Is the unitarity of the quark-mixing CKM matrix violated in neutron beta-decay?

H Abele; M Astruc Hoffmann; S Baessler; D Dubbers; F Glück; U Müller; V Nesvizhevsky; J Reich; O Zimmer

doi:10.1103/PhysRevLett.88.211801

Is the unitarity of the quark-mixing CKM matrix violated in neutron beta-decay?

Phys Rev Lett. 2002 May 27;88(21):211801. doi: 10.1103/PhysRevLett.88.211801. Epub 2002 May 13.

Authors

H Abele¹, M Astruc Hoffmann, S Baessler, D Dubbers, F Glück, U Müller, V Nesvizhevsky, J Reich, O Zimmer

Affiliation

¹ Physikalisches Institut der Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany.

PMID: 12059473
DOI: 10.1103/PhysRevLett.88.211801

Abstract

We report on a new measurement of neutron beta-decay asymmetry. From the result A(0) = -0.1189(7), we derive the ratio of the axial vector to the vector coupling constant lambda = g(A)/g(V) = -1.2739(19). When included in the world average for the neutron lifetime tau = 885.7(7) s, this gives the first element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix V(ud). With this value and the Particle Data Group values for V(us) and V(ub), we find a deviation from the unitarity condition for the first row of the CKM matrix of Delta = 0.0083(28), which is 3.0 times the stated error.