Jet Observables of Parton Energy Loss in High-Energy Nuclear Collisions

While strong attenuation of single particle production and particle correlations has provided convincing evidence for large parton energy loss in the QGP, its application to jet tomography has inherent limitations due to the inclusive nature of the measurements. Generalization of this suppression to full jet observables leads to an unbiased, more differential and thus powerful approach to determining the characteristics of the hot QCD medium created in high-energy nuclear collisions. In this article we report on recent theoretical progress in calculating jet shapes and the related jet cross sections in the presence of QGP-induced parton energy loss. (i) A theoretical model of intra-jet energy flow in heavy-ion collisions is discussed. (ii) Realistic numerical simulations demonstrate the nuclear modification factor $R_{AA}(p_T)$ evolves continuously with the jet cone size $R^{\max}$ or the acceptance cut $\omega_{\min}$ - a novel feature of jet quenching. The anticipated broadening of jets is subtle and most readily manifested in the periphery of the cone for smaller cone radii.Comment: Proceedings for Quark Matter 2009, updated version with minor correction

The conical flow from quenched jets in sQGP

Starting with a reminder of what is strongly coupled Quark-Gluon Plasma (sQGP), we proceed to recent advances in jet quenching and heavy quark diffusion, with a brief summary of various results based on AdS/CFT correspondence. The conical flow is a hydrodynamical phenomenon created by energy and entropy deposited by high energy jets propagating in matter, similar in nature to well known sonic boom from the supersonic planes. After a brief review, we discuss excitations of two hydro modes -- sound and ``diffuson'' -- which can be excited in this way. We also study expanding matter case, with a variable sped of sound, and use adiabatic invariants to show that the parameter $v/T$ ($v$ velocity in the wave, $T$ temperature) is increasing, up to a factor 3, during expansion. At the end we discuss recent results of the Princeton group which derived conical flow from AdS/CFT.Comment: 17 pages, a talk at Hard Probes 06, Monterey July 200

Testing the theory of QGP-induced energy loss at RHIC and the LHC

We compare an analytic model of jet quenching, based on the GLV non-Abelian energy loss formalism, to numerical results for the centrality dependent suppression of hadron cross sections in Au+Au and Cu+Cu collisions at RHIC. Simulations of neutral pion quenching versus the size of the colliding nuclear system are presented to high transverse momentum pT. At low and moderate pT, we study the contribution of medium-induced gluon bremsstrahlung to single inclusive hadron production. In Pb+Pb collisions at the LHC, the redistribution of the lost energy is shown to play a critical role in yielding nuclear suppression that does not violate the participant scaling limit.Comment: 9 pages, 7 figures, as published in Phys.Lett.B, (1 figure, 1 reference and discussion included

Multiparton Tomography of Hot and Cold Nuclear Matter

Multiple parton interactions in relativistic heavy ion reactions result in transverse momentum diffusion and medium induced non-Abelian energy loss of the hard probes traversing cold and hot nuclear matter. A systematic study of the interplay of nuclear effects on the $p_T \geq 2$ GeV inclusive hadron spectra demonstrates that the competition between nuclear shadowing, multiple scattering and jet quenching leads to distinctly different enhancement/suppression of moderate and high-$p_T$ hadron production in $d+Au$ and $Au+Au$ collisions at RHIC. The associated increase of di-jet acoplanarity, measured via the broadening of the back-to-back di-hadron correlation function, provides an additional experimental tool to test the difference in the dynamical properties of the media created in such reactions.Comment: Prepared for the CIPANP 2003 conference proceedings. 4 pages, 4 figure

Testing the mechanism of QGP-induced energy loss

We present an analytic model of jet quenching, based on the (D)GLV energy loss formalism, to describe the system size dependence of QGP-induced parton absorption in relativistic heavy ion collisions. Numerical simulations of the transverse momentum dependence of jet quenching are given for central Au+Au and Cu+Cu reactions. Low pT dijet correlations are shown to be sensitive to the reappearance of the lost energy as soft hadrons. At high pT we find that the attenuation of dihadrons is similar to that of single inclusive particles. Comparison to recent data from PHENIX and STAR is given as test of the jet quenching theory.Comment: Poster proceedings for Quark Matter 2005. As published in Heavy Ion Physics, 5 pages, 3 figure