Signatures of toponium formation in LHC run 2 data
Benjamin Fuks (Institut Universitaire de France, 103 boulevard Saint-Michel, 75005 Paris, France, Sorbonne Université, CNRS, Laboratoire de Physique Théorique et Hautes Énergies, LPTHE, F-75005 Paris, France); Kaoru Hagiwara (KEK Theory Center, Tsukuba 305-0801, Japan); Kai Ma (International Centre for Theoretical Physics Asia-Pacific, Beijing/Hangzhou, China, School of Fundamental Physics and Mathematical Science, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310024, Zhejiang, China, Department of Physics, Shaanxi University of Technology, Hanzhong 723000, Shaanxi, China); Ya-Juan Zheng (Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA)
We study reported deviations between observations and theoretical predictions associated with the production of a pair of dileptonically decaying top quarks at the LHC, and we examine the possibility that they reflect a signal of toponium formation. We investigate the production by gluon fusion of a color-singlet spin-0 toponium bound state of a top and antitop quark, that then decays dileptonically (). We find strong correlations favoring the production of dilepton systems featuring a small angular separation in azimuth and a small invariant mass. Although toponium production only contributes to 0.8% of the total top-quark pair-production cross section at the 13 TeV LHC, there is a possibility that it can account for observed excesses in the narrow edges of phase space. We propose a method to discover toponium formation by “reconstructing” both its top and antitop quark constituents in the dilepton channel.