Measurement of the electron asymmetry parameter in the decay of polarised Σ − hyperons

• Published in: Nuclear physics. B 1972-04, Vol.39, p.77-105
• Main Authors: Ellis, R.J., Blair, I.M., Taylor, A.E., Astbury, A., Axen, D., Kalmus, P.I.P., Sherman, H.J., Williams, D.T., Gibson, W.R., Bloodworth, I., Gouanere, M., Meyer, S.L., Efremenko, V.
• Format: Article
• Language: English
• ISSN: 0550-3213; 1873-1562
• DOI: 10.1016/0550-3213(72)90361-6

We wish to report on a measurement made at the Rutherford Laboratory of the electron asymmetry parameter in the decay Σ − → ne − ν using counters and wire spark chambers. Polarised Σ − were produced in the reaction π −p → Σ −K + at an incident momentum of 1.13 GeV/ c. The mean Σ − polarisation for detected events was P Σ − = −0.32 ± 0.11. The value obtained for the electron asymmetry parameter was α e =+0.39 −0.53 +1.9 based on 43 events. This yields a value for the ratio of axial vector to vector coupling constants for this decay of g A/ g V = −0.4 −1.5 +0.52. The Cabibbo prediction for this decay is +0.3. We use the sign convention that g A g V for neutron beta decay is −1.23.