118650147
Minimal Lepton Flavor Violation and renormalization group evolution of lepton masses and mixing
We study the renormalization group equations (RGEs) of the neutrino parameters in models of Minimal Lepton Flavor Violation. In such models, the RGEs can be described in terms of flavor spurions, such that only the coefficients depend on the specific model. We explicitly demonstrate this method for the SM and MSSM for both Type-I and Type-III seesaw models. For that purpose, the RGEs of neutrino parameters in the MSSM Type-III seesaw have been computed. We have extended this method to get the evolution equations at second order. The implications for leptogenesis are also discussed.
119875035
New physics signals at long baseline experiments
We develop a formalism that gives analytically tractable expressions for flavor conversion probabilities at long baseline experiments, in the presence of any number of sterile neutrino species or with CPT violation. Using a perturbative expansion in the small parameters we show that, even in a completely general analysis, only certain specific combinations of the mixing parameters are relevant and hence can be probed in the experiments. We identify the long baseline experiments which will be able to probe those observable combinations in a clean manner and estimate their reach in measuring or constraining those observables.
118649508
Renormalization group evolution of neutrino masses and mixing in seesaw models: A Review
We consider different extensions of the standard model which can give rise to the small active neutrino masses through seesaw mechanisms, and their mixing. These tiny neutrino masses are generated at some high energy scale by the heavy seesaw fields which then get sequentially decoupled to give an effective dimension-5 operator. The renormalization group evolution of the masses and the mixing parameters of the three active neutrinos in the high energy as well as the low energy effective theory is reviewed in this article.
199675394
2540 km: Bimagic baseline for neutrino oscillation parameters
We consider a low energy neutrino factory setup with a detector placed at a distance of 2540 km. At this baseline, for both normal and inverted hierarchical neutrino mass spectrum, the wrong‐sign muon event spectrum is almost independent of CP phase δ and the mixing angle θ13 in a specific energy window. This leads to an unambiguous determination of the hierarchy. In addition, a part of the muon spectrum remain sensitive to δ and θ13, so that the same setup can be used to probe these parameters as well using a broadband beam.
118317908
CP asymmetry in the decays B ---> (X(s), X(d)) mu+ mu- with four generations
We estimate the CP asymmetry A CP (q 2 ) in the decays B → X s μ + μ - and B → X d μ + μ in the standard model (SM) with an additional fourth generation. We use a parametrization that allows us to explore the complete parameter space of the 4 X 4 quark mixing matrix, and constrain these parameters from the current data on B decays. We find that the enhancement in A CP (q 2 ) depends strongly on the mass of the t 1 , the up-type quark in the fourth generation. For m t 1 around 400 GeV, the CP asymmetry in the high-q 2 region (q 2 > 14.4 GeV 2 ) can be enhanced by more than an order of magnitude for B → X s μ + μ - and up to a factor of 6 for B → X d μ + μ - . There is no enhancement in the low-q 2 region (1 < q 2 < 6 GeV 2 ). With increasing m t 1 , A CP (q 2 ) in the high-q 2 (low-q 2 ) region first decreases (increases) and then saturates at a value a few times the SM prediction. In the high-q 2 region of B → X s μ + μ - , this saturation value may be up to 25 times the SM expectation.
119869500
Lower bounds on the smallest lepton mixing angle
We give minimal values for the smallest lepton mixing parameter |U{sub e3}|, applying 2-loop renormalization group equations in an effective theory approach. This is relevant in scenarios that predict an inverted neutrino mass spectrum with the smallest mass and |U{sub e3}| being zero at tree level, a situation known to be preserved at 1-loop order. At 2-loop, |U{sub e3}| is generated at a level of 10{sup -12}-10{sup -14}. Such small values are of interest in supernova physics. Corresponding limits for the normal mass ordering are several orders of magnitude larger. Our results show that |U{sub e3}| can in general be expected to be nonzero.
119119882
DARK ENERGY MODELS WITH VARIABLE EQUATION OF STATE PARAMETER
Two phenomenological variable Λ models, viz.Λ ~ (ȧ/a)2 and Λ ~ ρ, have been studied under the assumption that the equation of state parameter ω is a function of time. The selected Λ models are found to be equivalent both in four and five dimensions. The possibility of signature flip of the deceleration parameter is also shown.
15882822
Entropy & viscosity bound of strange stars
At finite temperature (T) there is a link with general relativity and hydrodynamics that leads to a lower bound for the ratio of shear viscosity and entropy density (\eta/s). We find that the bound is saturated in the simple model for quark matter that we use for strange stars at T = 80 MeV, at the surface of a strange star. At this T we have the possibility of cosmic separation of phases. We find that, although strongly correlated, the quark matter at the surface of strange stars constitute the most perfect interacting fluid permitted by nature. At the centre of the star, however, the density is higher and conditions are more like the results found for perturbative QCD.
119346899
ELECTRICALLY CHARGED COMPACT STARS
We review here the classical argument used to justify the electrical neutrality of stars and show that if the pressure and density of the matter and gravitational field inside the star are large, then a charge and a strong electric field can be present. For a neutron star with high pressure (~ 10^{33} to 10^{35} dynes /cm^2) and strong gravitational field (~ 10^{14} cm/s^2), these conditions are satisfied. The hydrostatic equation which arises from general relativity, is modified considerably to meet the requirements of the inclusion of the charge. In order to see any appreciable effect on the phenomenology of the neutron stars, the charge and the electrical fields have to be huge (~ 10^{21} Volts/cm). These stars are not however stable from the viewpoint that each charged particle is unbound to the uncharged particles, and thus the system collapses one step further to a charged black hole
15558768
Relativistic Electromagnetic Mass Models: Charged Dust Distribution in Higher Dimensions
Electromagnetic mass models are proved to exist in higher dimensional theory of general relativity corresponding to charged dust distribution. Along with the general proof a specific example is also sited as a supporting candidate.
119265074
Central density dependent anisotropic compact stars
Stars can be treated as a self-gravitating fluid. In this connection, we propose a model for an anisotropic star under the relativistic framework of Krori and Barua (J. Phys. A, Math. Gen. 8:508, 1975) spacetime. It is shown that the solutions are regular and singularity free. The uniqueness of the model is that interior physical properties of the star solely depend on the central density of the matter distribution.