Eur. Phys. J. A (2016) 52: 152
https://doi.org/10.1140/epja/i2016-16152-8

Review

Transverse-momentum-dependent fragmentation functions in e⁺e^- annihilation

¹ INFN Sezione di Ferrara, I-44122, Ferrara, Italy
² University of Illinois at Urbana-Champaign, Urbana-Champaign, IL, USA

^* e-mail: garzia@fe.infn.it

Received: 31 July 2015
Accepted: 8 September 2015
Published online: 16 June 2016

Abstract

Fragmentation functions are non-perturbative functions used to describe the formation of colorless, observable hadrons starting from a colored, partonic initial state. The knowledge of these functions are based on the experimental data, and a good parameterization of the fragmentation processes can shed light on the confining aspect of QCD, and are also a key ingredient in accessing nucleon parton distribution functions in semi-inclusive deep inelastic scattering and proton-proton collisions. In the last decade, a strong interest has risen about the transverse-momentum-dependent (TMD) fragmentation functions, which can be used as tools to probe the 3D-structure of nucleons, and to investigate the Q² evolution of TMD objects. In this review we will summarize the existing light-quarks fragmentation related measurements from the BaBar, Belle, and BESIII e ⁺ e ^- experiments; in particular, we will focus on the polarized TMD Collins fragmentation functions, emerging from correlations between the transverse polarization of the fragmenting parton and the direction of the resulting hadrons.