P.J. Sutton

Implications of scaling violations of F2 at HERA for perturbative QCD

Abstract We critically examine the QCD predictions for the Q 2 dependence of the electron-proton deep-inelastic structure function F 2 ( x , Q 2 ) in the small x region, which is being probed at HERA. The standard results based on next-to-leading order Altarelli-Parisi evolution are compared with those that follow from the BFKL equation, which corresponds to the resummation of the leading log ( 1 x ) terms. The effects of parton screening are also quantified. The theoretical predictions are confronted with each other, and with existing data from HERA.

Probing the Lipatov singular small x behaviour at HERA

Abstract We examine the feasibility of using deep-inelastic events containing a measured jet to identify the x − λ singular type of behaviour at small x , which is predicted by perturbative QCD via the Lipatov equation. We calculate the cross sections at HERA for relevant choices of the deep-inelastic and jet kinematic variables and we indicate the signature of the x − λ behaviour.

Description of F2 at small x incorporating angular ordering.

We study the perturbative QCD description of the DESY HERA measurements of {ital F}{sub 2}({ital x},{ital Q}{sup 2}) using a gluon distribution that is obtained from an evolution incorporating angular ordering of the gluon emissions, and which embodies both GLAP and BFKL dynamics. We compare the predictions with recent HERA data for {ital F}{sub 2} and its charm component {ital F}{sup {ital c}}{sub 2}. We also present estimates of the longitudinal structure function {ital F}{sub {ital L}}. {copyright} {ital 1996 The American Physical Society.}

The small x behaviour of the gluon

Abstract The very small x behaviour of the gluon distribution in a proton is investigated by solving the Lipatov equation with the nonlinear shadowing term included. We find, with decreasing x , the emergence of an x − λ behaviour and the eventual taming of this singularity by the shadowing term. We compare our dynamically generated gluon with that obtained in a recent QCD structure function analysis which incorporated the Lipatov and shadowing effects.

Description of {ital F}{sub 2} at small {ital x} incorporating angular ordering

We study the perturbative QCD description of the DESY HERA measurements of {ital F}{sub 2}({ital x},{ital Q}{sup 2}) using a gluon distribution that is obtained from an evolution incorporating angular ordering of the gluon emissions, and which embodies both GLAP and BFKL dynamics. We compare the predictions with recent HERA data for {ital F}{sub 2} and its charm component {ital F}{sup {ital c}}{sub 2}. We also present estimates of the longitudinal structure function {ital F}{sub {ital L}}. {copyright} {ital 1996 The American Physical Society.}

Identifying the Lipatov x−λ behaviour at HERA

Abstract We discuss whether deep-inelastic events containing a measured jet at HERA will be able to identify the x−Λ behaviour at small x which is predicted by perturbative QCD via the Lipatov equation.