Related papers: Solving cosmological problem in universal extra di…
In this work we extend the SM by introducing only exotic scalars and leptons and show that within the reasonable error limits, both the observed anomalies in $R(D^{(*)})$ and $R_{K^{(*)}}$ can be explained along with satisfying all the…
In this paper we consider the possibility of neutrino mass varying during the evolution of the Universe and study its implications on leptogenesis. Specifically, we take the minimal seesaw model of neutrino masses and introduce a coupling…
We revisit the physics of neutrino magnetic moments, focusing in particular on the case where the right-handed, or sterile, neutrinos are heavier (up to several MeV) than the left-handed Standard Model neutrinos. The discussion is centered…
We propose a new Universal Extra Dimensional model that is defined on a six-dimensional spacetime which has a two-sphere orbifold $S^2/Z_2$ as an extra-space. We specify our model by choosing the gauge symmetry as…
Present experimental data do not exclude fast oscillation of the neutron $n$ to its degenerate twin from a hypothetical parallel sector, the so called mirror neutron $n'$. We show that this effect brings to a remarkable modifications of the…
We argue that the long-standing issues of neutrino mass and dark matter can be manifestly solved in a dark gauge symmetry $U(1)_D$ that transforms nontrivially only for three right-handed neutrinos $\nu_{1,2,3R}$ -- the counterparts of…
Models that involve extra dimensions have introduced completely new ways of looking up on old problems in theoretical physics. The aim of the present notes is to provide a brief introduction to the many uses that extra dimensions have found…
We review the phenomenology of models with flat, compactified extra dimensions where all of the Standard Model fields are allowed to propagate in the bulk, known as Universal Extra Dimensions (UED). UED make for an interesting TeV-scale…
A model is presented where there exists another U(1) gauge group which is extremely weakly coupled to that of QED except inside the core of domain walls. It is possible to choose parameters such that standard model photons crossing such a…
The seesaw mechanism that explains the small neutrino masses comes naturally with supersymmetric (SUSY) grand unification and leptogenesis. However, the framework suffers from the SUSY flavor and CP problems, and has a severe cosmological…
We explore the dynamics of neutrinos in a vacuum dominated cosmology. First we show that such a geometry will induce a phase change in the eigenstates of a massive neutrino and we calculate the phase change. We also calculate the delay in…
We conjecture that three light Majorana neutrinos and their right-handed counterparts may have a universal geometric mass hierarchy. Incorporating this phenomenological conjecture with the Fritzsch texture of lepton mass matrices in a…
We try to envision that there might be a dark-matter world and neutrinos, especially the right-handed ones, might be coupled directly with dark-matter particles in the dark-matter world. The candidate model would be the extended Standard…
In Split Supersymmetry scenarios the possibility of having a very heavy gravitino opens the door to alleviate or completely solve the worrisome "gravitino problem'' in the context of supersymmetric baryogenesis models. Here we assume that…
Relic neutrinos play an important role in the evolution of the Universe, modifying some of the cosmological observables. We summarize the main aspects of cosmological neutrinos and describe how the precision of present cosmological data can…
The cosmology of KK gravitinos in models with extra dimensions is considered. The main result is that the production of such KK modes is not compatible with an epoch of non--standard expansion after inflation. This is so because the BBN…
Recent theoretical developments have shown that extra spacetime dimensions can lower the fundamental GUT, Planck, and string scales. However, recent evidence for neutrino oscillations suggests the existence of light non-zero neutrino…
Recently, there has been a growing interest in extensions of the Standard Model in which naturally small Dirac neutrino masses arise due to existence of a symmetry which protects neutrino's Diracness. Motivated by this, we consider an…
We explore scenarios where the highest energy cosmic rays are produced by new particle physics near the grand unification scale. Using detailed numerical simulations of extragalactic nucleon, gamma-ray, and neutrino propagation, we show the…
Even though neutrinos and antineutrinos are everywhere in the Universe, their critical importance might be overlooked, especially because that at least one species of neutrinos has the mass 0.058 eV, far larger than the cosmic…