Semi-inclusive back-to-back production of a hadron pair and a single hadron in e+e− annihilation

Abstract

Inclusive hadron production in e + e − annihilation has long been used to study both single hadron fragmentation functions (FF) and dihadron fragmentation functions (DiFF). In particular, the polarized DiFFs can be accessed in electron-positron annihilation by measuring azimuthal correlations between two back-to-back pairs of hadrons in the center of mass system, where the relevant structure functions can be expressed as convolutions of two (polarized) DiFFs. Here we explore the advantages of measuring the inclusive back-to-back production of a single hadron on one side against a hadron pair on the opposite side of the detector in two jet events. The leading twist cross section for this process contains convolutions of the corresponding single hadron FFs on one side and the DiFFs for the hadron pair on the other side, which furnishes several interesting new opportunities. A measurement of the unpolarized cross section with a number of different types of observed hadrons will help in untangling the quark flavor dependence of the unpolarized DiFFs, when the results are analyzed together with the inclusive measurements of dihadron pairs, such as those recently performed by the BELLE collaboration. Even more interesting, with a polarized hyperon on one side we can study the quark spin-dependent DiFFs of an unpolarized hadron pair on the other side. This, in turn, will allow us to test the universality of the spin-dependent DiFFs entering the cross sections of electron-positron annihilation and semi-inclusive deep inelastic scattering processes.

Observation of Transverse Λ/Λ¯ Hyperon Polarization in e+e−Guan1, Vossen2, Adachi3 et al. 2019Phys. Rev. Lett.522660View full textAdd to dashboardCite

“…It depends on the fractional energy z of the fragmenting quark carried by the observed hyperon and the transverse momentum of the hyperon p ⊥ relative to the parent quark. Beyond its connection to the phenomenology of Λ production, D ⊥Λ=q 1T has recently been a focus of intense theoretical interest [7][8][9][10][11][12] because it is time-reversal odd (T odd). It is known that the gauge structure of QCD universality is modified for the Sivers function, which can be seen as the counterpart of D ⊥Λ=q 1T for the parton distribution function [13][14][15][16][17].…”

Working Group 6 Summary: Spin and 3D Structure

“…Further interesting measurements related to study of FFs and dihadron FFs via extraction of various weighted asymmetries at Belle, CLAS12 and future EIC have been suggested during the conference [8,9].…”

“…M. Radici reported on updates of extractions of the proton tensor charge obtained from Mellin moments of the transversity distribution, which is important for high precision beyond-the-standard -model searches, and interesting tension with recent lattice calculations [22,47,48] was described. Dihadron fragmentation functions (DiFFs), a type of collinear fragmentation function involving pairs of hadrons, have certain advantages such as allowing transversity to be probed in semiinclusive measurements of deep-inelastic lepton-nucleon scattering (SIDIS) without the need for TMD functions, and some new applications of DiFFs were discussed [8,9].…”

New way to access the quark fragmentation functions in electron-positron annihilation

“…Recently we proposed a new measurement in e + e − annihilation [7], exploiting the production of a single inclusive hadron (generically noted as Λ) back-to-back to a hadron pair, where the relevant cross section should involve convolutions of FFs for the single hadron in one jet and the DiFFs for the hadron pair produced in the opposite jet. The purpose of such a measurement is two-fold, and will leverage our knowledge of the single hadron FFs.…”

“…2. Some of the results for weighted asymmetries from [7] are: 1. The weighted asymmetry induced by the Collins effect for unpolarized hadron Λ:…”