Wick Haxton’s scientific contributions

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Publications (1)


Figure 3.1: A Cartoon of the BEST experiment configuration.
Figure 3.2: A photograph of the two-target volume during assembly.
Figure 3.4: A photograph of the BEST source as it is being removed from its transport container. To the right side of the photo, the calorimeter can be seen.
Figure 3.5: A photograph of a BEST proportional counter.
Figure 4.1: The dimensionless distribution L(D) which encodes detector and source geometry needed to compute the distribution of neutrino captures within the Ga volumes as a function of baseline (the distance D between the points where the neutrino is produced in the source and detected in the Ga volume). The total rate in the presence of oscillations is proportional to the integral over the convolution of L(D) with the oscillation probability Pee(E i ν , D) (see Sec. 2.4). Figure courtesy of Ralph Massarczyk.

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The Gallium Anomaly
  • Preprint
  • File available

June 2023

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138 Reads

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2 Citations

Steven R. Elliott

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Vladimir Gavrin

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Wick Haxton

In order to test the end-to-end operations of gallium solar neutrino experiments, intense electron-capture sources were fabricated to measure the responses of the radiochemical SAGE and GALLEX/GNO detectors to known fluxes of low-energy neutrinos. Such tests were viewed at the time as a cross-check, given the many tests of 71Ge recovery and counting that had been routinely performed, with excellent results. However, the four 51Cr and 37Ar source experiments yielded rates below expectations, a result commonly known as the Ga anomaly. As the intensity of the electron-capture sources can be measured to high precision, the neutrino lines they produce are fixed by known atomic and nuclear rates, and the neutrino absorption cross section on 71Ga is tightly constrained by the lifetime of 71Ge, no simple explanation for the anomaly has been found. To check these calibration experiments, a dedicated experiment BEST was performed, utilizing a neutrino source of unprecedented intensity and a detector optimized to increase statistics while providing some information on counting rate as a function of distance from the source. The results BEST obtained are consistent with the earlier solar neutrino calibration experiments, and when combined with those measurements, yield a Ga anomaly with a significance of approximately 4sigma, under conservative assumptions. But BEST found no evidence of distance dependence and thus no explicit indication of new physics. In this review we describe the extensive campaigns carried out by SAGE, GALLEX/GNO, and BEST to demonstrate the reliability and precision of their experimental procedures, including 71Ge recovery, counting, and analysis. We also describe efforts to define uncertainties in the neutrino capture cross section. With the results from BEST, an anomaly remains.

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