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Flow effects on jet profile

N. Armesto. Flow effects on jet profile. 2nd International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions Asilomar Conference Grounds, June 9th-16th, 2006. N éstor Armesto Departamento de Física de Partículas and Instituto Galego de Física de Altas Enerxías

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Flow effects on jet profile

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  1. N. Armesto Flow effects on jet profile 2nd International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions Asilomar Conference Grounds, June 9th-16th, 2006 Néstor Armesto Departamento de Física de Partículas and Instituto Galego de Física de Altas Enerxías Universidade de Santiago de Compostela See the talks by M. Djordjevic, R. Fries, R. Hwa, G. Ma, A. Majumder, K. Rajagopal, T. Renk, C. Salgado, E. Shuryak, I. Vitev, U. Wiedemann, and many experimental talks... 1

  2. N. Armesto Contents 1. Motivation. 2. Radiation in a flowing medium (with C. A. Salgado and U. A. Wiedemann, PRL93 (2004) 242301; PRC72 (2005) 064910) 3. v2, and the determination of qhat. (with C. A. Salgado and U. A. Wiedemann, PRC72 (2005) 064910; T. Renk and J. Ruppert, C72 (2005) 044901; T. Renk, hep-ph/0602045) 4. Conclusions. For other proposals, see S. A. Voloshin, nucl-th/0312065. 2 Flow effects on jet profile

  3. N. Armesto Dainese, talk at PANIC05 Eskola et al '04 (Quark Matter 05) Dainese et al '04 1. Motivation (I) Unsatisfactory aspects in available formalisms for radiative eloss: s=1/3-1/2 STAR'06 3 Flow effects on jet profile

  4. N. Armesto d+Au, 40-100% Au+Au, 0-5% 3 < pT(trig) < 6 GeV2 < pT(assoc) < pT(trig) 1. Motivation (II) Suggestive (preliminary) experimental data: STAR Preliminary 4<pttrig<6 GeV, 0.15<ptass<4 GeV near: ||<1.1, ||<1.4 away: ||<2, ||<1.1 Magestro at HP04 F.Wang at QM04 4 Flow effects on jet profile

  5. N. Armesto 1. Motivation (III) Measurable jet shapes: Salgado, Wiedemann, '04 • Jet shapes and associated multiplicities will be measured at the LHC by ALICE, ATLAS and CMS (see the talks by the LHC exps.). • Compromise between energy calibration and fluctuations: 5 Flow effects on jet profile

  6. N. Armesto 1. Motivation (IV) Dilution of the medium already taken into account (Baier et al, '98; Gyulassy, Vitev, Wang, '01; Salgado, Wiedemann, '02; '03): But what if the hard parton is not produced in the frame comoving with the medium, either longitudinally or transversely? 6 Flow effects on jet profile

  7. N. Armesto 2. Radiation in a flowing medium (I) Usual assumption: c~2 (pQCD); c~10 (Eskola et al, '04; Dainese et al '04) from RHIC RAAlight analysis. The success of ideal hydro: For h=0.5, 1, 1.5, one gets Dp/p=1,5,18 which may lead to a substantial increase in radiative eloss. 7 Flow effects on jet profile

  8. N. Armesto 2. Radiation in a flowing medium (II) Assumption for longitudinal expansion: hard partons are not produced in the medium comoving frame, so momentum exchanges with the radiating partons become anisotropic. At first order in the opacity expansion (Gyulassy, Levai, Vitev, '00; Wiedemann, '00) Our ansatz In the comoving frame, <kT>~m, DE~asn0m2L2; flow contributionq0~m. 8 Flow effects on jet profile

  9. N. Armesto 2. Radiation in a flowing medium (III) We compute Energy deposition asymmetric due to: • Random emission. • t- or pT-ordering in emission. • Jacobian: Vacuum: D0 parametrization (Abbott et al, '97); vacuum (medium) regulated for R<0.04 (0.01). 9 Flow effects on jet profile

  10. N. Armesto 2. Radiation in a flowing medium (IV) q0=m, DEmed=23 GeV, Ejet=100 GeV. Asymmetry clearly visible. Symmetrized h <-> -h: Low shift in the calorimetric center. 10 Flow effects on jet profile

  11. N. Armesto 3. v2, and the determination of qhat (I) The defect in v2 triggers the inclusion of flow effects: in terms of the BDMPS parameters nT compute Our proposal: j 11 Flow effects on jet profile

  12. N. Armesto 3. v2, and the determination of qhat (II) Using a blast wave parametrization of flow profile at freeze-out (Lisa, Retiere, '03). Flow may affect our extraction of qhat. 12 Flow effects on jet profile

  13. N. Armesto 3. v2, and the determination of qhat (III) Renk, Ruppert, PRC72(2005)044901: dynamical model for expansion, LO, quenching weights. c=4, as=0.3, vTi=0.1 • c~10 with no flow effect. • Small longitudinal effect for h~0. • Sensitive to initial flow and to flow profile. • A 'moderately optimistic scenario' leads to c~2 (pQCD). as=0.45 13 Flow effects on jet profile

  14. N. Armesto 3. v2, and the determination of qhat (IV) Renk, hep-ph/0602045: associated particle production from dAu. pTtrig>8 GeV, 4<pTass<6 GeV • Surface emission weakened. • Yields/trigger reproduced. Dainese et al, '04 14 Flow effects on jet profile

  15. N. Armesto Determination of qhat? • Analysis of RAA for light particles with quenching weights, geometry and Bjorken expansion give qhat~10 GeV2/fm (4-15; dNg/dy~1000(-3500)). • RAA for electrons shows uncertainties to be clarified. • More stringent upper bound to come, hopefully, from less inclusive measurements. • pQCD predicts values ~5 times smaller; lower bound. • AdS/CFT correspondence give values ~3 GeV2/fm for T~300 MeV: upper bound? • Consideration of flow may reduce qhat. STAR‘ 06 15 Flow effects on jet profile

  16. N. Armesto 4. Conclusions • Flow should modify the pattern of medium-induced radiation if the hard parton is produced in a frame not comoving with the medium. Even the absence of such effect would tell us about its dynamical expansion. • An exploratory study illustrates two examples of such effect: * Longitudinal elongation of the jet shape. * Moderate increase of v2. • More elaborated implementations show the influence on the determination of the transport coefficient and on the picture of the medium: flow may mimic the effect of a larger energy density. • More exclusive studies than RAA will be crucial, together with heavy flavors, to set this matter: hadrons at RHIC and the LHC, and calorimetric measurements at the LHC. This demands new theoretical tools under development. 16 Flow effects on jet profile

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