Analysing toponium at the LHC using Recursive Jigsaw Reconstruction

Abstract Recent results from the ATLAS and the CMS experiments at the Large Hadron Collider indicate the presence of a top-quark pair bound state near the threshold region. We present a way to reconstruct a toponium state at the $$t\bar{t}$$ t t ¯ threshold region formed at the Large Hadron Collider using the Recursive Jigsaw Reconstruction. We have considered the non-relativistic QCD based toponium model implemented in MadGraph5_aMC@NLO. The final states considered consist of two b-jets, two oppositely charged leptons, and missing energy that arises from two neutrinos. The goal of the Recursive Jigsaw Reconstruction is to make use of rules that can help resolve combinatorics ambiguity in preparing the decay tree for a given physics event. Additionally, missing energy coming from two neutrinos needs to be resolved in order to reconstruct the event. We apply four different methods within the RestFrames package and compare the reconstruction resulting from each of the methods. Due to this method, one can also access kinematic variables in the rest frames belonging to intermediate particle states, providing additional means to discriminate the SM $$t\bar{t}$$ t t ¯ background from the toponium signal. We propose using two angular variables to enhance sensitivity to the toponium signal. Our preliminary results indicate that the improvement in sensitivity can be as much as 12% over the current strategy in the LHC’s Run 3 configuration. This method may be useful for gaining additional insight into the physics phenomenology in the $$t\bar{t}$$ t t ¯ threshold region.