Ben-Wei Zhang

Jet quenching and radiative energy loss in dense nuclear matter

We review recent finite opacity approaches (GLV, WW, WOGZ) to the computation of the induced gluon radiative energy loss and their application to the tomographic studies of the density evolution in ultra-relativistic nuclear collisions.

O(αs3) analysis of inclusive jet and di-jet production in heavy ion reactions at the Large Hadron Collider

Abstract Jets physics in heavy ion reactions is an important new area of active research at the Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC) that paves the way for novel tests of QCD multi-parton dynamics in dense nuclear matter. At present, perturbative QCD calculations of hard probes in elementary nucleon–nucleon reactions can be consistently combined with the effects of the nuclear medium up to O ( α s 3 ) . While such accuracy is desirable but not necessary for leading particle tomography, it is absolutely essential for the new jet observables. With this motivation, we present first results and predictions to O ( α s 3 ) for the recent LHC lead–lead (Pbxa0+xa0Pb) run at a center-of-mass energy of 2.76 TeV per nucleon–nucleon pair. Specifically, we focus on the suppression of the single and double inclusive jet cross sections. Our analysis includes not only final-state inelastic parton interactions in the QGP, but also initial-state cold nuclear matter effects and an estimate of the non-perturbative hadronization corrections. We demonstrate how an enhanced di-jet asymmetry in central Pbxa0+xa0Pb reactions at the LHC, recently measured by the ATLAS and CMS experiments, can be derived from these results. We show quantitatively that a fraction of this enhancement may be related to the ambiguity in the separation between the jet and the soft background medium and/or the diffusion of the parton shower energy away from the jet axis through collisional processes. We point to a suite of measurements that can help build a consistent picture of parton shower modification in heavy ion collisions at the LHC.

Momentum imbalance of isolated photon-tagged jet production at RHIC and LHC.

In collisions of ultrarelativistic nuclei, photon-tagged jets provide a unique opportunity to compare jet production and modification due to parton shower formation and propagation in strongly interacting matter at vastly different center-of-mass energies. We present first results for the cross sections of jets tagged by an isolated photon to O(α(em)α(s)(2)) in central Au+Au reactions with sqrt[s(NN)] = 200 GeV at RHIC and central Pb + Pb reactions with sqrt[s(NN)] = 2.76 TeV at LHC. We evaluate the increase in the transverse momentum imbalance of the observed γ + jet state, induced by the dissipation of the parton shower energy due to strong final-state interactions. Theoretical predictions to help interpret recent and upcoming experimental data are presented.

Multiple parton scattering in nuclei: beyond helicity amplitude approximation

Multiple parton scattering and induced parton energy loss in deeply inelastic scattering (DIS) off heavy nuclei is studied within the framework of generalized factorization in perturbative QCD with a complete calculation beyond the helicity amplitude (or soft bremsstrahlung) approximation. Such a calculation gives rise to new corrections to the modified quark fragmentation functions. The effective parton energy loss is found to be reduced by a factor of 5/6 from the result of helicity amplitude approximation.

The Physics of

Electroweak bosons produced in conjunction with jets in high-energy collider experiments is one of the principle final-state channels that can be used to test the accuracy of perturbative Quantum Chromodynamics calculations and to assess the potential to uncover new physics through comparison between data and theory. In this paper we present results for the

Z^0/\gamma^*

Z^0/gamma^*

-tagged jets at the LHC

+jet production cross sections at the LHC at leading and next-to-leading orders. In proton-proton reactions we elucidate up to

Multiple parton scattering in nuclei: heavy quark energy loss and modified fragmentation functions

{cal O}(G_Falpha_s^2)

Production of Z0 and W +/ W− in relativistic heavy-ion collisions at the LHC

the constraints that jet tagging via the

Quantifying jet transport properties via large p_T hadron production

Z^0/gamma^*