David Delepine

A light stop and electroweak baryogenesis

The possibility of creating baryon asymmetry at the electroweak phase transition in the minimal supersymmetric standard model is considered for the case when right-handed squarks are much lighter than left-handed ones. It is shown that the usual requirement v(T_c)/T_c > 1 for baryogenesis can be satisfied in a range of the parameters of the model, consistent with present experimental bounds. Comment: Latex file, 11 pages, 2 postscript figures

NEUTRINO MIXING AND THE PATTERN OF SUPERSYMMETRY BREAKING

Abstract We study the implications of a large ν μ – ν τ mixing angle on lepton flavour violating radiative transitions in supersymmetric extensions of the standard model. The transition rates are calculated to leading order in ϵ , the parameter which characterizes the flavour mixing. The uncertainty of the predicted rates is discussed in detail. For models with modular invariance the branching ratio BR ( μ → eγ ) mostly exceeds the experimental upper limit. In models with radiatively induced flavour mixing the predicted range includes the upper limit, if the Yukawa couplings in the lepton sector are large, as favoured by Yukawa coupling unification.

NEUTRINO MIXING AND FLAVOUR CHANGING PROCESSES

We study the implications of a large νμ–ντ mixing angle on flavour changing transitions of quarks and leptons in supersymmetric extensions of the standard model. Two patterns of supersymmetry breaking are considered, models with modular invariance and the standard scenario of universal soft breaking terms at the GUT scale. The analysis is performed for two symmetry groups G⊗U(1)F, with G=SU(5) and G=SU(3)3, where U(1)F is a family symmetry. Models with modular invariance are in agreement with observations only for restricted scalar quark and gaugino masses, Mq2/mg2≃7/9 and mb>350 GeV. A characteristic feature of models with large tanβ and radiatively induced flavour mixing is a large branching ratio for μ→eγ. For both symmetry groups and for the considered range of supersymmetry breaking mass parameters we find BR(μ→eγ)>10−14.

Top flavour violating decays in general supersymmetric models

Abstract We analyse the top flavour violating decays in general supersymmetric model using the mass insertion approximation. In particular, we discuss the impact of a light right-handed top-squark and large mixing between the first or second and third generation of up-squarks on processes as t → q γ , g . We also take into account the relevant experimental constraints from B -physics and the requirements for a successfull electroweak baryogenesis on squark mixings. We show that for general large mixings in squarks mass matrix, the branching ratio of the t → q γ , g ( q = u , c ) can be as large as 10 − 6 .

Indirect bounds on Z→μe, and lepton flavor violation at future colliders

Abstract Motivated by the interest in lepton number violating processes, we study the connection between the rate of Z → μe decay and those of the low-energy processes μ →3 e , and μ → e conversion in nuclear field, assuming that the relevant form factors are constant or weakly q 2 dependent. We show that if the vector or axial Z form factors are dominant, Br( Z → μe ) is not observable, while if the Z dipole form factors are dominant, the relatively weak indirect bound Br( Z → μe ) −9 does not fully preclude a signal at future colliders, as TESLA. We finally comment on the relation of Z → μe with Z → τe and Z → τμ decays, and suggest a simple scaling law for these three processes.

Equivalence of the sine-Gordon and massive Thirring models at finite temperature

Using the path-integral approach, the quantum massive Thirring and sine-Gordon models are proven to be equivalent at finite temperature. This result is an extension of Colemans proof of the equivalence between both theories at zero temperature. The usual identifications among the parameters of these models also remain valid at

Final state interaction phases in (B ---> K pi) decay amplitudes

T \neq 0

TeV scale leptogenesis in B − L model with alternative cosmologies

. Comment: 9 pages, standard LaTeX

Supersymmetry and C P violation in | Δ S | = 1 τ decays

A simple Regge pole model for

Constraining New Physics with D meson decays

K\pi