Electroweak Physics

The results of high precision weak neutral current (WNC), Z-pole, and high energy collider electroweak experiments have been the primary prediction and test of electroweak unification. The electroweak program is briefly reviewed from a historical perspective. Current changes, anomalies, and things to watch are summarized, and the implications for the standard model and beyond discussed.Comment: 12 pages, invited talk presented at the Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2003), New York, May 200

Higgs production and decay: Analytic results at next-to-leading order QCD

The virtual two-loop corrections for Higgs production in gluon fusion are calculated analytically in QCD for arbitrary Higgs and quark masses. Both scalar and pseudo-scalar Higgs bosons are considered. The results are obtained by expanding the known one-dimensional integral representation in terms of m_H/m_q, and matching it with a suitably chosen ansatz of Harmonic Polylogarithms. This ansatz is motivated by the known analytic result for the Higgs decay rate into two photons. The method also allows us to check this result and to extend it to the pseudo-scalar decay rate.Comment: LaTeX, 16 pages, 5 figures (8 eps-files

Photon Radiation with MadDipole

We present the automation of a subtraction method for photon radiation using the dipole formalism within the MadGraph framework. The subtraction terms are implemented both in dimensional regularization and mass regularization for massless and massive cases and non-collinear-safe observables are accounted for.Comment: 23 pages, 2 figures, minor additions, references added, version published in JHE

Super AutoDipole

The publicly available package for an automated dipole subtraction, AutoDipole, is extended to include the SUSY dipoles in the MSSM. All fields in the SM and the MSSM are available. The code is checked against the analytical expressions for a simple process. The extended package makes it possible to compute the QCD NLO corrections to SUSY multi-parton processes like the stop pair production plus jets at the LHC.Comment: 16 pages, 1 figure, v2: a few typos to match the published version in Eur. Phys. J.

Challenging SO(10) SUSY GUTs with family symmetries through FCNC processes

We perform a detailed analysis of the SO(10) SUSY GUT model with D3 family symmetry of Dermisek and Raby (DR). The model is specified in terms of 24 parameters and predicts, as a function of them, the whole MSSM set of parameters at low energy scales. Concerning the SM subset of such parameters, the model is able to give a satisfactory description of the quark and lepton masses, of the PMNS matrix and of the CKM matrix. We perform a global fit to the model, including flavour changing neutral current (FCNC) processes Bs --> mu+ mu-, B --> Xs gamma, B --> Xs l+ l- and the B(d,s) - bar B(d,s) mass differences Delta M(d,s) as well as the flavour changing (FC) process B+ --> tau+ nu. These observables provide at present the most sensitive probe of the SUSY mass spectrum and couplings predicted by the model. Our analysis demonstrates that the simultaneous description of the FC observables in question represents a serious challenge for the DR model, unless the masses of the scalars are moved to regions which are problematic from the point of view of naturalness and probably beyond the reach of the LHC. We emphasize that this problem could be a general feature of SUSY GUT models with third generation Yukawa unification and weak-scale minimal flavour violation.Comment: 1 + 37 pages, 5 figures, 11 tables. v3: minor typos fixed. Matches JHEP published versio

Light MSSM Higgs boson mass to three-loop accuracy

The light CP even Higgs boson mass, Mh, is calculated to three-loop accuracy within the Minimal Supersymmetric Standard Model (MSSM). The result is expressed in terms of DRbar parameters and implemented in the computer program H3m. The calculation is based on the proper approximations and their combination in various regions of the parameter space. The three-loop effects to Mh are typically of the order of a few hundred MeV and opposite in sign to the two-loop corrections. The remaining theory uncertainty due to higher order perturbative corrections is estimated to be less than 1 GeV.Comment: 39 pages, 13 figures. v2: minor changes, typos fixe

Electroweak physics

Work on electroweak precision calculations and event generators for electroweak physics studies at current and future colliders is summarized

Mass Bounds on a Very Light Neutralino

Within the Minimal Supersymmetric Standard Model (MSSM) we systematically investigate the bounds on the mass of the lightest neutralino. We allow for non-universal gaugino masses and thus even consider massless neutralinos, while assuming in general that R-parity is conserved. Our main focus are laboratory constraints. We consider collider data, precision observables, and also rare meson decays to very light neutralinos. We then discuss the astrophysical and cosmological implications. We find that a massless neutralino is allowed by all existing experimental data and astrophysical and cosmological observations.Comment: 36 pages, 13 figures, minor modification in astro-physical bounds. EPJC versio