Invariant-mass distribution of jet pairs produced in association with a $W$ boson in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ using the full CDF Run II data set

We report on a study of the dijet invariant-mass distribution in events with one identified lepton, a significant imbalance in the total event transverse momentum, and two jets. This distribution is sensitive to the possible production of a new particle in association with a $W$ boson, where the boson decays leptonically. We use the full data set of proton-antiproton collisions at 1.96 TeV center-of-mass energy collected by the Collider Detector at the Fermilab Tevatron, corresponding to an integrated luminosity of $8.9{\mathrm{fb}}^{-1}$. The data are found to be consistent with standard model expectations, and a 95% confidence level upper limit is set on the production cross section of a $W$ boson in association with a new particle decaying into two jets.

Figure 1

Derived energy scale corrections for simulated quark jets and gluon jets as a function of jet $E_T$. The open triangles represent corrections derived jointly from the $\gamma +\text{jet}$ and $Z+\text{jet}$ balancing samples, while the filled triangles in the low-jet $E_T$ region are obtained from the $Z+\text{jet}$ sample only, assuming a constant correction for the quark-jet-energy scale. Error bars are from statistical sources only. The short-dashed lines show the fits to constant energy corrections, and the long-dashed lines represent the total systematic uncertainty bands on the correction determined by the fit.

Figure 2

Relative difference in the combined electron and muon samples between the nominal dijet-mass distribution and the one obtained by varying the jet-energy scale by $\pm 1\sigma$ in $W+\text{jets}$ events.

Figure 3

Transverse-energy distribution of jets matched to identified electrons in the multijet-enriched control region in data (circles), uncorrected multijets model (dark shaded histogram), and $W/Z+\text{jets}$ simulation (light shaded histogram). The magnitude of $W/Z+\text{jets}$ contributions is normalized to the NLO calculations [23], while the magnitude of the multijet model is obtained from the data. In subsequent analysis, the multijet model is reweighted such that the predicted and observed energy spectra agree.

Figure 4

Transverse-momentum distribution of the two-jet system in the multijet-enriched control sample as observed in the data (circles) and as predicted by the $W/Z+\text{jets}$ simulation (light shaded histogram) and the nonelectron-based model (dark shaded histogram) before (a) and after (b) application of tunings to the nonelectron-based multijet model. The magnitude of $W/Z+\text{jets}$ contributions is normalized to the NLO calculations [23], while the magnitude of the multijet model is obtained from the data.

Figure 5

Transverse-momentum distribution of the two-jet system in the selected event sample with looser selection criteria as observed in the data and as predicted by the models before (a) and after (b) application of tunings to the nonelectron-based multijet model.

Figure 6

Missing transverse-energy distribution for events containing electrons (a) and muons (b) from the selected sample. The distributions of observed data are shown with fit background overlaid.

Figure 7

Dijet mass distribution with fit results overlaid in the combined electron and muon data sets prior to incorporating the improvements discussed in the text, equivalent to updating the analysis described in Ref. [4] to the full CDF data set. The bottom panel shows data with all fit background contributions subtracted except those from diboson production.

Figure 8

Same distribution as in Fig. 7 shown separately for the electron (a) and muon (b) samples.

Figure 9

$\mathrm{\Delta }R(j_1,j_2)$ distribution in the muon sample as observed in the data and as predicted by the models incorporating improved jet-energy-scale corrections for simulated quark and gluon jets. The diboson distribution (red line) magnified by a factor of 8 is also shown as a example of the $\mathrm{\Delta }R(j_1,j_2)$ distribution for a heavy-particle decay.

Figure 10

Dijet mass distribution with fit results overlaid in the combined electron and muon data sets selected by applying an additional $\mathrm{\Delta }R(j_1,j_2)>0.7$ requirement and prior to incorporating the improvements discussed in the text. The bottom panel shows data with all fit background contributions subtracted except those from diboson production.

Figure 11

Same distribution as in Fig. 10 shown separately for the electron (a) and muon (b) samples.

Figure 12

Dijet mass distribution with fit results overlaid in the electron (a) and muon data sets (b) incorporating improved jet-energy-scale corrections for simulated quark and gluon jets but no tuning on the multijet-background modeling. The bottom panel shows data with all fit background contributions subtracted except those from diboson production.

Figure 13

Dijet mass distribution with fit results overlaid in the electron data set incorporating improved jet-energy-scale corrections for simulated quark and gluon jets and tunings on the multijet-background modeling. The bottom panel shows data with all fit background contributions subtracted except those from diboson production.

Figure 14

Dijet mass distribution with fit results overlaid in the combined electron and muon data sets incorporating improved jet-energy-scale corrections for simulated quark and gluon jets and tunings on the multijet-background modeling. The bottom panel shows data with all fit background contributions subtracted except those from diboson production.