Breakdown of Coherence ?

In a recent paper, Albrecht Kyrieleis, Jeff Forshaw and I discovered a new tower of super-leading logarithms in gaps between jets cross sections. After discussions with the referee of our paper and further investigation, we have come to view this as a breakdown of naive coherence for initial state radiation. In this talk I illustrate this statement in a simple way, and show how it results in the super-leading logarithms.Comment: 10 pages, Talk given at 12th International Conference on Elastic and Diffractive Scattering (EDS '07), May 21st-25th 2007, DESY, Hambur

News from HERWIG

I review the current status and future plans of the HERWIG collaboration.Comment: 4 pages, Contribution to Proceedings of XLth Rencontres de Moriond, QCD and High Energy Hadronic Interactions, La Thuile, Italy, March 12th-19th, 200

Monte Carlo for the LHC

I review the status of the general-purpose Monte Carlo event generators for the LHC, with emphasis on areas of recent physics developments. There has been great progress, especially in multi-jet simulation, but I mention some question marks that have recently arisen.Comment: 10 pages, to appear in the proceedings of Physics at the LHC 2010, DESY, Hamburg, 7-12 June 201

NLO calculations in QCD: a general algorithm

We briefly describe a new general algorithm for carrying out QCD calculations to next-to-leading order in perturbation theory. The algorithm can be used for computing arbitrary jet cross sections in arbitrary processes and can be straightforwardly implemented in general-purpose Monte Carlo programs.Comment: 10 pages, uses espcrc2.sty. Talk presented at the DESY-Zeuthen Workshop QCD and QED in Higher Orders, Rheinsberg, Germany, April 1996. This paper can also be obtained from http://surya11.cern.ch/users/seymour/pubs/rheinsberg.ps.

QCD jet calculations in DIS based on the subtraction method and dipole formalism

We briefly describe a new general algorithm for carrying out QCD calculations to next-to-leading order in perturbation theory. The algorithm can be used for computing arbitrary jet cross sections in arbitrary processes and can be straightforwardly implemented in general purpose Monte Carlo programs. We show numerical results for the specific case of jet cross sections in deep inelastic scattering.Comment: 5 pages, 2 figures. Presented at the International Workshop on Deep Inelastic Scattering and Related Phenomena (DIS 96), Rome, Italy, 15-19 Apr 1996. This paper can also be obtained from http://surya11.cern.ch/users/seymour/pubs/rome.ps.

The Forward-Backward Asymmetry in NNLO QCD

We have recently calculated the second-order QCD corrections to the forward-backward asymmetry in e+e- annihilation (hep-ph/9905424). Here we recall the results and compare them to others in the literature.Comment: 14 pages, LaTeX, uses lathuile.sty (included). Talk given by M. Seymour at 13th Rencontres de Physique de la Vallee d'Aoste, Results and Perspectives in Particle Physics, La Thuile, Aosta Valley, Italy, February 28th-March 6th, 199

Matrix-Element Corrections to Parton Shower Algorithms

We discuss two ways in which parton shower algorithms can be supplemented by matrix-element corrections to ensure the correct hard limit: by using complementary phase-space regions, or by modifying the shower itself. In the former case, existing algorithms are self-consistent only if the total correction is small. In the latter case, existing algorithms are never self-consistent, a problem that is particularly severe for angular-ordered parton shower algorithms. We show how to construct self-consistent algorithms in both cases. The postscript file for this paper can also be obtained by anonymous ftp from thep.lu.se in the file pub/Preprints/lu_tp_94_17.psComment: 11 pages, LU TP 94-1

Underlying events in Herwig++

In this contribution we describe the new model of multiple partonic interactions (MPI) that has been implemented in Herwig++. Tuning its two free parameters is enough to find a good description of CDF underlying event data. We show extrapolations to the LHC and compare them to results from other models.Comment: 4 pages, 3 figures, to appear in the proceedings of the "HERA and the LHC" worksho