Search for new heavy particles decaying to $Z^0{Z}^0\to eeee$ in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$

We report the results of a search for the anomalous production of a massive particle decaying to four electrons via two $Z^0$ bosons in $1.1{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ collected by the CDF II detector at Fermilab. We employ optimized electron identification criteria to maximize acceptance and efficiency. We estimate the backgrounds in the invariant mass range $500–1000\mathrm{GeV}/c^2$ to be $0.028\pm 0.009(\mathrm{stat})\pm 0.011(\mathrm{syst})$ events. We observe zero events in this search region. Assuming a Randall-Sundrum graviton production model, we set 95% C.L. limits on $\sigma \times \mathrm{BF}(G\to Z^0{Z}^0)<4–6\mathrm{pb}$, depending on the graviton mass.

Figure 1

Distribution of $m_{ee}$ for events with a single $Z^0$ candidate formed from a seed electron candidate together with a second electron candidate (a), and the subset of $Z^0$ candidates formed from a seed electron candidate and an isolated track (b).

Figure 2

Distribution of ${\chi }^2$ for simulated Randall-Sundrum signal scenario ($m_G=500\mathrm{GeV}/c^2$) (top). Four-electron invariant mass distribution for events satisfying ${\chi }^2<50$ (gray) and for events which fail this requirement (black) (bottom).

Figure 3

Acceptance for Randall-Sundrum graviton decaying to $Z^0{Z}^0$ versus its mass.

Figure 4

Invariant mass distribution of one central electron satisfying trigger requirements and one hadronic candidate in data.

Figure 5

Distribution of ${\chi }^2$ vs $m_{eeee}$ for control samples containing one, two, three, or four hadron candidates with the number of events in the plot increasing with the number of hadron candidates used in the combination.

Figure 6

Projections of fit to invariant mass in control samples of varying number of electron and hadronic candidates with same ordering as in Fig. 5. Data are shown with the fit projection overlaid.

Figure 7

Distribution of ${\chi }^2$ vs $m_{eeee}$ for four-electron candidates in data. The signal region is ${\chi }^2<50$ and $m_{eeee}>500\mathrm{GeV}/c^2$, the boundaries of which are shown by the dashed line.

Figure 8

Limits on $\sigma \times \mathrm{BF}(G\to Z^0{Z}^0)$ versus mass.