Antonio Masiero

A complete analysis of FCNC and CP constraints in general SUSY extensions of the standard model

Abstract We analyze the full set of constraints on gluino- and photino-mediated SUSY contributions to FCNC and CP violating phenomena. We use the mass insertion method, hence providing a model-independent parameterization which can be readily applied in testing extensions of the MSSM. In addition to clarifying controversial points in the literature, we provide a more exhaustive analysis of the CP constraints, in particular concerning e′/e. As physically meaningful applications of our analysis, we study the implications in SUSY-GUTs and effective supergravities with flavour nonuniversality. This allows us to detail the domain of applicability and the correct procedure of implementation of the FC mass insertion approach.

A Natural Solution to the mu Problem in Supergravity Theories

Abstract We propose a “natural” way to avoid the introduction by hand of a small mass scale μ in the observable sector of N = 1 supergravity theories. In our approach, μ automatically arises from the general couplings of broken supergravity. In this way, all low energy mass parameters arise only from supergravity breaking and, in particular, SU (2) × U (1) is left unbroken in the limit of exact supersymmetry. Our solution of the μ-problem presents interesting connections with the strong CP puzzle through the implementation of symmetriesala Peccei and Quinn.

Light gravitinos as mixed dark matter

Abstract In theories with a gauge-mediated mechanism of supersymmetry breaking the gravitino is likely to be the lightest superparticle and, hence, a candidate for dark matter. We show that the decay of the next-to-lightest superparticle into a gravitino can yield a non-thermal population of gravitinos which behave as a hot dark matter component. Together with the warm component, which is provided by the population of gravitinos of thermal origin, they can give rise to viable schemes of mixed dark matter. This realization has some specific and testable features both in particle physics and astrophysics. We outline under which conditions the mechanism remains viable even when R -parity is broken.

Flavour changing neutral currents and CP violating processes in generalized supersymmetric theories

Abstract We consider supersymmetric extensions of the standard model with general non-universal soft breaking terms. We analyse in a model-independent way the constraints on these terms at the electroweak energy scale coming from gluino mediated flavour (F) changing neutral current and CP-violating processes. We have computed the complete ΔF = 1 and ΔF = 2 effective hamiltonian for gluino mediated processes, including for the first time the effect of box diagrams in the evaluation of ϵ′ ϵ . We present numerical results for the constraints on these non-universal soft breaking terms for different values of the parameters, extending the analysis also to the leptonic sector. A comparison with previous results in the literature is given.

CP VIOLATING B DECAYS IN THE STANDARD MODEL AND SUPERSYMMETRY

We study the uncertainties of the standard model (SM) predictions for CP violating B decays and investigate where and how supersymmetric (SUSY) contributions may be disentangled. The first task is accomplished by letting the relevant matrix elements of the effective Hamiltonian vary within certain ranges. The SUSY analysis makes use of a formalism which allows one to obtain model-independent results. We show that in some cases it is possible (a) to measure the CP B‐BB mixing phase and (b) to discriminate the SM and SUSY contributions to the CP decay phases. The gold-plated decays in this respect are the B ! fKS and B ! KSp 0 channels. [S0031-9007(97)03711-3] PACS numbers: 11.30.Er, 12.15.Hh, 12.60.Jv, 13.25.Hw

The Formation of cosmic structures in a light gravitino dominated universe

We analyse the formation of cosmic structures in models where the dark matter is dominated by light gravitinos with mass of

Hybrid inflation from supersymmetric SU(5)

100

CPviolation in a supersymmetric model with nondegenerateAterms

eV -- 1 keV, as predicted by gauge-mediated supersymmetry (SUSY) breaking models. After evaluating the number of degrees of freedom at the gravitinos decoupling (

Bounds on heavy chiral fermions

g_*

Low energy implications of minimal superstring unification

), we compute the transfer function for matter fluctuations and show that gravitinos behave like warm dark matter (WDM) with free-streaming scale comparable to the galaxy mass scale. We consider different low-density variants of the WDM model, both with and without cosmological constant, and compare the predictions on the abundances of neutral hydrogen within high-redshift damped Ly--