Diquark Higgs at LHC

Abstract

Existence of color sextet diquark Higgs fields with TeV masses will indicate a fundamentally different direction for unification than conventional grand unified theories. There is a class of partial unification models based on the gauge group $SU(2)_L\times SU(2)_R\times SU(4)_c$ that implement the seesaw mechanism for neutrino mass with seesaw scale around $10^{11}$ GeV, where indeed such light fields appear naturally despite the high gauge symmetry breaking scale. They couple only to up-type quarks in this model. We discuss phenomenological constraints on these fields and show that they could be detected at LHC via their decay to either $tt$ or single top + jet. We also find that existing Tevatron data gives a lower bound on its mass somewhere in the 400-500 GeV, for reasonable values of its coupling.

Figures (3)

• Figure 1: The cross sections of $tt$ (dotted line) and $tj$ (dashed line) productions mediated by the diquark Higgs in s-channel at Tevatron with $E_{\rm CMS}=1.96$ TeV.
• Figure 2: The differential cross sections for $tj$ (dashed line), $tt$ (dotted line), $\overline{t}j$ (dashed-dotted line) and $\overline{t}\overline{t}$ (dashed-dotted-dotted line) as a function of the invariant mass of final state $M_{u_iu_j}$. The left peak corresponds to $m_\Delta=600(\rm GeV)$ and the right one to $m_\Delta=1$ TeV. The solid line is the standard model $t\overline{t}$ background.
• Figure 3: Angular distribution of the cross section for $m_{\Delta}=600$ GeV with $M_{\rm cut}=550$ GeV, together with the $t \overline{t}$ production in the standard model. The same line convention as in the Fig. \ref{['Fig2']} has been used.