Measurement of the Xi-p Scattering Cross Sections at Low Energy

In this paper we report cross-section measurements for $\Xi^-p$ elastic and inelastic scatterings at low energy using a scintillating fiber active target. Upper limit on the total cross-section for the elastic scattering was found to be 24 mb at 90% confidence level, and the total cross section for the $\Xi^-p\to\Lambda\Lambda$ reaction was found to be $4.3^{+6.3}_{-2.7}$ mb. We compare the results with currently competing theoretical estimates.Comment: 9 page

Phenomenological Tests of Supersymmetric A_4 Family Symmetry Model of Neutrino Mass

Recently Babu, Ma and Valle proposed a model of quark and lepton mixing based on $A_4$ symmetry. Within this model the lepton and slepton mixings are intimately related. We perform a numerical study in order to derive the slepton masses and mixings in agreement with present data from neutrino physics. We show that, starting from three-fold degeneracy of the neutrino masses at a high energy scale, a viable low energy neutrino mass matrix can indeed be obtained in agreement with constraints on lepton flavour violating $\mu$ and $\tau$ decays. The resulting slepton spectrum must necessarily include at least one mass below 200 GeV which can be produced at the LHC. The predictions for the absolute Majorana neutrino mass scale $m_0 \geq 0.3$ eV ensure that the model will be tested by future cosmological tests and $\beta\beta_{0\nu}$ searches. Rates for lepton flavour violating processes $\ell_j \to \ell_i + \gamma$ in the range of sensitivity of current experiments are typical in the model, with BR(\mu \to e \gamma) \gsim 10^{-15} and the lower bound BR$(\tau \to \mu \gamma) > 10^{-9}$. To first approximation, the model leads to maximal leptonic CP violation in neutrino oscillations.Comment: 23 pages, 7 figure

Nuclear and nucleon transitions of the H di-baryon

We consider 3 types of processes pertinent to the phenomenology of an H di-baryon: conversion of two $\Lambda$'s in a doubly-strange hypernucleus to an H, decay of the H to two baryons, and -- if the H is light enough -- conversion of two nucleons in a nucleus to an H. We compute the spatial wavefunction overlap using the Isgur-Karl and Bethe-Goldstone wavefunctions, and treat the weak interactions phenomenologically. The observation of $\Lambda$ decays from doubly-strange hypernuclei puts a constraint on the H wavefunction which is plausibly satisfied. In this case the H is very long-lived as we calculate. An absolutely stable H is not excluded at present. SuperK can provide valuable limits

Time and Amplitude of Afterpulse Measured with a Large Size Photomultiplier Tube

We have studied the afterpulse of a hemispherical photomultiplier tube for an upcoming reactor neutrino experiment. The timing, the amplitude, and the rate of the afterpulse for a 10 inch photomultiplier tube were measured with a 400 MHz FADC up to 16 \ms time window after the initial signal generated by an LED light pulse. The time and amplitude correlation of the afterpulse shows several distinctive groups. We describe the dependencies of the afterpulse on the applied high voltage and the amplitude of the main light pulse. The present data could shed light upon the general mechanism of the afterpulse.Comment: 11 figure

Coupling Unification, GUT-Scale Baryogenesis and Neutron-Antineutron Oscillation in SO(10)

We show that unification of the three gauge couplings can be realized consistently in a class of non-supersymmetric SO(10) models with a one-step breaking to the Standard Model if a color-sextet scalar field survives down to the TeV scale. Such scalars, which should be accessible to the LHC for direct detection, arise naturally in SO(10) as remnants of the seesaw mechanism for neutrino masses. The diquark couplings of these scalars lead to \Delta B = 2 baryon number violating processes such as neutron-antineutron oscillation. We estimate the free neutron-antineutron transition time to be \tau_{n-\bar{n}} \approx (10^9-10^{12}) sec., which is in the interesting range for next generation n-\bar{n} oscillation experiments. These models also realize naturally the recently proposed (B-L)-violating GUT scale baryogenesis which survives to low temperatures unaffected by the electroweak sphaleron interactions.Comment: 15 pages, 4 eps figures, references added, to appear in Phys. Lett.

Faddeev calculations for the A=5,6 Lambda-Lambda hypernuclei

Faddev calculations are reported for Lambda-Lambda-5H, Lambda-Lambda-5He and Lambda-Lambda-6He in terms of two Lambda hyperons plus the respective nuclear clusters, using Lambda-Lambda central potentials considered in past non-Faddeev calculations of Lambda-Lambda-6He. The convergence with respect to the partial-wave expansion is studied, and comparison is made with some of these Lambda-Lambda hypernuclear calculations. The Lambda-Lambda Xi-N mixing effect is briefly discussed.Comment: submitted for publicatio

Lepton Flavour Violation in a Class of Lopsided SO(10) Models

A class of predictive SO(10) grand unified theories with highly asymmetric mass matrices, known as lopsided textures, has been developed to accommodate the observed mixing in the neutrino sector. The model class effectively determines the rate for charged lepton flavour violation, and in particular the branching ratio for $\mu -> e \gamma$, assuming that the supersymmetric GUT breaks directly to the constrained minimal supersymmetric standard model (CMSSM). We find that in light of the combined constraints on the CMSSM parameters from direct searches and from the WMAP satellite observations, the resulting predicted rate for $\mu -> e \gamma$ in this model class can be within the current experimental bounds for low $\tan \beta$, but that the next generation of $\mu -> e \gamma$ experiments would effectively rule out this model class if LFV is not detected.Comment: 23 page

Is weak temperature dependence of electron dephasing possible?

The first-principle theory of electron dephasing by disorder-induced two state fluctuators is developed. There exist two mechanisms of dephasing. First, dephasing occurs due to direct transitions between the defect levels caused by inelastic electron-defect scattering. The second mechanism is due to violation of the time reversal symmetry caused by time-dependent fluctuations of the scattering potential. These fluctuations originate from an interaction between the dynamic defects and conduction electrons forming a thermal bath. The first contribution to the dephasing rate saturates as temperature decreases. The second contribution does not saturate, although its temperature dependence is rather weak, $\propto T^{1/3}$. The quantitative estimates based on the experimental data show that these mechanisms considered can explain the weak temperature dependence of the dephasing rate in some temperature interval. However, below some temperature dependent on the model of dynamic defects the dephasing rate tends rapidly to zero. The relation to earlier studies of the dephasing caused by the dynamical defects is discussed.Comment: 14 pages, 6 figures, submitted to PR

Variable Modified Chaplygin Gas in Anisotropic Universe with Kaluza-Klein Metric

In this work, we have consider Kaluza-Klein Cosmology for anisotropic universe where the universe is filled with variable modified chaplygin gas (VMCG). Here we find normal scalar field $\phi$ and the self interacting potential $V(\phi)$ to describe the VMCG Cosmology. Also we graphically analyzed the geometrical parameters named {\it statefinder parameters} in anisotropic Kaluza-Klein model. Next, we consider a Kaluza-Klein model of interacting VMCG with dark matter in the Einstein gravity framework. Here we construct the three dimensional autonomous dynamical system of equations for this interacting model with the assumption that the dark energy and the dark matter are interact between them and for that we also choose the interaction term. We convert that interaction terms to its dimensionless form and perform stability analysis and solve them numerically. We obtain a stable scaling solution of the equations in Kaluza-Klein model and graphically represent solutions.Comment: 11 pages, 13 figure

High scale mixing unification and large neutrino mixing angles

Starting with the hypothesis that quark and lepton mixings are identical at or near the GUT scale, we show that the large solar and atmospheric neutrino mixing angles together with the small reactor angle $U_{e3}$ can be understood purely as a result of renormalization group evolution. The only requirements are that the three neutrinos must be quasi degenerate in mass and have same CP parity. It predicts that the common Majorana mass for the neutrinos must be larger than 0.1 eV making the idea testable in the currently planned or ongoing experiments searching for neutrinoless-double-beta decay.Comment: 10 pages, eight figure, two tables; new material added; results remain unchange