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Maurizio Lusignoli

Publications and source records attributed to Maurizio Lusignoli.

14 recordsLinked to original sources
arXiv2013

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.

hep-ph↗
arXiv2013

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 σ_{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 (σ_{el} + σ_{diff})/σ_{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.

hep-ph↗
arXiv2011

Relic Antineutrino Capture on 163-Ho decaying Nuclei

The electron capture decay of the isotope 163-Ho 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. In this paper we note that a direct observation of the cosmic antineutrino background could be made using a target made of this isotope. We further discuss the requests for an experiment aiming to obtain this result.

hep-ph↗
arXiv2011

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.

hep-ph↗
arXiv2009

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.

hep-ph↗
arXiv2007

Flavor Composition and Energy Spectrum of Astrophysical Neutrinos

The measurement of the flavor composition of the neutrino fluxes from astrophysical sources has been proposed as a method to study not only the nature of their emission mechanisms, but also the neutrino fundamental properties. It is however problematic to reconcile these two goals, since a sufficiently accurate understanding of the neutrino fluxes at the source is needed to extract information about the physics of neutrino propagation. In this work we discuss critically the expectations for the flavor composition and energy spectrum from different types of astrophysical sources, and comment on the theoretical uncertainties connected to our limited knowledge of their structure.

astro-ph↗
arXiv2001

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.

hep-ph↗
arXiv1999

The $ν_μ\leftrightarrow ν_s$ interpretation of the atmospheric neutrino data and cosmological constraints

The data on atmospheric neutrinos can be explained assuming the existence of oscillations between muon neutrinos and light sterile neutrinos with mixing close to maximal, and Delta_m^2 approximately equal to 3 E-3 (eV^2). This interpretation of the data is in potential conflict with the successes of big bang nucleosynthesis (BBN), since oscillations can result in a too large contribution of the sterile state to the energy density of the universe at the epoch of nucleosynthesis. The possibility to evade these cosmological constraints has been recently the object of some controversy. In this work we rediscuss this problem and find that the inclusion of a small mixing of the sterile state with tau neutrino can result in the generation of a large lepton asymmetry that strongly suppress the muon-sterile neutrino oscillations eliminating the possible conflict with BBN bounds. In this scheme the mass of the tau neutrino must be larger than few eV's and is compatible with cosmological bounds. Our calculation is performed using a Pauli-Boltzmann method. In this approach it is also possible to develop analytic calculations that allow physical insight in the processes considered and give support to the numerical results.

hep-ph↗
arXiv1999

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.

hep-ph↗
arXiv1999

On Exotic Solutions of the Atmospheric Neutrino Problem

The measurements of the fluxes of atmospheric neutrinos give evidence for the disappearance of muon neutrinos. The determination of the dependence of the disappearance probability on the neutrino energy and trajectory allows in principle to establish unambiguosly the existence of neutrino oscillations. Alternative mechanisms for the disappearance of the neutrinos have been proposed, but do not provide a viable description of the data, if one includes both events where the neutrinos interact in the detector and $ν$-induced upward going muons. The proposed mechanisms differ in the energy dependence of the disappearance probability and the upward going muon data that are produced by high energy neutrinos give a crucial constraint.

hep-ph↗
arXiv1998

Comparison of ν_μ<-> ν_τand and ν_μ<-> ν_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 $ν_μ$--$ν_e$ mixing, but the transitions $ν_μ\to ν_τ$ and $ν_μ\to ν_s$ 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 $E_ν/|Δm^2| \aprge 10^3$ GeV/eV$^2$. We confront the theoretical predictions with existing data on contained events and neutrino--induced upward going muons.

hep-ph↗
arXiv1997

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 $ν$--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 $ν$--induced muons has the statistical power to confirm or refute the $ν$--oscillation solution of the atmospheric neutrino problem.

hep-ph↗
arXiv1994

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 $σ_{CC}$ 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 $ν$--induced upward going muons (both stopping and passing) are discussed.

hep-ph↗