G. Pagliaroli

Neutrinos from Supernovae as a Trigger for Gravitational Wave Search

Exploiting an improved analysis of the nue signal from the explosion of a galactic core collapse supernova, we show that it is possible to identify within about 10 ms the time of the bounce, which is strongly correlated to the time of the maximum amplitude of the gravitational signal. This allows us to precisely identify the gravitational wave burst timing.

Searching for prompt signatures of nearby core-collapse supernovae by a joint analysis of neutrino and gravitational wave data

We discuss the science motivations and prospects for a joint analysis of gravitational wave (GW) and low-energy neutrino data to search for prompt signals from nearby supernovae (SNe). Both gravitational wave and low-energy neutrinos are expected to be produced in the innermost region of a core-collapse supernova, and a search for coincident signals would probe the processes which power a supernova explosion. It is estimated that the current generation of neutrino and gravitational wave detectors would be sensitive to galactic core-collapse supernovae, and would also be able to detect electromagnetically dark SNe. A joint GW-neutrino search would enable improvements to searches by way of lower detection thresholds, larger distance range, better live-time coverage by a network of GW and neutrino detectors, and increased significance of candidate detections. A close collaboration between the GW and neutrino communities for such a search will thus go far toward realizing a much sought-after astrophysics goal of detecting the next nearby supernova.

The fraction of muon tracks in cosmic neutrinos

The study of the distintive signatures of the ultra high energy events recently seen by IceCube [1-4] can allow to single the neutrino origin out. The detection of tau neutrinos would be a clear way to prove that they come from cosmic distances, but at the highest energies currently seen, about 1 PeV, an experimental characterization of tau events is difficult. The study of the fraction of the muon tracks seems more promising. In fact, for any initial composition, because of the occurrence of flavor oscillations and despite their uncertainties, the fraction of muon tracks in the cosmic neutrinos is smaller than the one of atmospheric neutrinos, even hypothesizing an arbitrarily large contribution from charmed mesons. A good understanding of the detection efficiencies and the optimization of the analysis cuts, along with a reasonable increase in the statistics, should provide us with a significant test of the cosmic origin of these events.

Testing nonradiative neutrino decay scenarios with IceCube data

We test the hypothesis of non-radiative neutrinos decay using the latest IceCube data. Namely, we calculate the track-to-shower ratio expected in IceCube for the normal and inverted neutrino mass hierarchy taking into account the uncertainties in neutrino oscillation parameters. We show that the subset of data with energy above 60 TeV actually excludes the possibility of a neutrinos decay at the 1 sigma level of significance for both neutrino mass hierarchies.

Spectrum of supernova neutrinos in ultra-pure scintillators

There is a great interest in measuring the non-electronic component of neutrinos from core collapse supernovae by observing, for the first time, also neutral-current reactions. In order to assess the physics potential of the ultra-pure scintillators in this respect, we study the entire expected energy spectrum in the Borexino, KamLAND and SNO+ detectors. We examine the various sources of uncertainties in the expectations, and in particular, those due to specific detector features and to the relevant cross sections. We discuss the possibility to identify the different neutrino flavors, and we quantify the effect of confusion, due to other components of the energy spectrum, overlapped with the neutral-current reactions of interest.

Expectations for high energy diffuse galactic neutrinos for different cosmic ray distributions

The interaction of cosmic rays with the gas contained in our Galaxy is a guaranteed source of diffuse high energy neutrinos. We provide expectations for this component by considering different assumptions for the cosmic ray distribution in the Galaxy which are intended to cover the large uncertainty in cosmic ray propagation models. We calculate the angular dependence of the diffuse galactic neutrino flux and the corresponding rate of High Energy Starting Events in IceCube by including the effect of detector angular resolution. Moreover we discuss the possibility to discriminate the galactic component from an isotropic astrophysical flux. We show that a statistically significant excess of events from the galactic plane in present IceCube data would disfavour models in which the cosmic ray density is uniform, thus bringing relevant information on the cosmic ray radial distribution.

The diffuse supernova neutrino background: expectations and uncertainties derived from SN1987A

Context. The detection of the diffuse supernova neutrino background may be imminent, but theoretical predictions are affected by substantial uncertainties. Aims. We calculate the signal and its uncertainty with the present configuration of Super-Kamiokande and consider the possibi lity of lowering the threshold by means of gadolinium loading. Methods. We model neutrino emission following the analysis of SN1987A by Pagliaroli and collaborators 2009 and use the number of expected events in the neutrino detector as a free paramet er of the fit. The best-fit value of this parameter and its error are evaluated by means of standard maximum likelihood procedures, taking into account properly the correlations. Results. The uncertainties in the astrophysics of the emission dominates the total uncertainty in the expected signal rate, whic h conservatively ranges from 0.3 to 0.9 events per year and from 1.1 to 2.9 with gadolinium.

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.

Analysis of Neutrino Signals from SN1987A

We study SN1987A neutrino events through a likelihood analysis with one-component (cooling) and two-component (accretion and cooling) emission model. We show that there is a 3.2σ hint for the initial accretion phase.

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.