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arXiv · 1709.07827

Positivity bounds on gluon TMDs for hadrons of spin $\le$ 1

Sabrina Cotogno·Tom van Daal·Piet J. Mulders
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Abstract

We consider the transverse momentum dependent gluon distribution functions (called gluon TMDs) by studying the light-front gluon-gluon correlator, extending the results for unpolarized and vector polarized targets to also include tensor polarized targets -- the latter type of polarization is relevant for targets of spin $\ge1$. The light-front correlator includes process-dependent gauge links to guarantee color gauge invariance. As from the experimental side the gluon TMDs are largely unknown, we present positivity bounds for combinations of leading-twist gluon distributions that may be used to estimate their maximal contribution to observables. Since the gluonic content of hadrons is particularly relevant in the small-$x$ kinematic region, we also study these bounds in the small-$x$ limit for the dipole-type gauge link structure using matrix elements of a single Wilson loop.

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Sabrina Cotogno, Tom van Daal, Piet J. Mulders. 2017-09-22. Positivity bounds on gluon TMDs for hadrons of spin $\le$ 1. https://doi.org/10.1007/jhep11(2017)185

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