Low-mass enhancement of kaon pairs in B + → D<em> (*)</em> 0 K + K 0 and B 0 → D<em> (*) -</em> K + K 0 decays

Abstract

Very recently, the Belle II collaboration presented a measurement for the decays + →¯ (*)⁢0⁢ +⁢¯ 0 and 0 → (*)−⁢ +⁢¯ 0, with the bulk of observed ⁡( +⁢ 0 ) distributions showing low-mass structures in all four channels. In this work, we study the contributions of ⁢(770,1450)+, 2⁢(1320)+, and 0⁢(980,1450)+ resonances to these decay processes. The intermediate states ⁢(770,1450)+ are found to dominate the low-mass distribution of kaon pairs roughly contributing to half of the total branching fraction in each of the four decay channels. The contribution of the tensor 2⁢(1320)+ meson is found to be negligible. Near the threshold of the kaon pair, the state 0⁢(980)+ turns out to be much less important than expected, not being able to account for the enhancement of events in that energy region observed in the + →¯ (*)⁢0⁢ +⁢¯ 0 decays. Further studies both from the theoretical and experimental sides are needed to elucidate the role of the nonresonant contributions governing the formation of +⁢¯ 0 pairs near their threshold in these decay processes.