The Higgs Working Group: Summary report

In this working group we have investigated the prospects for Higgs boson searches at the Tevatron and LHC and, in particular, the potential of these colliders to determine the Higgs properties once these particles have been found. The analyses were done in the framework of the Standard Model (SM) and its supersymmetric extensions as the minimal (MSSM) and next-to-minimal (NMSSM) supersymmetric extensions. The work for the discovery potential of the LHC mainly concentrated on the difficult regions of previous analyses as those which are plagued by invisible Higgs decays and Higgs decays into supersymmetric particles. Moreover, the additional signatures provided by the weak vector-boson fusion process (WBF) have been addressed and found to confirm the results of previous analyses. A major experimental effort has been put onto charged Higgs boson analyses. The final outcome was a significant improvement of the discovery potential at the Tevatron and LHC than previous analyses suggested. For an accurate determination of Higgs boson couplings, the theoretical predictions for the signal and background processes have to be improved. A lot of progress has been made during and after this workshop for the gluon-fusion gg {yields} H + (0, 1, 2jets) and the associated t{bar t}H production process. A thorough study of the present theoretical uncertainties of signal and background processes has been initialized, culminating in a list of open theoretical problems. A problem of major experimental interest is the proper treatment of processes involving bottom quark densities, which is crucial for some important signal and background processes. Further theoretical improvements have been achieved for the MSSM Higgs boson masses and Higgs bosons in the NMSSM. This report summarizes our work. The first part deals with theoretical developments for the signal and background processes. The second part gives an overview of the present status of Higgs boson searches at the Tevatron. The third part analyzes invisible Higgs boson decays at the LHC and the forth part the Higgs boson search in the WBF channel. Part 5 summarizes the progress that has been achieved for A/H {yields} {tau}{sup +}{tau}{sup -}. decays in the MSSM. In part 6 the status of the Higgs boson search in t{bar t}H production is presented. Finally, part 7 describes the charged Higgs boson analyses in detail