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High P T and QGP

High P T and QGP. Ivan Vitev Iowa State University, Ames, IA 50011. AGS-RHIC Annual Users’ Meeting May 10 – May 14, 2004 Brookhaven National Lab, Upton NY. Ivan Vitev, ISU. If no “effects”: R AA < 1 in regime of soft physics R AA = 1 at high-p T where hard

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High P T and QGP

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  1. High PT and QGP Ivan Vitev Iowa State University, Ames, IA 50011 AGS-RHIC Annual Users’ Meeting May 10 – May 14, 2004 Brookhaven National Lab, Upton NY Ivan Vitev, ISU Ivan Vitev, ISU

  2. If no “effects”: RAA < 1 in regime of soft physics RAA = 1 at high-pT where hard scattering dominates Suppression: RAA < 1 at high-pT Motivation: Address this Deviations from the Hard Scattering Regime Main focus: 62 GeV Au+Au Will also mention: 200 GeV d+Au p+A collisions are ideal since the deviations from the QCD factorization can be systematically computed nucleon-nucleon cross section <Nbinary>/sinelp+p AA AA Rapidity dependence, centrality dependence Ivan Vitev, ISU Ivan Vitev, ISU

  3. Predictive Power of pQCD J.Collins, D.Soper, G.Sterman, Nucl.Phys.B223 (1983) • Factorization theorem: Scale of hadron wave function: Scale of hard partonic collision: Factorization: Process-dependent: Process-independent: • Predictive power:universality of infrared safety of • Address the deviations: power corrections radiative energy loss (dynamical nuclear shadowing) (jet quenching) Ivan Vitev, ISU Ivan Vitev, ISU

  4. Results for A- and Bjorken x- Dependence Generated by the multiple final state scattering of the struck quark Scale of higher twist Q2dependence, Longitudinal structure function J.W.Qiu and I.V., hep-ph/0309094 Ivan Vitev, ISU Ivan Vitev, ISU

  5. Data is for qualitative • comparison (pions versus baryons) • The power corrections • modify the ratio from low • pT to high pT • (not vice versa) The Single Inclusive Spectra Revisited I. Arsene et al., nucl-ex/0403050 Power corrections ~ 0.4 – 0.5 GCG GCG It makes no sense to try and fit the charded hadrons at low pT and these rapidities Looks like 0.5! Ivan Vitev, ISU Ivan Vitev, ISU

  6. Starting Point: LO pQCD Resum the multiple final state scattering of the parton “d” with the remnants of the nucleus A p Isolate all the xb dependence of the integrand: The results look like LO pQCD with the substitution: J.W.Qiu, I.V., hep-ph/0405068 Cd = 1 for quarks, 9/4 for gluons Ivan Vitev, ISU Ivan Vitev, ISU

  7. single and double inclusive • shift in ~ 2 /t Numerical Results for the Power Corrections • Similar power corrections • modification to single and double • inclusive hadron production - increases with rapidity - increases with centrality • disappears at high pTin accord with • the QCD factorization theorems • Dominated by dynamical gluon • shadowing Small at midrapidity C.M. energy 200 GeV Even smaller at midrapidity C.M. energy 62 GeV J.W.Qiu, I.V., hep-ph/0405068 Ivan Vitev, ISU Ivan Vitev, ISU

  8. + + Medium Induced Non-Abelian Energy Loss Reaction opeartor Iterative solution M.Gyulassy, P.Levai, I.V., Nucl.Phys. B594 (2001); Phys.Rev.Lett.85 (2000) • Explicitly the Landau- • Pomeranchuk-Migdal • destructive interference • effect in QCD Inverse formation times • Incorporatesfinite • kinematics and small • number of scatterings Color current propagators • Applicable for realistic • systems Ivan Vitev, ISU Ivan Vitev, ISU

  9. Beyond average : need ansatz • Independent Poisson emission • Guaranteed to be violated • By simple kinematics • Usefulness • Allows the system to adjust itself • Minimizes the effect of energy loss Analytic Limits For Energy Loss transport coefficient a) Static medium: b) Bjorken expanding medium: M.Gyulassy, I.V., X.N.Wang, Phys.Rev.Lett. 86 (2001) Npart 0 400 R.Baier et al., JHEP (2001) M.Gyulassy, P.Levai, I.V., Phys.Lett.B538 (2002) Ivan Vitev, ISU Ivan Vitev, ISU

  10. 17 GeV 62 GeV 200 GeV Calculated Gluon Spectra Estimate: Isospin symmetry Parton-hadron duality B.Back et al., Phys.Rev.Lett. 88 (2002) • Already large fractional energy • loss • Important: • The radiative quanta may be • experimentally observable • Difference in the manifestation • of large e-loss in the probabilistic • interpretation Kinematic modification I.V., nucl-th/0404052 Ivan Vitev, ISU Ivan Vitev, ISU

  11. Jet Quenching at C.M. Energy of 62 GeV • At SPSCronin • effect dominates. Even with energy • loss may exhibit enhancement • Cronin effect, shadowing and • jet quenching conspire to give flat • suppression pattern out to the • highest pT at RHIC • At RHIC and no • e-loss: Strong • cancellationbetweenCronin effect • and energy loss. Net quenching. • Weak • dependence I.V., nucl-th/0404052 SPS relative to D.d’Enterria, nucl-ex/0403055 S.S.Adler, et al., Phys.Rev.Lett.91 (2003) Baryons and the charged hadrons:expected to be different Ivan Vitev, ISU Ivan Vitev, ISU

  12. Possible most interesting outcome • Strong deviation from the perturbative • prediction • Strong nonlinearity of in dNg/dy In a Polyakov loop model A.Dumitru, R.Pisarski, Phys.Lett.B 525 (2002) Discussion of Jet Quenchingat Intermediate RHIC Energies • The result, if confirmed, would not be • unexpected • Follow from energy loss jet quenching • calculations • Naturally interpolatebetween the SPS • and the top RHIC energies • X.N.Wang, Phys.Lett.B579 (2004) • RAA=0.5 at pT=4 GeV The nuclear modification ratio • Sensitively depends on the underlying • partonic spectrum • In their power law behavior the 62 GeV • spectra are much closer to the 130 GeV • and the 200 GeV cross sections than • to the 17 GeV ones Ivan Vitev, ISU Ivan Vitev, ISU

  13. Conclusions • Dynamical nuclear shadowing from resummed QCD power corrections. Results consistent with its x-, Q2- and A- dependence. Neutrino-nucleus DIS. Modification of the QCD sum rules. • First calculations of dynamical power corrections for hadronic collisions, .Results for the centrality and rapidity dependent suppression of single inclusive spectra and the dihadron correlations. • The power corrections disappear at high pT. They are small at 62 GeV and would not affect the extraction of RAA • In central Au+Au collisions at C.M. energy of 62 GeVneutral pions were found to be suppressed by a factor of 2-3 by jet quenching. Relatively weak pT dependence of RAA • Interpretation of the rapidity density in 1+1D Bjorken expansion: at the energy density - already significantly above the current critical value. • Charged hadrons, especially baryons, are expected to be less suppressed and are beyond the reach of the current perturbative techniques Ivan Vitev, ISU Ivan Vitev, ISU

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