Publications (12)7.37 Total impact
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Article: Extended evolution equations for neutrino propagation in astrophysical and cosmological environments
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ABSTRACT: We derive the evolution equations for a system of neutrinos interacting among themselves and with a matter background, based upon the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. This theoretical framework gives an (unclosed) set of first-order coupled integro-differential equations governing the evolution of the reduced density matrices. By employing the hierarchy, we first rederive the mean-field evolution equations for the neutrino one-body density matrix associated with a system of neutrinos and anti-neutrinosinteracting with matter and with an anisotropic neutrino background. Then, we derive extended evolution equations to determine neutrino flavour conversion beyond the commonly used mean-field approximation. To this aim we include neutrino-antineutrino pairing correlations to the two-body density matrix. The inclusion of these new contributions leads to an extended evolution equation for the normal neutrino density and to an equation for the abnormal one involving the pairing mean-field. We discuss the possible impact of neutrino-antineutrino correlations on neutrino flavour conversion in the astrophysical and cosmological environments, and possibly upon the supernova dynamics. Our results can be easily generalized to an arbitrary number of neutrino families.02/2013; -
Article: Search for new physics with neutrinos at Radioactive Ion Beam facilities
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ABSTRACT: We propose applications of Radioactive Ion Beam facilities to investigate physics beyond the Standard Model. In particular, we focus on the possible measurement of coherent neutrino-nucleus scattering and on a search for sterile neutrinos, by means of a low energy beta-beam with a Lorentz boost factor $\gamma \approx 1$. In the considered setup the collected radioactive ions are sent inside a 4$\pi$ detector. For the first application we provide the number of events associated with neutrino-nucleus coherent scattering, when the detector is filled in with a noble liquid. For the sterile search we consider that the spherical detector is filled in with a liquid scintillator, and that the neutrino detection channel is inverse-beta decay. We provide the exclusion curves for the sterile neutrino mixing parameters, based upon the 3+1 formalism, depending upon the achievable ion intensity. Our results are obtained both from total rates, and including spectral information with binning in energy and in distance. The proposed experiment represents a possible alternative to clarify the current anomalies observed in neutrino experiments.03/2012; -
Article: Neutrinos and core-collapse supernovae
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ABSTRACT: We discuss the recent progress in our understanding of neutrino flavour conversion in core-collapse supernovae and focus on the effects coming from the neutrino-neutrino interaction. The latter has been shown to engender new phenomena, modifying significantly the neutrino fluxes and supernova observations. In particular, we make the link between the spectral split and the magnetic resonance phenomenon. Moreover, recent investigations have demonstrated the existence of leptonic CP violation effects on the supernova neutrino fluxes. We summarize these findings.08/2011; -
Article: The neutrino signal at HALO: learning about the primary supernova neutrino fluxes and neutrino properties
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ABSTRACT: Core-collapse supernova neutrinos undergo a variety of phenomena when they travel from the high neutrino density region and large matter densities to the Earth. We perform analytical calculations of the supernova neutrino fluxes including collective effects due to the neutrino-neutrino interactions, the Mikheev-Smirnov-Wolfenstein (MSW) effect due to the neutrino interactions with the background matter and decoherence of the wave packets as they propagate in space. We predict the numbers of one- and two-neutron charged and neutral-current electron-neutrino scattering on lead events. We show that, due to the energy thresholds, the ratios of one- to two-neutron events are sensitive to the pinching parameters of neutrino fluxes at the neutrinosphere, almost independently of the presently unknown neutrino properties. Besides, such events have an interesting sensitivity to the spectral split features that depend upon the presence/absence of energy equipartition among neutrino flavors. Our calculations show that a lead-based observatory like the Helium And Lead Observatory (HALO) has the potential to pin down important characteristics of the neutrino fluxes at the neutrinosphere, and provide us with information on the neutrino transport in the supernova core.05/2011; -
Article: The neutrino spectral split in core-collapse supernovae: a magnetic resonance phenomenon
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ABSTRACT: A variety of neutrino flavour conversion phenomena occur in core-collapse supernova, due to the large neutrino density close to the neutrinosphere, and the importance of the neutrino-neutrino interaction. Three different regimes have been identified so far, usually called the synchronization, the bipolar oscillations and the spectral split. Using the formalism of polarization vectors, within two-flavours, we focus on the spectral split phenomenon and we show for the first time that the physical mechanism underlying the neutrino spectral split is a magnetic resonance phenomenon. In particular, we show that the precession frequencies fulfill the magnetic resonance conditions. Our numerical calculations show that the neutrino energies and the location at which the resonance takes place in the supernova coincide well with the neutrino energies at which a spectral swap occurs. The corresponding adiabaticity parameters present spikes at the resonance location.03/2011; -
Article: Turbulence effects on supernova neutrinos
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ABSTRACT: Multi-dimensional core-collapse supernova simulations exhibit turbulence of large amplitude and over large scales. As neutrinos pass through the supernova mantle the turbulence is expected to modify their evolution compared to the case where the explosion is free of turbulence. In this paper we study this turbulence effect upon the neutrinos modelling the turbulence expected from multi-dimensional simulations by adding matter density fluctuations to density profiles taken from one-dimensional hydrodynamical simulations. We investigate the impact upon the supernova neutrino transition probabilities as a function of the neutrino mixing angle theta_13 and turbulence amplitude. In the high (H) resonant channel and with large theta_13 values we find that turbulence is effectively two flavor for fluctuation amplitudes <~ 1% and have identified a new effect due to the combination of turbulence and multiple H resonances that leads to a sensitivity to fluctuations amplitudes as small as ~ 0.001%. At small values of theta_13, beyond the range achievable in Earth based experiments, we find that turbulence leads to new flavor transient effects in the channel where the MSW H resonance occurs. Finally, we investigate large amplitude fluctuations which lead to three flavor effects due to broken HL factorization and significant non-resonant transitions and identify two non-resonant turbulence effects, one depending on the theta_13, and the other independent of this angle and due to the low (L) MSW resonance. Comment: New figure added06/2010; -
Article: Dynamical collective calculation of supernova neutrino signals.
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ABSTRACT: We present the first calculations with three flavors of collective and shock wave effects for neutrino propagation in core-collapse supernovae using hydrodynamical density profiles and the S matrix formalism. We explore the interplay between the neutrino-neutrino interaction and the effects of multiple resonances upon the time signal of positrons in supernova observatories. A specific signature is found for the inverted hierarchy and a large third neutrino mixing angle and we predict, in this case, a dearth of lower energy positrons in Cherenkov detectors midway through the neutrino signal and the simultaneous revelation of valuable information about the original fluxes. We show that this feature is also observable with current generation neutrino detectors at the level of several sigmas.Physical Review Letters 08/2009; 103(7):071101. · 7.37 Impact Factor -
Article: Shockwaves in Supernovae: New Implications on the Diffuse Supernova Neutrino Background
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ABSTRACT: We investigate shock wave effects upon the diffuse supernova neutrino background using dynamic profiles taken from hydrodynamical simulations and calculating the neutrino evolution in three flavors with the S-matrix formalism. We show that the shock wave impact is significant and introduces modifications of the relic fluxes by about $20 \%$ and of the associated event rates at the level of $10-20 \%$. Such an effect is important since it is of the same order as the rate variation introduced when different oscillation scenarios (i.e. hierarchy or $\theta_{13}$) are considered. In addition, due to the shock wave, the rates become less sensitive to collective effects, in the inverted hierarchy and when $\sin^2 2 \theta_{13}$ is between the Chooz limit and $10^{-5}$. We propose a simplified model to account for shock wave effects in future predictions. Comment: 8 pages, 9 figures06/2009; -
Article: An "archaeological" quest for galactic supernova neutrinos
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ABSTRACT: We explore the possibility to observe the effects of electron neutrinos from past galactic supernovae, through a geochemical measurement of the amount of Technetium 97 produced by neutrino-induced reactions in a Molybdenum ore. The calculations we present take into account the recent advances in our knowledge of neutrino interactions, of neutrino oscillations inside a supernova, of the solar neutrino flux at Earth and of possible failed supernovae. The predicted Technetium 97 abundance is of the order of 10^7 atoms per 10 kilotons of ore, which is close to the current geochemical experimental sensitivity. Of this, 10-20% is from supernovae. Considering the comparable size of uncertainties, more precision in the modeling of neutrino fluxes as well as of neutrino cross sections is required for a meaningful measurement. Comment: PDFLateX, 22 pages, 2 Tables, 6 figures01/2009; -
Article: Collective neutrino oscillations in matter and CP violation
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ABSTRACT: We explore CP violation effects on the neutrino propagation in dense environments, such as in core-collapse supernovae, where the neutrino self-interaction induces nonlinear evolution equations. We demonstrate that the electron (anti)neutrino fluxes are not sensitive to the CP violating phase if the muon and tau neutrinos interact similarly with matter. On the other hand, we numerically show that new features arise, because of the nonlinearity and the flux dependence of the evolution equations, when the muon and tau neutrinos have different fluxes at the neutrinosphere (due to loop corrections or physics beyond the standard model). In particular, the electron (anti)neutrino probabilities and fluxes depend upon the CP violating phase. We also discuss the CP effects induced by radiative corrections to the neutrino refractive index.Phys. Rev. D. 10/2008; 78(8). -
Article: Collective neutrinos oscillation in matter and CP-violation
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ABSTRACT: We explore CP violation effects on the neutrino propagation in dense environments, such as in core-collapse supernovae, where the neutrino self-interaction induces non-linear evolution equations. We demonstrate that the electron (anti)neutrino fluxes are not sensitive to the CP violating phase if the muon and tau neutrinos interact similarly with matter. On the other hand, we numerically show that new features arise, because of the non-linearity and the flux dependence of the evolution equations, when the muon and tau neutrinos have different fluxes at the neutrinosphere (due to loop corrections or of physics beyond the Standard Model). In particular, the electron (anti)neutrino probabilities and fluxes depend upon the CP violating phase. We also discuss the CP effects induced by radiative corrections to the neutrino refractive index.08/2008; -
Article: Shock waves in supernovae: New implications on the diffuse supernova neutrino background
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ABSTRACT: We investigate shock wave effects upon the diffuse supernova neutrino background using dynamic profiles taken from hydrodynamical simulations and calculating the neutrino evolution in three flavors with the S-matrix formalism. We show that the shock wave impact is significant and introduces modifications of the relic fluxes by about 20% and of the associated event rates at the level of 10%–20%. Such an effect is important since it is of the same order as the rate variation introduced when different oscillation scenarios (i.e., hierarchy or θ13) are considered. In addition, due to the shock wave, the rates become less sensitive to collective effects, in the inverted hierarchy and when sin22θ13 is between the Chooz limit and 10-5. We propose a simplified model to account for shock wave effects in future predictions.Phys. Rev. D. 81(5).
