Topic
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: The first explicit formulae for the complete set of one-loop helicity amplitudes necessary for computing next-to-leading order corrections for e + e − annihilation into four jets, for W, Z or Drell-Yan production in association with two jets at hadron colliders, and for three-jet production in deeply inelastic scattering experiments were presented in this article.
455 citations
TL;DR: In this paper, a new analysis of parton distributions of the proton is presented, which incorporates a wide range of new data, an improved treatment of heavy flavours and a re-examination of prompt photon production.
Abstract: We present a new analysis of parton distributions of the proton. This incorporates a wide range of new data, an improved treatment of heavy flavours and a re-examination of prompt photon production. The new set (MRST) shows systematic differences from previous sets of partons which can be identified with particular features of the new data and with improvements in the analysis. We also investigate the sensitivities of the results to (i) the uncertainty in the determination of the gluon at large
$x$
, (ii) the value of
$\alpha_S (M_Z^2)$
and (iii) the minimum
$Q^2$
cut on the data that are included in the global fit.
450 citations
TL;DR: The results from the STAR Collaboration on directed flow (v(1), elliptic flow, and the fourth harmonic in the anisotropic azimuthal distribution of particles from Au+Au collisions at root s(NN) = 200 GeV are summarized and compared with results from other experiments and theoretical models.
Abstract: The results from the STAR Collaboration on directed flow (v(1)), elliptic flow (v(2)), and the fourth harmonic (v(4)) in the anisotropic azimuthal distribution of particles from Au+Au collisions at root s(NN) = 200 GeV are summarized and compared with results from other experiments and theoretical models. Results for identified particles are presented and fit with a blast-wave model. Different anisotropic flow analysis methods are compared and nonflow effects are extracted from the data. For v(2), scaling with the number of constituent quarks and parton coalescence are discussed. For v(4), scaling with v(2)(2) and quark coalescence are discussed.
448 citations
TL;DR: In this paper, an exact all-order expression for the Drell-Yan cross section at small transverse momentum is derived directly in q676 T672 space, in which all large logarithms are resummed.
Abstract: Using methods from effective field theory, an exact all-order expression for the Drell–Yan cross section at small transverse momentum is derived directly in q
T
space, in which all large logarithms are resummed. The anomalous dimensions and matching coefficients necessary for resummation at NNLL order are given explicitly. The precise relation between our result and the Collins–Soper–Sterman formula is discussed, and as a by-product the previously unknown three-loop coefficient A
(3) is obtained. The naive factorization of the cross section at small transverse momentum is broken by a collinear anomaly, which prevents a process-independent definition of x
T
-dependent parton distribution functions. A factorization theorem is derived for the product of two such functions, in which the dependence on the hard momentum transfer is separated out. The remainder factors into a product of two functions of longitudinal momentum variables and $x_{T}^{2}$
, whose renormalization-group evolution is derived and solved in closed form. The matching of these functions at small x
T
onto standard parton distributions is calculated at $\mathcal{O}(\alpha_{s})$
, while their anomalous dimensions are known to three loops.
447 citations
TL;DR: In this article, a Born and one-loop approximation was used to extract quark and gluon distributions from a source consisting of a nucleus of heavy quarkonium bound states, states well understood in QCD.
445 citations