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Title: Experimental results on TMDs

Abstract

QCD factorisation for semi-inclusive deep inelastic scattering at low transverse momentum in the current-fragmentation region has been established recently, providing a rigorous basis to study the Transverse Momentum Dependent distribution and fragmentation functions (TMDs) of partons from Semi-Inclusive DIS data using different spin-dependent and spin-independent observables. The main focus of the experiments were the measurements of various single- and double-spin asymmetries in hadron electro-production (ep{up-arrow} --> ehX ) with unpolarised, longitudinally and transversely polarised targets. The joint use of a longitudinally polarised beam and longitudinally and transversely polarised targets allowed to measure double-spin asymmetries (DSA) related to leading-twist distribution functions describing the transverse momentum distribution of longitudinally and transversely polarised quarks in a longitudinally and transversely polarised nucleons (helicity and worm-gear TMDs). Furthermore, the single-spin asymmetries (SSA) measured with transversely polarised targets, provided access to specific leading-twist parton distribution functions: the transversity, the Sivers function and the so-called 'pretzelosity' function. In this review we present the current status and some future measurements of TMDs worldwide.

Authors:
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1264169
Report Number(s):
JLAB-PHY-16-2225; DOE/OR/23177-3862
Journal ID: ISSN 1434-6001; PII: 518
Grant/Contract Number:
AC05-06OR23177
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
European Physical Journal. A
Additional Journal Information:
Journal Volume: 52; Journal Issue: 6; Journal ID: ISSN 1434-6001
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

None, None. Experimental results on TMDs. United States: N. p., 2016. Web. doi:10.1140/epja/i2016-16150-x.
None, None. Experimental results on TMDs. United States. doi:10.1140/epja/i2016-16150-x.
None, None. Mon . "Experimental results on TMDs". United States. doi:10.1140/epja/i2016-16150-x. https://www.osti.gov/servlets/purl/1264169.
@article{osti_1264169,
title = {Experimental results on TMDs},
author = {None, None},
abstractNote = {QCD factorisation for semi-inclusive deep inelastic scattering at low transverse momentum in the current-fragmentation region has been established recently, providing a rigorous basis to study the Transverse Momentum Dependent distribution and fragmentation functions (TMDs) of partons from Semi-Inclusive DIS data using different spin-dependent and spin-independent observables. The main focus of the experiments were the measurements of various single- and double-spin asymmetries in hadron electro-production (ep{up-arrow} --> ehX ) with unpolarised, longitudinally and transversely polarised targets. The joint use of a longitudinally polarised beam and longitudinally and transversely polarised targets allowed to measure double-spin asymmetries (DSA) related to leading-twist distribution functions describing the transverse momentum distribution of longitudinally and transversely polarised quarks in a longitudinally and transversely polarised nucleons (helicity and worm-gear TMDs). Furthermore, the single-spin asymmetries (SSA) measured with transversely polarised targets, provided access to specific leading-twist parton distribution functions: the transversity, the Sivers function and the so-called 'pretzelosity' function. In this review we present the current status and some future measurements of TMDs worldwide.},
doi = {10.1140/epja/i2016-16150-x},
journal = {European Physical Journal. A},
number = 6,
volume = 52,
place = {United States},
year = {Mon Jun 13 00:00:00 EDT 2016},
month = {Mon Jun 13 00:00:00 EDT 2016}
}

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  • Transverse momentum dependent parton distribution functions are a key ingredient in the description of spin and azimuthal asymmetries in deep-inelastic scattering processes. Recent results from non-perturbative calculations in effective approaches are reviewed, with focus on relations among different parton distribution functions in QCD and models.
  • 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.
  • Over the past decades, the colinear parton model has been very successful in describing the structure of nucleons. However, in the past years it became evident, that to fully describe the structure of the nucleon this picture has to be extended taking into account the transverse momentum of the partons. This gives rise to a new set of distribution and fragmentation functions entering the cross sections, namely the transverse momentum dependent (TMD) functions.The measurement of these functions in semi-inclusive deep inelastic scattering (SIDIS) in the framework of the COMPASS and HERMES experiments is presented in this contribution.
  • The main properties of the leading-twist transverse momentum dependent parton distributions in a light-cone constituent quark model of the nucleon are reviewed, with focus on the role of the spin-spin and spin-orbit correlations of quarks. Results for azimuthal single spin asymmetries in semi-inclusive deep inelastic scattering are also discussed.
  • We present a comprehensive formalism for dilepton production from the collision of two polarized spin-(1/2) hadronsby identifying the general angular distribution of the cross section in combination with a complete set of structure functions. The various structure functions are computed in the parton model approximation where we mainly consider the case when the transverse momentum of the dilepton pair is much smaller than its invariant mass. In this kinematical region dilepton production can be described in terms of transverse momentum dependent parton distributions.