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Jet Quenching in Thin Plasmas - the Prediction Before the Experiment

Jet Quenching in Thin Plasmas - the Prediction Before the Experiment

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Jet Quenching in Thin Plasmas - the Prediction Before the Experiment

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  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 Ivan Vitev

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

  3. Motivation: WA98, central versus peripheral All approaches require: For a nucleus can be applicable only if you have a few (3-5) scatterings. Does leave the room for an improved calculation. 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). So long as: R.Baier et al., Nucl.Phys. B 483, (1997). (Also see: Zakharov; Wiedemann) Linear otherwise 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). Ivan Vitev

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

  5. Quenching in a Toy Model Using JETSET(Quark-Antiquark String Fragmentation) B. Andersson et al., Phys. Rep. 97 (1983) What is now usually labeled I.V.(S. Bass et al.), Nucl.Phys. A 661, (1999). RAA Focus on the typical moderate pT RAA=0.2-0.5 • 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 RAA . Ivan Vitev

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

  7. Induced Bremsstrahlung to All Orders in Opacity Convergence: Ivan Vitev

  8. High-pT Azimuthal Asymmetry v2(pT) Any jet correlations have been discarded: perfect coupling to thereaction geometry M. Gyulassy, I.V. and X.N. Wang, Phys.Rev.Lett. 86 (2001) • In the limit of large energy loss the sharp • cylinder geometry applies. See also: E. Shuryak, Phys.Rev. C 66 (2002). Predicted: saturation, plateau and subsequent decrease. Ivan Vitev

  9. Comparison to Data (and its Time Evolution) • There is a quantitative difference • Calculations/fits with flat • or continuously growing Check against high-pT data (200 AGeV) b=7 fm b~7 fm C. Adler et al. [STAR Collab.], arXiv: nucl-ex/0206006 Same for 0-50% • The decrease with pT is now • supported by data • For minimum bias this rate is • slightly slower K. Filimonov [STAR Collab.], arXiv: nucl-ex/0210027 See: N.Borghini, P.Dinh, J-Y.Ollitrault, Phys.Rev. C 64 (2001) 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) Trivial application: scale See e.g.: H. Bethe, Phys. Rev. 89 (1953) Bothenhancement and suppression are an integral part of the Cronin effect. Understood in terms of momentum and probabilityconservation and redistribution. Y. Zhang et al., Phys.Rev. C65, (2002) Ivan Vitev

  11. d+Au: 250% Au+Au: 400% SPS d+Au: 30% Au+Au: 60% RHIC d+Au: 4% Au+Au: 10% LHC Predicted (Y=0) Shadowing+Cronin in d+Au and Au+Au at 17, 200, 5500 AGeV 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 LHCshadowing/antishadowing dominate. Cronin effect is reduced due to the much harder spectra. Ivan Vitev

  12. 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

  13. Quenched Hadron Spectra: Comparison to Data 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. I.V. and M.Gyulassy, Phys.Rev.Lett. 89 (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 predictedpT-systematics is now supported by data. • We have shown how d+A data can help disentangle initial and final state nuclear effects. Tomography results Ivan Vitev

  15. Positron emission tomography  e+e-  g L g g g g Lsmall Lbig Why Tomography? Conventional X-rayposition 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 X-ray Calibrated source Image Jet tomography Azimuthal tomography 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). Ivan Vitev

  16.  xP P … X 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, antishadowing, EMC effect RHIC Shadowing: Partonic model A.Mueller and J.Qiu Antishadowing: Generalized vector dominance model Constructive interference J.Qiu, S.Brodsky EMC effect: Partonic model J.Qiu Fermi motion: Nuclear swelling E.Predazzi, L.Frankfurt, M.Strikman Quark cluster models H.Pirner and J.Vary Gain from the motion inside the nucleus Ivan Vitev

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

  18. Qs with Qs2=6.6 GeV2 Compared A.Dumitru and J.Jalilian-Marian, Phys.Rev.Lett. 89, (2002) • Strong suppressionbelow Qs • and RAB=1above Predicted Cronin Effect+Shadowing at Forward and Backward Rapidities I.V. and M.Gyulassy • Note the scales: if Cronin effect • is detectable (20%-30%) at Y=0 • then it should be detectable at Y=3 • ForpT<2 GeV:suppression • comparable to standard Cronin • measurements. For pT>2 GeV – • a much broader enhancement Ivan Vitev

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