Explanation of IceCube spectrum with ν→3ν\nu\rightarrow 3 \nu neutrino splitting in a ν\nu2HDM model

A single power law flux spectrum of high energy neutrinos does not adequately explain the entire 60 TeV to 10 PeV event spectrum observed at IceCube, specially the excess of PeV events and the lack of Glashow resonance events expected at 6.3 PeV cannot be simultaneously explained by a single power law source neutrino flux. Here we consider a model of neutrino splitting $\nu\rightarrow 3 \nu$ over cosmological distances. Starting from a single power-law spectrum expected from the astrophysical sources, we show that by adjusting the decay length and spectral index one can give a better fit to the observed IceCube events over the entire 1 TeV -6 PeV, compared to that from a single power spectrum. For $\nu\rightarrow 3\nu$ neutrino splitting, the flavor ratios of the daughter neutrinos are different from the standard oscillation or invisible decay cases and can be used as a test of this scenario. We propose a $\nu$2HDM where a light Higgs ($\sim 0.1$~eV) mediates neutrino splitting via a one-loop box diagram. The split in the masses of the scalars in the doublet gives a large contribution to the oblique T parameter which is severely constrained. This constraint from the S,T,U oblique parameters can be evaded by the introduction of an extra vector lepton doublet and with mass $\sim 200$ GeV.Comment: 19 pages, 8 figures, Journal version to appear in JHE

Robust test for detecting nonstationarity in data from gravitational wave detectors

It is difficult to choose detection thresholds for tests of nonstationarity that assume a priori a noise model if the data are statistically uncharacterized to begin with. This is a potentially serious problem when an automated analysis is required, as would be the case for the huge data sets that large interferometric gravitational wave detectors will produce. A solution is proposed in the form of a robust time-frequency test for detecting nonstationarity whose threshold for a specified false alarm rate is almost independent of the statistical nature of the ambient stationary noise. The efficiency of this test in detecting bursts is compared with that of an ideal test that requires prior information about both the statistical distribution of the noise and also the frequency band of the burst. When supplemented with an approximate knowledge of the burst duration, this test can detect, at the same false alarm rate and detection probability, bursts that are about 3 times larger in amplitude than those that the ideal test can detect. Apart from being robust, this test has properties which make it suitable as an online monitor of stationarity

Hierarchical search strategy for the detection of gravitational waves from coalescing binaries: Extension to post-Newtonian waveforms

The detection of gravitational waves from coalescing compact binaries would be a computationally intensive process if a single bank of template wave forms (one step search) is used. In an earlier paper we presented a detection strategy, called a two step search, that utilizes a hierarchy of template banks. It was shown that in the simple case of a family of Newtonian signals, an on-line two step search was ≃8 times faster than an on-line one step search (for the initial LIGO). In this paper we extend the two step search to the more realistic case of zero spin post1.5-Newtonian wave forms. We also present formulas for detection and false alarm probabilities which take statistical correlations into account. We find that for the case of a post1.5-Newtonian family of templates and signals, an on-line two step search requires ∼1/21 the computing power that would be required for the corresponding on-line one step search. This reduction is achieved when signals having a strength S=10.34 are required to be detected with a probability of 0.95, at an average of one false event per year, and the noise power spectral density used is that of the advanced LIGO. For the initial LIGO, the reduction achieved in computing power is ∼1/27 for S=9.98 and the same probabilities for detection and false alarm as above. The increase in the efficacy of a two step search in the post1.5-Newtonian case comes about chiefly because of an increase in the number of signal parameters since the post1.5-Newtonian signal depends on the binary masses m1 and m2 separately unlike the Newtonian case where only a combination of these masses enters the signal parametrization. The shift to post1.5-Newtonian signals also gives rise to some new problems which are not encountered in the analysis of Newtonian wave forms. We describe these problems and take them into account in our analysis

Non-universal gaugino mass GUT models in the light of dark matter and LHC constraints

We perform a comprehensive study of $SU(5)$, $SO(10)$ and $E(6)$ supersymmetric GUT models where the gaugino masses are generated through the F-term breaking vacuum expectation values of the non-singlet scalar fields. In these models the gauginos are non-universal at the GUT scale unlike in the mSUGRA scenario. We discuss the properties of the LSP which is stable and a viable candidate for cold dark matter. We look for the GUT scale parameter space that leads to the the lightest SM like Higgs mass in the range of 122-127 GeV compatible with the observations at ATLAS and CMS, the relic density in the allowed range of WMAP-PLANCK and compatible with other constraints from colliders and direct detection experiments. We scan universal scalar ($m_0^G$), trilinear coupling $A_0$ and $SU(3)_C$ gaugino mass ($M_3^G$) as the independent free parameters for these models. Based on the gaugino mass ratios at the GUT scale, we classify 25 SUSY GUT models and find that of these only 13 models satisfy the dark matter and collider constraints. Out of these 13 models there is only one model where there is a sizeable SUSY contribution to muon $(g-2)$.Comment: 22 pages, 6 tables, 7 figures; new results added along with discussion; matches version to be published in JHE

Detection and estimation of unmodeled narrowband nonstationary signals: application of particle swarm optimization in gravitational wave data analysis

The extraction of weak signals from instrumental noise is a critical task in ongoing searches for gravitational waves. A detection and estimation method, made feasible by Particle Swarm Optimization, is presented for a particularly challenging class of signals expected from astrophysical sources