Solar Neutrino Results from the Sudbury Neutrino Observatory

We describe here the measurement of the flux of neutrinos created by the decay of solar ^8B by the Sudbury Neutrino Observatory (SNO). The neutrinos were detected via the charged current (CC) reaction on deuterium and by the elastic scattering (ES) of electrons. The CC reaction is sensitive exclusively to $\nu_e$'s, while the ES reaction also has a small sensitivity to $\nu_{\mu}$'s and $\nu_{\tau}$'s. The flux of $\nu_e$'s from ^8B decay measured by the CC reaction rate is $\phi^CC (\nu_e) = 1.75 \pm 0.07 (stat.)^{+0.1 2}_{-0.11} (sys.) \pm 0.05 (theor.) \times 10^6 cm^-2 s^-1$. Assuming no flavor transformation, the flux inferred from the ES reaction rate is $\phi^ES (\nu_x)=2.39\pm 0.34 (stat.) ^{+0.16}_{-0.14} (sys.) \times 10^6 cm^-2 s^-1$. Comparison of $\phi^CC (\nu_e)$ to the Super-Kamiokande Collaboration's precision value of $\phi^ES (\nu_x)$ yields a $3.3\sigma$ difference, assuming the systematic uncertainties are normally distributed, providing evidence that there is a non-electron flavor active neutrino component in the solar flux. The total flux of active ^8B neutrinos is thus determined to be $5.44\pm 0.99 \times 10^6 cm^-2 s^-1$, in close agreement with the predictions of solar models.Comment: Talk given at the XX International Symposium on Lepton and Photon Interactions at High Energie

Recent Results from the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) measures both the flux of the electron-type neutrinos and the total flux of all active flavours of neutrinos originating from the Sun. A model-independent test of neutrino flavour transformation was performed by comparing these two measurements. In 2002, this flavour transformation was definitively demonstrated. In this talk, results from these measurements and the current status of the SNO detector are presented.Comment: Proceedings of the International Europhysics Conference on High Energy Physics (EPS2003) 3 pages, 2 figures, 2 table

Relation between CKM and MNS Matrices Induced by Bi-Maximal Rotations in the Seesaw Mechanism

It is found that the seesaw mechanism not only explains the smallness of neutrino masses but also accounts for the large mixing angles simultaneously, even if the unification of the neutrino Dirac mass matrix with that of up-type quark sector is realized. In this mechanism, we show that the mixing matrix of the Dirac-type mass matrix gets extra rotations from the diagonalization of Majorana mass matrix. Assuming that the mixing angles to diagonalize the Majorana mass matrix are extremely small, we find that the large mixing angles of leptonic sector found in atmospheric and long baseline reactor neutrino oscillation experiments can be explained by these extra rotations. We also find that provided the mixing angle around y-axis to diagonalize the Majorana mass matrix vanishes, we can derive the information about the absolute values of neutrino masses and Majorana mass responsible for the neutrinoless double beta decay experiment through the data set of neutrino experiments. In the simplified case that there is no CP phase, we find that the neutrino masses are decided as $m_1:m_2:m_3\approx 1:2:8$ and that there are no solution which satisfy $m_3<m_1<m_2$ (inverted mass spectrum). Then, including all CP phases, we reanalyze the absolute values of neutrino masses and Majorana mass responsible for the neutrinoless double beta decay experiment.Comment: 19 pages, 7 figures, revtex4, to appear in J.PHYS.SOC.JA

Evidence of Antineutrinos from Distant Reactors Using Pure Water at SNO+

The SNO+ Collaboration reports the first evidence of reactor antineutrinos in a Cherenkov detector. The nearest nuclear reactors are located 240 km away in Ontario, Canada. This analysis uses events with energies lower than in any previous analysis with a large water Cherenkov detector. Two analytical methods are used to distinguish reactor antineutrinos from background events in 190 days of data and yield consistent evidence for antineutrinos with a combined significance of 3.5σ

Results from the Sudbury Neutrino Observatory Phase III

The third and last phase of the Sudbury Neutrino Observatory (SNO) used a technique independent of previous methods, to measure the rate of neutral-current interactions in heavy water and determine precisely the total active {sup 8}B solar neutrino flux. The total flux obtained is 5.54{sub -0.31}{sup +0.33}(stat){sub -0.34}{sup +0.36}(syst) x 10{sup 6} cm{sup -2}s{sup -1}, in agreement with previous measurements and standard solar models. Results from a global analysis of solar and reactor neutrino give {Delta}m{sup 2} = 7.59{sub -0.21}{sup +0.19} x 10{sup -5} eV{sup 2} and {theta} = 34.4{sub -1.2}{sup +1.3} degrees with a reduced uncertainty on the mixing angle compared to previous phases

The effect of massive neutrinos on the matter power spectrum

We investigate the impact of massive neutrinos on the distribution of matter in the semi-non-linear regime (0.1<k<0.6 h/Mpc). We present a suite of large-scale N-body simulations quantifying the scale dependent suppression of the total matter power spectrum, resulting from the free-streaming of massive neutrinos out of high-density regions. Our simulations show a power suppression of 3.5-90 per cent at k~0.6 h/Mpc for total neutrino mass, m_nu=0.05-1.9 eV respectively. We also discuss the precision levels that future cosmological datasets would have to achieve in order to distinguish the normal and inverted neutrino mass hierarchies.Comment: 10 pages, 10 figures, 1 table, changes made to address referee repor

Neutron detection in the SNO+ water phase

SNO+ is a multipurpose neutrino experiment located approximately 2 km underground in SNOLAB, Sudbury, Canada. The detector started taking physics data in May 2017 and is currently completing its first phase, as a pure water Cherenkov detector. The low trigger threshold of the SNO+ detector allows for a substantial neutron detection efficiency, as observed with a deployed ^{241}Am^{9}Be source. Using a statistical analysis of one hour AmBe calibration data, we report a neutron capture constant of 208.2 + 2.1(stat.) us and a lower bound of the neutron detection efficiency of 46% at the center of the detector.Peer Reviewe

The HLMA project: determination of high delta-m^2 LMA mixing parameters and constraint on |U_e3| with a new reactor neutrino experiment

In the forthcoming months, the KamLAND experiment will probe the parameter space of the solar large mixing angle (LMA) MSW solution as the origin of the solar neutrino deficit with \nuebar's from distant nuclear reactors. If however the solution realized in nature is such that \Dm2_{sol} \gsim 2 \cdot 10^{-4} eV$^2$ (thereafter named the HLMA region), KamLAND will only observe a rate suppression but no spectral distortion and hence it will not have the optimal sensitivity to measure the mixing parameters. In this case, we propose a new medium baseline reactor experiment located at Heilbronn (Germany) to pin down the precise value of the solar mixing parameters. In this paper, we present the Heilbronn detector site, we calculate the \nuebar interaction rate and the positron spectrum expected from the surrounding nuclear power plants. We also discuss the sensitivity of such an experiment to |U_e3| in both normal and inverted neutrino mass hierarchy scenarios. We then outline the detector design, estimate background signals induced by natural radioactivity as well as by in-situ cosmic ray muon interaction, and discuss a strategy to detect the anti-neutrino signal 'free of background'.Comment: 22 pages, 5 figures; v2: added references, caption of Fig.4 and typos corrected; v3: accepted for publication in Astroparticle Physics, references added, typo in Sec. 6.3 correcte

Fake CPT Violation in Disappearance Neutrino Oscillations

We make an analysis of the fake CPT-violating asymmetries between the survival probabilities of neutrinos and antineutrinos, induced by the terrestrial matter effects, in three different scenarios of long-baseline neutrino oscillation experiments with L=730 km, L=2100 km and L=3200 km. In particular, the dependence of those asymmetries on the Dirac-type CP-violating phase of the lepton flavor mixing matrix is examined.Comment: RevTex 8 pages (including 3 PS figures). To be publishe

Hybrid Textures of Neutrinos

We present numerical and comprehensive analyses of the sixty hybrid textures of neutrinos, which have an equality of matrix elements and one zero. These textures are possibly derived from the discrete symmetry. Only six textures among sixty ones are excluded by the present experimental data. Since there are many textures which give similar predictions, the textures are classified based on the numerical results. The neutrinoless double beta decay is also examined in these textures. Our results suggest that there remain still rich structures of the neutrino mass matrix in the phenomenological point of view.Comment: 19 pages, 9 figures; analytical discussions added, table and reference adde