Abstract. Physics and programming aspects are discussed for a Fortran 77 Monte Carlo program to simulate complete events in deep inelastic leptonnucleon scattering. The parton level interaction is based on the standard model electroweak cross sections, which are fully implemented in leading order for any lepton of arbitrary polarization, and different parametrizations of parton density functions can be used. First order QCD matrix elements for gluon radiation and boson-gluon fusion are implemented and higher order QCD radiation is treated using parton showers. Hadronization is performed using the Lund string model, implemented in Jetset/Pythia. Rapidity gap events are generated through a model based on soft colour interactions.

The hadronic decays of the τ lepton can be used to determine the effective charge α τ (m 2 τ ′ ) for a hypothetical τ -lepton with mass in the range 0 < m τ ′ < m τ . This definition provides a fundamental definition of the QCD coupling at low mass scales. We study the behavior of α τ at low mass scales directly from first principles and without any renormalization-scheme dependence by looking at the experimental data from the OPAL Collaboration. The results are consistent with the freezing of the physical coupling at mass scales s = m 2 τ ′ of order 1 GeV 2 with a magnitude α τ ∼ 0.9 ± 0.1.

We present the program 2HDMC and how it can be used to explore the physics of general CPconserving two Higgs doublet models.

We have developed the Monte Carlo simulation program Jewel 1.0 (Jet Evolution With Energy Loss), which interfaces a perturbative final state parton shower with medium effects occurring in ultrarelativistic heavy ion collisions. This is done by comparing for each jet fragment the probability of further perturbative splitting with the density-dependent probability of scattering with the medium. A simple hadronisation mechanism is included. In the absence of medium effects, we validate Jewel against a set of benchmark jet measurements. For elastic interactions with the medium, we characterise not only the medium-induced modification of the jet, but also the jet-induced modification of the medium. Our main physics result is the observation that collisional and radiative medium modifications lead to characteristic differences in the jet fragmentation pattern, which persist above a soft background cut. We argue that this should allow to disentangle collisional and radiative parton energy loss mechanisms by measuring the n-jet fraction or a class of jet shape observables.

This writeup is a compilation of the predictions for the forthcoming Heavy Ion Program at the Large Hadron Collider, as presented at the CERN Theory Institute ‘Heavy Ion Collisions at the LHC—Last Call for Predictions’, held from 14th May to 10th June 2007.