Improving Identification of Dijet Resonances at Hadron Colliders

The experimental detection of resonances has played a vital role in the development of subatomic physics. The overwhelming multijet backgrounds at the Large Hadron Collider (LHC) necessitate the invention of new techniques to identify resonances decaying into a pair of partons. In this Letter we introduce an observable that achieves a significant improvement in several key measurements at the LHC: the Higgs boson decay to a pair of $b$ quarks; $W^{\pm }/Z^0$ vector-boson hadronic decay; and extensions of the standard model (SM) with a new hadronic resonance. Measuring the Higgs decay to $b$ quarks is a central test of the fermion mass generation mechanism in the SM, whereas the $W^{\pm }/Z^0$ production rates are important observables of the electroweak sector. Our technique is effective in large parts of phase space where the resonance is mildly boosted and is particularly well suited for experimental searches dominated by systematic uncertainties, which is true of many analyses in the high-luminosity running of the LHC.

Figure 1

Top: Histograms of both the dominant $W+\mathrm{jets}$ background as well as signal before applying the cut on $\zeta$, but after all of the selection criteria described in the text. Middle: The same distributions but after applying the $\zeta$ cut. Bottom: Binned $S/B$ improvement for ${\zeta }_c=0.08$, 0.1, and 0.12. The corresponding signal efficiencies are approximately 3%, 10%, and 25%, respectively.

Figure 2

In the upper two panels, we show the invariant mass of the $b$-tagged jets before and after the cut, Eq. (5), for both signal and background. In the lower two panels, we show the relative signal efficiency as well as its ratio with background efficiency as a function of $R_c$ in the mass window and the $p_T$ region indicated.