432 research outputs found
Order-by-order Analytic Solution to the BFKL Equation
We propose a regularization of the BFKL equation which allows for its
solution in each order of perturbation theory by means of a sum over multiple
poles. This sum can be presented in a rather simple formula for the Fourier
transform in the azimuthal angle of the gluon Green function. In order to test
our method, we have compared a few orders in the expansion to previous results
by Del Duca, Dixon, Duhr and Pennington, finding agreement. Our formalism is
general and can be applied to other, more complicated, kernels.Comment: 23 pages, 1 figur
Two aspects of the Regge limit in QCD: Double Logs in Exclusive observables and Infrared Effects in Cross Sections
Two relevant points related to the application of the BFKL formalism to
phenomenology are discussed. First, we have presented a set of observables
characterizing multi-jet configurations event by event (average transverse
momentum, average azimuthal angle, average ratio of jet rapidities) which can
be used to find distinct signals of BFKL dynamics at the LHC. A numerical
analysis has been shown using the Monte Carlo event generator BFKLex, modified
to include higher-order collinear corrections in addition to the
transverse-momentum implementation of the NLO kernel. We require to have two
tagged forward/backward jets in the final state. Second, the structure of the
BFKL equation changes if infrared boundary conditions are imposed when
considering the running of the coupling. The cut in the complex angular
momentum plane becomes an infinite series of Regge poles. Integrating along a
contour off the real axis we find a strong dependence of the intercepts and
collinear regions on the choice of the boundary conditions. The mean transverse
scales dominant in the gluon ladder increase. This could have interesting
phenomenological consequences.Comment: 6 pages, presented by A. Sabio Vera at the 25th International
Workshop on Deep Inelastic Scattering and Related Topics, 3-7 April 2017,
Birmingham, U
Gluon Regge trajectory at two loops from Lipatov's high energy effective action
We present the derivation of the two-loop gluon Regge trajectory using
Lipatov's high energy effective action and a direct evaluation of Feynman
diagrams. Using a gauge invariant regularization of high energy divergences by
deforming the light-cone vectors of the effective action, we determine the
two-loop self-energy of the reggeized gluon, after computing the master
integrals involved using the Mellin-Barnes representations technique. The
self-energy is further matched to QCD through a recently proposed subtraction
prescription. The Regge trajectory of the gluon is then defined through
renormalization of the reggeized gluon propagator with respect to high energy
divergences. Our result is in agreement with previous computations in the
literature, providing a non-trivial test of the effective action and the
proposed subtraction and renormalization framework.Comment: 22 page
The quark induced Mueller-Tang jet impact factor at next-to-leading order
We present the NLO corrections for the quark induced forward production of a
jet with an associated rapidity gap. We make use of Lipatov's QCD high energy
effective action to calculate the real emission contributions to the so-called
Mueller-Tang impact factor. We combine them with the previously calculated
virtual corrections and verify ultraviolet and collinear finiteness of the
final result.Comment: 29 pages, many figure
Dijet Production at Large Rapidity Separation in N=4 SYM
Ratios of azimuthal angle correlations between two jets produced at large
rapidity separation are studied in the N=4 super Yang-Mills theory (MSYM). It
is shown that these observables, which directly prove the SL(2,C) symmetry
present in gauge theories in the Regge limit, exhibit an excellent perturbative
convergence. They are compared to those calculated in QCD for different
renormalization schemes concluding that the momentum-substraction (MOM) scheme
with the Brodsky-Lepage-Mackenzie (BLM) scale-fixing procedure captures the
bulk of the MSYM results.Comment: 13 pages, 7 figure
The next-to-leading order vertex for a forward jet plus a rapidity gap at high energies
We present the results for the calculation of the forward jet vertex
associated to a rapidity gap (coupling of a hard pomeron to the jet) in the
Balitsky-Fadin-Kuraev-Lipatov (BFKL) formalism at next-to-leading order (NLO).
We handle the real emission contributions making use of the high energy
effective action proposed by Lipatov, valid for multi-Regge and
quasi-multi-Regge kinematics. This result is important since it allows,
together with the NLO non-forward gluon Green function, to perform NLO studies
of jet production in diffractive events (Mueller-Tang dijets, as a well-known
example).Comment: 12 pages, some figure
Inclusive Four-jet Production at 7 and 13 TeV: Azimuthal Profile in Multi-Regge Kinematics
Recently, new observables in LHC inclusive events with three tagged jets were
proposed. Here, we extend that proposal to events with four tagged jets. The
events are characterised by one jet in the forward direction, one in the
backward direction with a large rapidity distance from the first one and
two more jets tagged in more central regions of the detector. In our setup,
non-tagged associated mini-jet multiplicity is present and needs to be
accounted for by the inclusion of BFKL gluon Green functions. The projection of
the cross section on azimuthal-angle components opens up the opportunity for
defining new ratios of correlation functions of the azimuthal angle differences
among the tagged jets that can be used as probes of the BFKL dynamics.Comment: 19 pages, 8 figures; v2: published versio
Probing the BFKL dynamics in inclusive three jet production at the LHC
We propose the study of new observables in LHC inclusive events with three
tagged jets, one in the forward direction, one in the backward direction and
both well-separated in rapidity from the each other (Mueller-Navelet jets),
together with a third jet tagged in central regions of rapidity. Since
non-tagged associated mini-jet multiplicity is allowed, we argue that
projecting the cross sections on azimuthal-angle components can provide several
distinct tests of the BFKL dynamics. Realistic LHC kinematical cuts are
introduced.Comment: 8 pages. Talk given by G. Chachamis at the 5th International
Conference on New Frontiers in Physics (ICNFP2016), 6-14 July 2016,
Kolymbari, Crete, Greec
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