Weak radiative decay ${\Lambda }_c^{+}\to {\Sigma }^{+}\gamma$ using light-cone sum rules

Abstract

We calculate the decay width of the ${\Lambda }_c^{+}\to {\Sigma }^{+}\gamma$ using light-cone sum rules. For the initial quark radiation an effective Hamiltonian is constructed, where the internal quark line shrinks to a point. The final quark radiation is studied within the full theory. The leading twist light-cone distribution amplitudes of the ${\Sigma }^{+}$ serve as the non-perturbative input for the sum rules calculation, and the perturbative kernel is calculated at leading order. The branching fraction we obtain is $\mathcal{B}({\Lambda }_c^{+}\to {\Sigma }^{+}\gamma )=1.03\pm 0.36\times 10^{-4}$, which is below the recent upper limit $<2.6\times 10^{-4}$ given by the Belle collaboration.

Comments: 13 pages, 3 figures and 2 tables