Dihadron interference fragmentation functions in proton-proton collisions

Abstract

We study the production of hadron pairs in proton-proton collisions, selecting pairs with large total transverse momentum with respect to the beam, and small relative transverse momentum, i.e., belonging to a single jet with large transverse momentum. We describe the process in terms of dihadron fragmentation functions. We consider the production of one pair in polarized collisions (with one transversely polarized proton) and the production of two pairs in unpolarized collisions. In the first case, we discuss how to observe the quark transversity distribution in connection with a specific class of dihadron fragmentation functions, named interference fragmentation functions. In the second case, we suggest how to determine the latter and also how to observe linearly polarized gluons.

Di-hadron production at Jefferson Laboratory

“…The structure functions can be written in terms of PDFs and Di-hadron Fragmentation Functions (DiFF) in the following way [20] …”

“…In fact, the measurement of single-spin asymmetries with longitudinally polarized targets or beams is sensitive, in particular, to the twist-3 chiral-odd distribution functions e and h L , in combination with the chiral-odd interference fragmentation function H 1 [20], making di-hadron production a unique tool to study the higher twist effects appearing as sin φ modulations in target or beam spin dependent azimuthal moments of the SIDIS cross section.…”

Studies of the nucleon structure in back-to-back SIDIS

“…Much higher Q 2 range accessible at JLab12 with CLAS12 and EIC would allow for studies of Q 2 -dependence of different higher twist spin-azimuthal asymmetries, which, apart from providing important information on quark-gluon correlations are needed for understanding of possible corrections from higher twists to leading twist observables. An important process which can provide independent information on twist-3 TMDs is the di-hadron production in SIDIS described by interference functions [37][38][39][40][41][42][43]. In fact, the measurement of SSAs with longitudinally polarized target or beam is sensitive in particular to the twist-3 chiral-odd distribution functions e and h L , in combination with the chiral-odd interference fragmentation function H < ) 1 [41].…”

“…An important process which can provide independent information on twist-3 TMDs is the di-hadron production in SIDIS described by interference functions [37][38][39][40][41][42][43]. In fact, the measurement of SSAs with longitudinally polarized target or beam is sensitive in particular to the twist-3 chiral-odd distribution functions e and h L , in combination with the chiral-odd interference fragmentation function H < ) 1 [41]. This effect survives after integration over quark transverse momenta and can be analyzed in the framework of collinear factorization.…”

Dihadron fragmentation functions from the NJL-jet model and their QCD evolution

“…Transversity distributions are one of the three leading-twist distribution functions that do not vanish when integrated over the transverse momentum. They describe the quark structure of the nucleon (the other two being unpolarized and helicity quark distribution functions) and these functions enter into asymmetries with chiral-odd versions of a special type of DFF known as interference fragmentation functions [78][79][80][81][82]. Interference fragmentation functions are DFFs with a dependence on the polarization of the fragmenting quark.…”