Search for $R$-Parity Violating Supersymmetry in Two-Muon and Four-Jet Topologies

We present results of a search for $R$-parity-violating decay of the neutralino ${\tilde{\chi }}_1^0$, taken as the lightest supersymmetric particle, to a muon and two jets. The decay proceeds through a lepton-number violating coupling ${\lambda }_{2jk}^{\prime }$ ($j=1,2$; $k=1,2,3$), with $R$-parity conservation in all other production and decay processes. In the absence of candidate events from $77.5\pm 3.9\mathrm{p}{\mathrm{b}}^{\mathrm{-}\mathrm{1}}$ of data collected by the D0 experiment at the Fermilab Tevatron in $p\overline{p}$ collisions at $\sqrt{s}=1.8\mathrm{T}\mathrm{e}\mathrm{V}$, and with an expected background of $0.18\pm 0.03\pm 0.02$ events, we set limits on squark and gluino masses within the framework of the minimal low-energy supergravity-supersymmetry model.

Figure 1

Distribution in the number of jets per MC event at a typical signal point ($m_0=140\mathrm{G}\mathrm{e}\mathrm{V}/c^2$, $m_{1/2}=90\mathrm{G}\mathrm{e}\mathrm{V}/c^2$) (dashed line) and for background from, $Z(\to \mu \mu )+\mathrm{\text{jets}}$ (solid line), both normalized to $77.5\mathrm{p}{\mathrm{b}}^{\mathrm{-}\mathrm{1}}$ integrated luminosity. The vertical arrow indicates the position of the cutoff applied in the search.

Figure 2

Exclusion contour in the $(m_0,m_{1/2})$ plane for $\tan \beta =2$, $\mu <0$, $A_0=0$, and finite ${\lambda }_{2jk}^{\prime }$ ($j=1,2$; $k=1,2,3$) coupling. The region below the bold line is excluded at the 95% C.L. The crosshatched region is excluded for theoretical reasons (see text). $m_{\tilde{q}}$ and $m_{\tilde{g}}$ denote squark and gluino masses, respectively.

Figure 3

Exclusion contour in the $(m_0,m_{1/2})$ plane for $\tan \beta =6$, $\mu <0$, $A_0=0$, and finite ${\lambda }_{2jk}^{\prime }$ ($j=1,2$; $k=1,2,3$) coupling.