In these lectures I briefly review the Higgs mechanism of electroweak symmetry breaking and focus on the most relevant aspects of the phenomenology of the Standard Model Higgs boson at hadron colliders, namely the Tevatron and the Large Hadron Collider. Emphasis is put in particular on the Higgs-physics program of both LHC experiments and on the theoretical activity that has entailed from the the need of providing accurate predictions for both signal and background in Higgs-boson searches.
As of version 8.150 of Pythia, the isotropic decay model of tau-leptons has been replaced with sophisticated tau-lepton decay machinery. The decays and spin correlations for tau-leptons in Pythia 8 are described, including the spin correlation algorithm, the available tau-lepton production processes, the tau-lepton decay models, the user interface, and the implementation.
A study of several observables characterising fragment distributions of medium-modified parton showers using the JEWEL and Q-PYTHIA models is presented, with emphasis on the relation between the different observables.
We report on our exploration of matching matrix element calculations with the parton-shower models contained in the event generators HERWIG and Pythia. We describe results for e+e- collisions and for the hadroproduction of W bosons and Drell--Yan pairs. We compare methods based on (1) a strict implementation of ideas proposed by Catani, et al., (2) a generalization based on using the internal Sudakov form factors of HERWIG and Pythia, and (3) a simpler proposal of M. Mangano. Where appropriate, we show the dependence on various choices of scales and clustering that do not affect the soft and collinear limits of the predictions, but have phenomenological implications. Finally, we comment on how to use these results to state systematic errors on the theoretical predictions.
We present an updated set of parameters for the PYTHIA 8 event generator. We reevaluate the constraints imposed by LEP and SLD on hadronization, in particular with regard to heavy-quark fragmentation and strangeness production. For hadron collisions, we combine the updated fragmentation parameters with a new NNPDF2.3 LO PDF set. We use minimum-bias, Drell-Yan, and underlying-event data from the LHC to constrain the initial-state-radiation and multi-parton-interaction parameters, combined with data from SPS and the Tevatron to constrain the energy scaling. Several distributions show significant improvements with respect to the current defaults, for both ee and pp collisions, though we emphasize that interesting discrepancies remain in particular for strange particles and baryons. The updated parameters are available as an option starting from PYTHIA 8.185, by setting Tune:ee = 7 and Tune:pp = 14.