Seeking Sgluons

TL;DR

This paper analyzes sgluons, the color-octet scalar partners of Dirac gluinos, within the minimal R-symmetric supersymmetric Standard Model (MRSSM). It derives their mass spectrum, loop-induced couplings to quarks and gluons, and explores flavor-violating effects, showing that heavy sgluons can evade stringent FCNC bounds. The authors study collider phenomenology, focusing on pair production with decays to like-sign tops, and emphasize the importance of accurately modeling QCD jets to distinguish signal from background, concluding that LHC searches could probe sgluon masses up to about 1 TeV, with flavor constraints pushing masses above ~600 GeV. Overall, the work highlights a distinctive LHC signature and the role of jet dynamics in testing MRSSM scenarios with Dirac gauginos.

Abstract

Scalar gluons -- or sgluons -- are color octet scalars without electroweak charges. They occur in supersymmetric models of Dirac gauginos as the scalar partners of the gluino and carry Standard-Model type R charge. This allows them to interact with ordinary matter and to be produced at the LHC, singly as well as in pairs. Sgluons dominantly decay into gluons, top pairs, and a top quark plus a light quark. A pair of sgluons decaying into like-sign tops would provide a striking signature at the LHC. In our discussion of this channel we especially focus on the proper treatment of QCD jets.

Figures (8)

• Figure 1: Feynman diagrams for sgluon interactions with quarks.
• Figure 2: Feynman diagrams for single sgluon interactions with gluons.
• Figure 3: Solid lines: effective scales characterizing the four fermion operators mediated by sgluons contributing to (bottom to top) $B_d$ mixing (2 curves), $D$ mixing, $K$ mixing with $m_{\tilde{g}} = 1$ TeV and an average $m_{\tilde{q}} = 500$ GeV, and $K$ mixing with $m_{\tilde{g}} = m_{\tilde{q}} = 1$ TeV. Dashed lines: current bounds on the operators (bottom to top), $Q_5^{bd}$, $Q_4^{bd}$, $Q^{cu}_4$, and $Q^{sd}_5$ (imaginary part), obtained from the global fit Bona:2007vi.
• Figure 4: Inclusive production cross sections for sgluons at the Tevatron and at the LHC. For the LHC we show pair production (solid) and single production (dashed) as a function of the sgluon mass. The two curves for single sgluon production assume a gluino mass of 1 TeV and squark masses of 500 GeV (upper curve) and 1 TeV (lower curve).
• Figure 5: Branching ratios for sgluon decays into $gg$, $t\bar{t}$, $\bar{q}t+\bar{t}q$ for $q=u,c$ and $\tilde{q} \tilde{q}^*$ as a function of sgluon mass and for two choices of left-handed squark and gluino masses. Right-handed squark masses are set to $90\%$ of the left-handed squark masses. We assume maximal up-squark mixing.