8 research outputs found
Resummation of threshold logarithms in deeply-virtual Compton scattering
I derive an all-order resummation formula for the logarithmically enhanced
contributions proportional to in the coefficient function of deeply-virtual-Compton scattering
and the pion-photon transition form factor in momentum space. The resummation
is performed at the next-to-next-to-leading logarithmic accuracy. The key
observation is that the non-singlet coefficient function itself factorizes in
the limit, which allows for a resummation using
renormalization group equations
Two-loop coefficient functions in deeply virtual Compton scattering: flavor-singlet axial-vector and transversity case
We calculate the two-loop flavor-singlet axial-vector and gluon transversity
coefficient functions for deeply virtual Compton scattering in QCD. We observe
interesting properties regarding the transcendentality of the transversity
coefficient function. Our results complete the calculation of the full
next-to-next-to-leading order coefficient function in deeply virtual Compton
scattering. Numerically, the two-loop corrections in the axial-vector and
transversity channel are comparable to their vector counterpart at moderate
skewness parameter {\xi} and hence indispensable for analyzing the upcoming
high-precision data from the Electron-Ion Collider.Comment: 22 pages, 6 figures, 1 ancillary file "axial_and_transversity_CF.m'
Deeply-virtual Compton scattering at the next-to-next-to-leading order
Deeply-virtual Compton scattering gives access to the generalized parton
distributions that encode the information on the transverse position of quarks
and gluons in the proton in dependence in their longitudinal momentum. In
anticipation of the high-precision experimental data in a broad kinematic range
from the Electron-Ion Collider, we have calculated the two-loop,
next-to-next-to-leading (NNLO) DVCS coefficient functions associated with the
dominant Compton form factors and at large energies.
The NNLO correction to the imaginary part of appears to be rather
large, up to factor two at the input scale GeV for simple GPD
models, due to a cancellation between quark and gluon contributions.Comment: 9 pages, 3 figure
Breakdown of collinear factorization in the exclusive photoproduction of a pair with large invariant mass
We study the exclusive photoproduction of a pair with
large invariant mass , which is sensitive to the exchange
of either two quarks or two gluons in the -channel. In this letter, we
show that the process involving two-gluon exchanges does not factorize in the
Bjorken limit at the leading twist. This can be explicitly demonstrated by the
fact that there exist diagrams, which contribute at the leading twist, for
which Glauber gluons remain trapped, due to the pinching of the contour
integrations of both the plus and minus component of the Glauber gluon
momentum. For the same reason, -nucleon scattering to two photons also
suffers from the same issue. On the other hand, we stress that there are no
issues with respect to collinear factorization for the quark channels. By
considering an analysis of all potential reduced diagrams of leading pinch
surfaces, we argue that the quark channel is safe from Glauber pinches, and
therefore, a collinear factorization in that case follows through without any
problems. This means that processes where gluon exchanges are forbidden, such
as the exclusive photoproduction of and , are unaffected by the factorization breaking effects we point out in
this letter.Comment: 11 pages, 4 figure
Deeply Virtual Compton Scattering at Next-to-Next-to-Leading Order
Deeply virtual Compton scattering gives access to the generalized parton distributions that encode the information on the transverse position of quarks and gluons in the proton with dependence on their longitudinal momentum. In anticipation of the high-precision experimental data in a broad kinematic range from the Electron-Ion Collider, we have calculated the two-loop, next-to-next-to-leading order (NNLO) deeply virtual Compton scattering coefficient functions associated with the dominant Compton form factors H and E at large energies. The NNLO correction to the imaginary part of H appears to be rather large, up to factor 2 at the input scale Q2=4 GeV2 for simple generalized parton distribution models, due to a cancellation between quark and gluon contribution
Breakdown of collinear factorization in the exclusive photoproduction of a pair with large invariant mass
International audienceWe study the exclusive photoproduction of a pair with large invariant mass , which is sensitive to the exchange of either two quarks or two gluons in the -channel. In this letter, we show that the process involving two-gluon exchanges does not factorize in the Bjorken limit at the leading twist. This can be explicitly demonstrated by the fact that there exist diagrams, which contribute at the leading twist, for which Glauber gluons remain trapped, due to the pinching of the contour integrations of both the plus and minus component of the Glauber gluon momentum. For the same reason, -nucleon scattering to two photons also suffers from the same issue. On the other hand, we stress that there are no issues with respect to collinear factorization for the quark channels. By considering an analysis of all potential reduced diagrams of leading pinch surfaces, we argue that the quark channel is safe from Glauber pinches, and therefore, a collinear factorization in that case follows through without any problems. This means that processes where gluon exchanges are forbidden, such as the exclusive photoproduction of and , are unaffected by the factorization breaking effects we point out in this letter