First search for the weak radiative decays ${\Lambda }_c^{+}\to {\Sigma }^{+}\gamma$ and ${\Xi }_c^0\to {\Xi }^0\gamma$

Abstract

We present the first search for the weak radiative decays ${\Lambda }_c^{+}\to {\Sigma }^{+}\gamma$ and ${\Xi }_c^0\to {\Xi }^0\gamma$ using a data sample of 980~fb${}^{-1}$ collected by the Belle detector operating at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. There are no evident ${\Lambda }_c^{+}\to {\Sigma }^{+}\gamma$ or ${\Xi }_c^0\to {\Xi }^0\gamma$ signals. Taking the decays ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$ and ${\Xi }_c^0\to {\Xi }^{-}{\pi }^{+}$ as normalization channels, the upper limits at 90\% credibility level on the ratios of branching fractions $\mathcal{B}({\Lambda }_c^{+}\to {\Sigma }^{+}\gamma )/\mathcal{B}({\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+})<4.0\times 10^{-3}$ and $\mathcal{B}({\Xi }_c^0\to {\Xi }^0\gamma )/\mathcal{B}({\Xi }_c^0\to {\Xi }^{-}{\pi }^{+})<1.2\times 10^{-2}$ are determined. We obtain the upper limits at 90\% credibility level on the absolute branching fractions $\mathcal{B}({\Lambda }_c^{+}\to {\Sigma }^{+}\gamma )<2.6\times 10^{-4}$ and $\mathcal{B}({\Xi }_c^0\to {\Xi }^0\gamma )<1.8\times 10^{-4}$.

Comments: 10 pages, 6 pages; accepted for publication as a Regular Article in Physical Review D