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.
Highlights
JHEP10(2018)008 own transverse momentum in the quark fragmentation process and is a chiral-even function
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 dihadron fragmentation functions (DiFF), when the results are analyzed together with the inclusive measurements of dihadron pairs, such as those recently performed by the BELLE collaboration
In SIDIS with a final state hyperon detected, it couples to the well-determined unpolarized PDF, while in e+e− annihilation with back-to-back hyperon and unpolarized hadron production, it couples to the corresponding unpolarized fragmentation functions (FF)
Summary
We detail the derivation of the leading twist cross section for the process e+e− → h1h2 + Λ + X, where the electron and positron with momenta l and l annihilate into an intermediate virtual photon with momentum q = l + l. We detect a hadron Λ with momentum PΛ, produced back-to-back to the unpolarized hadron pair h1, h2 of momenta P1 and P2, as illustrated in figure 1. Λ denotes either an unpolarized hadron ( for example π, K, etc ) hadron, or a spin 1/2 baryon withe a polarization vector SΛ. We restrict our consideration to the case where the center-of-mass energy of the electron-positron pair is far below the mass of the Z boson. In the subsection we first describe the kinematics of the process and detail the calculation of the cross section in the following subsection
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