Speaker
Guillaume Beuf
(ECT* Trento)
Description
Deep Inelastic Scattering (DIS) is the cleanest tool available
to probe the content of a fast proton or nucleus. In the regime
of low Bjorken x, one enters in the nonlinear regime of gluon
saturation, where the gluons are better described as a strong
coherent semi-classical field than as a collection of quasi
on-shell partons. Hence, that regime lies outside the validity
range of the collinear factorization, and is better described
within the dipole factorization of DIS observables which allows
to resum coherent multiple scattering on the target, and also
to resum the high-energy leading logarithms (LL).
One of the motivations to study in detail the regime of gluon
saturation in proton and nuclei is that it drives the physics
of the earliest stages of heavy collisions, up to the formation
of the Quark-Gluon Plasma.
So far, phenomenological studies have been performed successfully
at LO in the dipole factorization, with LL resummation,
using HERA data for proton DIS. However, in order to reach
precision, NLO corrections should be included, as well as
high-energy NLL resummations. This is important not only to extract
as much knowledge as possible out of the HERA data, but also in
prevision of future electron-proton and/or electron-nucleus colliders.
In this talk, I will present an update on the calculation of the
(fixed order) NLO corrections to DIS structure functions on a dense
target in the dipole factorization picture. In earlier studies, only
one part of the NLO corrections has been calculated, the one
corresponding to a quark-antiquark-gluon Fock state interacting with
the target. By contrast, I will present the first direct calculation of
the other part of NLO corrections, for which a quark-antiquark Fock
state interacts with the target. I will also discuss issues related
with the combination of the two pieces, which is complicated by the
presence of UV divergences. Along the way, various techniques have been
developped, which will simplify the calculation of NLO corrections
to most other observables relevant for gluon saturation.
Primary author
Guillaume Beuf
(ECT* Trento)
