28 research outputs found
In pursuit of Pomeron loops: the JIMWLK equation and the Wess-Zumino term
We derive corrections to the JIMWLK equation in the regime where the charge
density in the hadronic wave function is small. We show that the framework of
the JIMWLK equation has to be significantly modified at small densities in
order to properly account for the noncommutativity of the charge density
operators. In particular the weight function for the calculation of averages
can not be real, but is shown to contain the Wess-Zumino term. The corrections
to the kernel of the JIMWLK evolution which are leading at small density are
resummed into a path ordered exponential of the functional derivative with
respect to the charge density operator, thus hinting at intriguing duality
between the high and the low density regimes.Comment: 8 pages, no figures. References added. Version to appear in Phys.
Rev.
Equivalence of the Parke-Taylor and the Fadin-Kuraev-Lipatov amplitudes in the high-energy limit
We give a unified description of tree-level multigluon amplitudes in the
high-energy limit. We represent the Parke-Taylor amplitudes and the
Fadin-Kuraev-Lipatov amplitudes in terms of color configurations that are
ordered in rapidity on a two-sided plot. We show that for the helicity
configurations they have in common the Parke-Taylor amplitudes and the
Fadin-Kuraev-Lipatov amplitudes coincide.Comment: LaTeX, 24 pages (including 4 tar-compressed uuencoded figures
Dijet Production at Large Rapidity Intervals
We examine dijet production at large rapidity intervals at Tevatron energies,
by using the theory of Lipatov and collaborators which resums the leading
powers of the rapidity interval. We analyze the growth of the Mueller-Navelet
-factor in this context and find it to be negligible. However, we do find a
considerable enhancement of jet production at large transverse momenta. In
addition, we show that the correlation in transverse momentum and azimuthal
angle of the tagging jets fades away as the rapidity interval is increased.Comment: 12 pages, preprint DESY 93-139, SCIPP 93/3
Saturation and Wilson Line Distributions
We introduce a Wilson line distribution function bar{W}_tau(v) to study gluon
saturation at small Feynman x_F, or large tau=ln(1/x_F). This new distribution
can be obtained from the distribution W_tau(alpha) of the Color Glass
Condensate model and the JIMWLK renormalization group equation. bar{W}_tau(v)
is physically more relevant, and mathematically simpler to deal with because of
unitarity of the Wilson line v. A JIMWLK equation is derived for bar{W}_tau(v);
its properties are studied. These properties are used to complete Mueller's
derivation of the JIMWLK equation, though for bar{W}_tau(v) and not
W_tau(alpha). They are used to derive a generalized Balitsky-Kovchegov equation
for higher multipole amplitudes. They are also used to compute the unintegrated
gluon distribution at x_F=0, yielding a completely flat spectrum in transverse
momentum squared k^2, with a known height. This is similar but not identical to
the mean field result at small k^2.Comment: One reference and two short comments added. To appear in Physical
Revies
QCD Predictions for the Transverse Energy Flow in Deep-Inelastic Scattering in the Small x HERA Regime
The distribution of transverse energy, , which accompanies
deep-inelastic electron-proton scattering at small , is predicted in the
central region away from the current jet and proton remnants. We use BFKL
dynamics, which arises from the summation of multiple gluon emissions at small
, to derive an analytic expression for the flow. One interesting
feature is an increase of the distribution with
decreasing , where . We perform a
numerical study to examine the possibility of using characteristics of the
distribution as a means of identifying BFKL dynamics at HERA.Comment: 16 pages, REVTEX 3.0, no figures. (Hardcopies of figures available on
request from Professor A.D. Martin, Department of Physics, University of
Durham, DH1 3LE, England.) Durham preprint : DTP/94/0
What is the Evidence for the Color Glass Condensate?
I introduce the concept of the Color Glass Condensate. I review data from
HERA and RHIC which suggest that such a universal form of matter has been
found
Finite sum of gluon ladders and high energy cross sections
A model for the Pomeron at is suggested. It is based on the idea of a
finite sum of ladder diagrams in QCD. Accordingly, the number of -channel
gluon rungs and correspondingly the powers of logarithms in the forward
scattering amplitude depends on the phase space (energy) available, i.e. as
energy increases, progressively new prongs with additional gluon rungs in the
-channel open. Explicit expressions for the total cross section involving
two and three rungs or, alternatively, three and four prongs (with
and as highest terms, respectively) are fitted to the proton-proton
and proton-antiproton total cross section data in the accelerator region. Both
QCD calculation and fits to the data indicate fast convergence of the series.
In the fit, two terms (a constant and a logarithmically rising one) almost
saturate the whole series, the term being small and the next one,
, negligible. Theoretical predictions for the photon-photon total
cross section are also given.Comment: 18 pages, LaTeX, 2 EPS figures, uses axodraw.st
QCD Reggeon Field Theory for every day: Pomeron loops included
We derive the evolution equation for hadronic scattering amplitude at high
energy. Our derivation includes the nonlinear effects of finite partonic
density in the hadronic wave function as well as the effect of multiple
scatterings for scattering on dense hadronic target. It thus includes Pomeron
loops. It is based on the evolution of the hadronic wave function derived in
\cite{foam}. The kernel of the evolution equation defines the second quantized
Hamiltonian of the QCD Reggeon Field Theory, beyond the limits
considered so far. The two previously known limits of the evolution: dilute
target (JIMWLK limit) and dilute projectile (KLWMIJ limit) are recovered
directly from our final result. The Hamiltonian is applicable for the
evolution of scattering amplitude for arbitrarily dense hadronic
projectiles/targets - from "dipole-dipole" to "nucleus-nucleus" scattering
processes.Comment: 35 pages, 5 figure
Diffractive light vector meson production at large momentum transfers
The diffractive process (where are the vector mesons, consisted of light quarks, represents the
hadrons to that a proton dissociates) is studied. We consider the region of
large momentum transfers, , and large energies, s. In the
leading log approximation of perturbative QCD ( using BFKL equation ) the
asymptotic behaviour of the cross section in the limit is obtained.
We compare the results derived from BFKL equation with that obtained in the
lowest order of QCD (two--gluon exchange in the - channel). The possibility
to investigate these reactions at HERA is discussed.Comment: 14 pages (LateX), one LaTeX figure using feynman.te
Interaction of Reggeized Gluons in the Baxter-Sklyanin Representation
We investigate the Baxter equation for the Heisenberg spin model
corresponding to a generalized BFKL equation describing composite states of n
Reggeized gluons in the multi-color limit of QCD. The Sklyanin approach is used
to find an unitary transformation from the impact parameter representation to
the representation in which the wave function factorizes as a product of Baxter
functions and a pseudo-vacuum state. We show that the solution of the Baxter
equation is a meromorphic function with poles (lambda - i r)^{-(n-1)} (r= 0,
1,...) and that the intercept for the composite Reggeon states is expressed
through the behavior of the Baxter function around the pole at lambda = i . The
absence of pole singularities in the two complex dimensional lambda-plane for
the bilinear combination of holomorphic and anti-holomorphic Baxter functions
leads to the quantization of the integrals of motion because the holomorphic
energy should be the same for all independent Baxter functions.Comment: LaTex, 48 pages, 1 .ps figure, to appear in Phys. Rev.