Earth matter effects on the supernova neutrino spectra

We explore the earth matter effects on the energy spectra of neutrinos from a supernova. We show that the observations of the energy spectra of $\nu_e$ and $\bar{\nu}_e$ from a galactic supernova may enable us to identify the solar neutrino solution, to determine the sign of $\Delta m^2_{32}$, and to probe the mixing matrix element $|U_{e3}|^2$ to values as low as $10^{-3}$. We point out scenarios in which the matter effects can even be established through the observation of the spectrum at a single detector.Comment: 8 pages LaTeX, 2 eps figures, uses Rinton-P9x6.cls. Talk given at CICHEP '2001, Cairo, Egypt, January 200

No-go for exactly degenerate neutrinos at high scale?

We show in a model independent manner that, if the magnitudes of Majorana masses of neutrinos are exactly equal at some high scale, the radiative corrections cannot reproduce the observed masses and mixing spectrum at the low scale, irrespective of the Majorana phases or the mixing angles at the high scale.Comment: 12 pages ReVTeX, A few typos corrected in the 2nd versio

Resolving ambiguities in the neutrino mass-flavour spectrum from supernova neutrinos

We analyze the neutrino conversions inside a supernova in the 3$\nu$ mixing scheme, and their effects on the neutrino spectra observed at the earth. We find that the observations of the energy spectra of neutrinos from a future galactic supernova may enable us to identify the solar neutrino solution, to determine the sign of $\Delta m^2_{32}$, and to probe the mixing matrix element |U_{e3}|^2 to values as low as 10^{-4}-10^{-3}.Comment: 3 pages, 1 eps figure. Talk given at TAUP-99. To be published in Nucl. Phys. B, Proc. Supp

Quantum mismatch: a powerful measure of "quantumness" in neutrino oscillations

The quantum nature of neutrino oscillations would be reflected in the mismatch between the neutrino survival probabilities with and without an intermediate observation. We propose this ``quantum mismatch'' as a measure of quantumness in neutrino oscillations, which precisely extracts the interference term in the two-flavor limit. In the full three-flavor scenario, we provide modified definitions of the Leggett-Garg and quantum mismatch measures. These are applicable for long-baseline and reactor neutrino experiments that measure neutrino survival probabilities with negligible matter effects.Comment: 6 pages, 4 figure

How large can the branching ratio of Bs→τ+τ−B_s \to \tau^+ \tau^- be ?

Motivated by the large like-sign dimuon charge asymmetry observed recently, whose explanation would require an enhanced decay rate of $B_s \to \tau^+ \tau^-$, we explore how large a branching ratio of this decay mode is allowed by the present constraints. We use bounds from the lifetimes of $B_d$ and $B_s$, constraints from the branching ratios of related $b \to s \tau^+ \tau^-$ modes, as well as measurements of the mass difference, width difference and CP-violating phase in the $B_s$-$\bar{B}_s$ system. Using an effective field theory approach, we show that a branching ratio as high as 15% may be allowed while being consistent with the above constraints. The model with a scalar leptoquark cannot increase the branching ratio to a per cent level. However, an enhancement up to 5% is possible in the model with an extremely light $Z'$ with flavor-dependent interactions, even after all the couplings are taken to be perturbative. This however cannot account for the dimuon anomaly completely by itself.Comment: Typos corrected, some discussions added, accepted for publication in Phys.Rev.

Identifying Earth matter effects on supernova neutrinos at a single detector

The neutrino oscillations in Earth matter introduce modulations in the supernova neutrino spectra. These modulations can be exploited to identify the presence of Earth effects on the spectra, which would enable us to put a limit on the value of the neutrino mixing angle $\theta_{13}$ and to identify whether the mass hierarchy is normal or inverted. We demonstrate how the Earth effects can be identified at a single detector without prior assumptions about the flavor-dependent source spectra, using the Fourier transform of the ``inverse-energy'' spectrum of the signal. We explore the factors affecting the efficiency of this method, and find that the energy resolution of the detector is the most crucial one. In particular, whereas water Cherenkov detectors may need a few ten thousand events to identify the Earth effects, a few thousand may be enough at scintillation detectors, which generically have a much better energy resolution. A successful identification of the Earth effects through this method can also provide $\Delta m^2_\odot$ to a good accuracy. The relative strength of the detected Earth effects as a function of time provides a test for supernova models.Comment: 18 pages, 10 figures, JCAP format. Final version to be published in JCAP. References and some minor clarifications added to the original versio

Radiative magnification of neutrino mixings and a natural explanation of the neutrino anomalies

We show that the neutrino mixing pattern with the large mixing required for the atmospheric neutrino problem and the small mixing angle MSW solution for the solar neutrino problem can be naturally generated through radiative magnification, even though all the mixing angles at the seesaw scale may be small. This can account for the neutrino anomalies as well as the CHOOZ constraints in the context of quark-lepton unified theories, where the quark and lepton mixing angles are expected to be similar in magnitude at the high scale. We also indicate the 4$\nu$ mixing scenarios for which this mechanism of radiative magnification can provide a natural explanation.Comment: 14 pages RevTex, 2 eps figure

Resolving a Discrete Ambiguity in the CKM Angle β\beta through Bu,d→J/ψK∗B_{u,d} \to J/\psi K^\ast and Bs→J/ψϕB_s \to J/\psi \phi Decays

It is well known that $\sin(2\beta)$, where $\beta$ is one of the angles of the unitarity triangle of the CKM matrix, can be determined in a theoretically clean way by measuring mixing-induced CP violation in the decay $B_d \to J/\psi K_S$. Another clean extraction of this CKM angle is provided by the time-dependent angular distribution for the decay products of $B_d \to J/\psi(\to l^+l^-) K^{\ast0}(\to \pi^0 K_S)$, where we have more observables at our disposal than in the case of $B_d \to J/\psi K_S$, so that in addition to $\sin(2\beta)$ also $\cos(2\beta)$ can be probed in a direct way. Unfortunately a sign ambiguity remains in $\cos(2\beta)$. If it could be resolved, a discrete ambiguity in the extraction of the CKM angle $\beta$ could be resolved as well, which would allow a more incisive test of the CKM model of CP violation. This note shows that detailed time-dependent studies of $B_{u,d} \to J/\psi K^{\ast}$ and $B_s \to J/\psi \phi$ decay processes can determine the sign of $\cos(2\beta)$, thereby removing the corresponding ambiguity in the extraction of the CKM angle $\beta$.Comment: 5 pages, LaTeX, no figure