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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 |
| Institution: | 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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