118358667
Hawking radiation as tunneling derived from black hole thermodynamics through the quantum horizon
We show that the first law of the black hole thermodynamics can lead to the tunneling probability through the quantum horizon by calculating the change of entropy with the quantum gravity correction and the change of surface gravity is presented clearly in the calculation. The method is also applicable to the general situation which is independent on the form of black hole entropy and this verifies the connection of black hole tunneling with thermodynamics further. In the end we discuss the crucial role of the relation between the radiation temperature and surface gravity in this derivation. (C) 2008 Elsevier B.V. All rights reserved.
123328820
Entropy Conservation in the Transition of Schwarzschild-de Sitter Space to de Sitter Space through Tunneling
We revisit Parikh-Wilczek tunneling through the de Sitter horizon and obtain the tunneling rate in Schwarzschild-de Sitter space, which is non-thermal and closely related to the change of entropy. We discuss the thermodynamics of Schwarzschild-de Sitter space and show existence of correlation which can ensure conservation of the total entropy in the transition process of Schwarzschild-de Sitter space to de Sitter space. The correlation and the conserved entropy provide a way to explain the entropy in empty de Sitter space.
118566042
A possible determination of the quark radiation length in cold nuclear matter
Abstract We calculate the differential Drell–Yan production cross section in proton–nucleus collisions by including both next-to-leading order perturbative effects and effects of the nuclear medium. We demonstrate that dilepton production in fixed target experiments is an excellent tool to study initial-state parton energy loss in large nuclei and to accurately determine the stopping power of cold nuclear matter. We provide theoretical predictions for the attenuation of the Drell–Yan cross section at large values of Feynman x F and show that for low proton beam energies experimental measurements at Fermilabʼs E906 can clearly distinguish between nuclear shadowing and energy loss effects. If confirmed by data, our results may help determine the quark radiation length in cold nuclear matter X 0 ∼ 10 − 13 m .
118480026
A systematic study of direct photon production in heavy ion collisions
Abstract A theoretical derivation of photon bremsstrahlung, induced by the interactions of an energetic quark in a hot and dense quark–gluon plasma, is given in the framework of the reaction operator approach. For the physically relevant case of hard jet production, followed by few in-medium interactions, we find that the Landau–Pomeranchuk–Migdal suppression of the bremsstrahlung photon intensity is much stronger than in the previously discussed limit of on-shell quarks and a large number of soft scatterings. This result is incorporated in the first systematic study of direct photon production in minimum bias d + Cu and d + Au and central Cu + Cu and Au + Au heavy ion collisions at the Relativistic Heavy Ion Collider at center of mass energies s = 62.4 GeV and 200 GeV. We find that the contribution of the photons created via final-state interactions is limited to 35% for 2 GeV p T 5 GeV and at high transverse momenta the modification of the direct photon cross section is dominated by initial-state cold nuclear matter effects.
119375105
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.
119119086
The theory and phenomenology of jets in nuclear collisions
We report selected results from a recent in-depth study of jet shapes and jet cross sections in ultra-relativistic reactions with heavy nuclei at the LHC. We demonstrate that at the highest collider energies these observables become feasible as a new, differential and accurate test of the underlying QCD theory. Our approach allows for detailed simulations of the experimental acceptance/cuts that help isolate jets emerging from a dense QGP. We show for the first time that the pattern of stimulated gluon emission can be correlated with a variable quenching of the jet rates and provide an approximately model-independent approach to determining the characteristics of the medium-induced bremsstrahlung spectrum. The connection between such cross section attenuation and the in-medium jet shapes is elucidated.