1. December 13-15, 2002 Ivan Vitev 1 Jet Quenching in Thin Plasmas - the Prediction Before the Experiment Ivan Vitev Iowa State University, Ames, IA 50011 First Two Years at RHIC: Theory vs. Experiments December 13-14, 2002, INT-Seattle, WA

2. December 13-15, 2002 Ivan Vitev 2 Outline of the Talk  The motivation: multipart on interaction PQCD program: Focus on heavy ion reactions (L~5 fm, dynamical, evolution) The WA98 puzzle (R AA = 2-3, enhancement not suppression)  Gluon radiation and hadron suppression, QM’99: Necessity for large probability corrections to dN g : (dominance of the lowest order in-medium correlations) Jet quenching with R AA = 0.2-0.5 (toy model using JETSET)  Predictions of the GLV approach vs experiment: Dominant lowest order in the opacity result (including unitarity corrections ) High-p T azimuthal asymmetry (hydo + jet energy loss) Suppression of hadron production (with Cronin + shadowing)

3. December 13-15, 2002 Ivan Vitev 3 Gluon Radiation and the Landau- Pomeranchuk-Migdal (LPM) Effect In QCD: a) Gyulassy-Wang: multiple interactions, arbitrary medium, the transverse gluon dynamics is neglected b) Baier et al. (BDMPS): thick medium, large number of scatterings, exclusively the LPM regime M.Gyulassy and X.N.Wang, Nucl. Phys. B 420 (1994). R.Baier et al., Nucl.Phys. B 483, (1997). (Also see: Zakharov; Wiedemann) So long as: Linear otherwise WA98, central versus peripheral All approaches require: Motivation: For a nucleus can be applicable only if you have a few (3-5) scatterings. Does leave the room for an improved calculation. The “apparent” lack of energy loss at the SPS. X.-N. Wang, Phys.Rev.Lett. 81, (1998). M.M. Aggarwal et al., Phys.Rev.Lett. 81, (1998).

4. December 13-15, 2002 Ivan Vitev 4 Gluon Radiation, Scaling with n s Consider only the direct diagrams: M. Gyulassy, P. Levai, I.V., Nucl. Phys. B 571 (2000) Exponential sensitivity to n s – need for unitarity conserving factors (here imposed a posteriori with ) Insensitivity of the radiative spectrum to the higher order correlations (orders in opacity)

5. December 13-15, 2002 Ivan Vitev 5 Quenching in a Toy Model Using JETSET (Quark-Antiquark String Fragmentation) RAARAA What is now usually labeled Focus on the typical moderate p T Indications of 2-5 fold suppression (toy model results). The actual hadronic spectra are a superposition of the distributions like the above, leading to a flatter R AA. R AA =0.2-0.5 B. Andersson et al., Phys. Rep. 97 (1983) I.V.(S. Bass et al.), Nucl.Phys. A 661, (1999).

6. December 13-15, 2002 Ivan Vitev 6 Virtual Corrections to the Medium Induced Radiation M. Gyulassy, P. Levai, I.V., Phys.Rev.Lett. 85 (2000), M. Gyulassy, P. Levai, I.V., Nucl.Phys. B 594 (2001). + + GLV Reaction Operator approach: Even for small E and thin media: For Bjorken expansion: Power suppressed

7. December 13-15, 2002 Ivan Vitev 7 Induced Bremsstrahlung to All Orders in Opacity Convergence:

8. December 13-15, 2002 Ivan Vitev 8 High-p T Azimuthal Asymmetry v 2 (p T ) M. Gyulassy, I.V. and X.N. Wang, Phys.Rev.Lett. 86 (2001) Predicted: saturation, plateau and subsequent decrease. Any jet correlations have been discarded: perfect coupling to the reaction geometry In the limit of large energy loss the sharp cylinder geometry applies. See also: E. Shuryak, Phys.Rev. C 66 (2002).

9. December 13-15, 2002 Ivan Vitev 9 Comparison to Data (and its Time Evolution) C. Adler et al. [STAR Collab.], arXiv: nucl-ex/0206006 K. Filimonov [STAR Collab.], arXiv: nucl-ex/0210027 b=7 fm b~7 fm There is a quantitative difference Calculations/fits with flat or continuously growing Check against high-p T data (200 AGeV) Same for 0-50% The decrease with p T is now supported by data For minimum bias this rate is slightly slower See: N.Borghini, P.Dinh, J-Y.Ollitrault, Phys.Rev. C 64 (2001)

10. December 13-15, 2002 Ivan Vitev 10 Initial Parton Broadening via the GLV Elastic Reaction Operator Elastic scattering case: + + M.Gyulassy, P.Levai, I.V., Phys.Rev. D66, (2002) B. Kopeliovich et al., Phys.Rev.Lett. 88, (2002) Y. Zhang et al., Phys.Rev. C65, (2002) Both enhancement and suppression are an integral part of the Cronin effect. Understood in terms of momentum and probability conservation and redistribution. Trivial application: scale See e.g.: H. Bethe, Phys. Rev. 89 (1953)

11. December 13-15, 2002 Ivan Vitev 11 Predicted (Y=0) Shadowing+Cronin in d+Au and Au+Au at 17, 200, 5500 AGeV SPS RHIC LHC d+Au: 250% Au+Au: 400% d+Au: 30% Au+Au: 60% d+Au: 4% Au+Au: 10% 1. At SPS the Cronin effect is large: does leave room for small suppression due to the non-Abelian energy loss. 2. At RHIC the Cronin effect is comparable (~50% larger) to estimates by X.N.Wang and B.Kopeliovich. In A+A the effect has not been presented. 3. At LHC shadowing/antishadowing dominate. Cronin effect is reduced due to the much harder spectra.

12. December 13-15, 2002 Ivan Vitev 12 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 2. Cronin effect, shadowing, and jet quenching conspire to give flat suppression pattern out to the highest p T at RHIC 3.At LHC the nuclear modification is completely dominated by energy loss. Predicts below quenching, strong dependence Feedback!

13. December 13-15, 2002 Ivan Vitev 13 Quenched Hadron Spectra: Comparison to Data I.V. and M.Gyulassy, Phys.Rev.Lett. 89 (2002) The data at RHIC is still preliminary 1. There is qualitative agreement between data and theory. 2. There are some quantitative deviations but data has to be finalized before their evaluation. 3. The most interesting question is whether the systematics of will be confirmed at the LHC.

14. December 13-15, 2002 Ivan Vitev 14 Conclusions  Perturbatively computable multi-parton processes in QCD matter (both cold nuclear matter and the quark-gluon plasma) present an exciting new frontier for theoretical studies.  At RHIC the observed large azimuthal anisotropy and the large suppression of the hadronic spectra signal of a strong radiative energy loss. The predicted p T -systematics is now supported by data.  We have shown how d+A data can help disentangle initial and final state nuclear effects. Cold ASPSRHICLHC Tomography results

15. December 13-15, 2002 Ivan Vitev 15 Why Tomography? X-ray Calibrated source Image Conventional X-ray position tomography creates an image based on the attenuation of the flux from a calibrated source:  Information about the shape of the object  Information about the density of the object g g L I.V. and M.Gyulassy, Phys.Rev.Lett. 89 (2002); M.Gyulassy, P.Levai,and I.V., Nucl.Phys. B 583 (2002); Phys.Rev.Lett. 85 (2000). M.Gyulassy, I.V.,and X.N.Wang, Phys.Rev.Lett. 86 (2001); M.Gyulassy, I.V.,X.N.Wang, and P.Huovinen, Phys.Lett. B526 (2002). Azimuthal tomography Jet tomography g g L big g L small   e+e-e+e- Positron emission tomography

16. December 13-15, 2002 Ivan Vitev 16 Nuclear Effects on Hadron Production (The Point of View of Relativistic Heavy Ions) Nuclear shadowing, antishadowing, EMC effect P xPxP X …  Shadowing: Partonic model A.Mueller and J.Qiu Generalized vector dominance model Practical approach: EKS’98 parameterization K.Eskola,V.Kolhinen,and C.Salgado, Eur.Phys.J. C9 (1999) EMC effect: Nuclear swelling E.Predazzi, L.Frankfurt, M.Strikman Quark cluster models H.Pirner and J.Vary Fermi motion: Antishadowing: Constructive interference J.Qiu, S.Brodsky Partonic model J.Qiu Gain from the motion inside the nucleus RHIC

17. December 13-15, 2002 Ivan Vitev 17 The Cronin Effect Faster than linear scaling of the p+A cross section with the number of binary collisions p A Glauber model b Models of the Cronin effect are based on multiple initial state scattering – helps to gain p T at moderate p T (and compensates at small p T ) Hadronic scattering Partonic scattering Gaussian approximation Deviations in the case of few collisions M.Gyulassy, P.Levai, and I.V., Phys.Rev. D66, (2002)

18. December 13-15, 2002 Ivan Vitev 18 Predicted Cronin Effect+Shadowing at Forward and Backward Rapidities Note the scales: if Cronin effect is detectable (20%-30%) at Y=0 then it should be detectable at Y=3 For p T <2 GeV: suppression comparable to standard Cronin measurements. For p T >2 GeV – a much broader enhancement A.Dumitru and J.Jalilian-Marian, Phys.Rev.Lett. 89, (2002) with Q s 2 =6.6 GeV 2 QsQs Strong suppression below Q s and R AB =1 above Compared I.V. and M.Gyulassy

19. December 13-15, 2002 Ivan Vitev 19 Suppression vs. Enhancement of High-p T Hadrons ATLAS simulation at LHC WA98, central versus peripheral STAR, nucl-exp/0206011, PRL central peripheral ,K,p… Binary scaling Preliminary Jet Quenching Cronin Effect PHENIX