F.L. Villante

The early mirror universe: inflation, baryogenesis, nucleosynthesis and dark matter

Abstract There can exist a parallel ‘mirror’ world which has the same particle physics as the observable world and couples the latter only gravitationally. The nucleosynthesis bounds demand that the mirror sector should have a smaller temperature than the ordinary one. By this reason its evolution should be substantially deviated from the standard cosmology as far as the crucial epochs like baryogenesis, nucleosynthesis etc. are concerned. Starting from an inflationary scenario which could explain the different initial temperatures of the two sectors, we study the time history of the early mirror universe. In particular, we show that in the context of the GUT or electroweak baryogenesis scenarios, the baryon asymmetry in the mirror world should be larger than in the observable one and in fact the mirror baryons could provide the dominant dark matter component of the universe. In addition, analyzing the nucleosynthesis epoch, we show that the mirror helium abundance should be much larger than that of ordinary helium. The implications of the mirror baryons representing a kind of self-interacting dark matter for the large scale structure formation, the CMB anysotropy, the galactic halo structures, microlensing, etc. are briefly discussed.

Atmospheric neutrino flux supported by recent muon experiments

We present a new one-dimensional calculation of low and intermediate energy atmospheric muon and neutrino fluxes, using up-to-date data on primary cosmic rays and hadronic interactions. We study several sources of uncertainties relevant to our calculations. A comparison with the muon fluxes and charge ratios measured in several modern balloon-borne experiments suggests that the atmospheric neutrino flux is essentially lower than one used for the standard analyses of the sub-GeV and multi-GeV neutrino induced events in underground detectors.

How to observe 8B solar neutrinos in liquid scintillator detectors

Abstract We show that liquid organic scintillator detectors (e.g., KamLAND and Borexino) can measure the 8 B solar neutrino flux by means of the ν e charged current interaction with the 13 C nuclei naturally contained in the scintillators. The neutrino events can be identified by exploiting the time and space coincidence with the subsequent decay of the produced 13 N nuclei. We perform a detailed analysis of the background in KamLAND, Borexino and in a possible liquid scintillator detector at SNOlab, showing that the 8 B solar neutrino signal can be extracted with a reasonable uncertainty in a few years of data taking. KamLAND should be able to extract about 18 solar neutrino events from the already collected data. Prospects for gigantic scintillator detectors (such as LENA) are also studied.

Superkamiokande and solar antineutrinos

We propose to exploit the angular distribution of the positrons emitted in the reaction νe + p → n+ e + to extract a possible antineutrino signal from the Superkamiokande background. From the statistics collected in just 101.9 days one obtains a model independent upper bound on the antineutrino flux ��(E� > 8.3MeV ) 8.3MeV ) < 6� 10 4 cm −2 s −1 . Within three years of data taking, the sensitivity to νe → νe transition probability will reach the 1% level, thus providing a stringent test of hybrid oscillation models.

Non-standard neutrino propagation and pion decay

A bstractMotivated by the findings of the OPERA experiment, we discuss the hypothesis that neutrino propagation does not obey Einstein special relativity. Under a minimal set of modifications of the standard model Lagrangian, we consider the implications of non standard neutrino propagation on the description of neutrino interactions and, specifically, on the pion decay processes. We show that all the different dispersion relations which have been proposed so far to explain OPERA results, imply huge departures from the standard expectations. The decay channel π+ → e+νe becomes significantly larger than in the standard scenario, and may even dominate over π+ → μ+νμ. Moreover, the spectral distribution of neutrinos produced in the decay processes and the probability that a pion decays in flight in neutrinos show large deviations from the standard results.

Formation of quark phases in compact stars and SN explosion

We describe possible scenarios of quark deconfinement in com pact stars and we analyze their astrophysical implications. The quark deconfinement process can proceed rapidly, as a strong deflagration, releasing a huge amount of energy in a short tim e and generating an extra neutrino burst. If energy is transferred efficiently to the surface, l ike e.g. in the presence of convective instabilities, this burst could contribute to revitalize a partially failed SN explosion. We discuss how the neutrino observations from SN1987A would fit in this s cenario. Finally, we focus on the fate of massive and rapidly rotating progenitors, discussi ng possible time separations between the moment of the core collapse and the moment of quark deconfinem ent. This mechanism can be at the basis of the interpretation of gamma ray bursts in which lines associated with heavy elements are present in the spectrum.

The Sun and the Newton constant

Abstract Several properties of the solar interior are determined with a very high accuracy, which in some cases is comparable to that achieved in the determination of the Newton constant G N . We find that the present uncertainty ΔG N / G N =±1.5×10 −3 has significant effects on the profile of density and pressure, however, it has negligible influence on the solar properties which can be measured by means of helioseismology and 8 B neutrinos. Our results do not support recent claims that observational solar data can be used to determine the value of G N with an accuracy of few part in 10 −4 . Present data cannot constrain G N to much better than 10 −2 .

Helioseismology and screening of nuclear reactions in the Sun

Abstract We show that models for screening of nuclear reactions in the Sun can be tested by means of helioseismology. As well known, solar models using the weak screening factors are in agreement with data. We find that the solar model calculated with the anti-screening factors of Tsytovich is not consistent with helioseismology, both for the sound speed profile and for the depth of the convective envelope. Moreover, the difference between the no-screening and weak screening model is significant in comparison with helioseismic uncertainty. In other words, the existence of screening can be proved by means of helioseismology.

On the Goals of Neutrino Astronomy

What do we mean by neutrino astronomy? Which information is it able to provide us and which is its potential? To address these questions, we discuss three among the most relevant sources of neutrinos: the Sun; the core collapse supernovae; the supernova remnants. For each of these astronomical objects, we describe the state of the art, we present the expectations and we outline the most actual problems from the point of view of neutrino astronomy.

Detection of 8B solar neutrinos in liquid scintillators

We show that liquid organic scintillator detectors (e. g., KamLAND and Borexino) can measure the 8B solar neutrino flux by means of the νe charged current interaction with the 13C nuclei naturally contained in the scintillators. The neutrino events can be identified by exploiting the time and space coincidence with the subsequent decay of the produced 13N nuclei.