Understanding Supernova Neutrino Physics using Low-Energy Beta-Beams

We show that fitting linear combinations of low-energy beta-beam spectra to supernova-neutrino energy-distributions reconstructs the response of a nuclear target to a supernova flux in a very accurate way. This allows one to make direct predictions about the supernova-neutrino signal in a terrestrial neutrino detector.Comment: To appear in the proceedings of International School of Nuclear Physics: 27th Course: "Neutrinos in Cosmology, in Astro, Particle and Nuclear Physics". Erice, Sicily, Italy, 16-2

Reconstructing supernova-neutrino spectra using low-energy beta-beams

Only weakly interacting, neutrinos are the principal messengers reaching us from the center of a supernova. Terrestrial neutrino telescopes, such as SNO and SuperKamiokande, can provide precious information about the processes in the core of a collapsing and exploding star. But the information about the supernova that a neutrino detector can supply, is restricted by the fact that little experimental data on the neutrino-nucleus cross sections exists and by the uncertainties in theoretical calculations. In this letter, we propose a novel procedure that determines the response of a target nucleus in a supernova-neutrino detector directly, by using low-energy beta-beams. We show that fitting 'synthetic' spectra, constructed by taking linear combinations of beta-beam spectra, to the original supernova-neutrino spectra reproduces the folded differential cross sections very accurately. Comparing the response in a terrestrial detector to these synthetic responses provides a direct way to determine the main parameters of the supernova-neutrino energy-distribution.Comment: 4 page

Thermodynamical properties of a mean-field plus pairing model and applications for the Fe nuclei

A mean-field plus pairing model for atomic nuclei in the Fe region was studied using a finite-temperature quantum Monte-Carlo method. We present results for thermodynamical quantities such as the internal energy and the specific heat. These results give indications of a phase transition related to the pairing amongst nucleons, around temperatures of 0.7 MeV. The influence of the residual interaction and of the size of the model space on the nuclear level densities is discussed too.Comment: 23 pages, including 17 eps figure

Pion production within the hybrid relativistic plane wave impulse approximation model at MiniBooNE and MINERvA kinematics

The hybrid model for electroweak single-pion production (SPP) off the nucleon, presented in [Gonz\'alez-Jim\'enez et al., Phys. Rev. D 95, 113007 (2017)], is extended here to the case of incoherent pion-production on the nucleus. Combining a low-energy model with a Regge approach, this model provides valid predictions in the entire energy region of interest for current and future accelerator-based neutrino-oscillation experiments. The Relativistic Mean-Field model is used for the description of the bound nucleons while the outgoing hadrons are considered as plane waves. This approach, known as Relativistic Plane-Wave Impulse Approximation (RPWIA), is a first step towards the development of more sophisticated models, it is also a test of our current understanding of the elementary reaction. We focus on the charged-current $\nu$($\bar\nu$)-nucleus interaction at MiniBooNE and MINERvA kinematics. The effect on the cross sections of the final-state interactions, which affect the outgoing hadrons on their way out of the nucleus, is judged by comparing our results with those from the NuWro Monte Carlo event generator. We find that the hybrid-RPWIA predictions largely underestimate the MiniBooNE data. In the case of MINERvA, our results fall below the $\nu$-induced 1$\pi^0$ production data, while a better agreement is found for $\nu$-induced 1$\pi^+$ and $\bar\nu$-induced 1$\pi^0$ production.Comment: 13 pages, 10 figure

Untangling supernova-neutrino oscillations with beta-beam data

Recently, we suggested that low-energy beta-beam neutrinos can be very useful for the study of supernova neutrino interactions. In this paper, we examine the use of a such experiment for the analysis of a supernova neutrino signal. Since supernova neutrinos are oscillating, it is very likely that the terrestrial spectrum of supernova neutrinos of a given flavor will not be the same as the energy distribution with which these neutrinos were first emitted. We demonstrate the efficacy of the proposed method for untangling multiple neutrino spectra. This is an essential feature of any model aiming at gaining information about the supernova mechanism, probing proto-neutron star physics, and understanding supernova nucleosynthesis, such as the neutrino process and the r-process. We also consider the efficacy of different experimental approaches including measurements at multiple beam energies and detector configurations.Comment: 13 pages, 11 figures, accepted for publication in Phys. Rev.

Extracting the Weinberg angle at intermediate energies

A recent experiment by the NuTeV collaboration resulted in a surprisingly high value for the weak mixing angle $\sin^2 \theta_W$. The Paschos-Wolfenstein relation, relating neutrino cross sections to the Weinberg angle, is of pivotal importance in the NuTeV analysis. In this work, we investigate the sensitivity of the Paschos-Wolfenstein relation to nuclear structure aspects at neutrino energies in the few GeV range. Neutrino-nucleus cross sections are calculated for $^{16}$O and $^{56}$Fe target nuclei within a relativistic quasi-elastic nucleon-knockout model.Comment: To appear in the proceedings of International School of Nuclear Physics: 27th Course: "Neutrinos in Cosmology, in Astro, Particle and Nuclear Physics", Erice, Sicily, Italy, 16-24 Sep 200

Identifying neutrinos and antineutrinos in neutral-current scattering reactions

We study neutrino-induced nucleon knockout from nuclei. Expressions for the induced polarization are derived within the framework of the independent-nucleon model and the non-relativistic plane-wave approximation. Large dissimilarities in the nucleon polarization asymmetries are observed between neutrino- and antineutrino-induced processes. These asymmetries represent a potential way to distinguish between neutrinos and antineutrinos in neutral-current neutrino-scattering on nuclei. We discuss astrophysical applications of these polarization asymmetries. Our findings are illustrated for neutrino scattering on $^{16}$O and $^{208}$Pb.Comment: 5 pages, 5 figures, accepted for publication in Phys. Rev. Let

Electroweak interactions in a relativistic Fermi gas

We present a relativistic model for computing the neutrino mean free path in neutron matter. Thereby, neutron matter is described as a non-interacting Fermi gas in beta-equilibrium. We present results for the neutrino mean free path for temperatures from 0 up to 50 MeV and a broad range of neutrino energies. We show that relativistic effects cause a considerable enhancement of neutrino-scattering cross-sections in neutron matter. The influence of the $Q^2$-dependence in the electroweak form factors and the inclusion of a weak magnetic term in the hadron current is discussed. The weak-magnetic term in the hadron current is at the origin of some selective spin dependence for the nucleons which are subject to neutrino interactions.Comment: 11 pages, 7 figures, accepted to Phys. Rev. C, minor changes and updates of the figures are mad

Seagull and pion-in-flight currents in neutrino-induced 1N1N and 2N2N knockout

[Background] The neutrino-nucleus ($\nu A$) cross section is a major source of systematic uncertainty in neutrino-oscillation studies. A precise $\nu A$ scattering model, in which multinucleon effects are incorporated, is pivotal for an accurate interpretation of the data. [Purpose] In $\nu A$ interactions, meson-exchange currents (MECs) can induce two-nucleon ($2N$) knockout from the target nucleus, resulting in a two-particle two-hole (2p2h) final state. They also affect single nucleon ($1N$) knockout reactions, yielding a one-particle one-hole (1p1h) final state. Both channels affect the inclusive strength. We present a study of axial and vector, seagull and pion-in-flight currents in muon-neutrino induced $1N$ and $2N$ knockout reactions on $^{12}$C. [Method] Bound and emitted nucleons are described as Hartree-Fock wave functions. For the vector MECs, the standard expressions are used. For the axial current, three parameterizations are considered. The framework developed here allows for a treatment of MECs and short-range correlations (SRCs). [Results] Results are compared with electron-scattering data and with literature. The strengths of the seagull, pion-in-flight and axial currents are studied separately and double differential cross sections including MECs are compared with results including SRCs. A comparison with MiniBooNE and T2K data is presented. [Conclusions] In the 1p1h channel, the effects of the MECs tend to cancel each other, resulting in a small effect on the double differential cross section. $2N$ knockout processes provide a small contribution to the inclusive double differential cross section, ranging from the $2N$ knockout threshold into the dip region. A fair agreement with the MiniBooNE and T2K data is reached.Comment: 16 pages, 10 figure