Sandhya Choubey

Impact of the first SNO results on neutrino mass and mixing

Abstract We investigate the implications of the SNO charged-current (CC) and electron scattering (ES) measurements of solar 8 B neutrino fluxes for neutrino mass and mixing parameters by performing a global and unified χ 2 analysis of the solar neutrino data in the framework of two neutrino mixing. We consider both ν e – ν active and ν e – ν sterile solutions and perform (i) analysis of the total rates data of Cl, Ga, SK and SNO experiments and (ii) global analysis including the total rates data, the recoil electron spectrum data of SK and the CC spectrum observed at SNO. For the ν e – ν active case the inclusion of the SNO results in the analysis of the total rates reduces (enhances) the goodness-of-fit (GOF) of the SMA (LMA) solution. The flat spectrum observed at SK further favours the LMA solution over the SMA solution and no allowed area is obtained in the SMA region at 3 σ level from the global analysis. For the ν e – ν sterile case, with the inclusion of the SNO results, all the solutions are disfavoured with a probability of more than 99% from the total rates analysis while for the global analysis the GOF of these become much worse.

Constraints on neutrino oscillation parameters from the SNO salt phase data

Abstract The physics implications of the just published salt phase data from the SNO experiment are examined. The effect of these data on the allowed ranges of the solar neutrino oscillation parameters, Δ m 21 2 and sin2θ12, are studied in the cases of two- and three-neutrino mixing. In the latter case we derive an upper limit on the angle θ13. Constraints on the solar νe transitions into a mixture of active and sterile neutrinos are also presented. Finally, we give predictions for the day–night asymmetry in the SNO experiment, for the event rate in the BOREXINO and LowNu experiments, and discuss briefly the constraints on the solar neutrino oscillation parameters which can be obtained with prospective KamLAND data.

Exploring the sensitivity of current and future experiments to

The first results from the KamLAND experiment in conjunction with the global solar neutrino data has demonstrated striking ability to constrain them 2 (�m 2 ) very pre- cisely. However the allowed range of �� (�12) did not change much with the inclusion of the KamLAND results. In this paper we probe if future data from KamLAND can increase the accuracy of the allowed range in �� and conclude that even after 3 kton-year of statistics and most optimistic error estimates, KamLAND may find it hard to significantly improve the bounds on the mixing angle obtained from the solar neutrino data. We discuss the �12 sensitivity of the survival probabilities in matter (vacuum) as is relevant for the solar (Kam- LAND) experiments. We find that the presence of matter effects in the survival probabilities for 8 B neutrinos give the solar neutrino experiments SK and SNO an edge over KamLAND, as far as �12 sensitivity is concerned, particularly near maximal mixing. Among solar neu- trino experiments we identify SNO as the most promising candidate for constraining �12 and make a projected sensitivity test for the mixing angle by reducing the error in the neutral current measurement at SNO. Finally we argue that the most accurate bounds on �12 can be achieved in a reactor experiment, if the corresponding baseline and energy can be tuned to a minimum in the survival probability. We propose a new reactor experiment which can give the value of tan 2 �12 to within 14%. We also discuss the future Borexino and LowNu experiments.

Global Analysis of Neutrino Oscillation

We present the constraints on neutrino oscillation parameters Δ m ⊙ 2 and θ ⊙ governing the solar neutrino oscillations from two generation analysis of solar and KamLAND data. We include the latest 766.3 ton year KamLAND data in our analysis. We also present the allowed values of parameters Δ m a t m 2 and sin 2 θ a t m from two generation oscillation analysis of SuperKamiokande atmospheric and K2K data. For both cases we discuss the precision achieved in the present set of experiments and also how the precision can be improved in future. We also obtain the bounds on θ 13 from three generation analysis of global oscillation data. We emphasise on the roles played by different data sets in constraining the allowed parameter ranges.

Three generation neutrino oscillation parameters after SNO

We examine the solar neutrino problem in the context of the realistic three neutrino mixing scenario including the SNO charged current (CC) rate. The two independent mass squared differences

Viability of bimaximal solution of the Zee mass matrix

Delta m^2_{21}

Status of the neutrino decay solution to the solar neutrino problem

and

Is neutrino decay really ruled out as a solution to the atmospheric neutrino problem from Super-Kamiokande data?

Delta m^2_{31} approx Delta m^2_{32}

On the measurement of solar neutrino oscillation parameters with KamLAND

are taken to be in the solar and atmospheric ranges respectively. We incorporate the constraints on

Reviving the energy independent suppression of the solar neutrino flux

Delta