Search for New $T^\prime$ Particles in Final States with Large Jet Multiplicities and Missing Transverse Energy in ppbar Collisions at sqrt(s) = 1.96 TeV

Abstract

We present a search for a new particle T' decaying to a top quark via T' -> t + X, where X goes undetected. We use a data sample corresponding to 5.7 fb-1 of integrated luminosity of ppbar collisions with sqrt{s} = 1.96 TeV, collected at Fermilab by the CDF II detector. Our search for pair production of T' is focused on the hadronic decay channel, ppbar -> T'T' -> tt +XX -> bbqqqq + XX. We interpret our results in terms of a model where T' is an exotic fourth generation quark and X is a dark matter candidate. The data are consistent with standard model expectations. We set a limit on the generic production of T'T'->tt+XX, excluding the fourth generation exotic quarks T' at 95% confidence level up to m_T' = 400 GeV/c2 for m_X < 70 GeV/c2.

Figures (4)

• Figure 1: Distribution of $\Delta\phi (\hbox{$\raisebox{0.3ex}{$\not$}\hbox{$\vec{E}_T$}$}, \hbox{$\raisebox{0.3ex}{$\not$}\hbox{$\vec{p}_T$}$})$ for the preselection data, and two scenarios with different values of $m_{T^\prime}$ and $m_{X}$. All histograms are normalized to unit area.
• Figure 2: Top plot shows the $\hbox{$\raisebox{0.3ex}{$\not$}\hbox{$E_T$}$} \, sig$ distribution in events with four jets and large $\hbox{$\raisebox{0.3ex}{$\not$}\hbox{$E_T$}$}$. Bottom plot shows the ${N}_{jets}$ distribution in event with $5 \leq N_{jets} \leq 10$ and $\hbox{$\raisebox{0.3ex}{$\not$}\hbox{$E_T$}$} \, sig < 3\,\sqrt{GeV}$.
• Figure 3: $\hbox{$\raisebox{0.3ex}{$\not$}\hbox{$E_T$}$} \, sig$ distributions for the standard model backgrounds, the observed data, and for two scenarios with different values of $m_{T^\prime}$ and $m_{X}$.
• Figure 4: Expected (exp) and observed (obs) 95% C.L. exclusion region in the ($m_{T^{\prime}}, m_{X}$) parameters space.