Michael Spira

SUSY Les Houches accord: interfacing SUSY spectrum calculators, decay packages, and event generators

An accord specifying a unique set of conventions for supersymmetric extensions of the Standard Model together with generic file structures for 1) supersymmetric model specifications and input parameters, 2) electroweak scale supersymmetric mass and coupling spectra, and 3) decay tables is presented, to provide a universal interface between spectrum calculation programs, decay packages, and high energy physics event generators.

Effective Lagrangian for a light Higgs-like scalar

A bstractWe reconsider the effective Lagrangian that describes a light Higgs-like boson and better clarify a few issues which were not exhaustively addressed in the previous literature. In particular we highlight the strategy to determine whether the dynamics responsible for the electroweak symmetry breaking is weakly or strongly interacting. We also discuss how the effective Lagrangian can be implemented into automatic tools for the calculation of Higgs decay rates and production cross sections.

Neutral Higgs boson pair production at hadron colliders: QCD corrections

Neutral Higgs-boson pair production provides the possibility of studying the trilinear Higgs couplings at future high-energy colliders. We present the QCD corrections to the gluon-initiated processes in the limit of a heavy top quark in the loops and the Drell-Yan-like pair production of scalar and pseudoscalar Higgs particles. The pp cross sections are discussed for LHC energies within the Standard Model and its minimal supersymmetric extension. The QCD corrections are large, enhancing the total cross sections significantly.

Two-photon decay widths of Higgs particles

Abstract Two-photon decays of Higgs bosons are important channels for the search of these particles in the intermediate mass range at the pp colliders LHC and SSC. Dynamical aspects of the Higgs coupling to two photons can also be studied by means of the γγ fusion of Higgs particles at high-energy e + e − linear colliders. Extending earlier analyses which had been restricted to the Standard Model, we present in this note the QCD radiative corrections to the γγ decay widths of scalar and pseudoscalar Higgs particles in multi-doublet extensions of the Higgs sector, as realized for instance in supersymmetric theories.

Higgs radiation off bottom quarks at the Fermilab Tevatron and the CERN LHC

Higgs-boson production in association with bottom quarks, pp/pp{yields}bbH+X, is one of the most important discovery channels for supersymmetric Higgs particles at the Tevatron and the LHC. We have calculated the next-to-leading-order QCD corrections to the parton processes qq,gg{yields}bbH and present results for total cross sections and for distributions in the transverse momenta of the bottom quarks. The QCD corrections reduce the renormalization and factorization scale dependence and thus stabilize the theoretical predictions, especially when the Higgs-boson is produced in association with high-p{sub T} bottom quarks. The next-to-leading-order predictions for the total cross-section are in reasonable numerical agreement with calculations based on bottom-quark fusion bb{yields}H.

SUSY Higgs production at proton colliders

Abstract We present the QCD corrections to the gluon fusion processes of the scalar Higgs particles h , H and the pseudoscalar Higgs particle A in the minimal supersymmetric extension of the Standard Model. These corrections are in general large and positive, increasing the production cross section up to factors of about 2. While they depend only weakly on the Higgs masses, they are strongly dependent on the parameter tg β.

MSSM Higgs boson decays to bottom quark pairs reexamined

We present an update of neutral Higgs boson decays into bottom quark pairs in the minimal supersymmetric extension of the Standard Model. In particular the resummation of potentially large higher-order corrections due to the soft SUSY breaking parameters A_b and mu is extended. The remaining theoretical uncertainties due to unknown higher-order SUSY-QCD corrections are analyzed quantitatively.

A Note on doubly charged Higgs pair production at hadron colliders

We analyze the next-to-leading order QCD corrections to the production of doubly-charged Higgs particles at hadron colliders in extensions of the SM with Higgs isospin triplets. At both the Tevatron and the LHC, these corrections are found to be moderate in size increasing the cross sections by about 20--30%. The residual theoretical uncertainties are of the order of 10--15% which is sufficient for experimental searches for these particles at the Tevatron and LHC.

Higgs boson production via gluon fusion: Squark loops at NLO QCD

The loop-induced processes gg → h,H,A provide the dominant Higgs boson production mechanisms at the Tevatron and LHC in a large range of the minimal supersymmetric extension of the Standard Model. For squark masses below ∼ 400 GeV squark loop contributions become important in addition to the top and bottom quark loops. The next-to-leading order QCD corrections to the squark contributions of these processes are determined including the full squark and Higgs mass dependences. They turn out to be large and thus important for the Tevatron and LHC experiments. Squark mass effects of the K factors can be of O(20%). In addition we derive the QCD corrections to the squark contributions of the rare photonic Higgs decays h,H → , which play a role for the Higgs searches at the LHC.

The Photon Collider at Tesla

High energy photon colliders (γγ,γe) are based on e-e- linear colliders where high energy photons are produced using Compton scattering of laser light on high energy electrons just before the interaction point. This paper is a part of the Technical Design Report of the linear collider TESLA.1 Physics program, possible parameters and some technical aspects of the photon collider at TESLA are discussed.