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T. D. Steiger

Publications and source records attributed to T. D. Steiger.

5 recordsLinked to original sources
arXiv2007

An array of low-background $^3$He proportional counters for the Sudbury Neutrino Observatory

An array of Neutral-Current Detectors (NCDs) has been built in order to make a unique measurement of the total active flux of solar neutrinos in the Sudbury Neutrino Observatory (SNO). Data in the third phase of the SNO experiment were collected between November 2004 and November 2006, after the NCD array was added to improve the neutral-current sensitivity of the SNO detector. This array consisted of 36 strings of proportional counters filled with a mixture of $^3$He and CF$_4$ gas capable of detecting the neutrons liberated by the neutrino-deuteron neutral current reaction in the D$_2$O, and four strings filled with a mixture of $^4$He and CF$_4$ gas for background measurements. The proportional counter diameter is 5 cm. The total deployed array length was 398 m. The SNO NCD array is the lowest-radioactivity large array of proportional counters ever produced. This article describes the design, construction, deployment, and characterization of the NCD array, discusses the electronics and data acquisition system, and considers event signatures and backgrounds.

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arXiv2003

Precise measurement of the ^7Be(p,gamma)^8B S-factor

We present new measurements of the ^7Be(p,gamma)^8B cross section from \bar{E}_{cm} = 116 to 2460 keV, that incorporate several improvements over our previously published experiment, also discussed here. Our new measurements lead to S_{17}(0) = 22.1 +- 0.6(expt) +- 0.6(theor) eV b based on data from \bar{E}_{cm} = 116 to 362 keV, where the central value is based on the theory of Descouvemont and Baye. The theoretical error estimate is based on the fit of 12 different theories to our low energy data. We compare our results to other S_{17}(0) values extracted from both direct (^7Be(p,gamma)^8B) and indirect (Coulomb dissociation and heavy-ion reaction) measurements, and show that the results of these 3 types of experiments are not mutually compatible. We recommend a "best" value, S_{17}(0) = 21.4 +- 0.5(expt) +- 0.6(theor) eV b, based on the mean of all modern direct measurements below the 1^+ resonance. We also present S-factors at 20 keV which is near the center of the Gamow window: the result of our measurements is S_{17}(20) = 21.4 +- 0.6(expt) +- 0.6(theor) eV b, and the recommended value is S_{17}(20) = 20.7 +- 0.5(expt) +- 0.6(theor) eV b.

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arXiv2001

7Be(p,gamma)8B astrophysical S-factor from precision cross section measurements

We measured the 7Be(p,gamma)8B cross section from E_cm = 186 to 1200 keV, with a statistical-plus-systematic precision per point of better than +- 5%. All important systematic errors were measured including 8B backscattering losses. We obtain S_17(0) = 22.3 +- 0.7(expt) +- 0.5(theor) eV-b from our data at E_cm <= 300 keV and the theory of Descouvemont and Baye.

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arXiv2000

New Limit on the D Coefficient in Polarized Neutron Decay

We describe an experiment that has set new limits on the time reversal invariance violating D coefficient in neutron beta-decay. The emiT experiment measured the angular correlation J . p_e x p_p using an octagonal symmetry that optimizes electron-proton coincidence rates. The result is D=[-0.6+/-1.2(stat)+/-0.5(syst)]x10^(-3). This improves constraints on the phase of g_A/g_V and limits contributions to T violation due to leptoquarks. This paper presents details of the experiment, data analysis, and the investigation of systematic effects.

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