Search for pair-produced dijet resonances in four-jet final states in $pp$ collisions at $\sqrt{s}\mathbf{=}7\mathrm{TeV}$

A search for the pair production of a heavy, narrow resonance decaying into two jets has been performed using events collected in $\sqrt{s}=7\mathrm{TeV}$ $pp$ collisions with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of $5.0{\mathrm{fb}}^{-1}$. Events are selected with at least four jets and two dijet combinations with similar dijet mass. No resonances are found in the dijet mass spectrum. The upper limit at 95% confidence level on the product of the resonance pair production cross section, the branching fractions into dijets, and the acceptance varies from 0.22 to 0.005 pb, for resonance masses between 250 and 1200 GeV. Pair-produced colorons decaying into $q\overline{q}$ are excluded for coloron masses between 250 and 740 GeV.

Figure 1

The distribution of $\Delta =\sum _{i=1,2}(p_{\mathrm{T}}{)}_i-m_{\mathrm{avg}}$ versus $m_{\mathrm{avg}}$ for QCD multijet background alone (main plot) and background plus coloron signal (insets), for simulated events. We remove events with an entry below the horizontal line at 25 GeV. There are two entries per event (one for each of the two dijet pairs).

Figure 2

The average paired dijet mass distribution (black points) in data compared with a smooth background fit using Eq. (1) (blue solid curve) and the result of the fit of the same function (dash-dotted red curve) to QCD simulated data (not shown). Also shown are examples of simulation of hypothetical coloron resonances decaying 100% to $q\overline{q}$ (dashed green curves) with masses $m_C=400$ and 800 GeV. The bin-by-bin fit pulls are shown below.

Figure 3

The observed and expected 95% C.L. limits on the product of the resonance pair production cross section, the square of the branching fraction to dijets, and the detector acceptance, given by the solid and dot-dashed black curves, respectively. The shaded regions indicate the $1\sigma$ and $2\sigma$ bands around the expected limits. Predictions of a coloron model and a SUSY model are also shown.