Bounds on an Anomalous Dijet Resonance in $W+\mathrm{\text{jets}}$ Production in $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$

We present a study of the dijet invariant mass spectrum in events with two jets produced in association with a $W$ boson in data corresponding to an integrated luminosity of $4.3{\mathrm{fb}}^{-1}$ collected with the D0 detector at $\sqrt{s}=1.96\mathrm{TeV}$. We find no evidence for anomalous resonant dijet production and derive upper limits on the production cross section of an anomalous dijet resonance recently reported by the CDF Collaboration, investigating the range of dijet invariant mass from 110 to $170\mathrm{GeV}/c^2$. The probability of the D0 data being consistent with the presence of a dijet resonance with 4 pb production cross section at $145\mathrm{GeV}/c^2$ is $8\times {10}^{-6}$.

Figure 1

Dijet invariant mass summed over electron and muon channels after the fit without (a) and with (b) subtraction of SM contributions other than that from the SM diboson processes, along with the $\pm 1$ s.d. systematic uncertainty on all SM predictions. The ${\chi }^2$ fit probability, $P({\chi }^2)$, is based on the residuals using data and MC statistical uncertainties. Also shown is the relative size and shape for a model with a Gaussian resonance with a production cross section of 4 pb at $M_{jj}=145\mathrm{GeV}/c^2$.

Figure 2

Upper limits on the cross section (in pb) at the 95% C.L. for a Gaussian signal in dijet invariant mass. Shown are the limit expected using the background prediction, the observed data, and the regions corresponding to a 1 and 2 s.d. fluctuation of the backgrounds.

Figure 3

Log-likelihood ratio test statistic as a function of probed dijet mass. Shown are the expected LLR for the background prediction (dashed black) with regions corresponding to a 1 and 2 s.d. fluctuation of the backgrounds, for the $\mathrm{\text{signal}}+\mathrm{\text{background}}$ prediction (dashed red), for the observed data (solid black), and for data with a dijet invariant mass resonance at $145\mathrm{GeV}/c^2$ injected with a cross section of 4 pb (solid red).

Figure 4

Distribution of $p$ values for the $\mathrm{\text{signal}}+\mathrm{\text{background}}$ hypothesis with a Gaussian signal with mean of $M_{jj}=145\mathrm{GeV}/c^2$ as a function of hypothetical signal cross section (in pb). Shown are the $p$ values for the background prediction (dashed black) with regions corresponding to a 1 and 2 s.d. fluctuation of the backgrounds and the observed data (solid black).