Stephen R. Elliott

Solar neutrino flux measurements by the Soviet-American Gallium Experiment (SAGE) for half the 22 year solar cycle

We present the results of measurements of the solar neutrino capture rate in gallium metal by the Russian-American Gallium Experiment SAGE during slightly more than half of a 22-year cycle of solar activity. Combined analysis of the data of 92 runs during the 12-year period January 1990 through December 2001 gives a capture rate of solar neutrinos with energy more than 233 keV of 70.8 +5.3/-5.2 (stat.) +3.7/-3.2 (syst.) SNU. This represents only slightly more than half of the predicted standard solar model rate of 128 SNU. We give the results of new runs beginning in April 1998 and the results of combined analysis of all runs since 1990 during yearly, monthly, and bimonthly periods. Using a simple analysis of the SAGE results combined with those from all other solar neutrino experiments, we estimate the electron neutrino pp flux that reaches the Earth to be (4.6 +/- 1.1) E10/(cm^2-s). Assuming that neutrinos oscillate to active flavors the pp neutrino flux emitted in the solar fusion reaction is approximately (7.7 +/- 1.8) E10/(cm^2-s), in agreement with the standard solar model calculation of (5.95 +/- 0.06) E10/(cm^2-s).We present measurements of the solar neutrino capture rate on metallic gallium in the Soviet-American gallium experiment (SAGE) over a period of slightly more than half the 22-year solar cycle. A combined analysis of 92 runs over the twelve-year period from January 1990 until December 2001 yields a capture rate of 70.8−5.2+5.3 (stat)−3.2+3.7 (sys) SNU for solar neutrinos with energies above 0.233 MeV. This value is slightly more than half the rate predicted by the standard solar model, 130 SNU. We present the results of new runs since April 1998 and analyze all runs combined by years, months, and bimonthly periods beginning in 1990. A simple analysis of the SAGE results together with the results of other solar neutrino experiments gives an estimate of (4.6±1.2)× 1010 neutrinos cm−2 s−1 for the flux of the electron pp neutrinos that reach the Earth without changing their flavor. The flux of the pp neutrinos produced in thermonuclear reactions in the Sun is estimated to be (7.6 ± 2.0) × 1010 neutrinos cm−2 s−1, in agreement with the value of (5.95±0.06)×1010 neutrinos cm−2 s−1 predicted by the standard solar model.

Comment on "Evidence for Neutrinoless Double Beta Decay"

We comment on the recent claim for the experimental observation of neutrinoless double-beta decay. We discuss several limitations in the analysis provided in that paper and conclude that there is no basis for the presented claim.

Measurement of the solar neutrino capture rate in Sage

Abstract Combined analysis of the data of 92 runs of SAGE during the 12-year period January 1990 through December 2001 gives a capture rate of solar neutrinos with energy more than 233 keV of 70.9 −5.2 +5.3 (stat.) −3.2 +3.7 (syst.) SNU. This represents only 55% of the predicted standard solar model rate of ∼130 SNU. The results of individual runs as well as the results of combined analysis of all runs during yearly, monthly, and bimonthly periods are presented. No compelling evidence for temporal variations is observed. By an analysis of the SAGE results combined with those from all other solar neutrino experiments, we make the first estimate of the electron neutrino pp flux that reaches the Earth to be (4.6 ± 1.2) x 10 10 /(cm 2 s). Assuming that neutrinos oscillate to active flavors the pp neutrino flux emitted in the solar fusion reaction is approximately (7.6 ± 2.0) x 10 10 /(cm 2 s), in agreement with the standard solar model calculation of (5.95 ± 0.06) x 10 10 /(cm 2 s).

High-voltage microdischarge in ultra-low background /sup 3/He proportional counters

This paper discusses the phenomenon of surface microdischarge induced by high voltage, and techniques for the reduction and discrimination of such breakdowns in ultralow background proportional counters. An array of ultra-low background /sup 3/He-filled proportional counters will measure the neutral-current interaction rate of all active neutrino species in the Sudbury Neutrino Observatory. The sensitivity of these neutral current detectors and their stringent background criteria make it essential to minimize all spurious pulses including signals induced by high voltage. Such pulses can originate from microscopic surface discharges in the various proportional counter components. Studies have shown that this discharge effect occurs mainly at interfaces and in microscopic voids between dielectric surfaces, on contaminated surfaces, and on surfaces with imperfections. Because of its occurrence in various materials and environments, microdischarge is a concern for all low-background detectors that operate under high voltage.

The Majorana 76Ge double-beta decay project

Abstract The interest and relevance of next-generation 0 v ββ-decay experiments is increasing. Even with nonzero neutrino mass strongly suggested by solar and atmospheric neutrino experiments sensitive to δm 2 , 0 v ββ-decay experiments are still the only way to establish the Dirac or Majorana nature of neutrinos by measuring the effective electron neutrino mass, 〈 m v 〉. In addition, the atmospheric neutrino oscillation experiments imply that at least one neutrino has a mass greater than about 50 meV. The Majorana Experiment expects to probe an effective neutrino mass near this critical value. Majorana is a next-generation 76 Ge double-beta decay search. It will employ 500 kg of Ge, isotopically enriched to 86% in 76 Ge, in the form of ∼ 200 detectors in a close-packed array. Each crystal will be electronically segmented and each segment fitted with pulse-shape analysis electronics. This combination of segmentation and pulse-shape analysis significantly improves our ability to discriminate neutrinoless double beta-decay from internal cosmogenic 68 Ge and 60 Co . The half-life sensitivity is estimated to be 4.2 × 10 27 y corresponding to a 〈 m v 〉 range of ≤ 20 − 70 meV, depending on the nuclear matrix elements used to interpret the data.

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.

Neutrino detection using lead perchlorate

Abstract We discuss the possibility of using lead perchlorate as a neutrino detector. The primary neutrino interactions are given along with some relevant properties of the material.

Searching for time reversal invariance violation in polarized neutron decay

Time reversal invariance violation is tightly constrained in the Stan- dard Model, and the existence of a T-violating effect above the predicted level would be an indication of new physics. A sensitive probe of this symmetry in the weak interaction is the measurement of the D-coefficient in neutron decay. This parameter characterizes the triple-correlation of neutron spin, electron mo- mentum, and neutrino (or proton) momentum, which changes sign under time reversal. The emiT experiment, now on line, attempts to improve the measure- ment of D, whose current average is 0.3 + 1.5 x 10 -3.

The Russian-American gallium solar neutrino experiment

The Russian-American Gallium solar neutrino Experiment (SAGE) is described. The solar neutrino flux measured by 31 extractions through October, 1993 is presented. The result of 69 {+-} 10{sub {minus}7}{sup +5} SNU is to be compared with a standard solar model prediction of 132 SNU. The status of a {sup 51}Cr neutrino source irradiation to test the overall operation of the experiment is also presented.