147 research outputs found
Generalized parton distributions from neutrino experiments
The analysis of deeply virtual meson production is extended to
neutrino-production of the pseudo-Goldstone mesons (pions, kaons, eta-mesons)
on nucleons, with the flavor content of the recoil baryon either preserved, or
changed to a hyperon from the same SU(3) octet. We rely on the SU(3) relations
and express all the cross-sections in terms of the proton generalized parton
distributions (GPDs). The corresponding amplitudes are calculated at the
leading twist level and in the leading order in \alpha_{s}, using a
phenomenological parametrization of GPDs. We also included in the analysis the
electromagnetic O(alpha_{em})-corrections to neutrino-induced deeply virtual
meson production (\nuDVMP). We found that such electromagnetic corrections
decrease with Q^2 in the Bjorken regime less than the standard \nuDVMP handbag
contribution, so the electromagnetic mechanism dominates at large Q^2. The
electromagnetic corrections give rise to an angular correlation between the
lepton and hadron scattering planes with harmonics sensitive to the real and
imaginary parts of the DVMP amplitude. These corrections constitute a few
percent effect in the kinematics of the forthcoming MINERvA experiment at
Fermilab and should be taken into account in precise tests of GPD
parametrizations. For virtualities Q^2~100 GeV^2 these corrections become on a
par with \nuDVMP handbag contributions.Comment: 5 pages, 3 figures, to appear in the proceedings of the DIS 2013
Workshop, Marseille, France, 22-26 April 201
Leading twist nuclear shadowing, nuclear generalized parton distributions and nuclear DVCS at small x
We generalize the leading twist theory of nuclear shadowing and calculate
quark and gluon generalized parton distributions (GPDs) of spinless nuclei. We
predict very large nuclear shadowing for nuclear GPDs. In the limit of the
purely transverse momentum transfer, our nuclear GPDs become
impact-parameter-dependent nuclear parton distributions (PDFs). Nuclear
shadowing induces nontrivial correlations between the impact parameter b and
the light-cone fraction x. We make predictions for the deeply virtual Compton
scattering (DVCS) amplitude and the DVCS cross section on Pb-208 at high
energies. We calculate the cross section of the Bethe-Heitler (BH) process and
address the issue of the extraction of the DVCS signal from the e A \to e
\gamma A cross section. We find that the e A \to e \gamma A differential cross
section is dominated by DVCS at the momentum transfer t near the minima of the
nuclear form factor. We also find that nuclear shadowing leads to dramatic
oscillations of the DVCS beam-spin asymmetry, A_{LU}, as a function of t. The
position of the points where A_{LU} changes sign is directly related to the
magnitude of nuclear shadowing.Comment: 37 pages, 12 figures. Matches the published version, Phys. Rev. 79,
035210 (2009
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