R. G. Hamish Robertson

Solar Neutrinos: Status and Prospects

We describe the current status of solar neutrino measurements and of the theory—both neutrino physics and solar astrophysics—employed in interpreting measurements. Important recent developments include Super-Kamiokandes determination of the ν−e elastic scattering rate for 8B neutrinos to 3%; the latest Sudbury Neutrino Observatory (SNO) global analysis in which the inclusion of low-energy data from SNO I and II significantly narrowed the range of allowed values for the neutrino mixing angle θ12; Borexino results for both the 7Be and proton-electron-proton (pep) neutrino fluxes, the first direct measurements constraining the rate of proton-proton (pp) I and pp II burning in the Sun; global reanalyses of solar neutrino data that take into account new reactor results on θ13; a new decadal evaluation of the nuclear physics of the pp chain and CNO cycle defining best values and uncertainties in the nuclear microphysics input to solar models; recognition of an emerging discrepancy between two tests of solar me...

Constraining the leading weak axial two-body current by SNO and Super-K

We analyze the Sudbury Neutrino Observatory (SNO) and Super-Kamiokande (SK) data on charged current (CC), neutral current (NC) and neutrino electron elastic scattering (ES) reactions to constrain the leading weak axial two-body current parameterized by L{sub 1A}. This two-body current is the dominant uncertainty of every low energy weak interaction deuteron breakup process, including SNOs CC and NC reactions. Our method shows that the theoretical inputs to SNOs determination of the CC and NC fluxes can be self-calibrated, be calibrated by SK, or be calibrated by reactor data. The only assumption made is that the total flux of active neutrinos has the standard {sup 8}B spectral shape (but distortions in the electron neutrino spectrum are allowed). We show that SNOs conclusion about the inconsistency of the no-flavor-conversion hypothesis does not contain significant theoretical uncertainty, and we determine the magnitude of the active solar neutrino flux.

Multilayer Scintillator Responses for Mo Observatory of Neutrino Experiment Studied Using a Prototype Detector MOON-1

An ensemble of multilayer scintillators is discussed as an option of the high-sensitivity detector MOON (Mo Observatory of Neutrinos) for spectroscopic measurements of neutrinoless double beta decays. A prototype detector MOON-1, which consists of 6-layer plastic scintillator plates, was built to study the photon responses of the MOON-type detector. The photon responses, i.e., the number of scintillation photons collected and the energy resolution, which are key elements for high-sensitivity experiments, are found to be 1835 � 30 photoelectrons for 976 keV electrons and � ¼ 2:9 � 0:1% (� E=E ¼ 6:8 � 0:3% in FWHM) at the Q�� � 3 MeV region, respectively. The multilayer plastic scintillator structure with high energy resolution as well as a good signal for the background suppression of � –� rays is crucial for the MOON-type detector to achieve inverted-hierarchy neutrino-mass sensitivity. It will also be useful for medical and other rare-decay experiments as well.

Theory of neutrino oscillations with entanglement

We show that, despite appearances, a theoretical approach to neutrino oscillation in which the neutrino and its interaction partners are entangled yields the standard result for the neutrino oscillation wavelength. We also shed some light on the question of why plane-wave approaches to the neutrino oscillation problem can yield the correct oscillation wavelength even though they do not explicitly account for the localization of the neutrino source and the detector.

Data acquisition for the Helium and Lead Observatory

The Helium and Lead Observatory (HALO) is a dedicated supernova detector constructed in the underground facilities at SNOLAB in Sudbury, Canada. It is designed to detect neutrinos from a supernova within the Milky Way galaxy using lead blocks and 3He neutron detectors. Analysis of supernova neutrino events can produce new discoveries in astrophysics and fundamental particle physics. HALO will be a participant in the Supernova Early Warning System (SNEWS), which will rely on the time delay between neutrino emission and visible light emission to provide notification to astronomers of an imminent observable supernova. This article discusses the data acquisition system of HALO, including the software ORCA, electronics components, data flow, and the design of the high-voltage and signal connections for the 3He neutron detectors.

Neutrino mass and oscillations

The neutrino remains as exotic and challenging today as it was seventy years ago when first proposed by Pauli. What is known for certain about neutrinos is minimal indeed. They have spin 12, charge 0, negative helicity, and exist in 3 flavors, electron, mu, and tau. Strictly speaking, only 2 flavors are certain: direct observation of the tau neutrino has not yet been achieved, but an experiment, DONUT, at Fermilab is in progress with this objective [1]. Limits on the masses from direct, kinematic experiments (ones that do not require assumptions about the non-conservation of lepton family numbers) have been steadily lowered by experiments of ever-increasing sophistication over the years, with the results given in Table 1. As will be discussed below, there are stronger limits on the mass of νe from tritium beta decay [2, 3], but the data show curious distortions near the endpoint that are not at present understood.

MOON (Mo Observatory Of Neutrinos) for neutrino studies in 100Mo by double beta decays and solar-ν capture reactions

Neutrino mass is a key issue of current physics, and atmospheric, solar, and accelerator experiments strongly suggest ν oscillations due to non-zero ν-mass differences and flavor mixings. It is of great interest to study ν mass with sensitivity in the 0.05 eV range. Double beta decay may be the only probe presently able to access such small ν masses. It is possible with 100Mo to carry out both spectroscopic studies of double beta decays with the sensitivity of the order of 〈mν〉∼0.03 eV, and realtime exclusive studies of low energy solar ν.