1. L. Apolinário, N. Armesto, J. G. Milhano, C. Salgado TOWARDS JET CALCULUS IN A QCD MEDIUM

2. OUTLINE Quark-Gluon Plasma Jet-Quenching Jet-Quenching Models ASW Model On-going projects Summary ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 2

3. Collision of heavy ions  Formation of a hot and dense medium: quark-gluon plasma Measurement of transport and dynamical properties Lifetime very short Need hard probes well controlled by both experiment and theory (pQCD) Jets, γ, QUARK-GLUON PLASMA ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 3

4. JET-QUENCHING ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 4 Jet-Quenching: Collection of energy loss phenomena inside the medium High p T particles supressed (but not photons!) [Phys. Rev. C.75. 024909]

5. What happens to the particle inside the medium? Radiative energy loss (dominant at large E) Determination of energy loss allows to measure medium properties: Transport coefficient: Medium Scattering power JET-QUENCHING ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 5 [Wiedemann]

6. Scattering centers well separated Independent scatterings Multiple soft radiation Static medium No elastic energy loss Recoil is neglected Short time of propagation Frozen field profile No direct measurement of the traversing parton Parton produced in any point of the medium Medium evolving: time and space-dependent variables Medium is finite Models developed in the high- energy, eikonal approximation … JET-QUENCHING MODELS Difficulties Assumptions ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 6 Higher Twist (HT) Guo and Wang GLV Gyulassy, Lévai and Vitev ASW Armesto, Salgado and Wiedemann AMY Arnorld, Moore and Yaffe

7. ASW MODEL ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 7 Formalim used: Eikonal propagation Particles only acquire a phase (color rotation) Neglect transverse component Propagator in the medium: Wilson Line First correction to the Eikonal propagation Allow some motion in the transverse plane Keep terms proportional do p T 2 Propagator in the medium with Brownian motion: Green’s function

8. ON-GOING PROJECTS ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 8 Improve the existing formalism by making finite energy corrections Spectrum of the single emission in the limit x~0 done! Computation of the single emission spectrum for any x not possible analytically Solution: Compute the single emission spectrum in the opposite limit (x~1) Possible to interpolate into the intermediate region Reduce the uncertainty on the extraction of [Acta Phys. Polon. B38 : 3731, 07]

9. ON-GOING PROJECTS ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 9 Compute the double emission spectrum in the presence of a medium Monte Carlo programs are based on factorization (independent emissions) and on a probabilistic interpretation emission/no emission Proved for the vacuum case, but not for medium propagation (although vastly used) It also allows to see two particle correlations and modifications with the medium

10. SUMMARY ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 10 Jet-Quenching Recent and active field of research Provides a way of probing the hot and dense medium created in heavy ions collision (possibly, the quark-gluon plasma) ASW Model A model to describe the jet-quenching Already predicts the value of some parameters of the created medium There is still much work to be done: Single emission spectrum for other values than x~0 Double emission spectrum …

11. BACKUP SLIDES ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 11

12. ENHANCEMENT OF PHOTONS ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 12

13. MORE JET-QUENCHING PHENOMENA ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 13 Suppression of di-Jet Correlations

14. JET-QUENCHING MODELS ID PASC 2010 TOWARDS JET-CALCULUS IN A QCD MEDIUM 14 Higher Twist: parameter and temperature of the medium AMY: Hydrodynamical model Extended medium in equilibrium at asymptotically high temperature: GLV: Hard emissions Number of gluons