148 research outputs found
Calculation of Reggeon Vertices in QCD
The method of calculation of effective vertices of interaction of the
Reggeized gluon and quark with particles in QCD in the next-to-leading order is
developed. The method is demonstrated in the case of already known vertices of
both gluon-gluon and quark-quark transitions in the scattering of gluons and
quarks on the Reggeized gluon. It is used for the calculation of the
gluon-quark transition in the scattering on the Reggeized quark.Comment: 27 pages, LaTex, 1 figure, uses axodraw.st
The Quark Impact Factors
We calculate in the next-to-leading approximation the non-forward quark
impact factors for both singlet and octet color representation in the
-channel. The integral representation of the octet impact factor in the
general case of arbitrary space-time dimension and massive quark flavors is
used to check the so-called "second bootstrap condition" for the gluon
Reggeization at the next-to-leading logarithmic approximation in perturbative
QCD. We find that it is satisfied for both helicity conserving and
non-conserving parts. The integrations are then performed for the explicit
calculation of the impact factors in the massless quark case.Comment: 23 pages, LaTeX, 1 EPS figure, uses epsf.sty and axodraw.st
The quark part of the non-forward BFKL kernel and the ``bootstrap'' for the gluon Reggeization
We calculate the quark part of the kernel of the generalized non-forward BFKL
equation at non-zero momentum transfer in the next-to-leading logarithmic
approximation. Along with the quark contribution to the gluon Regge trajectory,
this part includes pieces coming from the quark-antiquark production and from
the quark contribution to the radiative corrections in one-gluon production in
the Reggeon-Reggeon collisions. The results obtained can be used for an
arbitrary representation of the colour group in the channel. Using the
results for the adjoint representation, we demonstrate explicitly the
fulfillment of the ``bootstrap'' condition for the gluon Reggeization in the
next-to-leading logarithmic approximation in the part concerning the quark
contribution.Comment: 26 pages, LaTeX, uses axodraw.sty; revised final comment; to appear
on Phys. Rev.
Electroproduction of two light vector mesons in next-to-leading BFKL: study of systematic effects
The forward electroproduction of two light vector mesons is the first example
of a collision process between strongly interacting colorless particles for
which the amplitude can be written completely within perturbative QCD in the
Regge limit with next-to-leading accuracy. In a previous paper we have given a
numerical determination of the amplitude in the case of equal photon
virtualities by using a definite representation for the amplitude and a
definite optimization method for the perturbative series. Here we estimate the
systematic uncertainty of our previous determination, by considering a
different representation of the amplitude and different optimization methods of
the perturbative series. Moreover, we compare our result for the differential
cross section at the minimum momentum transfer with a different approach, based
on collinear kernel improvement.Comment: 17 pages, 11 figures; journal version, new figures and discussion
adde
The Gluon Impact Factors
We calculate in the next-to-leading approximation the non-forward gluon
impact factors for arbitrary color state in the -channel. In the case of the
octet state we check the so-called "second bootstrap condition" for the gluon
Reggeization in QCD, using the integral representation for the impact factors.
The condition is fulfilled in the general case of an arbitrary space-time
dimension and massive quark flavors for both helicity conserving and
non-conserving parts.Comment: 32 pages, LaTeX, 1 EPS figure, uses epsf.sty and axodraw.st
Quark contribution to the reggeon-reggeon-gluon vertex in QCD
The quark loop contribution to the reggeon-reggeon-gluon vertex is calculated
in QCD, where the reggeon is the reggeized gluon. Compared with the vertex in
the Born approximation, this contribution exhibits a new spin structure as well
as the gluon loop one. A remarkable but not complete cancellation between gluon
and quark contributions to this new spin structure takes place for the case of
three massless quark flavours.Comment: 19 pages + 2 figures(appended as a postscript file), Late
A proof of the reggeized form of amplitudes with quark exchanges
A complete proof of the quark Reggeization hypothesis in the leading
logarithmic approximation for any quark--gluon inelastic process in the
multi--Regge kinematics in all orders of is given. First, we show
that the multi--Regge form of QCD amplitudes is guarantied if a set of
conditions on the Reggeon vertices and the trajectories is fulfilled. Then, we
examine these conditions and show that they are satisfied.Comment: 22 pages, 7 figures, use elsart.cl
A proof of fulfillment of the strong bootstrap condition
It is shown that the kernel of the BFKL equation for the octet color state of
two Reggeized gluons satisfies the strong bootstrap condition in the
next-to-leading order. This condition is much more restrictive than the one
obtained from the requirement of Reggeized form for the elastic scattering
amplitudes in the next-to-leading approximation. It is necessary, however, for
self-consistency of the assumption of Reggeized form of the production
amplitudes in multi-Regge kinematics, which are used in the derivation of the
BFKL equation. The fulfillment of the strong bootstrap condition for the kernel
opens a way to a rigorous proof of the BFKL equation in the next-to-leading
approximation.Comment: 20 pages; minor changes in the text in Section 1 (Introduction) and
in Section 4 (Discussion); one reference adde
Strong Bootstrap Conditions
We reformulate the so-called ``strong bootstrap'' conditions for the gluon
Reggeization in the next-to-leading approximation (NLA), firstly suggested by
Braun and Vacca, using a different approach, which is not based on properties
of the eigenstates of the NLA octet BFKL kernel. We write the second strong
bootstrap condition for the NLA octet impact factors in a form which makes
clear their dependence on the process. According to this condition, the NLA
octet impact factors must be given by the product of the corresponding Reggeon
interaction vertices with a universal coefficient function. This function can
be used also in the formulation of the first strong bootstrap condition for the
NLA BFKL kernel in the octet state.Comment: 10 page
Connection between complete and Moebius forms of gauge invariant operators
We study the connection between complete representations of gauge invariant
operators and their Moebius representations acting in a limited space of
functions. The possibility to restore the complete representations from Moebius
forms in the coordinate space is proven and a method of restoration is worked
out. The operators for transition from the standard BFKL kernel to the
quasi-conformal one are found both in Moebius and total representations.Comment: Changed title and a short paragraph in the section "Conclusion";
unchanged results. Version to appear on Nucl. Phys.
- âŠ