Search for Supersymmetry via Associated Production of Charginos and Neutralinos in Final States with Three Leptons

A search for associated production of charginos and neutralinos is performed using data recorded with the D0 detector at a $p\overline{p}$ center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. This analysis considers final states with missing transverse energy and three charged leptons, of which at least two are electrons or muons. No evidence for supersymmetry is found in a data set corresponding to an integrated luminosity of $320{\mathrm{pb}}^{-1}$. Limits on the product of the production cross section and leptonic branching fraction are set. For the minimal supergravity model, a chargino lower mass limit of 117 GeV at the 95% C.L. is derived in regions of parameter space with enhanced leptonic branching fractions.

Figure 1

Invariant di-muon mass $m_{\mu \mu }$ (upper left, $\mu \mu \ell$ selection), azimuthal di-muon opening angle $\Delta {\varphi }_{\mu \mu }$ (upper right, ${\mu }^{\pm }{\mu }^{\pm }$ selection), minimum transverse mass $m_T^{\min }$ (lower left, $e\mu \ell$ selection) and $p_T^{\ell 3}$, the transverse momentum of the third track (lower right, $ee\ell$ selection), for data (points), standard model backgrounds (shaded histograms), and SUSY signal (open histogram).

Figure 2

Limit on $\sigma \times \mathrm{BR}(3\ell )$ as a function of ${\tilde{\chi }}_1^{\pm }$ mass, in comparison with the expectation for several SUSY scenarios (see text). PDF and renormalization/factorization scale uncertainties are shown as shaded bands.

Figure 3

Limit on $\sigma \times \mathrm{BR}(3\ell )$ as a function of the mass difference between $\tilde{\ell }$ and ${\tilde{\chi }}_2^0$, in comparison with the expectation for the MSSM (no mixing) and the heavy-squarks scenario (see text). PDF and renormalization/factorization scale uncertainties are shown as shaded bands. $\mathrm{BR}(3\ell )$ drops sharply at $m_{\tilde{\ell }}\lesssim m_{{\tilde{\chi }}_2^0}$ as the phase space for two-body decays into real sleptons is minimal.