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Study of K^ - to pi ^0 e^ - overline nu _e gamma decay with ISTRA+ setup |
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| Authors: | S. A. Akimenko V. N. Bolotov G. I. Britvich K. V. Datsko V. A. Duk A. P. Filin E. N. Gushchin A. V. Inyakin V. A. Khmelnikov A. S. Konstantinov V. F. Konstantinov I. Yu. Korolkov S. V. Laptev V. A. Lebedev V. M. Leontiev A. E. Mazurov V. P. Novikov V. F. Obraztsov V. A. Polyakov A. Yu. Polyarush V. E. Postoev V. I. Romanovsky V. I. Shelikhov O. G. Tchikilev V. A. Uvarov O. P. Yushchenko |
| Affiliation: | 1. Institute for High Energy Physics, Protvino, Russia 2. Institute for Nuclear Research, Russian Academy of Sciences, Moscow, Russia |
| Abstract: | Results of study of the $K^ - to pi ^0 e^ - overline nu gamma $ decay at the ISTRA+ setup are presented. We observed 4476 events of this decay. The branching ratio is found to be $R = frac{{Br(K^ - to pi ^0 e^ - overline nu _e gamma )}}{{Br(K^ - to pi ^0 e^ - overline nu _e )}}$ = (1.81±0.03(stat.)±0.07(syst.)) × 10?2 for E*γ > 10 MeV and θ*eγ > 10°. For comparison with the previous experiment the branching ratio with cuts E*γ > 10 MeV, 0.6 < cos θ*eγ < 0.9 is calculated: R = $frac{{Br(K^ - to pi ^0 e^ - overline nu _e gamma )}}{{Br(K^ - to pi ^0 e^ - overline nu _e )}}$ = (0.47±0.02(stat.) ± 0.03(syst.)) × 10?2. For the cuts E*γ > 30 MeV and θ*eγ > 20°, used in most theoretical papers, Br = (3.06 ± 0.09(stat.) ± 0.14(syst.)) × 10?4. For the asymmetry we get A ξ = ?0.015 ± 0.021. At present it is the best estimate of this asymmetry. |
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