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What Can We Learn from the d+Au Run at RHIC ?

What Can We Learn from the d+Au Run at RHIC ? Probing Cold Nuclei via the Centrality and Rapidity Dependence of the Cronin Effect from Perturbative QCD. Ivan Vitev Iowa State University, Ames, IA 50011. Transverse Dynamics at RHIC March 6-8, 2003, BNL, Upton, NY. Outline of the Talk.

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What Can We Learn from the d+Au Run at RHIC ?

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  1. What Can We Learn from the d+AuRun atRHIC? Probing Cold Nuclei via theCentralityandRapidityDependence of theCronin EffectfromPerturbative QCD Ivan Vitev Iowa State University, Ames, IA 50011 Transverse Dynamics at RHIC March 6-8, 2003, BNL, Upton, NY Ivan Vitev

  2. Outline of the Talk  The Au+Au and d+Au programs: Observables (focus on high-pT versus inclusive observables ) • A systematic approach to nuclear effects in hadron production:I.V. and M.Gyulassy, Phys.Rev.Lett. 89, (2002) • 0productionin Au+Au (Cronin + shadowing + jet energy loss) • New results on the centrality and rapidity dependence of the Cronin effect:I.V.,nucl-th/0302002 • Incorporating initial state energy loss (mean elastic e-loss) • Differentiating between models (enhancement versus • suppression) • Constraints on cold nuclear matter (antishadowing, transport • coefficients) Ivan Vitev

  3. Inclusive Observables - b=0 fm HIJING 1.37 simulation; X.N.Wang and M.Gyulassy, Phys.Rev.Lett. 68, (1992) Z.W.Lin and C.M.Ko, nucl-th/0301025 • Vastly different models give comparable results. • May not be unexpected in view of existing precise p+p and Au+Au data at . • Do models stay within their range of validity??? D.Kharzeev, E.Levin and M.Nardi, hep-ph/0212316 Ivan Vitev

  4. ,K,p… central Cronin Effect Preliminary Binary scaling Jet Quenching peripheral STAR, Phys.Rev.Lett. 89, (2002) Suppression vs. Enhancement of High-pT Hadrons PHENIX Predictions Review: M.Gyulassy, I.V., X.-N.Wang, B.-W.Zhang, nucl-th/0302077 K.Filimonov, STAR nucl-ex/0210027 T.Hirano and Y.Nara, nucl-th/0301042 (see talk) Ivan Vitev

  5. Y=0 ~40% ~50% D.Kharzeev et al., hep-ph/0210033 ~200 –250% F.Gelis and J.Jalilian-Marian, hep-ph/0211363 Alternative Suggestions for d+A Y=3-4 A.Dumitru, J.Jalilian-Marian Phys.Rev.Lett. 89 (2002) The way for this saturation picture to hold together is to observe large 50% suppression at y=0 and large 2 enhancement at y=3-4 Ivan Vitev

  6. Experimental Facts RHIC • Includes both enhancement • and suppression • The effect decreases with • The peak and intercept are • pT-stable, i.e. • (Excludes a wavefunction nature) Practical approach: EKS’98 parameterization K.Eskola,V.Kolhinen,and C.Salgado, Eur.Phys.J. C9 (1999) Nuclear Effects on Hadron Production(The Point of View of Relativistic Heavy Ions) Nuclear shadowing Cronin effect Poorly constrained Ivan Vitev

  7. Multiple Parton Interactions via theGLV Reaction Operator Approach + + • A systematic expansion technique that describes the multiple elastic • and inelastic scatterings of fast partons in orders of For the elastic scattering case illustrated here : Reaction Operator = all possible on-shell cuts through a new Double Born interaction M.Gyulassy, P.Levai, I.V., Phys.Rev. D66, (2002) Ivan Vitev

  8. Applications ofMultipleElastic Scatterings 1. The Gaussianapproximation fails for small and moderate opacities Were M. Gyulassy, P. Levai, I.V., Phys.Rev.D 66 (2002) 2.Implementation ofinitial state energy loss, elastice-loss I.V., nucl-th/0302002 I.V. and J.W.Qiu, in preparation For the mean elastic E-loss Probability to loose a fraction of the initial momentum Ivan Vitev

  9. Understanding the Systematics of Low Energy Data Include nuclear-induced parton broadening Slight increase of with increasing fraction of gluons 1. EKS’98 shadowing/antishadowing/EMC effect 2. No strong antishadowing/EMC effect • Better agreement may be reached in case 2 • The constant and is • recovered • Including initial state elastic E-loss requires • ~20% increase of the transport coefficients I.V., nucl-th/0302002 Ivan Vitev

  10. jet g g g Jet E-loss in QCD via the GLV Formalism Algebraic recursive method(Reaction Operator Approach) is applied Applicable for realistic systems created in A+A collisions. Finite sizesystems and in-medium jet production. • Driven by a single parameter: initial gluon rapidity • densitydNg/dy • Includes dynamical 1+1D(and1+3D) expansion • of the interaction region • Solves for the double differential gluon spectra to • all orders in opacity (all-twist correlations) M.Gyulassy, P.Levai, I.V., Nucl.Phys. B594, (2001); Phys.Rev.Lett. 85, (2000). + + Ivan Vitev

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

  12. Impact Parameter Dependence of the Cronin Effect at RHIC 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% There is a factor of ~2.5difference between central (b=0 fm) and mid-peripheral (b=6 fm) reactions (30% versus 12%) In contrast: D.Kharzeev et al., hep-ph/0210033 gives argued to gives Alternatively a similar result since I.V., nucl-th/0302002 Ivan Vitev

  13. Rapidity Dependence of the Cronin Effect • At forward rapidity Y = +3multiple elastic • scatterings completely dominate over the • shadowing/antishadowing • Both the Cronin peak and intercept • are shifted to slightly higher • The notable difference/prediction is the • significantly extended Cronin enhancement • region to high pT • (understood from the pQCD predicted • softening of the spectra) • At backward rapidity Y = -3 there is no • enhancement – nucleus does not scatter • multiply on the deuteron • This region is more sensitive to energy loss • than the forward region • Can? provide some information for the EMC • modification to the PDFs nucl-th/0302002 Ivan Vitev

  14. Distinguishing between Different Scenarios Y=3 1. Call 2. Evolve with Y 3. Compute Y=0 HopefullyDATA will be the judge to distinguished between “standard” and saturated cold nuclear matter at RHIC energies Ivan Vitev

  15. Specific Calculations of the Cronin Effect B. Kopeliovich et al., Phys.Rev.Lett. 88, (2002) Y. Zhang et al., Phys.Rev. C65, (2002) Phenomenological best fit These calculations have addressed the Y=0 total inclusive Cronin Effect at RHIC All of the above find: at RHIC X.N. Wang, Phys.Rev. C 61, (2000) Ivan Vitev

  16. Conclusions • We have performed the firstsystematic jet-tomographic study that includes shadowing, Cronin effect, and jet energy loss as a function of . Initial state elastic and final state inelastic parton scattering has been computed within the same Reaction Operator (GLV) formalism. • The predicted nuclear modification factor is shown to be strikingly different, both in shape and magnitude, at SPS, RHIC, and LHC. • We have given the firstquantitative discussion of the centrality and rapidity dependence of the Cronin effect at RHIC extending a systematic analysis of low energy p+A data. • The predicted nuclear modification in d+A is distinctly different in shape and magnitude from any suggestedinterpretation of saturation. • The d+A data can help disentangle initial and final state nuclear effects and possibly constrain the properties of cold nuclear matter. Ivan Vitev

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