TeV-scale particles and LHC events with dijet pairs

Abstract

Scalar particles that couple to two up quarks may be produced at the LHC even if they are ultraheavy, in the $8-10$ TeV mass range. A renormalizable theory that includes a diquark particle of this type ($S_{uu}$), two vectorlike quarks (${\chi }_1,{\chi }_2$), and a gauge-singlet pseudoscalar, predicts LHC signals involving four or more jets of very high $p_T$. Two remarkable events observed by the CMS experiment, each involving four high $p_T$-jets, may be due to an $S_{uu}$ of mass near 8.5 TeV, and a ${\chi }_2$ mass of 2.1 TeV. A separate excess reported by CMS in the nonresonant dijet pair search is consistent with a ${\chi }_1$ mass of $0.95$ TeV. This hypothesis may be tested through CMS and ATLAS searches for signals with a pair of dijet resonances of masses clustered around 1 TeV, and separately around 2 TeV, which have $4j$ invariant masses in the $5-8$ TeV range. These additional signals would arise from cascade decays of $S_{uu}\to {\chi }_2{\chi }_2$, which lead to $5j$ and $6j$ events with invariant masses around 8 TeV. Depending on the couplings of the heavy colored particles, additional signals are possible, involving for example highly-boosted top quarks.

Comments: 25 pages