The nrMSSU(5) and universality of soft masses

We discuss the problem of universality of the soft, supersymmetry-breaking terms in the minimal supersymmetric SU(5) model (MSSU(5)) completed with flavor-dependent nonrenormalizable operators (NROs), or nrMSSU(5). These are exploited to correct the wrong fermion spectrum and to slow down the too-fast decay rate of the proton that the MSSU(5) model predicts. In general, the presence of such operators in the superpotential and K\"ahler potential gives rise to tree-level flavor- and CP-violating entries in the sfermion mass matrices at the cutoff scale, even when the mediation of supersymmetry (SUSY) breaking is generation and field-type independent. We identify the conditions under which such terms can be avoided.Comment: 4 pages, LateX, to appear in the proceedings of SUSY09, Boston, MA, USA, 5-10 June 200

Rare Supersymmetric Top Quark Decays

{Two supersymmetric decays of the top quark, \thb and \tstopneu, are discussed within the framework of the Minimal Supersymmetric Standard Model with radiatively induced breaking of $SU(2)\times U(1)$. The present possibility of detecting these decays, given the available bounds on supersymmetric parameters, is compared with the situation a Next $e^+e^-$ Linear Collider would face if supersymmetric particles were still undiscovered after LEP~II. The indirect implications for \thb and \tstopneu of a possible detection of the bottom quark decay \bsgamma at the Standard Model level are taken into account. } % Invited talk presented to the {\it Workshop on Physics and Experiments with Linear $e^+e^-$ Colliders}, Waikoloa, Hawaii, April 1993Comment: 7 pages, with 8 uuencoded PS figures, PREPRINT DESY 93-098; - few sentences added in the introduction, style file change

Minimal supersymmetric SU(5) model with nonrenormalizable operators: Seesaw mechanism and violation of flavour and CP

Flavour and CP violations that the neutrino-seesaw couplings of types I, II, and III induce radiatively in the soft massive parameters of the minimal supersymmetric SU(5) model, made realistic by nonrenormalizable operators, are analyzed. Effective couplings are used to parametrize the couplings of renormalizable operators and of the corrections that nonrenormalizable ones provide at the tree level. It is found that for a limited, but sufficient accuracy in the calculations of such violations, it is possible to extend the picture of effective couplings to the quantum level, all the way to the cutoff scale. The arbitrariness introduced by nonrenormalizable operators is analyzed in detail. It is shown that it can be drastically reduced in the Yukawa sector if the effective Yukawa couplings involving colored triplet Higgs bosons are tuned to suppress the decay rate of the proton. In the supersymmetry-breaking sector, the usual requirement of independence of flavour and field type for the mechanism of mediation of supersymmetry breaking is not sufficient to forbid arbitrary flavour and CP violations at the tree level. Special conditions to be added to this requirement, under which such violations can be avoided, are identified. Depending on how and whether these conditions are implemented, different phenomenological scenarios emerge. Flavour and CP violations of soft massive parameters induced by neutrino-seesaw couplings are discussed explicitly for the simplest scenario, in which no such violations are present at the tree level. Guidelines for studying them in other, less simple scenarios are given. Lists of all renormalization group equations needed for their calculations are provided for each of the three types of seesaw mechanism, at all energies between the TeV scale and Planck scale.Comment: 108 pages, 4 figs. v4: Minor improvements. Published version. The RGEs of App E can be found in a very explicit form at http://www.tuhep.phys.tohoku.ac.jp/~francescaB/rges.htm

The Higgs boson and the International Linear Collider

The Higgs boson will be subject of intense experimental searches in future high-energy experiments. In addition to the effort made at the Large Hadron Collider, where it was discovered, it will be the major subject of study at the International Linear Collider. We review here the reasons for that and some of the issues to be tackled at this future accelerator, in particular that of the precision of the Higgs-boson couplings.Comment: 7 pages, 4 figure