Supernova neutrinos: production, propagation and oscillations

I shall review some of the recent results concerning the astrophysics of a core collapse supernova (SN) and neutrino oscillations. Neutrinos play an important role in the SN explosion, and they also carry most of the energy of the collapse. The energy spectra of neutrinos and antineutrinos arriving at the Earth incorporate information on the primary neutrino fluxes as well as the neutrino mixing scenario. The analysis of neutrino propagation through the matter of the supernova and the Earth, combined with the observation of a neutrino burst from a galactic SN, enables us to put limits on the mixing angle $\theta_{13}$ and identify whether the mass hierarchy is normal or inverted. The neutrino burst also acts as an early warning signal for the optical observation, and in addition allows us to have a peek at the shock wave while still inside the SN mantle.Comment: 8 pages, uses espcrc2.sty (Nucl. Phys. B). Talk given at Neutrino 2004, Pari

Test of T violation in neutral B decays

T violation should be tested independently of CP violation. Besides K system, B meson decays provide another good place to study T violation. In the Standard Model, T violation in $B^0 \rightleftharpoons \bar{B^0}$ oscillation is expected to be small. The angular distribution of $B\to VV$ decay permits one to extract the T-odd correlation. In the absence of final state interaction, T violation in $B\to J/\psi(l^+ l^-) K^*(K_S\pi^0)$ decay can reach $4-7$ via $B^0-\bar{B^0}$ mixing.Comment: Latex, 11 pages, revised version will appear in PL

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

Signatures of heavy sterile neutrinos at long baseline experiments

Sterile neutrinos with masses $\sim 0.1$ eV or higher would 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 $\theta_{14}, \theta_{24}, \theta_{34}$, the deviation of $\theta_{23}$ from maximality,as well as $\theta_{13}$ and the ratio $\Delta m^2_\odot/\Delta m^2_{atm}$ 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_{24}\theta_{34} \gsim 0.005 and \theta_{14} \gsim 0.06 rad with the current bound of $\theta_{13} < 0.2$ rad; a better $\theta_{13}$ bound would allow probing smaller values of sterile mixing. We also generalize the formalism for any number of sterile 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.Comment: 28 pages, 12 figures, Revtex4 forma

Self-Calibration of Neutrino Detectors using characteristic Backgrounds

We introduce the possibility to use characteristic natural neutrino backgrounds, such as Geoneutrinos (\bar{\nu}_e) or solar neutrinos (\nu_e), with known spectral shape for the energy calibration of future neutrino detectors, e.g. Large Liquid Scintillator Detectors. This "CalEffect" could be used without the need to apply any modifications to the experiment in all situations where one has a suitable background with sufficient statistics. After deriving the effect analytically using \chi^2 statistics, we show that it is only tiny for reactor neutrino experiments, but can be applicable in other situations. As an example, we present its impact on the identification of the wiggles in the power spectrum of supernova neutrinos caused by Earth matter effects. The Self-Calibration Effect could be used for cross checking other calibration methods and to resolve systematical effects in the primary neutrino interaction processes, in particular in the low energy cross sections.Comment: 6 pages, 4 figure

Signatures of supernova neutrino oscillations in the Earth mantle and core

The Earth matter effects on supernova (SN) neutrinos can be identified at a single detector through peaks in the Fourier transform of their ``inverse energy'' spectrum. The positions of these peaks are independent of the SN models and therefore the peaks can be used as a robust signature of the Earth matter effects, which in turn can distinguish between different neutrino mixing scenarios. Whereas only one genuine peak is observable when the neutrinos traverse only the Earth mantle, traversing also the core gives rise to multiple peaks. We calculate the strengths and positions of these peaks analytically and explore their features at a large scintillation detector as well as at a megaton water Cherenkov detector through Monte Carlo simulations. We propose a simple algorithm to identify the peaks in the actual data and quantify the chances of a peak identification as a function of the location of the SN in the sky.Comment: 17 pages, 9 figure

Measurement of the Lifetime Difference of BdB_d Mesons: Possible and Worthwhile?

We estimate the decay width difference $\Delta Gamma_d / \Gamma_d$ in the $B_d$ system including $1/m_b$ contributions and next-to-leading order QCD corrections, and find it to be around 0.3%. We explicitly show that the time measurements of an untagged $B_d$ decaying to a single final state isotropically can only be sensitive to quadratic terms in $\Delta Gamma_d / \Gamma_d$, and hence the use of at least two different final states is desired. We discuss such pairs of candidate decay channels for the final states and explore the feasibility of a $\Delta Gamma_d / \Gamma_d$ measurement through them. The measurement of this width difference is essential for an accurate measurement of $\sin(2\beta)$ at the LHC. The nonzero width difference may also be used to identify new physics effects and to resolve a twofold discrete ambiguity in the $B_d$-$\bar{B}_d$ mixing phase. We also derive an upper bound on the value of $\Delta Gamma_d / \Gamma_d$ in the presence of new physics, and point out some differences in the phenomenology of width differences in the $B_s$ and $B_d$ systems.Comment: latex, 31 pages, revised versio