Gluonic pole cross sections and single spin asymmetries in hadron-hadron scattering

Abstract

The gauge-links connecting the parton field operators in the hadronic matrix elements appearing in the transverse momentum dependent distribution functions give rise to T -odd effects. Due to the process-dependence of the gauge-links the T -odd distribution functions appear with different prefactors. A consequence is that in the description of single spin asymmetries the parton distribution and fragmentation functions are convoluted with gluonic pole cross sections rather than the basic partonic cross sections. In this paper we calculate the gluonic pole cross sections encountered in single spin asymmetries in hadron-hadron scattering. The case of back-to-back pion production in polarized proton-proton scattering is worked out explicitly. It is shown how T -odd gluon distribution functions originating from gluonic pole matrix elements appear in twofold.

Dijet imbalance in hadronic collisions

“…Agreement is found between the results given in the present subsection and the explicit expressions of the partonic cross sections published, for example, in [51][52][53][54][55]. However, with respect to Ref.…”

Azimuthal and single spin asymmetries in hard scattering processes

“…Summarizing, the main findings are: i) by expanding the gauge link in the correlators entering the colour gauge invariant approach [154,156] at first order in the coupling constant one recovers the results of Refs. [158,159]; ii) by extending, and properly adapting, the calculations of Refs.…”

Model independent analysis of gluonic pole matrix elements and universality of transverse-momentum-dependent fragmentation functions

“…originate from the difference Φ [U+] (x, p T ) − Φ [U−] (x, p T ) of correlators with different gauge links and as a consequence will be convoluted with non-standard gluonic pole cross sections [13,14,35]. Our result also implies universality for the TMD fragmentation functions of gluons [36]; including for instance the T-even TMD fragmentation functions H ⊥(g)…”

“…They explain the appearance of single spin asymmetries (SSA) in high-energy scattering processes. These correlation functions show up in combination with calculable hard parts that may differ from the partonic cross sections through specific calculable factors and signs [9,13,14]. In this paper we use general properties of scattering amplitudes in Quantum Chromodynamics (QCD) to study the support properties of these parton correlation functions.…”