Gamma gamma \to mu tau b bbar in Susy Higgs mediated lepton flavor violation

The process gamma gamma \to mu tau b bbar is studied in the minimal supersymmetric standard model within a large tan_beta scenario imposing on the parameter space present direct and indirect constraints from B physics and rare LFV tau-decays. At a photon collider based on an e+e- linear collider with a center of mass energy of 800 GeV with the parameters of the TESLA proposal (expected integrated gamma-gamma luminosity L=200-500 inverse fb) the LFV signal can be probed for masses of the heavy neutral Higgs bosons A,H from 300 GeV up to the kinematical limit ~ 600 GeV for tan_beta in the range 30,60.Comment: Prepared for "Incontri di Fisica delle Alte Energie", IFAE 2009, Bari, Italy, 15-17 Aprile 2009. To appear in the proceedings to be published by the Societa' Italiana di Fisica in the Nuovo Cimento C - Colloquia on Physic

Leptogenesis and composite heavy neutrinos with gauge mediated interactions

Leptogenesis is an appealing framework to account for the baryon asymmetry in the universe. To this end physics beyond the Standard Model is demanded. In this paper we investigate the possibility to attain successful leptogenesis with composite Majorana neutrinos. We work in the framework of effective gauge mediated and contact interactions without any reference to an underlying compositeness theory. This approach is the one adopted in all current experimental searches for composite fermions at colliders. In the case of gauge mediated interactions, we calculate the CP asymmetry in heavy composite neutrino decays. Both the direct and indirect CP asymmetry are derived and resonant leptogenesis is also discussed. We find that the Sakharov conditions can be met and, for some choice of the parameters, the correct order of magnitude of the baryon asymmetry is reproduced.Comment: 26 pages, 7 figures, references update

Pseudo Hermitian interactions in the Dirac Equation

We consider $(2+1)$ dimensional massless Dirac equation in the presence of complex vector potentials. It is shown that such vector potentials (leading to complex magnetic fields) can produce bound states and the Dirac Hamiltonians are $\eta$-pseudo Hermitian. Some examples have been explicitly worked out.Comment: 8 pages, NO figure

Constraints on Composite-Models Effective Lagrangians from Neutrinoless Double Beta Decay

We give a brief review of the existing bounds on effective couplings for excited states ($e^*, \nu^*, u^*, d^*$) of the ordinary quarks and leptons arising from a composite model scenario. We then explore the phenomenological implications of the hypothesis that the excited neutrino $\nu^*$ might be of Majorana type. Recent bounds on the half-life of the $\Delta L =2$ neutrinoless double beta decay ($0\nu\beta\beta$) are used to constraint the compositeness effective couplings. We show that the bounds so obtained are roughly of the same order of magnitude as those available from high energy experiments.Comment: 20 pages; Latex file and World Scientific style files (uuendoded in a single file). 9 figures appended in a uuencoded file. Uses epsfig.sty; Invited Talk Presented at the International Workshop on Double Beta Decay, ECT*, April 24 - May 5 1995, Trento, Italy. To appear in the Proceeding

Unparticle Casimir effect

In this paper we present the un-Casimir effect, namely the study of the Casimir energy in the presence of an unparticle component in addition to the electromagnetic field contribution. The distinctive feature of the un-Casimir effect is a fractalization of metallic plates. This result emerges through a new dependence of the Casimir energy on the plate separation that scales with a continuous power controlled by the unparticle dimension. As long as the perfect conductor approximation is valid, we find bounds on the unparticle scale that are independent of the effective coupling constant between the scale invariant sector and ordinary matter. We find regions of the parameter space such that for plate distances around $5\mu$m and larger the un-Casimir bound wins over the other bounds.Comment: 13 pages, 3 figures; v2: improved discussion, additional references, v3: title slightly changed, version matching that in press on Physics Letters