Monte Carlo neutrino oscillations (original) (raw)

Simple and compact expressions for neutrino oscillation probabilities in matter

Journal of High Energy Physics, 2016

We reformulate perturbation theory for neutrino oscillations in matter with an expansion parameter related to the ratio of the solar to the atmospheric ∆m 2 scales. Unlike previous works, we use a renormalized basis in which certain first-order effects are taken into account in the zeroth-order Hamiltonian. We show that the new framework has an exceptional feature that leads to the neutrino oscillation probability in matter with the same structure as in vacuum to first order in the expansion parameter. It facilitates immediate physical interpretation of the formulas, and makes the expressions for the neutrino oscillation probabilities extremely simple and compact. We find, for example, that the ν e disappearance probability at this order is of a simple two-flavor form with an appropriately identified mixing angle and ∆m 2. More generally, all the oscillation probabilities can be written in the universal form with the channel-discrimination coefficient of 0, ±1 or simple functions of θ 23. Despite their simple forms they include all order effects of θ 13 and all order effects of the matter potential, to first order in our expansion parameter.

A Simple Parameterization of Matter Effects on Neutrino Oscillations

We present simple analytical approximations to matter-effect corrected effective neutrino mixing-angles and effective mass-squared-differences. The expressions clarify the dependence of oscillation probabilities in matter to the mixing angles and mass-squared-differences in vacuum, and are useful for analyzing long-baseline neutrino oscillation experiments.

Field-Theoretic Treatment of Mixed Neutrinos in a Neutrino and Matter Background

1995

We use the method of finite temperature field theory to examine the propagation of mixed neutrinos through dense media, putting the emphasis in those situations in which the neutrinos themselves are in the background. The evolution equation for the flavor amplitudes is deduced, and the expressions for the corresponding hamiltonian matrix are given explicitly. We find that, in order to include the nonlinear effects due to the nu\nunu-$\nu$ interactions, the neutrino propagator that must be used in the calculation of the neutrino self-energy diagrams that contain neutrinos in the internal lines is the propagator for the neutrino modes in the medium instead of the thermal free-field propagator. We also show how the absorptive contributions are included in terms of a non-hermitian part of the hamiltonian matrix, which we indicate how it is calculated. Our treatment provides a consistent generalization of a method that has been successfully applied to the study of neutrino oscillations in ...

Quasielastic neutrino-nucleus scattering in a continuum random phase approximation approach

Proceedings of 16th International Workshop on Neutrino Factories and Future Neutrino Beam Facilities — PoS(NUFACT2014), 2015

We present a continuum random phase approximation approach to study electron-and neutrinonucleus scattering cross sections, in the kinematic region where quasielastic scattering is the dominant process. We show the validity of the formalism by confronting inclusive (e, e ′) cross sections with the available data. We calculate flux-folded cross sections for charged-current quasielastic antineutrino scattering off 12 C and compare them with the MiniBooNE cross-section measurements. We pay special emphasis to the contribution of low-energy nuclear excitations in the signal of accelerator-based neutrino-oscillation experiments.

A New Monte Carlo Method for Time-Dependent Neutrino Radiation Transport

The Astrophysical Journal, 2012

Monte Carlo approaches to radiation transport have several attractive properties such as simplicity of implementation, high accuracy, and good parallel scaling. Moreover, Monte Carlo methods can handle complicated geometries and are relatively easy to extend to multiple spatial dimensions, which makes them potentially interesting in modeling complex multi-dimensional astrophysical phenomena such as core-collapse supernovae. The aim of this paper is to explore Monte Carlo methods for modeling neutrino transport in core-collapse supernovae. We generalize the implicit Monte Carlo photon transport scheme of Fleck & Cummings and gray discrete-diffusion scheme of Densmore et al. to energy-, time-, and velocity-dependent neutrino transport. Using our 1D spherically-symmetric implementation, we show that, similar to the photon transport case, the implicit scheme enables significantly larger timesteps compared with explicit time discretization, without sacrificing accuracy, while the discrete-diffusion method leads to significant speed-ups at high optical depth. Our results suggest that a combination of spectral, velocity-dependent, implicit Monte Carlo and discrete-diffusion Monte Carlo methods represents a robust approach for use in neutrino transport calculations in core-collapse supernovae. Our velocity-dependent scheme can easily be adapted to photon transport.

Continuum random phase approximation approach to charged-current neutrino-nucleus scattering

2002

During the last decades, neutrinos and their interactions with nuclei have been attracting a great deal of attention. It has become obvious that neutrinos play a prominent role in various astrophysical processes, especially in the dynamics of core-collapse supernovae and supernova-nucleosynthesis, with the detection of neutrinos from SN1987A as an outstanding example.

Analytical Calculation of Matter Effects in Two Mass-Scale Neutrino Oscillations

Modern Physics Letters A, 2003

We consider three active flavor neutrino oscillations where both the masssquare differences play a role in atmospheric neutrino problem. We calculate the matter effects arising due to propagation through earth. We demonstrate that these effects improve the fit to the electron data vis-a-vis vacuum oscillations but make the fit to the muon data far worse, thus worsening the overall fit. The results of our analytical calculation verify the numerical investigations of this scheme presented earlier by Fogli et al.

Analytical approximation of the neutrino oscillation matter effects at large θ 13

Journal of High Energy Physics, 2014

We argue that the neutrino oscillation probabilities in matter are best understood by allowing the mixing angles and mass-squared differences in the standard parametrization to 'run' with the matter effect parameter a = 2 √ 2G F N e E, where N e is the electron density in matter and E is the neutrino energy. We present simple analytical approximations to these 'running' parameters. We show that for the moderately large value of θ 13 , as discovered by the reactor experiments, the running of the mixing angle θ 23 and the CP violating phase δ can be neglected. It simplifies the analysis of the resulting expressions for the oscillation probabilities considerably. Approaches which attempt to directly provide approximate analytical expressions for the oscillation probabilities in matter suffer in accuracy due to their reliance on expansion in θ 13 , or in simplicity when higher order terms in θ 13 are included. We demonstrate the accuracy of our method by comparing it to the exact numerical result, as well as the direct approximations of Cervera et al., Akhmedov et al., Asano and Minakata, and Freund. We also discuss the utility of our approach in figuring out the required baseline lengths and neutrino energies for the oscillation probabilities to exhibit certain desirable features.