P. Wildenhain

Measurement of the solar electron neutrino flux with the Homestake chlorine detector

The Homestake Solar Neutrino Detector, based on the inverse beta-decay reaction νe +37Cl →37Ar + e-, has been measuring the flux of solar neutrinos since 1970. The experiment has operated in a stable manner throughout this time period. All aspects of this detector are reviewed, with particular emphasis on the determination of the extraction and counting efficiencies, the key experimental parameters that are necessary to convert the measured 37Ar count rate to the solar neutrino production rate. A thorough consideration is also given to the systematics of the detector, including the measurement of the extraction and counting efficiencies and the nonsolar production of 37Ar. The combined result of 108 extractions is a solar neutrino-induced 37Ar production rate of 2.56 ± 0.l6 (statistical) ± 0.16 (systematic) SNU.

Measurement of the solar neutrino capture rate with gallium metal

The solar neutrino capture rate measured by the Russian-American Gallium Experiment (SAGE) on metallic gallium during the period January 1990 through December 1997 is 67.2 (+7.2-7.0) (+3.5-3.0) SNU, where the uncertainties are statistical and systematic, respectively. This represents only about half of the predicted Standard Solar Model rate of 129 SNU. All the experimental procedures, including extraction of germanium from gallium, counting of 71Ge, and data analysis are discussed in detail.

Measurement of the response of a gallium metal solar neutrino experiment to neutrinos from a [Formula Presented] source

The neutrino capture rate measured by the Russian-American Gallium Experiment is well below that predicted by solar models. To check the response of this experiment to low energy neutrinos, a 517 kCi source of 51Cr was produced by irradiating 512.7 g of 92.4% enriched 50Cr in a high flux fast neutron reactor. This source, which mainly emits monoenergetic 747 keV neutrinos, was placed at the center of a 13.1 tonne target of liquid gallium and the cross section for the production of 71Ge by the inverse beta decay reaction Ga(νe, e −)71Ge was measured to be (5.55 ± 0.60 (stat.) ± 0.32 (syst.)) × 10−45 cm2. The ratio of this cross section to the theoretical cross section of Bahcall for this reaction is 0.95 ± 0.12 (exp.) +0.035 −0.027 (theor.) and to the cross section of Haxton is 0.87 ± 0.11 (exp.) ± 0.09 (theor.). This good agreement between prediction and observation implies that the overall experimental efficiency is correctly determined and provides considerable evidence for the reliability of the solar neutrino measurement. PACS codes: 26.65.+t, 13.15.+g, 95.85.Ry Typeset using REVTEX

Update on the measurement of the solar neutrino flux with the Homestake chlorine detector

The Homestake chlorine solar neutrino detector has been measuring the flux of v e from the decay of 7 Be and 8 B since 1970. The average measured flux is 2.55 ± 0.25 SNU.

The homestake chlorine solar neutrino experiment—past, present and future

The Homestake chlorine solar neutrino detector has measured the total flux of electron neutrinos from the Sun above 0.814 MeV as 2.56±0.16(stat)±0.16(syst) SNU compared to the predicted flux of 7.5 SNU. When combined with the recent SNO measurement of the electron neutrino flux from 8B decays, the Homestake measurement gives 0.55 ± 0.27 SNU for the “1 MeV” electron neutrino flux (7 Be, PeP and CNO) compared to the prediction of 1.83 SNU, assuming no neutrino flavor transitions.

Recent results from sage

A radiochemical {sup 71}Ga-{sup 71}Ge experiment to determine the primary flux of neutrinos from the Sun began measurements of the solar neutrino flux at the Baksan Neutrino Observatory in 1990. The number of {sup 71}Ge atoms extracted from initially 30 and later 57 tons of metallic gallium was measured in fifteen runs during the period of January 1990 to May 1992. The observed capture rate is 70{plus_minus}19 (stat){plus_minus}10 (syst) SNU. This is to be compared with 132 SNU predicted by the Standard Solar Model.

Solar neutrino observations with the Homestake 37Cl detector

The continuous twenty year record of these measurements of the solar neutrino flux with the Homestake chlorine detector, indicates that the average solar neutrino flux is 2.2±0.3 SNU and that this νe flux appears to vary with the 11 year solar activity cycle. Higher νe fluxes are observed during solar quiet periods and lower νe fluxes during solar active periods. When the Homestake data is combined with the Kamiokande results, the region of overlap between the two experiments is for an observed to predicted 8B neutrino flux ratio of about 0.4 and very little low energy neutrino flux. If the Kamiokande results are corrected for MSW effects, neutral current scatterings by non‐electron neutrinos, then both the 8B and the 7Be fluxes are about 1/3 of the Standard Solar Model predictions.

Solar-Neutrino Results from SAGE

The solar-neutrino-capture rate measured by the Russian-American Gallium Experiment on metallic gallium during the period from January 1990 to December 1997 is (67.2−7.0−3.0+7.2+3.5) SNU, where the uncertainties are statistical and systematic, respectively. This result represents a 7σ depression in the neutrino flux in relation to the predicted standard-solar-model rates. The experimental procedures used and data analysis are presented.

The new status of argon-37 artificial neutrino source project

Abstract Solution of the solar neutrino problem is significantly depends on the next generation of detectors that can measure the neutrino radiation from the Sun in intermediate energies. An intense (∼ 1 MCi) 37 Ar source would be an ideal tool for the calibration of new solar neutrino detectors. The technology of the production of such a source is based on the irradiation of a large mass of a Ca-containing target in a high-flux fast-neutron reactor. Produced 37 Ar extracted from this target, will be purified and encapsulated in a source holder. A joint scientific collaboration of Russian, US and Japanese institutions are researching and developing the initial steps of this work and are funded by ISTC and CRDF.

Solar neutrino results and present status

The solar neutrino capture rate measured by the Russian-American Gallium Experiment on a metallic gallium target SAGE during the time from January 1990 through December 2000 is 77.0−6.2 −3.0+6.2 +3.5 SNU, where the uncertainties are statistical and systematic, respectively. The experimental procedures and data analysis are presented.