Abstract
We investigate the Collins azimuthal asymmetry of hadrons produced inside jets in transversely polarized proton–proton collisions. Recently, the quark transversity distributions and the Collins fragmentation functions have been extracted within global analyses from data of the processes semi-inclusive deep inelastic scattering and electron–positron annihilation. We calculate the Collins azimuthal asymmetry for charged pions inside jets using these extractions for RHIC kinematics at center-of-mass energies of 200 and 500 GeV. We compare our results with recent data from the STAR Collaboration at RHIC and find good agreement, which confirms the universality of the Collins fragmentation functions. In addition, we further explore the impact of transverse momentum dependent evolution effects.
Highlights
The transverse momentum dependent parton distribution functions and fragmentation functions have recently received an increased interest from both the experimental and theoretical communities [1,2,3]
The quark transversity distributions and the Collins fragmentation functions have been extracted within a global analysis in the parton model framework in Ref. [18], i.e. without Transverse momentum dependent distributions (TMDs) evolution
We investigated the Collins azimuthal asymmetry for hadron production inside jets in transversely polarized p↑ p collisions
Summary
The transverse momentum dependent parton distribution functions and fragmentation functions have recently received an increased interest from both the experimental and theoretical communities [1,2,3]. The transverse spin of the fragmenting quark correlates with the transverse momentum of the hadron with respect to the jet axis, which leads to a nontrivial Collins asymmetry of the azimuthal angular distribution of hadrons inside (quark) jets [19,20]. It is possible to predict the Collins azimuthal asymmetries for hadron production inside jets at RHIC by using the quark transversity distributions and Collins fragmentation functions determined from SIDIS and electron–positron annihilation. The evolution effects have been implemented in a global analysis of the Collins azimuthal asymmetries in SIDIS and electron–positron annihilation [17] It has been demonstrated in [22] that the same TMD evolution applies to the relevant TMD fragmentation functions encountered in the transverse momentum distribution of hadrons inside jets.
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