366 research outputs found
On the QCD evolution of transverse momentum dependent distributions
No full textAbstractWe reconsider the evolution equations for transverse momentum dependent distributions recently proposed by us and recast them in a form which allows the comparison with results recently appeared in the literature. We show under which conditions the obtained results are consistent with each other
NLO semi-inclusive Drell–Yan cross-section in quantum chromodynamics as a factorization analyzer
No full textAbstractWe evaluate in perturbative QCD the semi-inclusive Drell–Yan cross-section for the production of a single hadron accompanying the lepton pair. We demonstrate to one loop level a collinear factorization formula within the fracture functions approach. We propose such a process as a factorization analyzer in hadronic collisions. Phenomenological implications at the hadron colliders are briefly discussed
Relativistic effects in model calculations of double parton distribution functions
No full textpeer reviewedIn this paper we consider double-parton distribution functions (dPDFs), which are the main nonperturbative ingredients appearing in the double-parton scattering cross section formula in hadronic collisions. By using recent calculation of dPDFs by means of constituent quark models within the so-called light-front approach, we investigate the role of relativistic effects on dPDFs. We find, in particular, that the so-called Melosh operators, which allow us to properly convert the LF spin into the canonical one and incorporate a proper treatment of boosts, produce sizeable effects on dPDFs. We discuss specific partonic correlations induced by these operators in the transverse plane which are relevant to the proton structure, and we study under which conditions these results are stable against variations in the choice of the proton wave function. © 2017 American Physical Society
Transverse momentum in semi-inclusive deep inelastic scattering
No full textAbstractWithin the framework of perturbative quantum chromodynamics we derive the evolution equations for transverse momentum dependent distributions and apply them to the case of semi-inclusive deep inelastic scattering. The evolution equations encode the perturbative component of transverse momentum generated by collinear parton branchings. The current fragmentation is described via transverse momentum dependent parton densities and fragmentation functions. Target fragmentation instead is described via fracture functions. We present, to leading logarithmic accuracy, the corresponding semi-inclusive deep inelastic scattering cross-section, which applies to the entire phase space of the detected hadron. Some phenomenological implications and further developments are briefly outlined
An application of transverse momentum dependent evolution equations in QCD
No full textAbstractThe properties and behaviour of the solutions of the recently obtained kt-dependent QCD evolution equations are investigated. When used to reproduce transverse momentum spectra of hadrons in Semi-Inclusive DIS, an encouraging agreement with data is found. The present analysis also supports at the phenomenological level the factorization properties of the Semi-Inclusive DIS cross-sections in terms of kt-dependent distributions. Further improvements and possible developments of the proposed evolution equations are envisaged
Evolution Equations for Extended Dihadron Fragmentation Functions.
No full textAbstractWe consider dihadron fragmentation functions, describing the fragmentation of a parton in two unpolarized hadrons, and in particular extended dihadron fragmentation functions, explicitly dependent on the invariant mass, Mh, of the hadron pair. We first rederive the known results on Mh-integrated functions using jet calculus techniques, and then we present the evolution equations for extended dihadron fragmentation functions. Our results are relevant for the analysis of experimental measurements of two-particle-inclusive processes at different energies
Asymmetries involving dihadron fragmentation functions: from DIS to e+e- annihilation
No full textUsing a model calculation of dihadron fragmentation functions, we fit the spin asymmetry recently extracted by HERMES for the semi-inclusive pion pair production in deep-inelastic scattering on a transversely polarized proton target. By evolving the obtained dihadron fragmentation functions, we make predictions for the correlation of the angular distributions of two pion pairs produced in electron-positron annihilations at BELLE kinematics. Our study shows that the combination of two-hadron inclusive deep-inelastic scattering and electron-positron annihilation measurements can provide a valid alternative to Collins effect for the extraction of the quark transversity distribution in the nucleon
Scale evolution of kt-distributions
No full textWe review some of the features of the evolutions equations for transverse momentum dependent parton distributions recently proposed by us. We briefly describe the new ingredients entering the equations and their relationship with ordinary evolution equations. We comment on possible choices for the initial conditions and then show results for the evolved distributions obtained by numerical implementation of the equations. By computing the average transverse momentum at different scale we highlight some general properties of the solutions. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.SCOPUS: cp.pinfo:eu-repo/semantics/publishe
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