Searching for New Physics in $D^0\to {\mu }^{+}{\mu }^{-},e^{+}{e}^{-},{\mu }^{\pm }{e}^{\mp }$ at BES and/or Super Charm-Tau Factory

Abstract

In contrast with $B^0-{\bar{B}}^0$, $B_s-{\bar{B}}_s$ mixing where the standard model (SM) contributions overwhelm that of new physics beyond standard model (BSM), a measured relatively large $D^0-{\bar{D}}^0$ mixing where the SM contribution is negligible, definitely implies the existence of new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the rare decay $D^0\to {\mu }^{+}{\mu }^{-}$ could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of new physics BSM in the leptonic decays of $D^0$, concretely we discuss the contributions of unparticle or an extra gauge boson $Z^{\prime }$ while imposing the constraints set by fitting the $D^0-{\bar{D}}^0$ mixing data. We find that the long-distance SM effects for $D^0\to l\bar{l}$ still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as $D^0\to {\mu }^{\pm }{e}^{\mp }$, the new physics contribution would be significant.

Comments: 14 pages, 1 figure, 2 tables