ISSN:
1434-6052
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The charged hyperon beam at the CERN Super Proton Synchrotron (SPS) has been used to collect data on semileptonic decays of Σ−, Ξ−, andΛ. A magnetic channel selected 100 GeV/c negatively charged particles produced in the forward direction by interaction of a 210 GeV/c proton beam on a BeO target. The Σ− and Ξ− hyperons were concurrently identified in a DISC Čerenkov counter, and their decay products were analysed by a magnetic spectrometer. Electron-hadron discrimination was achieved by the combined use of lead glass and lead/scintillator counters, transition radiation detectors, and a Čerenkov counter. In this article we report results on the $$\Xi \to \Lambda \pi (\Lambda \to pe\bar v), \Xi \to \Lambda e\bar v(\Lambda \to p\pi ),$$ and $$\Xi \to \sum ^0 e\bar v(\sum ^0 \to \Lambda \gamma ) (\Lambda \to p\pi )$$ decay modes. Samples of 7,111 $$\Lambda \to pe\bar v, 2,608 \Xi \to \Lambda e\bar v$$ , and $$154 \Xi \to \Sigma ^0 e\bar v$$ were used in our analysis. The branching ratio measurements gave values of (8.57±0.36)×10−4, (5.64±0.31)×10−4, and (0.87±0.17)×10−4 for $$\Lambda \to pe\bar v, \Xi \to \Lambda e\bar v$$ , and $$ \Xi \to \sum ^0 e\bar v$$ , respectively. Measurements of the Λ polarization and of the centre-of-mass distributions yield the axial vector to vector form factor ratio,g 1/f 1=+0.70±0.03 for $$\Lambda \to pe\bar v$$ , andg 1/f 1=+0.25±0.05 for $$\Xi \to \Lambda e\bar v$$ . The effects ofq 2-dependence off 1 andg 1 and of radiative corrections, the measurement of the weak magnetism termf 2, and the effect of possible second-class current terms are discussed. Results on the $$\sum \to \Lambda e\bar v$$ and $$\sum \to ne\bar v$$ decay modes are reported in separate articles.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01648771
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