Earth matter effect in ⁷Be solar neutrino experiments

Abstract

We determine the sensitivity of the KamLAND and Borexino experiments to the neutrino regeneration effect in the Earth as a function of ∆m 2 and θ, using realistic numbers for the signal and background rates. We compare the results obtained with the χ 2 method with those obtained from the conventional day-night asymmetry analysis. We also investigate how well one should be able to measure the neutrino oscillation parameters if a large day-night asymmetry is observed, taking the LOW solution as an example. We present an enlarged parameter space, which contains mixing angles greater than π/4 where the heavy mass eigenstate is predominantly ν e , and determine the electron neutrino survival probability for this traditionally neglected scenario. We emphasize that this portion of the parameter space yields different physics results when dealing with the MSW solutions to the solar neutrino puzzle and should not be neglected.

Nanomechanical Switch formed by Focused-Ion-Beam Chemical Vapor Deposition

“…In absence of oscillations, Borexino (KamLAND) is expected to have a signal rate of 59 (280) events/day for the central value of the Beryllium, CNO, pep fluxes predicted by [31] and a background rate of 19 (130) events/day, known with δb = 10% (50% 5 ) error. Even if the background were more uncertain, the seasonal variation of the solar neutrino flux (due to the excentricity of the earth orbit) would allow a measurement of the signal rate with an interesting accuracy [8,30]. We concentrate on Borexino and consider only the signal due to the Beryllium line (46 events/day), after three years of running.…”

“…We perform our analysis along the lines of [30], but paying more attention to the determination of the oscillation parameters, rather than to the discovery of oscillation signals. We divide the simulated data into N bins = 8 + 1 zenith bins (8 night zenith bins equally spaced in cos θ zenith , plus one day bin) and define…”

“…[8,32,35]), rather than the day/night effects characteristic of the LOW region (see e.g. [8,30]). The regions considered in the rest of this paper will be soon disfavoured, if SNO finds a day/night asymmetry.…”

“…We assume that the fiducial volume will be 60% of KamLAND[8]; this is why our rates are 60% lower than those employed in[30,32].…”

Theory of Neutrino Masses and Mixings

“…contours for three years of Borexino running. 46 The LOW solution is completely covered. the other hand, the slow rise at higher energy depends both on the mixing angle and the mass-squared difference.…”