Heavy-meson physics and flavour violation with a single generation

We study flavour-violating processes which involve heavy B- and D-mesons and are mediated by Kaluza-Klein modes of gauge bosons in a previously suggested model where three generations of the Standard Model fermions originate from a single generation in six dimensions. We find the bound on the size R of the extra spatial dimensions 1/R>3.3 TeV, which arises from the three-body decay B_s to K mu e. Due to the still too low statistics this bound is much less stringent than the constraint arising from K to mu e, 1/R>64 TeV, which was found in a previous work (Frere et al., JHEP, 2003). Nevertheless, we argue that a clear signature of the model would be an observation of K to mu e and B_s to K mu e decays without observations of other flavour and lepton number changing processes at the same precision level.Comment: 15 page

Central pseudoscalar production in pp scattering and the gluon contribution to the proton spin

Central pseudoscalar production in $pp$ scattering is suppressed at small values of $Q_\perp$, where $Q$ is defined as the difference between the momenta transferred from the two protons. Such a behaviour is expected if the production occurs through the fusion of two vectors. Photon exchange could provide the dominant contribution at low transferred momenta, but we argue that an extension of the experiment could probe the gluon contribution to the proton spin.Comment: 12 pages, 2 figures and 3 tables, uses epsf.sty. Added references and tables. Minor changes include

Neutrino Mass Patterns within the See-saw Model from Multi-localization along Extra Dimensions

We study a multi-localization model for charged leptons and neutrinos, including the possibility of a see-saw mechanism. This framework offers the opportunity to allow for realistic solutions in a consistent model without fine-tuning of parameters, even if quarks are also considered. Those solutions predict that the large Majorana mass eigenvalues for right-handed neutrinos are of the same order of magnitude, although this almost common mass can span a large range (bounded from above by $\sim 10^{12}{\rm GeV}$). The model also predicts Majorana masses between $\sim 10^{-2}{\rm eV}$ and $\sim 5 \ 10^{-2}{\rm eV}$for the left-handed neutrinos, both in the normal and inverted mass hierarchy cases. This mass interval corresponds to sensitivities which are reachable by proposed neutrinoless double$\beta$decay experiments. The preferred range for leptonic mixing angle$\theta_{13}$is:$10^{-2} \lesssim \sin \theta_{13} \lesssim 10^{-1}$, but smaller values are not totally excluded by the model.Comment: 36 pages, 8 figure

Neutrino masses with a single generation in the bulk

In a class of multidimensional models, topology of the thick brane provides three chiral fermionic families with hierarchical masses and mixings in the effective four-dimensional theory, while the full model contains a single vector-like generation. We discuss how to incorporate three non-degenerate neutrino masses in these models with the help of only one singlet bulk fermion.Comment: 16 pages, 1 EPS figur

Lepton mixing and heavy neutrinos

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87612/2/189_1.pd

Fermions in the vortex background on a sphere

In 5+1 dimensions, we construct a vortex-like solution on a two-dimensional sphere. We study fermionic zero modes in the background of this solution and relate them to the replication of fermion families in the Standard Model. In particular, using a compactified space removes the need for the difficult localisation of gauge fields, while the present procedure (rather than naive compactification on a disk) also removes spurious fermionic modes.Comment: 13 pages, 1 eps figure, JHEP3 style required, references adde

Study of the eta-eta' system in the two mixing angle scheme

An analysis of various decay processes is performed using the two mixing angle description of the $\eta$-$\eta^\prime$ system, incorporating the link to the gluonic sector through anomalies. The agreement is excellent. For comparison with previous works, our results are expressed both in the ``octet-singlet'' and in the ``quark-flavour'' basis. It turns out that at the present experimental accuracy, the two angles are significantly different in the former, but not in the latter basis. The implications of our analysis for the Large $N_c$ $\chi$PT predictions are also discussed.Comment: 15 pages, JHEP style. Comments on the VMD description of the VPgamma decays, the error correlations,the scale dependence of f0, and the implications of the analysis for Large Nc ChpT are include

Fermionic zero modes in gauge and gravity backgrounds On T2T^2

In this note we study fermionic zero modes in gauge and gravity backgrounds taking a two dimensional compact manifold $T^2$ as extra dimensions. The result is that there exist massless Dirac fermions which have normalizable zero modes under quite general assumptions about these backgrounds on the bulk. Several special cases of gauge background on the torus are discussed and some simple fermionic zero modes are obtained.Comment: 8 pages, no figures, v2: more references, accepted by Mod.Phys.Lett.