37 research outputs found
Universal features of JIMWLK and BK evolution at small x
In this paper we present the results of numerical studies of the JIMWLK and
BK equations with a particular emphasis on the universal scaling properties and
phase space structure involved. The results are valid for near zero impact
parameter in DIS. We demonstrate IR safety due to the occurrence of a rapidity
dependent saturation scale Q_s(\tau). Within the set of initial conditions
chosen both JIMWLK and BK equations show remarkable agreement. We point out the
crucial importance of running coupling corrections to obtain consistency in the
UV. Despite the scale breaking induced by the running coupling we find that
evolution drives correlators towards an asymptotic form with near scaling
properties. We discuss asymptotic features of the evolution, such as the \tau-
and A-dependence of Q_s away from the initial condition.Comment: 30 page
Extension of the Color Glass Condensate Approach to Diffractive Reactions
We present an evolution equation for the Bjorken x dependence of diffractive
dissociation on hadrons and nuclei at high energies. We extend the formulation
of Kovchegov and Levin by relaxing the factorization assumption used there. The
formulation is based on a technique used by Weigert to describe interjet energy
flow. The method can be naturally extended to other exclusive observables
Running coupling and power corrections in nonlinear evolution at the high-energy limit.
A main feature of high-energy scattering in QCD is saturation in the number density of gluons.
This phenomenon is described by non-linear evolution equations, JIMWLK and BK, which have
been derived at leading logarithmic accuracy. In this paper we generalize this framework to
include running coupling corrections to the evolution kernel. We develop a dispersive representation
of the dressed gluon propagator in the background of Weiszšacker Williams fields and use
it to compute O(ÎČnâ1
0 αns
) corrections to the kernel to all orders in perturbation theory. The
resummed kernels present infrared-renormalon ambiguities, which are indicative of the form and
importance of non-perturbative power corrections. We investigate numerically the effect of the
newly computed perturbative corrections as well as the power corrections on the evolution and
find that at present energies they are both significant
Non-global jet evolution at finite N_c
Resummations of soft gluon emissions play an important role in many
applications of QCD, among them jet observables and small x saturation effects.
Banfi, Marchesini, and Smye have derived an evolution equation for non-global
jet observables that exhibits a remarkable analogy with the BK equation used in
the small x context. Here, this analogy is used to generalize the former beyond
the leading N_c approximation. The result shows striking analogy with the
JIMWLK equation describing the small x evolution of the color glass condensate.
A Langevin description allows numerical implementation and provides clues for
the formulation of closed forms for amplitudes at finite N_c. The proof of the
new equation is based on these amplitudes with ordered soft emission. It is
fully independent of the derivation of the JIMWLK equation and thus sheds new
light also on this topic.Comment: 22 page
JIMWLK and beyond : From concepts to observables
Volume: 112 Host publication title: 6th International Conference on Physics Opportunities at an Electron-Ion ColliderThe Color Glass Condensate and its associated evolution equation, the JIMWLK equation have applications to many observables far beyond totally inclusive observables. The phenomenology is so rich that little has been done to explore beyond scaling behavior of correlators. We show first examples that exemplify the considerations necessary to access additional information both experimentally and theoretically and demonstrate that the Wilson line correlators appearing throughout make it imperative to consistently take into account that one is dealing with correlators of group elements and demonstrate how this imposes physical and phenomenological constraints. Similar considerations apply also to jet observables at finite N-c.Peer reviewe
HERA-data in the light of small x evolution with state of the art NLO input
Both total and diffractive cross sections from HERA are successfully
confronted with JIMWLK evolution equations in the asymptotic pseudo-scaling
region. We present a consistent, simultaneous description of both types of
cross sections that includes NLO corrections in the form of running coupling
and energy conservation corrections. The inclusion of energy conservation
corrections allows to match all available data with x below .02 i.e. up to Q^2
of 1200 GeV^2. We discuss the effects of quark masses including charm, contrast
asymptotic and pre-asymptotic fit strategies, and survey non-perturbative
uncertainties related to impact parameter dependence.Comment: 61 pages, 27 figure