Fig. 2.

Dijet invariant mass distribution in the different $R_{xy}$ bins, for the 2012 data sample. For illustration, the best fit with a signal ${\mathit{\pi }}_{\text{v}}$ model with mass 35$\mathrm{GeV}/c^2$ and lifetime 10 ps is overlaid. The solid blue line indicates the total background model, the short-dashed green line indicates the signal model for signal strength $\mathit{\mu }=1$, and the long-dashed red line indicates the best-fit signal strength