Parity in left-right symmetric models

We considered parity breaking in some left-right symmetric models. We studied spontaneous and explicit parity violation in two cases with doublet and triplet Higgs scalars. The minimization condition in these two cases differ significantly. A comparative study of these models is presented emphasizing their phenomenological consequences.Comment: 14 pages latex file; corrected and rewritten introductio

On Symmetry Non-Restoration at High Temperature

We study the effect of next-to-leading order contributions on the phenomenon of symmetry non-restoration at high temperature in an $O(N_1)\times O(N_2)$ model.Comment: 8 pages. Two figures in a separate fil

Scaling in the Neutrino Mass Matrix

In an attempt to uncover any underlying structure in the neutrino mass matrix, we discuss the possibility that the ratios of elements of its Majorana mass matrix are equal. We call this "strong scaling Ansatz" for neutrino masses and study its phenomenological implications. Of three possible independent scale invariant possibilities, only one is allowed by current data, predicting in a novel way the vanishing of U_{e3} and an inverted hierarchy with the lightest neutrino having zero mass. The Ansatz has the additional virtue that it is not affected by renormalization running. We also discuss explicit models in which the scaling Ansatz is realized.Comment: 13 pages, 2 figures. To appear in PL

Heavy neutrino mass hierarchy from leptogenesis in left-right symmetric models with spontaneous CP-violation

We consider left-right symmetric model with spontaneous CP-violation. The Lagrangian of this model is CP invariant and the Yukawa couplings are real. Due to spontaneous breaking of the gauge symmetry, some of the neutral Higgses acquire complex vacuum expectation values, which lead to CP-violation. In the model considered here, we identify the neutrino Dirac mass matrix with that of Fritzsch type charged lepton mass matrix. We assume a hierarchical spectrum of the right handed neutrino masses and derive a bound on this hierarchy by assuming that the decay of the lightest right handed neutrino produces the baryon asymmetry via the leptogenesis route. It is shown that the mass hierarchy we obtain is compatible with the current neutrino oscillation data.Comment: References added, Journal version, to appear in Nucl.Phys.

CP violation in the lepton sector with Majorana neutrinos

We study CP violation in the lepton sector in extended models with right-handed neutrinos, without and with left-right symmetry, and with arbitrary mass terms. We find the conditions which must be satisfied by the neutrino and charged lepton mass matrices for CP conservation. These constraints, which are independent of the choice of weak basis, are proven to be also sufficient in simple cases. This invariant formulation makes apparent the necessary requirements for CP violation, as well as the size of CP violating effects. As an example, we show that CP violation can be much larger in left-right symmetric models than in models with only additional right-handed neutrinos, {\it i.e.}, without right-handed currents.Comment: 19 page

Electroweak-scale mirror fermions, μ→eγ\mu \to e \gamma and τ→μγ\tau \to \mu \gamma

The Lepton Flavour Violating (LFV) processes $\mu \to e \gamma$ and $\tau \to \mu \gamma$ are estimated in a model of electroweak-scale right-handed neutrinos. The present bounds on the branching ratios, $B(\mu \to e \gamma)< 1.2 \times 10^{-11}$, $B(\tau \to \mu \gamma) < 6.8 \times 10^{-8}$ (BaBar) and $< 4.5 \times 10^{-8}$ (Belle), puts strong constraints on the parameters of the model. This constraint links low energy rare decay processes to high-energy phenomena (e.g. decay lengths of the mirror charged leptons which are important in the search for the telltale like-sign dilepton events present in the model of electroweak-scale right-handed neutrinos).Comment: 8 double-column pages, 1 embedded figure. Version accepted for publication in Phys. Lett. B includes the following additions: one table, a few remarks, and three reference

Observable Neutron-Antineutron Oscillations in Seesaw Models of Neutrino Mass

We show that in a large class of supersymmetric models with spontaneously broken B-L symmetry, neutron--antineutron oscillations occur at an observable level even though the scale of B-L breaking is very high, v_{B-L} ~ 2 x 10^{16} GeV, as suggested by gauge coupling unification and neutrino masses. We illustrate this phenomenon in the context of a recently proposed class of seesaw models that solves the strong CP problem and the SUSY phase problem using parity symmetry. We obtain an upper limit on N-\bar{N} oscillation time in these models, \tau_{N-\bar{N}} < 10^{9} -10^{10} sec. This suggests that a modest improvement in the current limit on \tau_{N-\bar{N}} of 0.86 x 10^8 sec will either lead to the discovery of N-\bar{N} oscillations, or will considerably restrict the allowed parameter space of an interesting class of neutrino mass models.Comment: 11 pages RevTeX, 1 figur

Neutrinoless Double Beta Decay and Physics Beyond the Standard Model

The various mechanisms for neutrinoless double beta decay in gauge theories are reviewed and the present experimental data is used to set limits on physics scenarios beyond the standard model. The positive indications for nonzero neutrino masses in various experiments such as those involving solar, atmospheric and accelerator neutrinos are discussed and it is pointed out how some neutrino mass textures consistent with all data can be tested by the ongoing double beta decay experiments. Finally, the outlook for observable neutrinoless double beta decay signal in grand unified theories is discussed.Comment: 21 pages, latex; 10 figures available on request; Invited talk presented at the "International Workshop on Neutrinoless Double Beta Decay and relate topics", Trento, Italy; April, 1995; to appear in the proceedings to be published by World scientifi

Effect of inverse magnetic catalysis on conserved charge fluctuations in hadron resonance gas model

The effect of inverse magnetic catalysis (IMC) has been observed on the conserved charge fluctuations and the correlations along the chemical freeze-out curve in a hadron resonance gas model. The fluctuations and the correlations have been compared with and without charge conservations. The charge conservation plays an important role in the calculation of the fluctuations at nonzero magnetic field and for the fluctuations in the strange charge at zero magnetic field. The charge conservation diminishes the correlations $\chi_{BS}$ and $\chi_{QB}$, but enhances the correlation $\chi_{QS}$. The baryonic fluctuations (2nd order) at $B = 0.25$ ${GeV}^2$ increases more than two times compared to $B = 0$ at higher $\mu_{B}$. The fluctuations have been compared at nonzero magnetic field along the freeze-out curve i.e along fitted parameters of the chemical freeze-out temperature and chemical potentials, with the fluctuations at nonzero magnetic field along the freeze-out curve with the IMC effect, and the results are very different with the IMC effect. This is clearly seen in the products of different moments ${{\sigma}^2}/{M}$ and $S\sigma$ of net-kaon distribution.Comment: 12 pages,10 figures, Accepted by Phys. Rev.