272 research outputs found
Helicity amplitudes for high-energy scattering
We present a prescription to calculate manifestly gauge invariant tree-level
helicity amplitudes for arbitrary scattering processes with off-shell
initial-state gluons within the kinematics of high-energy scattering. We show
that it is equivalent to Lipatov's effective action approach, and show its
computational potential through numerical calculations for scattering processes
with several particles in the final state.Comment: 27 pages, reference adde
Transverse momentum dependent splitting functions at work: quark-to-gluon splitting
Using the recently obtained Pgq splitting function we extend the low x
evolution equation for gluons to account for contributions originating from
quark-to-gluon splitting. In order to write down a consistent equation we resum
virtual corrections coming from the gluon channel and demonstrate that this
implies a suitable regularization of the Pgq singularity, corresponding to a
soft emitted quark. We also note that the obtained equation is in a
straightforward manner generalized to a nonlinear evolution equation which
takes into account effects due to the presence of high gluon densities.Comment: 13 pages, 3 figures, published versio
Scattering amplitudes with off-shell quarks
We present a prescription to calculate manifestly gauge invariant tree-level
scattering amplitudes for arbitrary scattering processes with off-shell
initial-state quarks within the kinematics of high-energy scattering.Comment: 17 pages, references added, calculation included to indicate
equivalence with effective action approac
TMD splitting functions in kT factorization: the real contribution to the gluon-to-gluon splitting
We calculate the transverse momentum dependent gluon-to-gluon splitting
function within -factorization, generalizing the framework employed in the
calculation of the quark splitting functions in [1-3] and demonstrate at the
same time the consistency of the extended formalism with previous results.
While existing versions of factorized evolution equations contain already
a gluon-to-gluon splitting function i.e. the leading order
Balitsky-Fadin-Kuraev-Lipatov (BFKL) kernel or the
Ciafaloni-Catani-Fiore-Marchesini (CCFM) kernel, the obtained splitting
function has the important property that it reduces both to the leading order
BFKL kernel in the high energy limit, to the
Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) gluon-to-gluon splitting
function in the collinear limit as well as to the CCFM kernel in the soft
limit. At the same time we demonstrate that this splitting kernel can be
obtained from a direct calculation of the QCD Feynman diagrams, based on a
combined implementation of the Curci-Furmanski-Petronzio formalism for the
calculation of the collinear splitting functions and the framework of high
energy factorization.Comment: 29 pages, 5 figures, published versio
Parton shower contributions to jets from high rapidities at the LHC
We discuss current issues associated with the dependence of jet distributions
at the LHC on the behavior of QCD parton showers for high rapidities.Comment: Contribution at DIS2012, Univ. of Bonn, March 201
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