Search for High-Mass Resonances Decaying to $e\mu$ in $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$

We describe a general search for resonances decaying to a neutral $e\mu$ final state in $p\overline{p}$ collisions at a center-of-mass energy of 1.96 TeV. Using a data sample representing $344{\mathrm{pb}}^{-1}$ of integrated luminosity recorded by the Collider Detector at Fermilab II experiment, we compare standard model predictions with the number of observed events for invariant masses between 50 and $800\mathrm{GeV}/c^2$. Finding no significant excess (5 events observed vs $7.7\pm 0.8$ expected for $M_{e\mu }>100\mathrm{GeV}/c^2$), we set limits on sneutrino and $Z^{\prime }$ masses as functions of lepton family number violating couplings.

Figure 1

Observed and predicted $M_{e\mu }$ Distributions. The observed $e\mu$ invariant mass spectrum agrees well with that of the combined SM and fake lepton backgrounds. No events are observed in data beyond $159\mathrm{GeV}/c^2$.

Figure 2

Observed 95% C.L. upper limit on $\sigma \times \mathrm{BR}$ for $d\overline{d}\to {\tilde{\nu }}_{\tau }({\overline{\tilde{\nu }}}_{\tau })\to e\mu$ (solid line) and the NLO prediction (dashed line) as a function of $e\mu$ invariant mass. Their intersection gives a $530\mathrm{GeV}/c^2$ ${\tilde{\nu }}_{\tau }$ mass limit for the values of ${\lambda }_{311}^{\prime }$ and ${\lambda }_{132}$ indicated. Because of small differences in the signal acceptances, the 95% C.L. upper limit on the $Z^{\prime }$ $\sigma \times \mathrm{BR}$ (not shown) is larger than that of the sneutrino, $\sim 0.02\mathrm{pb}$ greater at $200\mathrm{GeV}/c^2$ and $\sim 0.003\mathrm{pb}$ greater at $600\mathrm{GeV}/c^2$, for example.

Figure 3

${\lambda }_{311}^{\prime }-M_{e\mu }$ exclusion regions. Regions to the left of the five curves shown represent ranges of ${\lambda }_{311}^{\prime }$ values that we exclude at 95% C.L. as a function of ${\tilde{\nu }}_{\tau }$ mass. Each region corresponds to a fixed value of ${\lambda }_{132}$.

Figure 4

$Q_{12}^l-M_{e\mu }$ exclusion regions depicting 95% C.L. upper limits on the LFV $Q_{12}^l$ coupling in extended $\psi$, $\chi$, $\eta$, and secluded $E_6$ models.