Umberto D'Alesio

Parton intrinsic motion in inclusive particle production: Unpolarized cross sections, single spin asymmetries and the Sivers effect

The relevance of intrinsic (or primordial) transverse momentum of partons in the inclusive production of particles at high energy and moderately large

Transverse Lambda polarization in semi-inclusive DIS

{p}_{T}

Collins and Sivers effects in p(transv. polarized) p --> jet pion X: Universality and process dependence

has been known for a long time, beginning with Drell-Yan and diphoton processes, and continuing with photon and meson production in hadronic collisions. In view of its renewed interest in the context of polarized processes and single spin asymmetries we perform, in the framework of perturbative QCD with the inclusion of spin and

TRANSVERSE Λ POLARIZATION IN INCLUSIVE PROCESSES

{\mathbit{k}}_{\ensuremath{\perp}}

Constraints on the Collins Function from New e^+e^- --> h_1 h_2 X Measurements in a Leading Order Analysis

effects, a detailed analysis of several such processes in different kinematical situations. We show that the inclusion of these effects leads, at the level of accuracy reachable in this approach, to an overall satisfactory agreement between theoretical predictions and experimental unpolarized data, thus giving support to the study of spin effects and single spin asymmetries within the same scheme. We present results for transverse single spin asymmetries, generated by the so-called Sivers effect, in inclusive pion and photon production in proton-proton collisions. We compare our results with the available experimental data and with previous results obtained using simplified versions of this approach.

Phenomenology of TMDs Using SCET

Following a previous description of Lambda and (U) over bar polarization in unpolarized p-p interactions, within a perturbative QCD factorization scheme with new polarizing fragmentation functions, here we investigate the transverse polarization of Lambdas and (U) over bar s produced in semi-inclusive DIS. Analytical expressions for both neutral and charged current exchange are given. Since quantitative predictions cannot be given at this stage and the comparison with existing data is not yet significant, we present the general formalism and a qualitative analysis displaying generic features of the Lambda and (U) over bar polarization for specific scenarios. Different kinematical situations are considered, corresponding to experiments currently able to study Lambda production in semi-inclusive DIS.

TMDs : Evolution, modeling, precision

In this paper we briefly review the transverse momentum dependent generalized parton model and its application to the study of azimuthal asymmetries in the distribution of leading hadrons (mainly pions) inside large transverse momentum jets inclusively produced in polarized proton-proton collisions. We put particular emphasis on the phenomenological interest of these observables, in combination with similar asymmetries measured in semi-inclusive deeply inelastic scattering, Drell-Yan processes and e + e − collisions, for the study of the universality properties of the transverse momentum dependent parton distribution and fragmentation functions. We present results for RHIC kinematics at center-of-mass energies √s = 200 and 500 GeV, for central and mainly forward jet rapidities, in particular for the Sivers distribution and the Collins fragmentation function, that are believed to be responsible for many of the largest asymmetries measured in the last years. We also briefly discuss the case of inclusive jet production and recent phenomenological applications of other theoretical approaches, like the colour gauge invariant generalized parton model and the collinear twist-three approach, aiming at clarifying the issues of the universality and process dependence of transverse momentum dependent functions.

Collins and sivers effects in p up arrow p -> jet pi X: Universality and process dependence

A formalism proposed to study transverse Λ polarization in unpolarized hadronic processes, based on a generalized pQCD factorization theorem, is extended to semi-inclusive DIS. Analytical expressions and examples of numerical estimates are given.

Azimuthal asymmetries in

Mariaelena Boglione∗ab, Mauro Anselminoab, Umberto D’Alesiocd , J.O. Gonzalez Hernandezab, Stefano Melisa, Francesco Murgiad and Alexei Prokudine a Dipartimento di Fisica, via Pietro Giuria 1, I-10125, Torino, Italy b INFN, Sezione di Torino, via Pietro Giuria 1, I-10125,Torino, Italy c Dipartimento di Fisica, Università di Cagliari, I-09042 Monserrato (CA), Italy dINFN, Sezione di Cagliari, C.P. 170, I-09042 Monserrato (CA), Italy e Division of Science, Penn State Berks, Reading, PA 19610, USA

p^\uparrow p \to {\rm jet}\, \pi\, X

We present a global fit of current available data for Drell-Yan and Z-boson production using the Transverse Momentum Dependent evolution formalism of Refs. [1–4]. We performed our analysis including perturbative calculable contributions up to next-to-next-to-leading-logarithmic accuracy. We took into account non-perturbative corrections both to the intrinsic nucleon structure and to the evolution kernel.