Determination of transverse momentum dependent gluon density from HERA structure function measurements

The transverse momentum dependent gluon density obtained with CCFM evolution is determined from a fit to the latest combined HERA structure function measurements.Comment: Contribution to DIS201

Small-x Physics and Forward Jet Production at THERA

We discuss some aspects of forward jet production as a signature for small $x$ physics at THERA energies.Comment: to appear in THERA Boo

Monte Carlo Generators and the CCFM Equation

We discuss three implementations of the CCFM evolution equations in event generator programs. We find that some of them are able to describe observables such as forward jet rates in DIS at HERA, but only if the so-called consistency constraint is removed. We also find that these results are sensitive to the treatment of non-singular terms in the gluon splitting function.Comment: 4 pages, 3 figures. Talk presented at the DIS 2000 workshop, Liverpool, England, April 200

Higgs production via gluon fusion from kT-factorisation

Theoretical studies of Higgs production via gluon fusion are frequently carried out in the limit where the top quark mass is much larger than the Higgs mass, an approximation which reduces the top quark loop to an effective vertex. We present a numerical analysis of the error thus introduced by performing a Monte Carlo calculation for gg->h in kT-factorisation, using the parton shower generator CASCADE. We proceed to compare CASCADE to the collinear Monte Carlos PYTHIA, MC@NLO and POWHEG. We study the dependence of parton radiation on the resummation of high-energy corrections taken into account by kT-factorisation, and its influence on predictions for the Higgs pT spectrum.Comment: Contribution to the Workshop Diffraction 2010, Otranto (Italy), September 201

Investigation of the energy dependence of the pT0 parameter in the Pythia 8 Monte Carlo event generator

By using predictions from the Pythia 8 Monte Carlo event generator, we determine the energy-dependent turn-over values (pT0) of the partonic cross section for the simulation of multiparton interactions. Since the observed energy dependence of the pT0 values is not well described by a power-law function, we introduce an additional energy-dependent term, to better describe the experimental observations in the energy range sqrt(s) = 0.3-13 TeV. We obtain a similar level of agreement for predictions using various parton densities.Comment: 10 pages, 6 figure

Matrix Elements with Vetoes in the CASCADE Monte Carlo Event Generator

We illustrate a study based on a veto technique to match parton showers and matrix elements in the Cascade Monte Carlo event generator, and present a numerical application to gluon matrix elements for jet production.Comment: Published in DIS 2012 proceeding

HZTool and Rivet: Toolkit and Framework for the Comparison of Simulated Final States and Data at Colliders

A common problem in particle physics is the requirement to reproduce comparisons between data and theory when the theory is a (general purpose) Monte Carlo simulation and the data are measurements of final state observables in high energy collisions. The complexity of the experiments, the obervables and the models all contribute to making this a highly non-trivial task. We describe an existing library of Fortran routines, HZTool, which enables, for each measurement of interest, a comparable prediction to be produced from any given Monte Carlo generator. The HZTool library is being maintained by CEDAR, with subroutines for various measurements contributed by a number of authors within and outside the CEDAR collaboration. We also describe the outline design and current status of a replacement for HZTool, to be called Rivet (Robust Independent Validation of Experiment and Theory). This will use an object-oriented design, implemented in C++, together with standard interfaces (such as HepMC and AIDA) to make the new framework more flexible and extensible than the Fortran HZTool.Comment: Contribution to CHEP06 conferenc