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P. Aurenche

Publications and source records attributed to P. Aurenche.

At least 37 records · Page 2Linked to original sources
arXiv2002

Enhanced thermal production of hard dileptons by $3\to 2$ processes

In the framework of the Hard Thermal Loop effective theory, we calculate the two-loop contributions to hard lepton pair production in a quark-gluon plasma. We show that the result is free of any infrared and collinear singularity. We also recover the known fact that perturbation theory leads to integrable singularities at the location of the threshold for $q\bar{q}\toγ^*$. It appears that the process calculated here significantly enhances the rate of low mass hard dileptons.

hep-ph↗
arXiv2000

Landau-Pomeranchuk-Migdal effect in thermal field theory

In recent studies, the production rate of photons or lepton pairs by a quark gluon plasma has been found to be enhanced due to collinear singularities. This enhancement pattern is very dependent on rather strict collinearity conditions between the photon and the quark momenta. It was estimated by neglecting the collisional width of quasi-particles. In this paper, we study the modifications of this collinear enhancement when we take into account the possibility for the quarks to have a finite mean free path. Assuming a mean free path of order $(g^2T\ln(1/g))^{-1}$, we find that only low invariant mass photons are affected. The region where collision effects are important can be interpreted as the region where the Landau-Pomeranchuk-Migdal effect plays a role in thermal photon production by bremsstrahlung. It is found that this effect modifies the spectrum of very energetic photons as well. Based on these results and on a previous work on infrared singularities, we end this paper by a reasonable physical picture for photon production by a quark gluon plasma, that should be useful to set directions for future technical developments.

hep-ph↗
arXiv2000

Comments on two papers by Kapusta and Wong

We critically examine recently published results on the thermal production of massive vector bosons in a quark-gluon plasma. We claim the production rate is a collinear safe observable.

hep-ph↗
arXiv2000

NLO Monte-Carlo approach in 1 or 2 jets Photoproduction

We present a method for calculating the photoproduction of jets at HERA based on Next to Leading Logarithm QCD calculations. It is implemented in a Monte-Carlo generator which allows us to easily compute any infra-red safe cross sections for 1 or 2 jet observables using various jet reconstruction algorithms. We focus on the possibility of extracting the gluon contents of the photon and of the proton from present and future H1 and ZEUS data.

hep-ph↗
arXiv2000

The QCD and Standard Model Working Group: Summary Report from Les Houches

The Les Houches Workshop on Physics at TeV Colliders took place from June 8-18, 1999. One of the three working groups at Les Houches concentrated on QCD issues, both at the Tevatron Collider and at the LHC. Besides the interest in QCD in its own right, QCD dynamics plays an important role in the production mechanisms for any new physics process that might be observed at either collider, as well as any processes that may form backgrounds to the new physics. This writeup serves both as a pedagogical overview of QCD as well as an update on the current status of the field.

hep-ph↗
arXiv2000

QCD

We discuss issues of QCD at the LHC including parton distributions, Monte Carlo event generators, the available next-to-leading order calculations, resummation, photon production, small x physics, double parton scattering, and backgrounds to Higgs production.

hep-ph↗
arXiv2000

KLN theorem, magnetic mass, and thermal photon production

We study the infrared singularities associated to ultra-soft transverse gluons in the calculation of photon production by a quark-gluon plasma. Despite the fact that the KLN theorem works in this context and provides cancellations of infrared singularities, it does not prevent the production rate of low invariant mass dileptons to be sensitive to the magnetic mass of gluons and therefore the rate to be non perturbative.

hep-ph↗
arXiv1999

Large-p_T Inclusive pi^0 Cross Sections and Next-to-Leading-Order QCD Predictions

We review the phenomenology of pi^0 production at large transverse momentum in proton-induced collisions. Uncertainties in the next-to-leading-order predictions of Quantum Chromodynamics are discussed. The comparison with data reveals that the disagreement between theory and experiment lies essentially in an overall normalization factor. The situation for pi^0 production is contrasted with that of prompt-photon production in hadronic collisions.

hep-ph↗
arXiv1998

A critical phenomenological study of inclusive photon production in hadronic collisions

We discuss fixed target and ISR inclusive photon production and attempt a comparison between theory and experiments. The dependence of the theoretical predictions on the structure functions, and on the renormalization and factorization scales is investigated. The main result of this study is that the data cannot be simultaneously fitted with a single set of scales and structure functions. On the other hand, there is no need for an additional intrinsic $k_{_T}$ to force the agreement between QCD predictions and experiments, with the possible exception of one data set. Since the data cover almost overlapping kinematical ranges this raises the question of consistency among data sets. A comparative discussion of some possible sources of experimental uncertainties is sketched.

hep-ph↗
arXiv1998

Bremsstrahlung and photon production in thermal QCD

In this paper, we extend the study of bremsstrahlung photon production in a quark-gluon plasma to the cases of soft static photons and hard real photons. The general framework of this study is the effective perturbative expansion based on the resummation of hard thermal loops. Despite the fact that bremsstrahlung only comes at two loops, we find that in both cases it generates contributions of the same order of magnitude as those already calculated by several other groups at one loop. Furthermore, a new process contained in the two-loop diagrams dominate the emission of a very hard real photon. In all cases, the rate of real or virtual photon production in the plasma is appreciably increased compared to the one-loop predictions.

hep-ph↗
arXiv1997

Inclusive hard processes in photon induced reactions

In the following some aspects of inclusive hard processes in photon induced reactions are reviewed. After a discussion on the properties of hard processes, the phenomenology of jet production and of charmonium production is presented in the context of the next-to-leading logarithm approximation of QCD.

hep-ph↗
arXiv1996

Some aspects of thermal field theories

Different formalisms used in the perturbative approach to Thermal Field Theory (TFT) are briefly reviewed. The rate of production of a virtual photon in a quark-gluon plasma is then discussed to illustrate some features of TFT before introducing the Hard Thermal Loop resummation which improves the behaviour of the theory in the infrared sector. Some of the successes of this appraoch are described before turning to the problems associated to the undamped transverse gluon oscillations and the light-cone singularities arising when on-shell and/or massless particles are involved.

hep-ph↗
arXiv1996

Breakdown of the Hard Thermal Loop expansion near the light-cone

We discuss the bremsstrahlung production of soft real and virtual photons in a quark-gluon plasma at thermal equilibrium beyond the Hard Thermal Loop (HTL) resummation. The physics is controlled by the ratio $Q^2/q_0^2$ of the virtuality to the energy. When $Q^2/q_0^2$ is much smaller than $g^2$, where $g$ is the strong coupling constant, the emission rate is enhanced by a factor $1/g^2$ over the HTL results due to light-cone singularities and the bremsstrahlung is induced by scattering of the quark via both transverse and longitudinal soft gluon exchanges. When $Q^2/q_0^2$ increases, the enhancement factor is given by $q_0^2/Q^2$. When this ratio is near unity, the bremsstrahlung contribution is of the same order as the rate predicted by the HTL resummation. In that case, the bremsstrahlung is induced by both soft and hard gluon exchanges.

hep-ph↗
arXiv1996

Enhanced photon production rate on the light--cone

Recent studies of the high temperature soft photon production rate on the light--cone using Braaten--Pisarski resummation techniques have found collinear divergences present. We show that there exist a class of terms outside the Braaten--Pisarski framework which, although also divergent, dominate over these previously considered terms. The divergences in these new terms may be alleviated by application of a recently developed resummation scheme for processes sensitive to the light--cone.

hep-ph↗