Quantum SUSY signatures in low and high energy processes

In the search for phenomenological evidence of supersymmetry through the indirect method of quantum signatures, it is useful to seek correlations of the non-standard quantum effects in low and high energy proceses, such as those involving on one hand the properties of the B-mesons and on the other hand the physics of the top quark and of the Higgs bosons. There are regions of the MSSM parameter space where the potential quantum SUSY signatures in the two energy regimes are strongly interwoven and therefore the eventual detection of these correlated quantum effects would strongly point towards the existence of underlying supersymmetric dynamics.Comment: 17 pages, LaTeX, 7 figs included with epsfig. Talk at the 5th International Workshop on High Energy Physics Phenomenology (WHEPP-5). To appear in the Proceeding

CP-odd Higgs boson production in association with Neutral gauge boson in High-Energy e+e−e^+e^- Collisions

We study the associated production of a CP-odd Higgs boson $A^0$ with a neutral gauge boson ($Z$ or photon) in high-energy $e^+ e^-$ collisions at the one-loop level in the framework of Two Higgs Doublet Models (THDM). We find that in the small $\tan\beta$ regime the top quark loop contribution is enhanced leading to significant cross-sections (about a few fb), while in the large $\tan\beta$ regime the cross-section does not attain observable rates.Comment: 16 pages Latex, 4 figures, figures in agreement with erratu

The one-loop renormalization of the MSSM Higgs sector and its application to the neutral scalar Higgs masses

The structure of the Higgs sector in the minimal supersymmetric standard model is reviewed at the one-loop level. An on-shell renormalization scheme of the MSSM Higgs sector is presented in detail together with the complete list of formulae for the neutral Higgs masses at the one-loop level. The results of a complete one- loop calculation for the mass spectrum of the neutral MSSM Higgs bosons and the quality of simpler Born-like approximations are discussed for sfermion and gaugino masses in the range of the electroweak scale.Comment: 32 pages, report KA-THEP-5-199

Fermionic decays of neutral MSSM Higgs bosons at the one-loop level

The results of a complete one-loop calculation for the fermionic decay width h^0, H^0, A^0 -> f bar(f) of the neutral MSSM Higgs bosons are presented and the dominant light Higgs decay channel h^0 -> b bar(b) is discussed in detail. The enhancement of the partial decay width h^0 -> b bar(b) compared to the standard Higgs decay is shown for pseudoscalar masses M_A < 300 GeV. Simpler approximation formulae for the Higgs decays are given and their quality is discussed by introducing an effective neutral scalar mixing angle sin(alpha)_eff. Finally the Higgs branching ratios in b bar(b), c bar(c), tau^+ tau^- are calculated.Comment: 31 pages, 6 figure

Higgs decays in the Two Higgs Doublet Model: Large quantum effects in the decoupling regime

We study the Higgs-boson decays h0 -> b \bar{b}, h0 -> \gamma \gamma and h0 -> \gamma Z within the framework of the Two Higgs Doublet Model (THDM) in the context of the decoupling regime, together with tree level unitarity constraints. We show that when the light CP-even Higgs boson of the THDM mimics the Standard-Model Higgs boson, not only the one-loop effects to h0 -> {\gamma \gamma ,\gamma Z} but also the one-loop contribution to h0 -> b \bar{b} can be used to distinguish between THDM and SM. The size of the quantum effects in h0 -> b \bar{b} are of the same order as in h0 -> {\gamma \gamma ,\gamma Z} and can reach 25% in both cases.Comment: LaTeX, 13 pages, 5 figures. Improved text, added references, appendix removed. Version to appear in PL

Scale-independent mixing angles

A radiatively-corrected mixing angle has to be independent of the choice of renormalization scale to be a physical observable. At one-loop in MS-bar, this only occurs for a particular value, p*, of the external momentum in the two-point functions used to define the mixing angle: p*^2=(M1^2+M2^2)/2, where M1, M2 are the physical masses of the two mixed particles. We examine two important applications of this to the Minimal Supersymmetric Standard Model: the mixing angle for a) neutral Higgs bosons and b) stops. We find that this choice of external momentum improves the scale independence (and therefore provides a more reliable determination) of these mixing angles.Comment: 14 pages, 11 ps figures Version to appear in PR

Improved full one-loop corrections to A^0 -> \sf_1 \sf_2 and \sf_2 -> \sf_1 A^0

We calculate the full electroweak one-loop corrections to the decay of the CP-odd Higgs boson A^0 into scalar fermions in the minimal supersymmetric extension of the Standard Model. For this purpose many parameters of the MSSM have to be properly renormalized in the on-shell renormalization scheme. We have also included the SUSY-QCD corrections. For the decay into bottom squarks and tau sleptons, especially for large \tan\b, the corrections can be very large making the perturbation expansion unreliable. We solve this problem by an appropriate definition of the tree-level coupling in terms of running fermion masses and running trilinear couplings A_f. We also discuss the decay of heavy scalar fermions into light scalar fermions and A^0. We find that the corrections can be sizeable and therefore cannot be neglected.Comment: 42 pages, 20 figures (23 eps-files