Azimuthal correlation in DIS

We introduce the azimuthal correlation for the deep inelastic scattering process. We present the QCD prediction to the level of next-to-leading log resummation, matching to the fixed order prediction. We also estimate the leading non-perturbative power correction. The observable is compared with the energy-energy correlation in e+e- annihilation, on which it is modelled. The effects of the resummation and of the leading power correction are both quite large. It would therefore be particularly instructive to study this observable experimentally.Comment: 33 pages, 4 figures, JHEP class included. One figure and some clarifications adde

Power Corrections to Fragmentation Functions in Flavour-Singlet Deep Inelastic Scattering

We investigate the power-suppressed corrections to fragmentation functions in flavour-singlet deep inelastic lepton scattering, to complement the previous results for the non-singlet contribution. Our method is a dispersive approach based on an analysis of Feynman graphs containing massive gluons. As in non-singlet deep inelastic scattering we find that the leading corrections are proportional to 1/Q^2.Comment: 15 pages, 3 figure

Resummed event-shape variables in DIS

We complete our study of resummed event-shape distributions in DIS by presenting results for the class of observables that includes the current jet mass, the C-parameter and the thrust with respect to the current-hemisphere thrust axis. We then compare our results to data for all observables for which data exist, fitting for alpha_s and testing the universality of non-perturbative 1/Q effects. A number of technical issues arise, including the extension of the concept of non-globalness to the case of discontinuous globalness; singularities and non-convergence of distributions other than in the Born limit; methods to speed up fixed-order Monte Carlo programs by up to an order of magnitude, relevant when dealing with many x and Q points; and the estimation of uncertainties on the predictions.Comment: 41 page

Towards Jetography

As the LHC prepares to start taking data, this review is intended to provide a QCD theorist's understanding and views on jet finding at hadron colliders, including recent developments. My hope is that it will serve both as a primer for the newcomer to jets and as a quick reference for those with some experience of the subject. It is devoted to the questions of how one defines jets, how jets relate to partons, and to the emerging subject of how best to use jets at the LHC.Comment: 95 pages, 28 figures, an extended version of lectures given at the CTEQ/MCNET school, Debrecen, Hungary, August 2008; v2 includes additional discussion in several places, as well as other clarifications and additional references