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.
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.
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.
118450272
Renormalization group evolution of neutrino masses and mixing in the Type-III seesaw mechanism
Abstract We consider the standard model extended by heavy right-handed fermions transforming as triplets under SU ( 2 ) L , which generate neutrino masses through the Type-III seesaw mechanism. At energies below their respective mass scales, the heavy fields get sequentially decoupled to give an effective dimension-5 operator. Above their mass thresholds, these fields also participate in the renormalization of the wavefunctions, masses and coupling constants. We compute the renormalization group evolution of the effective neutrino mass matrix in this model, with particular emphasis on the threshold effects. The evolution equations are obtained in a basis of neutrino parameters where all the quantities are well-defined everywhere, including at θ 13 = 0 . We also point out the important role of the threshold effects and Majorana phases in the evolution of mixing angles through illustrative examples.
118994296
Signatures of heavy sterile neutrinos at long baseline experiments
Sterile neutrinos with masses {approx}0.1 eV or higher, allowed with the current oscillation data, can potentially play an important role in astrophysics and cosmology. We explore possible signatures of such sterile neutrinos at long baseline experiments. We determine the neutrino conversion probabilities analytically in a 4-neutrino framework, including matter effects, treating the sterile mixing angles {theta}{sub 14}, {theta}{sub 24}, {theta}{sub 34}, the deviation of {theta}{sub 23} from maximality, as well as {theta}{sub 13} and the ratio {delta}m{sub {center_dot}}{sup 2}/{delta}m{sub atm}{sup 2} as small parameters for a perturbative expansion. This gives rise to analytically tractable expressions for flavor conversion probabilities from which effects of these parameters can be clearly understood. We numerically calculate the signals at a neutrino factory with near and far detectors that can identify the lepton charge, and point out observables that can discern the sterile mixing signals. We find that clean identification of sterile mixing would be possible for {theta}{sub 24}{theta}{sub 34} > or approx. 0.005 (3{sigma}) and {theta}{sub 14} > or approx. 0.06 rad (3{sigma}) with the current bound of {theta}{sub 13}<0.2 rad; a better {theta}{sub 13} bound would allow probing smaller values of sterile mixing. We also generalize the formalism for any number of sterilemore » neutrinos, and demonstrate that only certain combinations of sterile mixing parameters are relevant irrespective of the number of sterile neutrinos. This also leads to a stringent test of the scenario with multiple sterile neutrinos that currently is able to describe all the data from the short baseline experiments, including LSND and MiniBooNE.« less
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.
118535855
Singularity-free dark energy star
We propose a model for an anisotropic dark energy star where we assume that the radial pressure exerted on the system due to the presence of dark energy is proportional to the isotropic perfect fluid matter density. We discuss various physical features of our model and show that the model satisfies all the regularity conditions and is stable as well as singularity-free.
201043837
ORIGIN AND INTERPRETATION OF KILOHERTZ QPOS FROM STRANGE STARS IN X-RAY BINARY SYSTEM : THEORETICAL HYDRODYNAMICAL DESCRIPTION
We model and interpret the Kilohertz QPOs from the hydrodynamical description of accretion disk around a rapidly rotating compact strange star. The higher QPO frequency is described by the viscous effects of accretion disk leading to shocks, while the lower one is taken to be the Keplerian motion of the accreting matter. Comparing our results with the observations for two of the fastest rotating compact stellar candidates namely, 4U 1636−53 and KS 1731−260, we find that they match to a very good approximation, thus interpreting them as strange stars. Subject headings: accretion, accretion disks — hydrodynamics — shock waves — stars: neutron — stars: individual (4U 1636-53, KS 1731-260) — X-rays: binaries
119293098
Variable Equation of State for Generalized Dark Energy Model
We present a model for the present accelerating Universe and focus on the different important physical variables involved in the model under the phenomenological assumption Λ∝H2 with a prescription for equation of state parameter in the form $\omega(t)=\omega_{0}+\frac{\omega_{1}\tau}{t^{2}}$, where ω0 and ω1 are two constants and τ is a parameter having dimension of time t2. General expressions for the density parameter Ω and deceleration parameter q are obtained which under specific bound reproduce some of the previous results. We explore physical features of these parameters which (i) provide the scenario of complete evolution of the cosmos with ω(t) and (ii) agree mostly with the observational status of the present phase of the accelerating Universe.
15568020
PHYSICAL PROPERTIES OF TOLMAN–BAYIN SOLUTIONS: SOME CASES OF STATIC CHARGED FLUID SPHERES IN GENERAL RELATIVITY
In this article, Einstein–Maxwell space–time is considered in connection with some of the astrophysical solutions previously obtained by Tolman (1939) and Bayin (1978). The effect of inclusion of charge in these solutions is investigated thoroughly and the nature of fluid pressure and mass density throughout the sphere is discussed. Mass–radius and mass–charge relations are derived for various cases of the charged matter distribution. Two cases are obtained where perfect fluid with positive pressures gives rise to electromagnetic mass models such that gravitational mass is of purely electromagnetic origin.
6715665
ISOSPIN LATTICE GAS MODEL AND NUCLEAR-MATTER PHASE DIAGRAM AND PRESSURE-VOLUME ISOTHERMS
We study a cubic lattice gas model for nuclear matter where each lattice site can be either occupied, by one proton or one neutron, or unoccupied. A nearest-neighbor interaction of the form - ∑ Jijτziτzj is assumed. Our model is an isospin-1 Ising model, with τz= (1, 0, –1) representing respectively (proton, vacancy, neutron). A kinetic-energy term has been included in our model. Under the Bragg-Williams mean-field approximation our model exhibits the existence of a dense phase (liquid-like) and a rare phase (gas-like). The nuclear-matter p−v isotherms given by our model are discussed.