We report a measurement of the neutrino-electron elastic scattering rate from {sup 8}B solar neutrinos based on a 123 kton-day exposure of KamLAND. The background-subtracted electron recoil rate, ...above a 5.5-MeV analysis threshold is 1.49 {+-} 0.14(stat) {+-} 0.17(syst) events per kton-day. Interpreted as due to a pure electron flavor flux with a {sup 8}B neutrino spectrum, this corresponds to a spectrum integrated flux of 2.77 {+-} 0.26(stat) {+-} 0.32(syst) x 10{sup 6} cm{sup -2}s{sup -1}. The analysis threshold is driven by {sup 208}Tl present in the liquid scintillator, and the main source of systematic uncertainty is due to background from cosmogenic {sup 11}Be. The measured rate is consistent with existing measurements and with standard solar model predictions which include matter-enhanced neutrino oscillation.
We present a relationship, E_\nu^{max} = m_{\nu} M_{Planck}/M_{weak}, among the highest observed neutrino energy (~PeV) and the neutrino mass, the weak scale, and the Planck energy. We then discuss ...some tests of this relationship, and present some theoretical constructs which motivate the relationship. It is possible that all massive particles are subject to maximum energies given by similar relationships, although only the neutrino seems able to offer interesting phenomenology. We discuss implications which include no neutrino detections at energies greater than PeV, and changes in expectations for the highest energy cosmic rays. A virtue of this hypothesis is that it is easily invalidated should neutrinos be observed with energies much great than the PeV scale. An almost inescapable implication is that Lorentz Invariance is a low energy principle, yet it appears that violation may be only observable in high-energy astrophysical neutrinos.
Neutron tagging in Gadolinium-doped water may play a significant role in reducing backgrounds from atmospheric neutrinos in next generation proton-decay searches using megaton-scale Water Cherenkov ...detectors. Similar techniques might also be useful in the detection of supernova neutrinos. Accurate determination of neutron tagging efficiencies will require a detailed understanding of the number of neutrons produced by neutrino interactions in water as a function of momentum transferred. We propose the Atmospheric Neutrino Neutron Interaction Experiment (ANNIE), designed to measure the neutron yield of atmospheric neutrino interactions in gadolinium-doped water. An innovative aspect of the ANNIE design is the use of precision timing to localize interaction vertices in the small fiducial volume of the detector. We propose to achieve this by using early production of LAPPDs (Large Area Picosecond Photodetectors). This experiment will be a first application of these devices demonstrating their feasibility for Water Cherenkov neutrino detectors.
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