The Drell-Yan process with pions and polarized nucleons

Abstract

The Drell-Yan process provides important information on the internal struc- ture of hadrons including transverse momentum dependent parton distribution functions (TMDs). In this work we present calculations for all leading twist structure functions de- scribing the pion induced Drell-Yan process. The non-perturbative input for the TMDs is taken from the light-front constituent quark model, the spectator model, and available parametrizations of TMDs extracted from the experimental data. TMD evolution is im- plemented at Next-to-Leading Logarithmic precision for the first time for all asymmetries. Our results are compatible with the first experimental information, help to interpret the data from ongoing experiments, and will allow one to quantitatively assess the models in future when more precise data will become available.

Polarized gluon distribution in the proton from holographic light-front QCD

“…The single transversely polarized Drell-Yan process provides another way to obtain the Boer-Mulders function. In this process the sin(2ϕ − ϕ s ) asymmetry (with ϕ s , the azimuthal angle of target transverse spin) can be obtained through the convolution of the Boer-Mulders function h ⊥ 1 (x, k 2 ) and the transversity distribution h 1 (x, k 2 ) [45,46]. Recently, the sin(2ϕ − ϕ s ) asymmetry has been measured for the first time by the COMPASS experiment [47], which has used a pion beam to collide with a transversely polarized nucleon target.…”

“…The perturbative Sudakov form factor is perturbatively calculable, while the nonperturbative Sudakov form factor is usually obtained by phenomenological extraction from experimental data. Here, we probe the scale evolution of the pion Boer-Mulders function as well as the proton transversity to estimate the sin(2ϕ−ϕ S ) asymmetry at the COMPASS kinematics and compare our prediction with the latest COMPASS data [47] and the other theoretical predictions [46].…”

Combining nonperturbative transverse momentum dependence with TMD evolution

“…And, of course, there is no sharp distinction between what constitutes a Type I or a type II scenario. It is possible to merge treatments of hadron structure with the evolution formulas that were traditionally applied at much larger Q [3,[21][22][23][24], and indeed much activity over the past decade was devoted to implementing TMD evolution, in the context of hadron structure studies, in ways that include nonperturbative parts [25][26][27][28][29][30][31][32][33][34][35][36][37]. (The versions of TMD factorization and evolution that we will focus on in this paper are those rooted in, or very similar to, the CSS formalism as described in Ref.…”

“…In many models, the large transverse momentum tails are suppressed on the grounds that it is only the small transverse momentum dependence that is nonperturbative or intrinsic to the hadron structure. Examples include at least spectator models [40][41][42][43], light-cone wave function descriptions [44][45][46][47][48], bag models [49][50][51][52][53], the Nambu-Jones Lasinio model [54][55][56], calculations based on the Dyson-Schwinger equations [57], classic quark-hadron model approaches and many others [36,58,59]. As will become clear, it is easier to incorporate models like these into full evolution treatments when starting from a bottomup approach.…”

On the physics potential to study the gluon content of proton and deuteron at NICA SPD

“…The most powerful tools to study quark TMD PDFs are the measurements of the nucleon spin (in)dependent azimuthal asymmetries in SIDIS [1,4,5,7] and Drell-Yan processes [8,9]. Complementary information on TMD fragmentation process, necessary for the interpretation of SIDIS data, is obtained from e + e − measurements [10].…”