We present the latest developments of the MadGraph/MadEvent Monte Carlo event generator and several applications to hadron collider physics. In the current version events at the parton, hadron and detector level can be generated directly from a web interface, for arbitrary processes in the Standard Model and in several physics scenarios beyond it (HEFT, MSSM, 2HDM). The most important additions are: a new framework for implementing user-defined new physics models; a standalone running mode for creating and testing matrix elements; generation of events corresponding to different processes, such as signal(s) and backgrounds, in the same run; two platforms for data analysis, where events are accessible at the parton, hadron and detector level; and the generation of inclusive multi-jet samples by combining parton-level events with parton showers. To illustrate the new capabilities of the package some applications to hadron collider physics are presented:I. Higgs search in pp → H → W + W − : signal and backgrounds. II. Higgs CP properties: pp → Hjj in the HEFT. III. Spin of a new resonance from lepton angular distributions. IV. Single-top and Higgs associated production in a generic 2HDM. V. Comparison of strong SUSY pair production at the SPS points. VI. Inclusive W +jets matched samples: comparison with the Tevatron data.

Higgs boson production via weak boson fusion at the CERN Large Hadron Collider has the capability to determine the dominant CP nature of a Higgs boson, via the tensor structure of its coupling to weak bosons. This information is contained in the azimuthal angle distribution of the two outgoing forward tagging jets. The technique is independent of both the Higgs boson mass and the observed decay channel.The CERN Large Hadron Collider (LHC) is generally regarded as a tool that can guarantee direct observation of a Higgs boson, the remnant of the mechanism believed responsible for electroweak symmetry breaking and fermion mass generation, and the last unobserved element of the Standard Model (SM) of elementary particle physics. Furthermore, the LHC promises complete coverage of Higgs decay scenarios [1,2], including general MSSM parameterizations [1,3], and even invisible Higgs decays [4]. This capability has been greatly enhanced recently by the addition of the weak boson fusion (WBF) production channel to the search strategies [3,5,6]. While being extremely useful at the LHC, WBF has too low a rate and is too similar to background processes at the Fermilab Tevatron [7].Observation of a resonance in some expected decay channel is, however, only the beginning of Higgs physics. Continuing efforts will include the search for more than one Higgs boson, as predicted e.g. by two-Higgs doublet models, of which the MSSM [8,9] is a subset. At least as important is the detailed study of the properties of the Higgs-like resonance, not only at a future Linear Collider [10] but also at the LHC: determination of all the quantum numbers and couplings of the state. These include the gauge, Yukawa and self-couplings as well as the charge, color, spin, and CP quantum numbers. While charge and color identification is straightforward and a technique has been proposed for the gauge and Yukawa coupling determinations [11], the LHC has considerable difficulty in practice to determine the Higgs CP transformation properties for intermediate Higgs masses [12] via a weak boson coupling, and no technique has yet been proposed to identify the tensor structure of the Higgs-weak boson vertex in the intermediate mass range. The methods of Ref.[13] may be useful, but only for very light Higgs masses. Furthermore, this method does not involve the weak boson vertices at all.In this letter we propose a technique which achieves the CP measurement goal via a study of WBF events. WBF Higgs production, while not the largest cross section at the LHC, is useful because of its characteristic kinematical structure, involving two forward tagging jets and central Higgs decay products, which allows one to isolate the signal in a low background environment. The angular distribution of the two tagging jets carries unambiguous information on the CP properties of the Higgs couplings to weak bosons which is independent of the Higgs decay channel observed.As a theoretical framework we consider two possible ways to couple a spin zero field to two gauge bosons via hig...

We investigate Higgs boson pair production at hadron colliders for Higgs boson masses m H р140 GeV and the rare decay of one of the two Higgs bosons. While in the standard model the number of events is quite low at the CERN Large Hadron Collider ͑LHC͒, a first, albeit not very precise, measurement of the Higgs boson self-coupling is possible in the gg→HH→bb ␥␥ channel. A luminosity-upgraded LHC could improve this measurement considerably. A 200 TeV very large hadron collider could make a measurement of the Higgs self-coupling competitive with a next-generation linear collider. In the minimal supersymmetric standard model ͑MSSM͒ we find a significant region with observable Higgs boson pair production in the small tan ␤ regime, where resonant production of two light Higgs bosons might be the only hint at the LHC of a MSSM Higgs sector.

We show how LHC Higgs boson production and decay data can be used to extract gauge and fermion couplings of Higgs bosons. We show that very mild theoretical assumptions, which are valid in general multi-Higgs doublet models, are sufficient to allow the extraction of absolute values for the couplings rather than just ratios of the couplings. For Higgs masses below 200 GeV we find accuracies of 10 ÿ 40% for the Higgs boson couplings and total width after several years of LHC running. Slightly stronger assumptions on the Higgs gauge couplings even lead to a determination of couplings to fermions at the level of 10 ÿ 20%. We also study the sensitivity to deviations from SM predictions in several supersymmetric benchmark scenarios as a subset of the analysis.

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