Bulk fields with general brane kinetic terms

We analyse the effect of general brane kinetic terms for bulk scalars, fermions and gauge bosons in theories with extra dimensions, with and without supersymmetry. We find in particular a singular behaviour when these terms contain derivatives orthogonal to the brane. This is brought about by $\delta(0)$ divergences arising at second and higher order in perturbation theory. We argue that this behaviour can be smoothed down by classical renormalization.Comment: 31 pages, v2 few typos correcte

Impact of right-handed interactions on the propagation of Dirac and Majorana neutrinos in matter

Dirac and Majorana neutrinos can be distinguished in relativistic neutrino oscillations if new right-handed interactions exist, due to their different propagation in matter. We review how these new interactions affect neutrino oscillation experiments and discuss the size of this eventually observable effect for different oscillation channels, baselines and neutrino energies.Comment: 26 pages, 5 figure

Top effective operators at the ILC

We investigate the effect of top trilinear operators in t tbar production at the ILC. We find that the sensitivity to these operators largely surpasses the one achievable by the LHC either in neutral or charged current processes, allowing to probe new physics scales up to 4.5 TeV for a centre of mass energy of 500 GeV. We show how the use of beam polarisation and an eventual energy upgrade to 1 TeV allow to disentangle all effective operator contributions to the Ztt and gamma tt vertices.Comment: LaTeX 13 pages. Typos corrected. Final version in JHE

Comment on SU(16) grand unification

In a recent paper on SU(16) grand unification, because of the presence of intermediate-energy gauge groups containing products of U(1) factors which are not orthogonal among themselves, the renormalization-group treatment has a few small errors. I correct it. I emphasize that one should not switch gauge couplings at the various thresholds. It is easier, and it avoids errors, to use throughout the gauge couplings of the standard model, and compute at each threshold, in the usual way, the extra contributions to the beta functions from the extra non-decoupled fields. I also point out that the SU(16) grand unification theory, due to the large number of scalars present in it, is not asymptotically free. It becomes a strong-coupling theory at energies only slightly larger than the unification scale.Comment: 5 latex pages, 2 tables, no figure

Fermion localization on branes with generalized dynamics

In this letter we consider a specific model of braneworld with nonstandard dynamics diffused in the literature, specifically we focus our attention on the matter energy density, the energy of system, the Ricci scalar and the thin brane limit. As the model is classically stable and capable of localize gravity, as a natural extension we address the issue of fermion localization of fermions on a thick brane constructed out from one scalar field with nonstandard kinetic terms coupled with gravity. The contribution of the nonstandard kinetic terms in the problem of fermion localization is analyzed. It is found that the simplest Yukawa coupling $\eta\bar{\Psi}\phi\Psi$ support the localization of fermions on the thick brane. It is shown that the zero mode for left-handed can be localized on the thick brane depending on the values for the coupling constant $\eta$.Comment: 6 pages, 3 figure

Top effective operators at the ILC

We investigate the effect of top trilinear operators in t tbar production at the ILC. We find that the sensitivity to these operators largely surpasses the one achievable by the LHC either in neutral or charged current processes, allowing to probe new physics scales up to 4.5 TeV for a centre of mass energy of 500 GeV. We show how the use of beam polarisation and an eventual energy upgrade to 1 TeV allow to disentangle all effective operator contributions to the Ztt and gamma tt vertices.Comment: LaTeX 13 pages. Typos corrected. Final version in JHE

Z' Decays into Four Fermions

If a new $Z'$ is discovered with a mass $\sim 1 \ TeV$ at LHC/SSC, its (rare) decays into two charged leptons plus missing transverse energy will probe the $Z'$ coupling to the lepton doublet $(\nu,e)_L$ and to $W^+W^-$, allowing further discrimination among extended electroweak models.Comment: 9 pages plus 1 figure (not included but available), UG-FT-22/9

Quark mixings and flavor changing interactions with singlet quarks

Aspects of the quark mixings and flavor changing interactions are investigated in electroweak models with singlet quarks. The effects on the ordinary quark mixing are determined in terms of the quark masses and the parameters describing the mixing between the ordinary quarks q and the singlet quarks Q (q-Q mixing). Some salient features arise in the flavor changing interactions through the q-Q mixing. The unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix within the ordinary quark sector is violated, and the flavor changing neutral currents (FCNC's) appear both in the gauge and scalar couplings. The flavor changing interactions are calculated appropriately in terms of the q-Q mixing parameters and the quark masses, which really exhibit specific flavor structures. It is found that there are reasonable ranges of the model parameters to reproduce the ordinary quark mass hierarchy and the actual CKM structure even in the presence of q-Q mixing. Some phenomenological effects of the singlet quarks are also discussed. In particular, the scalar FCNC's may be more important in some cases, if the singlet quarks as well as the extra scalar particles from the singlet Higgs fields have masses $\sim$ 100 GeV -- 1 TeV.Comment: 32 pages, 7 figures, added reference