Search for heavy Majorana neutrino in lepton number violating decays of D-> K pi e+ e+

Abstract

Using the data sample of an integrated luminosity of 2.93 fb${}^{-1}$ taken at the center-of-mass energy of 3.773 GeV, we search for the Majorana neutrino in the lepton number violating decays $D\to K\ddot{I}€e^{+}{e}^{+}$. No significant signal is observed, and the upper limits on the branching fraction at the 90\% confidence level are set to be $\mathcal{B}(D^0\to K^{-}\ddot{I}{€}^{-}{e}^{+}{e}^{+})<2.8\times 10^{-6}$, $\mathcal{B}(D^{+}\to K_S^0\ddot{I}{€}^{-}{e}^{+}{e}^{+})<3.3\times 10^{-6}$ and $\mathcal{B}(D^{+}\to K^{-}\ddot{I}{€}^0{e}^{+}{e}^{+})<8.5\times 10^{-6}$. The Majorana neutrino is searched for with different mass assumptions ranging from 0.25 to 1.0 GeV/$c^2$ in the decays $D^0\to K^{-}{e}^{+}\hat{I}{½}_N(\ddot{I}{€}^{-}{e}^{+})$ and $D^{+}\to K_S^0{e}^{+}\hat{I}{½}_N(\ddot{I}{€}^{-}{e}^{+})$, and the upper limits on the branching fraction at the 90\% confidence level are extracted to be at the level of $10^{-7}\sim 10^{-6}$, depending on the mass of Majorana neutrino. The constraints on the mixing matrix element $|V_{eN}{|}^2$ are also evaluated.

9 pages,3 figures