Massive color-octet bosons and pairs of resonances at hadron colliders

TL;DR

This work studies collider signatures of massive color-octet bosons with suppressed quark couplings, focusing on pair production of spin-1 octets G_mu_prime and spin-0 octets G_H arising from SU(3)_1 x SU(3)_2 -> SU(3)_c. The dominant observable is a 4-jet final state with two dijet resonances of equal mass, with cross sections for the vector case largely model-independent and large at hadron colliders, while the scalar case is smaller and decays to heavy quarks. Tevatron reach is up to about 330–340 GeV for spin-1 and around 280 GeV for spin-0, and the LHC can probe up to ~1 TeV for spin-1 octets with modest luminosity, with somewhat lower reach for spin-0. The analysis demonstrates striking multi-jet resonance signatures and outlines angular-distribution methods to determine the octet spin, supporting robust discovery potential at the Tevatron and LHC.

Abstract

We analyze collider signatures of massive color-octet bosons whose couplings to quarks are suppressed. Gauge invariance forces the octets to couple at tree level only in pairs to gluons, with a strength set by the QCD gauge coupling. For a spin-1 octet, the cross section for pair production at hadron colliders is larger than that for a quark of equal mass. The octet decays into two jets, leading to a 4-jet signature with two pairs of jets forming resonances of the same mass. For a spin-0 octet the cross section is smaller, and the dominant decay is into b\bar{b}, or t\bar{t} if kinematically allowed. We estimate that discovery of spin-1 octets is possible for masses up to 330 GeV at the Tevatron, and 1 TeV at the LHC with 1 fb^{-1}, while the reach is somewhat lower for spin-0 octets.

Figures (5)

• Figure 1: $G_\mu^{\prime} G_\mu^{\prime}$ production from $gg$ initial state ($u$-channel $G_\mu^{\prime}$ exchange is not shown). Curly lines represent gluons, while wavy lines represent massive vector octets.
• Figure 2: $G_\mu^{\prime} G_\mu^{\prime}$ production from $q\bar{q}$ initial state ($u$-channel diagram is not shown). If couplings of standard model quarks ($q$) to $G_\mu^{\prime}$ are suppressed due to mixing with vectorlike quarks ($Q$), then $G_\mu^{\prime}$ or $q$ exchange contributions may be negligible.
• Figure 3: Tevatron cross sections for pair production of spin-1 ($G_\mu^\prime$) and spin-0 ($G_H$) octets and for backgrounds, as a function of octet mass. Four-jet final states with 0, 2 and 4 $b$-tags are shown (for both signal and background) as solid, dashed, and dot-dashed lines respectively, for given cuts. Dotted lines represent signal cross sections without cuts, with uncertainties indicated by shaded bands.
• Figure 4: Same as Fig. \ref{['fig:sigmaGmu']}, for the LHC.
• Figure 5: Invariant mass distributions for background (B) and signal (S) at the LHC, for $M_G = 900$ GeV, as a function of the smaller of the two dijet masses. The dijets chosen have the closest invariant masses of all possible pairings of the four jets in the final state. The number of events is normalized to a luminosity of 1 fb$^{-1}$.