arXiv subjects
Publications and source records attributed to S. Khalil.
We present a review of the present status of the problem of neutrino masses and mixing including a survey of theoretical motivations and models, experimental searches and implications of recently appeared solar and atmospheric neutrino data, which strongly indicate nonzero neutrino masses and mixing angles.
We study the predictions for the direct CP violation parameter epsilon'/epsilon in a class of string-inspired model with non-universal soft A-terms. We show that the non-universality of the A-terms plays an important rule in enhancing the supersymmetric contributions to the CP violation epsilon'/epsilon. In particular, the supersymmetric contribution to epsilon'/epsilon can be of order the KTeV result, epsilon'/epsilon ~ 10^(-3).
We study the inclusive branching ratio for B-> X_s gamma in a class of string-inspired SUSY models with non-universal soft-breaking A-terms. We show that b->s gamma do not severely constrain the non-universality of these models and the parameter regions which are important for generating sizeable contribution to epsilon'/epsilon, of order 2 x10^(-3), are not excluded. We also show that the CP asymmetry of this decay is predicted to be much larger than the standard model prediction in a wide region of the parameter space. In particular, it can be of order 10-15% which can be accessible at B factories.
We study the direct CP asymmetry in B -> X_s gamma decay in SUSY models with non-universal A-terms. We show that the flavour-dependent phases of the A-terms, unlike the flavour-independent ones, can give rise too large contribution to the CP asymmetry while respecting the experimental bounds on the branching ratio of B -> X_s gamma decay and the electric dipole moments of the electron and neutron. The CP asymmetry of this decay is predicted to be much larger than the standard model prediction in a wide region of the parameter space. In particular, it can be of order 10-15% which can be accessible at B factories.
The neutralino-nucleon cross section in the context of the MSSM with universal soft supersymmetry-breaking terms is compared with the limits from dark matter detectors. Our analysis is focussed on the stability of the corresponding cross sections with respect to variations of the initial scale for the running of the soft terms, finding that the smaller the scale is, the larger the cross sections become. For example, by taking $10^{10-12}$ GeV rather than $M_{GUT}$, which is a more sensible choice, in particular in the context of some superstring models, we find extensive regions in the parameter space with cross sections in the range of $10^{-6}$--$10^{-5}$ pb, i.e. where current dark matter experiments are sensitive. For instance, this can be obtained for $\tanβ\gsim 3$.
We analyse the predictions for the inclusive branching ratio for $b\to sγ$ decay in a class of string-inspired SUSY models with non-universal soft-breaking A-terms. These models are particularly interesting since the non-universality of the A-terms plays an important role in providing new significant contributions to CP violation effects in kaon physics while respecting the severe bounds on electric dipole moments. We show that $b\to sγ$ do not severely constrain the non-universality of these models. In particular, at low $\tanβ$ $(\tanβ\simeq 2)$, our predictions are close to the universal case. For large $\tanβ$ ($\tanβ\gsim 15$),the effect of non-universality is enhanced and stronger constraints hold. We find that the parameter regions which are important for generating sizeable contribution to $ε'/ε$, of order $2 \times 10^{-3}$, are not excluded.