Non-standard Neutrino Properties

A discussion of several exotic models and how well they are able to describe the data, with particular emphasis on atmospheric neutrinos.Comment: 6 pages, 5 figures. Invited paper presented at the NOW2000 workshop, Conca Specchiulla, Otranto (lecce), Italy, 9-16 September 200

163Ho as a target for cosmic antineutrinos

The electron capture decay of the isotope 163Ho has been proposed since a long time as a candidate for measuring the electron neutrino mass and recently the interest on this idea has been renewed. A direct observation of the cosmic antineutrino background could be made using a target made of this isotope. We discuss the requirements for an experiment aiming to obtain this result, comparing it with experiments using tritium as target

Multiple Parton Interactions in Hadron Collisions and Diffraction

Hadrons are composite objects made of quarks and gluons, and during a collision one can have several elementary interactions between the constituents. These elementary interactions, using an appropriate theoretical framework, can be related to the total and elastic cross sections. At high c.m. energy it also becomes possible to identify experimentally a high pt subset of the parton interactions and to study their multiplicity distribution. Predictions of the multiple interactions rates are difficult because in principle one needs to have a knowledge of the correlated Parton Distribution Functions that describe the probability to find simultaneously different partons in different elements of phase space. In this work we address this question and suggest a method to describe effectively the fluctuations in the instantaneous configuration of a colliding hadron. This problem is intimately related to the origin of the inelastic diffractive processes. We present a new method to include the diffractive cross section in an eikonal formalism that is equivalent to a multi-channel eikonal. We compare with data and present an extrapolation to higher energy.Comment: 34 pages, 9 figure

Interpretation of the measurements of total, elastic and diffractive cross sections at LHC

Recently at LHC one has obtained measurements of the total, elastic and diffractive cross sections in pp collisions at very high energy. The total cross section is in good agreement with predictions based on a leading behavior \sigma_{tot} (s) \propto (\ln s/s_0)^2, on the other hand the elastic cross section is lower than most expectations and the diffractive cross section is higher. It is remarkable that the ratio (\sigma_{el} + \sigma_{diff})/\sigma_{tot} calculated combining the results of the TOTEM and ALICE detectors is 0.495^{+0.05}_{-0.06}, very close to the maximum theoretically allowed value of 1/2 known as the Miettinen Pumplin bound. In this work we discuss these results using the frameworks of single and multi--channel eikonal models, and outline the main difficulties for a consistent interpretation of the data.Comment: 24 pages, 11 figure

Phenomenology of atmospheric neutrinos

The relevance of the data concerning upward--going muons for the solution of the atmospheric neutrino problem is stressed. In particular, their inclusion in the analysis confirms the goodness of the neutrino oscillation hypothesis and allows to exclude some alternative, exotic explanations such as neutrino decay, flavour changing neutral currents, violations of the equivalence principle (at least in their simplest forms), and also to discriminate, in principle, between different neutrino oscillation models (nu_mu nu_tau versus nu_mu nu_s), because of the difference in the matter effects.Comment: Talk presented at "The 17th International Workshop on Weak Interactions and Neutrinos (WIN99)," Capetown, South Africa, Jan. 1999, Latex 5 pages 3 figure

CP violation in D meson decays: would it be a sign of new physics ?

Ascribing the large SU(3) violations in the Cabibbo forbidden decays of neutral D mesons to the final state interactions, one gets large strong phase differences, necessary for substantial direct CP violation. While the absolute value of the CP violating asymmetries depend on the uncertain strength of the penguin contribution, we predict an asymmetry for the decays into charged pions more than twice as large and having opposite sign with respect to that for charged kaons.Comment: 9 pages, added references, minor changes in the text, results unchanged. Accepted for publication in Physical Review

Remarks on the forces generated by two-neutrino exchange

A brief up-to-date review of the long range forces generated by two neutrino exchange is presented. The potential due to exchange of a massive neutrino-antineutrino pair between particles carrying weak charge might be larger than expected if the neutrinos have not only masses but also magnetic moments close to the present experimental bounds. It still remains too small to be observable.Comment: 10 pages, 3 figures. One figure added. Accepted for publication in EPJ

The Energy and Zenith Angle Distribution of Upward Going Muons and Neutrino Oscillations

The energy and zenith angle distribution of neutrino induced, upward going muons can give direct information on the presence of $\nu$--oscillations in precisely the range of parameters suggested as a solution of the atmospheric neutrino problem. We discuss here the uncertainties in the theoretical prediction. The shape of the zenith angle distribution of the muon flux is quite insensitive to modifications of the theoretical input and is a good probe for the existence of neutrino oscillations. We conclude that the existing data sample on $\nu$--induced muons has the statistical power to confirm or refute the $\nu$--oscillation solution of the atmospheric neutrino problem.Comment: 8 pages Latex, with 3 embedded eps figure

The neutrino cross section and upward going muons

The charged current cross section for neutrinos with energy of a few GeV is reanalysed. In this energy range the cross section for the lowest multiplicity exclusive channels is an important fraction of $\sigma_{CC}$ and the approximation of describing the cross section with deep inelastic scattering formulae may be inaccurate. Possible consequences of our reanalysis of the cross section in the interpretation of the data obtained by deep underground detectors on $\nu$--induced upward going muons (both stopping and passing) are discussed.Comment: 9 pages, REVTEX, 1 uu-encoded compressed file with 3 figure

Comparison of \nu_\mu <-> \nu_\tau and and \nu_\mu <-> \nu_s oscillations as solutions of the atmospheric neutrino problem

The simplest explanation for the atmospheric neutrino anomaly is the transition of muon neutrinos and antineutrinos into states of different flavor. Data from the reactor experiment Chooz, and the measurement of the energy and angle distribution of electron--like events in Super--Kamiokande put strong constraints on $\nu_\mu$--$\nu_e$ mixing, but the transitions $\nu_\mu \to \nu_\tau$ and $\nu_\mu \to \nu_s$ are viable possibilites. If the muon neutrinos are mixed with a singlet sterile state, the energy and zenith angle dependence of the oscillation probability is modified by matter effects, that are important for E_\nu/|\Delta m^2| \aprge 10^3 GeV/eV$^2$. We confront the theoretical predictions with existing data on contained events and neutrino--induced upward going muons.Comment: 32 pages, Latex with included 16 figure