Search for Lepton Flavor Violating Decays of a Heavy Neutral Particle in $p\overline{p}$ Collisions at $\sqrt{s}=1.8\mathrm{T}\mathrm{e}\mathrm{V}$

We report on a search for a high mass, narrow width particle that decays directly to $e\mu$, $e\tau$, or $\mu \tau$. We use approximately $110\mathrm{p}{\mathrm{b}}^{\mathrm{-}\mathrm{1}}$ of data collected with the Collider Detector at Fermilab from 1992 to 1995. No evidence of lepton flavor violating decays is found. Limits are set on the production and decay of sneutrinos with $R$-parity violating interactions.

Figure 1

The angle in the plane transverse to the beam line between the direction of the missing energy and the electron versus the missing transverse energy: data (upper left); simulated $Z/\gamma \to \tau \tau \to e\mu \nu \nu$, the dominant background (upper right); and a hypothetical signal $\tilde{\nu }\to \mu \tau \to \mu e\nu$ for a sneutrino mass of $100\mathrm{G}\mathrm{e}\mathrm{V}/c^2$ (lower left) and $200\mathrm{G}\mathrm{e}\mathrm{V}/c^2$ (lower right). The requirement $\Delta \varphi (e,\mu )>120°$ has already been imposed.

Figure 2

The reconstructed mass of the lepton pairs. The points show the nineteen $e\mu$ candidates (upper), the four $e\tau$ candidates (lower left), and the twelve $\mu \tau$ candidates (lower right). The histograms show the total background in each sample. The $e\tau$ and $\mu \tau$ samples have no events in common; both are subsets of the $e\mu$ sample. ${\mathrm{E̸}}_T$ is used in computing $\tau$ momentum, as explained in the text.

Figure 3

$95\%$ C.L. upper limits on $\sigma \times B(\tilde{\nu }\to e\mu )$, $\sigma \times B(\tilde{\nu }\to e\tau )$, and $\sigma \times B(\tilde{\nu }\to \mu \tau )$ as a function of sneutrino mass, together with the next-to-leading order cross section for the reference parameters.