Constraints on the Neutrino Parameters from the ‘Rise-up’ in the Boron Neutrino Spectrum at Low Energies

The rise-up in boron neutrino spectrum at low energies has been studied within the framework of ‘pure LMA’ scenario. Indirect bounds on the spectral ‘upturn’ have been obtained from the available solar neutrino data. These bounds have been used to demonstrate the efficacy of the precision measurements of the ‘upturn’ for further constraining the neutrino parameter space allowed by SNO salt phase data. The sterile neutrino flux has been constrained in the light of the recent 766.3 Ty KamLAND spectral data. Neutrino Physics is passing through a phase of spectacular development. Vast amount of solar and atmospheric neutrino data has been accumulated and the neutrino deficits have been established to be the consequence of non-standard neutrino physics. The most recent steps in this direction are the pioneering results from SNO and KamLAND experiments. The SNO experiment provided a model independent proof of solar neutrino oscillations and the terrestrial disappearance of reactor νe in the KamLAND experiment has provided a further confirmation of the neutrino oscillation solution of the solar neutrino problem (SNP). This gives us confidence in the oscillation solution of the atmospheric neutrino anomaly. The neutral current measurements at SNO [1] have, conclusively, established the oscillations of solar neutrinos. After the evidence of terrestrial antineutrino disappearance in a beam of electron antineutrinos reported by KamLAND [2], all other [3] explanations of the solar neutrino deficit can, at best, be just subdominant effects. After these pioneering experiments, there is no scope for doubting the physical reality of neutrino mass and the consequent oscillations. KamLAND is the first experiment to explore the neutrino parameter space relevant to SNP with a beam of terrestrial neutrinos and has, convincingly, demonstrated the existence of neutrino oscillations confined to the large mixing angle (LMA) region. The total E–mail : [email protected] E–mail : [email protected]