Limits on right-handed charged weak currents from a polarization-asymmetry correlation experiment withIn107

Abstract

A new technique, based on relative measurements of the longitudinal polarization {P) of positrons emitted in two opposite directions with respect to the nuclear polarization {R =P ~/P^), is used to provide constraints on extensions of the standard model (/?o). The first result, i.e., /?//?o =0.926 ±0.041, was obtained with '^'^In. Interpreted in the framework of left-right symmetric models and assuming no mixing, it provides a 90% C.L. lower limit of 225 GeV/c^ for the mass of a possible right-handed charged H^ gauge boson, reducing the mass range allowed by other semileptonic experiments.

Prospects for precision measurements in nuclear decay in the LHC era

“…This would then result in a limit on the tensor couplings a factor of about 2 larger than given in Eq. (38). Note that, since the β particle end-point energy is rather large in 8 Li decay (16.1 MeV) the sensitivity to the Fierz term via the factor m/E e is 3.3 times smaller than in 6 He decay.…”

“…The measurements were carried out in 107 In [38] and 12 N [39,40]. Since these are relative measurements, the contribution of the Fierz term cancels and the remaining sensitivity to exotic left-handed couplings is strongly suppressed.…”

Tests of P-violation in neutron and nuclear beta decay

“…Four such measurements have been performed, with 12 N and 107 In [40][41][42][43][44], all using the already mentioned technique of positronium hyperfine spectroscopy. In these measurements one determined either the ratio R + = P − /P + or R 0 = P − /P 0 , with P −,+,0 the longitudinal polarization for positrons emitted opposite to (P − ) or in the direction of (P + ) the nuclear polarization, or by unpolarized nuclei (P 0 ).…”

14 Particle Decay Study of Oriented Nuclei

“…Presently, the formalism of ß-decay of oriented nuclei is well understood. Very recently, it has been shown that nuclear orientation even provides very advantageous means for the investigation of extensions beyond the Standard Model [6].…”

“…This has been demonstrated very convincingly in the late fifties by the parity violation experiments in ß-decay of polarized nuclei [5], More recently, NO in combination with a positron-polarimeter has been used to provide constraints on extensions of the Standard Model. New limits on right-handed charged weak currents have been established [6].…”