First observation of the decay π+ → e+νe+e− and a determination of the form factors FV, FA, R
1986; Elsevier BV; Volume: 175; Issue: 1 Linguagem: Inglês
10.1016/0370-2693(86)90338-2
ISSN1873-2445
AutoresS. Egli, R. Engfer, C. Grab, E.A. Hermes, H.S. Pruys, A. van der Schaaf, D. Vermeulen, R. Eichler, N. Kraus, C. Niebuhr, H. K. Walter, W. Bertl, N. Lordong, U. Bellgardt, G. Otter, T. Kozłowski,
Tópico(s)High-Energy Particle Collisions Research
ResumoThe radiative pion decay π+ → e+νe+e- has been observed for the first time. Information on the form factors was obtained from the kinematical distribution of 79 events. The vector form factor has the same sign as the pion decay constant fπ. The ratios of axial-vector form factors to the vector form factor are γ = FAFV = 0.7 ± 0.5 and ξ = RFV = 2.3 ± 0.6. The value for γ is in agreement with the small positive value (0.53 ± 0.06) and excludes the large negative value (−2.49 ± 0.06) of γ obtained in π+ → e+νγ experiments.
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