Speaker
Prof.
Vladimir Obraztsov
(" NIC KI" - IHEP)
Description
Several radiative decays are studied by OKA setup at U-70 synchrotron.
First, the radiative decay $K^+ \rightarrow \mu^+ \nu \gamma$($K_{\mu 2 \gamma}$) is studied on statistics of about 95K events for 25 MeV$\lt E^{*}_{\gamma}\lt$ 150 MeV. A clear destructive interference between bremsstrahlung and structure
dependent $SD^{-}$ term is observed. As a result, the vector and axial-vector form factors difference is measured:
$F_{V}-F_{A}=0.134 \pm 0.021(stat.) \pm 0.027(syst.) $ which is 2.3 $\sigma$ away from $\chi PT O(p^{4})$.
Second, the decay $K^{+} \to \pi^{+} \pi^{-} \pi^{+}\gamma$ is studied on statistics of about 450 events for 30 MeV$\lt E^{*}_{\gamma}\lt $ 70 MeV. The total and differential branching fractions of the decay are measured. Br($K^{+} \to \pi^{+} \pi^{-} \pi^{+}\gamma$)
$=(7.1 \pm 0.4(stat.) \pm 0.3(syst.))\cdot 10^{-6}$ to be compared with $\chi PT O(p^{4})$ $(6.65 \pm 0.05) \cdot 10^{-6}$.
In addition, a search for an up-down photon asymmetry with respect to the hadronic system decay plane is performed.
Primary author
Prof.
Vladimir Obraztsov
(" NIC KI" - IHEP)
