Search for Maximal Flavor Violating Scalars in Same-Charge Lepton Pairs in $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$

Models of maximal flavor violation (MxFV) in elementary particle physics may contain at least one new scalar SU(2) doublet field ${\Phi }_{\mathrm{FV}}=({\eta }^0,{\eta }^{+})$ that couples the first and third generation quarks ($q_1$, $q_3$) via a Lagrangian term ${\mathcal{L}}_{\mathrm{FV}}={\xi }_{13}{\Phi }_{\mathrm{FV}}{q}_1{q}_3$. These models have a distinctive signature of same-charge top-quark pairs and evade flavor-changing limits from meson mixing measurements. Data corresponding to $2{\mathrm{fb}}^{-1}$ collected by the Collider Dectector at Fermilab II detector in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ are analyzed for evidence of the MxFV signature. For a neutral scalar ${\eta }^0$ with $m_{{\eta }^0}=200\mathrm{GeV}/c^2$ and coupling ${\xi }_{13}=1$, $\sim 11$ signal events are expected over a background of $2.1\pm 1.8$ events. Three events are observed in the data, consistent with background expectations, and limits are set on the coupling ${\xi }_{13}$ for $m_{{\eta }^0}=180–300\mathrm{GeV}/c^2$.

Figure 1

Following the prescriptions in Refs. [6, 24], horizontal bands in measured $\xi$ are shown which include 95% of simulated experiments, for various values of true $\xi$, with $m_{{\eta }^0}=180\mathrm{GeV}/c^2$.

Figure 2

Jet multiplicity for background, observed data, and ${\mathrm{MxFV}}_1$ signal with best-fit value of $\xi =0.41$ for $M_{{\eta }^0}=180\mathrm{GeV}/c^2$.

Figure 3

Observed 95% C.L. regions in the $\xi -m_{{\eta }^0}$ plane.