Naslov
Investigation of Rare Pion Decays with the PIBETA Spectrometer

Autori
Počanić, D. ; Alonzi, L. P. ; Baranov, V. A. ; Bertl, W. ; Bystritsky, Yu. M. ; Bychkov, M. A. ; Velicheva, E. P. ; Vol’nykh, V. P. ; Kalinnikov, V. A. ; Kozlowski, T. ; Korenchenko, A. S. ; Korenchenko, S. M. ; Korolija, Milorad ; Kravchuk, N. P. ; Kuchinsky, N. A. ; Lehman, M. ; Mzhavia, D. A. ; Palladino, A. ; Robmann, P. ; Rozhdestvensky, A. M. ; Rondon-Aramayo, O. A. ; Supek, Ivan ; Truöl, P. ; Frlež, E. ; Khomutov, N. V. ; Tsamalaidze, Z. ; van der Schaaf, A.

Kolaboracija
A2 Collaboration at MAMI

Izvornik
Physics of Particles and Nuclei Letters (1547-4771) 15 (2018), 6; 610-620

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

Ključne riječi
axial form-factor ; branching ratio ; beta-decay ; probability ; symmetry

Sažetak
Experimental results on pion decays obtained with the PIBETA spectrometer at the Paul Scherrer Institute (PSI) are reviewed. For pion beta decay (+) (0)?(+) (), a precision measurement of relative probability yields ?() = [1.036 +/- 0.004(stat) +/- 0.004(syst) +/- 0.003((+)?(+))] x 10(-8), which implies V-ud = 0.9728(30) for the corresponding element of the Cabibbo-Kobayashi-Maskawa mixing matrix. Using a sample of 65 x 10(3) events, relative probability of the (+)?(+) radiative pion decay (RPD) in the kinematic region of E > 10 MeV and (e) > 40 degrees is measured as B-exp = 73.86(54) x 10(-8). A statistical analysis of measured Ee+ and E distributions for this decay yield the values F-V = 0.0258(17) and F-A = 0.0117(17) for the pion weak formfactors. Assuming that F-V linearly depends on the ?(+) invariant mass q(2) as F-V(q(2)) = F-V(0)(1 + aq(2)), the slope parameter is extracted as a = 0.10(6). The pion polarizability and neutral- pion lifetime are estimated as (E) = 2.78(10) x 10(-4) fm(3) and ((0)) = (8.5 +/- 1.1) x 10(-17) s, respectively. The data for decays pi(+) -> (+) and nu and mu+ -> e+nu(nu) over bar gamma have been collected and are being processed. The follow-up PEN experiment aims at reducing the uncertainty on the (+) ?(+) relative probability by almost an order of magnitude (to 5 x 10(-4)).

Izvorni jezik
Engleski

Znanstvena područja
Fizika

POVEZANOST RADA