Explanation for Y(4140) and X(3915)

Understand

The Y(4140) observed by CDF appears to have a novel explanation.

• Its mass and width coincide within experimental error with a two-step process.
• In the first step, Y(4140) -> D_sbar + pi + D_s where the pion is virtual.
• A loop diagram involving this virtual pion allows Y(4140) de-excitation to J/psi + phi.