Interference effects in the X(4260) signal

Abstract

We show that the long known puzzling branching ratios of open-charm decays in electron-positron annihilation can be reasonably described with a simple form factor, which strongly suppresses open channels far above threshold. Application to the electron-positron annihilation into J/psi+pion+pion data on the X(4260) enhancement recently reported by the BABAR Collaboration [arxiv:0808.1543] allows a good fit with a simple nonresonant cusp structure around the D(*)(s)+Dbar(*)(s) threshold. Moreover, we argue that a closer look at the data reveals an oscillatory pattern, which we model as an interference effect between a fast - OZI-allowed - and a slow - OZI-forbidden - J/psi+f(0)(980) mode. Other candidates for similar nonresonant enhancements are discussed.