Cronin effect dominates. Even with energy loss exhibit noticeable enhancement 1. Cronin effect, shadowing, and jet quenching conspire to give flat suppression pattern out to the highest p T at RHIC 1. At LHC the nuclear modification is completely dominated by energy loss. Predicts below quenching, strong dependence ?

May 23, 2003 Ivan Vitev 1 Differential Comparison and Discussion I.V. and M.Gyulassy, Phys.Rev. Lett., 89 (2002) PHENIX STAR charged There is no need (room) for “down-and-up” models. a) The hydro feedback at low p T, See e.g. b) The baryons. See e.g. Known issues P.Kolb,R.Rapp, hep-ph/ E.Wang,X.N.Wang, PRL 87 (2001) Z.Lin,C.M.Ko,S.Pal, nucl-th/ I.V.,M.Gyulassy, PRC 65 (2002) D.Teaney,J.Lauret,E.Shuryak, nucl-th/ X.F.Zhang,P.Levai,G.Fai, PRL 89 (2002) The shape of R AA, R CP is a function of the interplay of the known nuclear effects. One needs to compute the energy loss for the non-asymptotic RHIC ) Based on Veneziano, Rossi, Kharzeev baryon junctions

May 23, 2003 Ivan Vitev 1 Stability of the Centrality Dependence of R AA in GLV E-loss Full numerical calculation X.N.Wang, nucl-th/ M.Gyulassy, I.V. and X.N.Wang, Phys.Rev.Lett. 89 (2002) a) Gyulassy-Wang: transverse gluon dynamics is neglected b) Baier et al. (BDMPS): thick medium, large number of scatterings, LPM only c) Zakharov; Wiedemann: thick medium, path integral formalism d) Gyulassy et al. (GLV): thin media with few scatterings. Low order correlations (few scattering centers) dominate.

May 23, 2003 Ivan Vitev 1 Impact Parameter Dependence of the Cronin Effect at RHIC I.V., nucl-th/ , Phys.Lett.B 562 (2003) The Cronin peak is located at Antishadowing plays an important role for - an approximately constant contribution (experiments can constrain it) The maximum Cronin enhancement for the total invariant cross section is 20% The Cronin effect decreases in going from central to peripheral reactions In contrast: since D.Kharzeev et al., PLB 561 (2003) If it is initial wave-function More central More peripheral I.V. and M.Gyulassy, Phys.Rev.Lett. 89 (2002)

May 23, 2003 Ivan Vitev 1 Experimental Resolution: Part 1 PHENIX Preliminary 1  errors PHOBOS Preliminary STAR Preliminary

May 23, 2003 Ivan Vitev 1 Multiple Elastic Scatterings from Different Points of View X.N.Wang, nucl-th/ A.Accardi et al. pQCD partonic level Glauber-Gribov P.Levai et al. N.Nikolaev et al., hep-ph/ B.Kopeliovich et al., Phys.Rev.Lett. 88,(2002) J.Jallilian-Marian et al.

May 23, 2003 Ivan Vitev 1 Medium-induced Jet Acoplanarity = the mean transverse momentum of the hadron with respect to the jet axis in the plane perpendicular to the beam axis. = the mean effective transverse momentum of the two colliding partons in the plane perp. to the beam axis (+FS contribution in d+Au). Credit: P.Constantin, J.Rak, J.Lajoie, C.Ogilvie M.Tannenbaum G.Altarelli, R.K.Ellis, G.Martinelli, Phys.Lett. 151B (1985) Projection

May 23, 2003 Ivan Vitev 1 Experimental Resolution: Part 2 I.V., J.W.Qiu, to be published True monojets? Regge-Muller cut diagrams T.Hirano and Y.Nara, nucl-th/ NO true monojets at RHIC

May 23, 2003 Ivan Vitev 1 Measures of Energy Loss Preliminary From GLV energy loss STAR correlations Phys.Rev.Lett. Correspondence can be established between the different measures of E-loss

May 23, 2003 Ivan Vitev 1 Conclusions  The last 10 days (AGS-RHIC users’ meeting and CIPANP-2003) have been of critical importance to heavy ion physics (not only in resolving paradigms but also in demonstrating to the physics community the potential of the field  The combined evidence from p+p, d+Au, Au+Au (with amazing consistency between the experiments) suggests that Au+Au reactions at RHIC differ significantly in many aspects from lower energies or other systems (p+p, p+A).  Jet tomographic analysis indicates that the density of the matter created at RHIC is times normal nuclear matter density. This is well in excess of the critical temperature and energy density calculated on the lattice and in strong support of the QGP formation hypothesis.  As pointed by many speakers more quantitative analysis of the properties of QGP may be a direction of future research.