Eur. Phys. J. A 16, 139-147 (2003)
DOI: 10.1140/epja/i2002-10067-y

Beta-neutrino angular correlation in the decay of

Scalar coupling and interatomic interaction

V. Vorobel¹, Ch. Briançon², V. Brudanin³, V. Egorov³, J. Deutsch⁴, R. Prieels⁴, N. Severijns^{4, 5}, Yu. Shitov³, Ch. Vieu⁴, Ts. Vylov³, I. Yutlandov³ and Sh. Zaparov<sup>3

1</sup>  Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
²  Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, 91405 Orsay, France
³  Joint Institute for Nuclear Research, 141980 Dubna, Russia
⁴  Université Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
⁵  Katholieke Universiteit Leuven, B-3001 Leuven, Belgium

vorobel@ipnp.troja.mff.cuni.cz

(Received: 21 May 2002 / Revised version: 02 July 2002 / Published online: 17 January 2003)

Abstract
The positrons and coincident gamma-rays following the pure Fermi branch of -decay in were measured. The Doppler shift of the -quantum observed is sensitive to the beta-neutrino correlation coefficient, which is unity ( ) in the absence of scalar coupling. The interatomic interaction of recoiling daughters was noticed, which has prevented to obtain an improved result for scalar coupling despite of the excellent statistical accuracy of the measurement. At the same time, it was shown that the method described can be used as a very sensitive and flexible tool to probe the interatomic interactions in matter at the hundred eV energy level. Perspectives in this direction as well as the future angular-correlation experiments aimed to search for scalar coupling in beta-decay are discussed.

PACS
13.10.+q - Weak and electromagnetic interactions of leptons.
23.20.En - Angular distribution and correlation measurements.
23.40.Bw - Weak-interaction and lepton (including neutrino) aspects.
25.75.Gz - Particle correlations.

© Società Italiana di Fisica, Springer-Verlag 2003