Hybrid method to resolve the neutrino mass hierarchy by supernova (anti)neutrino induced reactions

We introduce a hybrid method to determine the neutrino mass hierarchy by simultaneous measurements of responses of at least two detectors to antineutrino and neutrino fluxes from accretion and cooling phases of core-collapse supernovae. The (anti)neutrino-nucleus cross sections for 56Fe and 208Pb are calculated in the framework of the relativistic nuclear energy density functional and weak interaction Hamiltonian, while the cross sections for inelastic scattering on free protons p(v¯e,e+)n are obtained using heavy-baryon chiral perturbation theory. The modelling of (anti)neutrino fluxes emitted from a protoneutron star in a core-collapse supernova include collective and Mikheyev-Smirnov-Wolfenstein effects inside the exploding star. The particle emission rates from the elementary decay modes of the daughter nuclei are calculated for normal and inverted neutrino mass hierarchy. It is shown that simultaneous use of (anti)neutrino detectors with different target material allows to determine the neutrino mass hierarchy from the ratios of ve- and v¯e-induced particle emissions. This hybrid method favors neutrinos from the supernova cooling phase and the implementation of detectors with heavier target nuclei (208Pb) for the neutrino sector, while for antineutrinos the use of free protons in mineral oil or water is the appropriate choice.Peer reviewedFinal Accepted Versio

The Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory is a second generation water Cherenkov detector designed to determine whether the currently observed solar neutrino deficit is a result of neutrino oscillations. The detector is unique in its use of D2O as a detection medium, permitting it to make a solar model-independent test of the neutrino oscillation hypothesis by comparison of the charged- and neutral-current interaction rates. In this paper the physical properties, construction, and preliminary operation of the Sudbury Neutrino Observatory are described. Data and predicted operating parameters are provided whenever possible.Comment: 58 pages, 12 figures, submitted to Nucl. Inst. Meth. Uses elsart and epsf style files. For additional information about SNO see http://www.sno.phy.queensu.ca . This version has some new reference

Measurement of the νe and total 8B solar neutrino fluxes with the Sudbury Neutrino Observatory phase-III data set

This paper details the solar neutrino analysis of the 385.17-day phase-III data set acquired by the Sudbury Neutrino Observatory (SNO). An array of 3He proportional counters was installed in the heavy-water target to measure precisely the rate of neutrino-deuteron neutral-current interactions. This technique to determine the total active 8B solar neutrino flux was largely independent of the methods employed in previous phases. The total flux of active neutrinos was measured to be 5.54-0.31+0.33(stat.)-0.34+0.36(syst.)×106 cm-2 s-1, consistent with previous measurements and standard solar models. A global analysis of solar and reactor neutrino mixing parameters yielded the best-fit values of Δm2=7.59-0.21+0.19×10 -5eV2 and θ=34.4-1.2+1.3degrees

Electron energy spectra, fluxes, and day-night asymmetries of boron-8 solar neutrinos from the 391-day salt phase sno data set

Results are reported from the complete salt phase of the Sudbury Neutrino Observatory experiment in which NaCl was dissolved in the D_2O target. The addition of salt enhanced the signal from neutron capture, as compared to the pure D_2O detector. By making a statistical separation of charged-current events from other types based on event-isotropy criteria, the effective electron recoil energy spectrum has been extracted. In units of 106 cm-2 s-1, the total flux of active-flavor neutrinos from 8B decay in the Sun is found to be 4.94+0.21_-0.21(stat)+0.38_-0.34(syst) and the integral flux of electron neutrinos for an undistorted 8B spectrum is 1.68+0.06_-0.06(stat)+0.08_-0.09(syst); the signal from (nu_x,e) elastic scattering is equivalent to an electron-neutrino flux of 2.35+0.22-0.22(stat)+0.15_-0.15(syst). These results are consistent with those expected for neutrino oscillations with the so-called Large Mixing Angle parameters, and also with an undistorted spectrum. A search for matter-enhancement effects in the Earth through a possible day-night asymmetry in the charged-current integral rate is consistent with no asymmetry. Including results from other experiments, the best-fit values for two-neutrino mixing parameters are Delta m2 = (8.0+0.6_-0.4) x 10-5 eV2 and theta = 33.9 +2.4_-2.2 degrees

Neutral current and day night measurements from the pure D2O phase of SNO

The Sudbury Neutrino Observatory is a 1000 T D2O Cerenkov detector that is sensitive to 8B solar neutrinos. The energy, radius, and direction with respect to the sun is measured for each neutrino event; these distributions are used to separately determine the rates of the charged current, neutral current and electron scattering reactions of neutrinos on deuterium. Assuming an undistorted 8B spectrum, the νe component of the 8B solar flux is φe = 1.76-0.05 +0.05 (stat. -0.09 +0.09 (syst.) × 106 cm-2s-1 based on events with a measured kinetic energy above 5 MeV. The non-νe component is φμτ = 3.41-0.45 +0.45 (stat. -0.45 +0.48 (syst.) × 106 cm-2s-1, 5.3σ greater than zero, providing strong evidence for solar νe flavor transformation. The total flux measured with the NC reaction is φNC = 5.09-0.43 +0.44(stat. -0.43 +0.46 (syst.) × 106 cm-2s-1, consistent with solar models. The night minus day rate is 14.0% ± 6.3%-1.4 +1.5% of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymmetry, the νe asymmetry is found to be 7.0% ± 4.9%-1.2 +1.3%. A global solar neutrino analysis in terms of matter-enhanced oscillations of two active flavors strongly favors the Large Mixing Angle (LMA) solution

Measurement of the nue and Total 8B Solar Neutrino Fluxes with the Sudbury Neutrino Observatory Phase I Data Set

This article provides the complete description of results from the Phase I data set of the Sudbury Neutrino Observatory (SNO). The Phase I data set is based on a 0.65 kt-year exposure of heavy water to the solar 8B neutrino flux. Included here are details of the SNO physics and detector model, evaluations of systematic uncertainties, and estimates of backgrounds. Also discussed are SNO's approach to statistical extraction of the signals from the three neutrino reactions (charged current, neutral current, and elastic scattering) and the results of a search for a day-night asymmetry in the ?e flux. Under the assumption that the 8B spectrum is undistorted, the measurements from this phase yield a solar ?e flux of ?(?e) = 1.76+0.05?0.05(stat.)+0.09?0.09 (syst.) x 106 cm?2 s?1, and a non-?e component ?(? mu) = 3.41+0.45?0.45(stat.)+0.48?0.45 (syst.) x 106 cm?2 s?1. The sum of these components provides a total flux in excellent agreement with the predictions of Standard Solar Models. The day-night asymmetry in the ?e flux is found to be Ae = 7.0 +- 4.9 (stat.)+1.3?1.2 percent (sys.), when the asymmetry in the total flux is constrained to be zero

First neutrino observations from the sudbury neutrino observatory

The first neutrino observations from the Sudbury Neutrino Observatory are presented from preliminary analyses. Based on energy, direction and location, the data in the region of interest appear to be dominated by 8B solar neutrinos, detected by the charged current reaction on deuterium and elastic scattering from electrons, with very little background. Measurements of radioactive backgrounds indicate that the measurement of all active neutrino types via the neutral current reaction on deuterium will be possible with small systematic uncertainties. Quantitative results for the fluxes observed with these reactions will be provided when further calibrations have been completed

An Array of low-background 3He proportional counters for the Sudbury Neutrino Observatory

An array of Neutral-Current Detectors (NCDs) has been built in order to make a unique measurement of the total active flux of solar neutrinos in the Sudbury Neutrino Observatory (SNO). Data in the third phase of the SNO experiment were collected between November 2004 and 2006, after the NCD array was added to improve the neutral-current sensitivity of the SNO detector. This array consisted of 36 strings of proportional counters filled with a mixture of 3He and CF4 gas capable of detecting the neutrons liberated by the neutrino-deuteron neutral-current reaction in the D2O, and four strings filled with a mixture of 4He and CF4 gas for background measurements. The proportional counter diameter is 5 cm. The total deployed array length was 398 m. The SNO NCD array is the lowest-radioactivity large array of proportional counters ever produced. This article describes the design, construction, deployment, and characterization of the NCD array, discusses the electronics and data acquisition system, and considers event signatures and backgrounds