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Color charge correlations in the proton at NLO: beyond geometry based intuition

by Risto Sakari Paatelainen (Helsinki Institute of Physics (FI))

Zoom (CERN)




Color charge correlators provide fundamental information about the proton structure. In this
Letter, we evaluate numerically two-point color charge correlations in a proton on the light cone
including the next-to-leading order corrections due to emission or exchange of a perturbative gluon.
Our results show that the correlator exhibits startlingly non-trivial behavior at large momentum
transfer or central impact parameters, and that the color charge correlation depends not only on
the impact parameter but also on the relative transverse momentum of the two gluon probes and
their relative angle. Furthermore, from the two-point color charge correlator, we compute the dipole
scattering amplitude. Its azimuthal dependence differs significantly from a impact parameter dependent McLerran-Venugopalan model based on geometry. Our results also provide initial conditions
for Balitsky-Kovchegov evolution of the dipole scattering amplitude. These initial conditions depend
not only on the impact parameter and dipole size vectors, but also on their relative angle and on
the light-cone momentum fraction x in the target.

Ref.: Adrian Dumitru, Heikki Mäntysaari, Risto Paatelainen, 2103.11682

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