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Parton
About: Parton is a research topic. Over the lifetime, 13484 publications have been published within this topic receiving 368877 citations.
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TL;DR: In this article, it was shown that if parton saturation sets in at sufficiently small energy, then in nucleus-nucleus collisions at RHIC and LHC energies the cross sections of semi-hard processes should scale approximately with the number of participants.
Abstract: We argue that the suppression of high p_t hadrons discovered recently in heavy ion collisions at RHIC may be a consequence of saturation in the Color Glass Condensate. We qualitatively and semi-quantitatively describe the data, in particular, the dependence upon the number of nucleon participants. We show that if parton saturation sets in at sufficiently small energy, then in nucleus-nucleus collisions at RHIC and LHC energies the cross sections of semi-hard processes should scale approximately with the number of participants, N_{part}. Our results provide a possible explanation of both the absence of apparent jet quenching at SPS energies and its presence at RHIC. Under the same assumption we predict that in semi--central and central pA (dA) collisions at collider energies the dependence of semi--hard processes on the number of participating nucleons of the nucleus will change to \sim (N_{part}^A)^{1/2}. The forthcoming data on dA collisions will provide a crucial test of this description.
215 citations
TL;DR: In this paper, a detailed study of the production of a high transverse-momentum lepton pair at hadron colliders, which includes the exact O(�) electroweak corrections properly matched with leading logarithmic effects due to multiple photon emission, is presented.
Abstract: We present a detailed study of the production of a high transverse-momentum lepton pair at hadron colliders, which includes the exact O(�) electroweak corrections properly matched with leading logarithmic effects due to multiple photon emission, as required by the experiments at the Fermilab Tevatron and the CERN LHC. Numerical results for the relevant observables of single Z-boson production at hadron colliders are presented. The impact of the radiative corrections is discussed in detail. The presence in the proton of a photon density is considered and the effects of the photon-induced partonic subprocesses are analyzed. The calculation has been implemented in the new version of the event generator HORACE, which is available for precision simulations of the neutral and charged current Drell-Yan processes.
215 citations
TL;DR: In this article, a formula for the two-loop infrared singularities of dimensionally regularized QCD scattering amplitudes with an arbitrary number of massive and massless legs is derived.
Abstract: A formula for the two-loop infrared singularities of dimensionally regularized QCD scattering amplitudes with an arbitrary number of massive and massless legs is derived. The singularities are obtained from the solution of a renormalization-group equation, and factorization constraints on the relevant anomalous-dimension matrix are analyzed. The simplicity of the structure of the matrix relevant for massless partons does not carry over to the case with massive legs, where starting at two-loop order new color and momentum structures arise, which are not of the color-dipole form. The resulting two-loop three-parton correlations can be expressed in terms of two functions, for which some general properties are derived. This explains observations recently made by Mitov et al. in terms of symmetry arguments.
214 citations
TL;DR: In this article, the authors presented a double unresolved Eikonal and Altarelli-Parisi splitting function for tree-level multiparton scattering amplitudes which are appropriate when two partons are unresolved.
214 citations
TL;DR: In this article, the soft-gluon contributions at next-to-next-toleading order (NNLO) were estimated for the top quark pair cross section at the Tevatron and the LHC.
Abstract: We present results for the top quark pair cross section at the Tevatron and the LHC. We use the resummed double differential cross section, employing the fully kinematics-dependent soft-anomalous-dimension matrices, to calculate the soft-gluon contributions at next-to-next-to-leading order (NNLO). We improve and update our previous estimates by refining our methods, including further subleading terms, and employing the most recent parton distribution function sets. The NNLO soft corrections significantly enhance the NLO cross section while considerably reducing the scale dependence. We provide a detailed discussion of all theoretical uncertainties in our calculation, including kinematics, scale, and parton distribution uncertainties, and clarify the differences between our work and other approaches in the literature.
213 citations