34 research outputs found
A Critical Appraisal of Some Concepts Used in Neutrino Physics
We examine the value of certain concepts highly regarded in the past decade,
that concern neutrino propagation, models for the leptonic mixing,
interpretations of neutrinoless double beta dec\ ay and of SN1987A
observations. We argue that it would useful to strengthen the role of the
discussions among experts of neutrino physics, regarding the hypotheses
underlying the theoretical investigations.Comment: 5 pages, 4 figures. Presented at IFAE 201
Neutrino mass bound in the standard scenario for supernova electronic antineutrino emission
Based on recent improvements of the supernova electron antineutrino emission
model, we update the limit on neutrino mass from the SN1987A data collected by
Kamiokande-II, IMB and Baksan. We derive the limit of 5.8 eV at 95 % CL, that
we show to be remarkably insensitive to the astrophysical uncertainties. Also
we evaluate the ultimate mass sensitivity of this method for a detector like
Super-Kamiokande. We find that the bound lies in the sub-eV region, 0.8 eV at
95 % CL being a typical outcome, competitive with the values that are presently
probed in laboratory. However, this bound is subject to strong statistical
fluctuations, correlated to the characteristics of the first few events
detected. We briefly comment on the prospects offered by future detectors.Comment: 16 pages, 3 figures. Accepted for publication in Astroparticle
Physic
Counting muons to probe the neutrino mass spectrum
The experimental evidence that \theta_{13} is large opens new opportunities
to identify the neutrino mass spectrum. We outline a possibility to investigate
this issue by means of conventional technology. The ideal setup turns out to be
long baseline experiment: the muon neutrino beam, with 10^{20} protons on
target, has an average energy of 6 (8) GeV; the neutrinos, after propagating
6000 (8000) km, are observed by a muon detector of 1 Mton and with a muon
energy threshold of 2 GeV. The expected number of muon events is about 1000,
and the difference between the two neutrino spectra is sizeable, about 30%.
This allows the identification of the mass spectrum just counting muon tracks.
The signal events are well characterized experimentally by their time and
direction of arrival, and 2/3 of them are in a region with little atmospheric
neutrino background, namely, between 4 GeV and 10 GeV. The distances from CERN
to Baikal Lake and from Fermilab to KM3NET, or ANTARES, fit in the ideal range.Comment: 14 pages, 5 figures. Version accepted for publication on EPJ
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 possibility 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 parameter 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, which conservatively ranges from 0.3 to 0.9 events per
year and from 1.1 to 2.9 with gadolinium.Comment: 4 pages, 5 figures, to appear in A&
Double pulses and cascades above 2 PeV in IceCube
IceCube collaboration has seen an unexpected population of high energy
neutrinos compatible with an astrophysical origin. We consider two categories
of events that can help to diagnose cosmic neutrinos: double pulse, that may
allow us to clearly discriminate the cosmic component of tau neutrinos;
cascades with deposited energy above 2 PeV, including events produced by
electron antineutrinos at the Glashow resonance, that can be used to
investigate the neutrino production mechanisms. We show that one half of the
double pulse signal is due to the neutrinos spectral region already probed by
IceCube. By normalizing to HESE data, we find that 10 more years are required
to obtain 90% probability to observe a double pulse. The cascades above 2 PeV
provide us a sensitive probe of the high energy tail of the neutrino spectrum
and are potentially observable, but even in this case, the dependence on type
of the source is mild. In fact we find that pp or p{\gamma} mechanisms give a
difference in the number of cascades above 2 PeV of about 25 % that can be
discriminated at 2{\sigma} in about 50 years of data taking.Comment: 20 pages, 7 figures, accepted for publication in EPJ