Studying the information content of TMDs using Monte Carlo generators

Abstract

Theoretical advances in studies of the nucleon structure have been spurred by recent measurements of spin and/or azimuthal asymmetries worldwide. One of the main challenges still remaining is the extraction of the parton distribution functions, generalized to describe transverse momentum and spatial distributions of partons from these observables with no or minimal model dependence. In this topical review we present the latest developments in the field with emphasis on requirements for Monte-Carlo event generators, indispensable for studies of the complex 3D nucleon structure, and discuss examples of possible applications.

Semi-inclusive deep-inelastic scattering in Wandzura-Wilczek-type approximation

“…To the best of our knowledge, it is the first complete study of all SIDIS structure functions up to twist-3 using systematically a common theoretical guideline. The results are useful for experiments prepared in the near term (JLab 12) or proposed in the long term (Electron-Ion Collider), and provide helpful input for Monte Carlo event generators [33]. Our predictions will help to pave the way towards a better understanding of the quark-gluon structure of the nucleon beyond leading twist.…”

“…The present work is the first study of all SIDIS structure functions up to twist-3 evaluated within one common systematic theoretical guideline. Our results are of importance for measurements performed or in preparation at COMPASS, HERMES, and JLab with 12 GeV beam-energy upgrade, or proposed in the long-term (Electron-Ion Collider), and provide helpful input for the development of Monte Carlo event generators [33].…”

Spin Orbit Correlations and the Structure of the Nucleon

“…The main goal of the Extraction and VAlidation framework (EVA) is to assist extraction of 3D PDFs, by testing different extraction procedures and estimating systematics related to different assumptions and models used in the extraction procedure [257]. The input of the extraction and validation framework will include also multiplicities and asymmetries, but the preferred input will be the table with Elementary Bin Counts (EBC).…”

Semi-inclusive π0 target and beam-target asymmetries from 6 GeV electron scattering with CLAS

“…momentum is correlated with spin orientation. Extraction of the underlying quark transverse momentum k T of the helicity distributions, however, will require an established framework for TMD extraction from a combination of measurements with unpolarized and polarized targets [44]. Studies of the Collins fragmentation functions at the e + e − machines, BELLE, [28,46,47], BABAR [48,29], and BESIII [30], indicate that the π ± Collins fragmentation functions H ⊥ 1 are large and have opposite signs for the favored and unfavored cases.…”

“…momentum is correlated with spin orientation. Extraction of the underlying quark transverse momentum k T of the helicity distributions, however, will require an established framework for TMD extraction from a combination of measurements with unpolarized and polarized targets [44].…”