Heavy octets and Tevatron signals with three or four b jets

Abstract

Hypothetical color-octet particles of spin 0, pair-produced at hadron colliders through their QCD coupling, may lead to final states involving three or four b jets. We analyze kinematic distributions of the 3b final state that differentiate the scalar octets from supersymmetric Higgs bosons. Studying the scalar sector that breaks an SU(3) \times SU(3) gauge symmetry down to the QCD gauge group, we find that the scalar octet is resonantly produced in pairs via a spin-1 octet (coloron). A scalar octet of mass in the 140 - 150 GeV range can explain the nonstandard shape of the b-jet transverse energy distributions reported by the CDF Collaboration, especially when the coloron mass is slightly above twice the scalar mass. The dominant decay mode of the scalar octet is into a pair of gluons, so that the production of a pair of dijet resonances is large in this model, of about 40 pb at the Tevatron. Even when a W boson is radiated from the initial state, the inclusive cross section for producing a dijet resonance near the scalar octet mass remains sizable, around 0.15 pb.

Figures (14)

• Figure 1: $G_H G_H$ production in hadronic collisions ($u$-channel $G_H$ exchange is not shown). Curly lines represent gluons, while dashed lines represent scalar octets.
• Figure 2: Scalar octet decay to gluons, due to the trilinear $G_H$ interaction of Eq. (\ref{['quartic']}). A diagram similar with the left one but with interchanged end points for the gluon lines is not shown.
• Figure 3: Effective couplings of a scalar octet to $b$ quarks and the Higgs VEV (left diagram), or to a gluon pair (right diagram), induced in the presence of a heavy vectorlike quark $\psi$ and leading to the $G_H \to b\bar{b}, gg, g\gamma, gZ$ decays.
• Figure 4: Leading-order cross section for production of a $G_H$ pair (solid line) at the Tevatron. Also shown are the cross sections after cuts for producing a pair of $G_H$ followed by each decaying with 100% branching fraction into $b\bar{b}$ and requiring that 3 (dashed line) or 4 (dotted line) jets pass the cuts and are $b$-tagged.
• Figure 5: Fraction of signal events having the invariant mass of the $i$th and $j$th jets, $m_{ij} \equiv m(b_i, b_j)$, within 20% of the octet mass $M_{G_H}$. The fractions for combinations with the 4th jet are below $1\%$ and are not shown here.