Naslov
Precise measurement of the pion axial form factor in the pi^+ --> e^+ ni gamma decay

Autori
Frlež, Emil ; Počanić, Dinko ; Baranov, V.A. ; Bertl, W. ; Bychkov, Khomutov, N.V. ; Korenchenko, A.S. ; Korenchenko, S.M. ; Kozlowski, T. ; Kravchuk, N.P. ; Kuchinsky, N.A. ; Li, W. ; Minehart, R.C. ; Mzhavia, D. ; Ritchie, B.G. ; Ritt, S. ; Rozhdestvensky, A.M. ; Sidorkin, V.V. ; Smith, L.C. ; Supek, Ivan ; Tsamalaidze, Z. ; VanDevender, B.A. ; Velicheva, E.P. ; Wang, Y. ; Wirtz, H.-P. ; Ziock, K.O.H.

Izvornik
Physical review letters (0031-9007) 93 (2004);

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
pion beta decay; branching ratio; Standard Model

Sažetak
We have studied radiative pion decays pi^+--e^+ni^gamma in three broad kinematic regions using the PIBETA detector and a stopped pion beam. Based on Dalitz distributions of 41 601 events we have evaluated absolute pi e ni^gamma branching ratios in the three regions. Minimum Ksi^2 fits to the integral and differential (Ee+, Egamma) distributions result in the axial-to-vector weak form factor ratio of gamma FA/FV = 0.443(15), or FA = 0.0115(4) with FV = 0.0259. However, deviations from standard model predictions in the high-Egamma– low-Ee+ kinematic region indicate the need for further theoretical and experimental work.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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