Search For Scalar Diquark Resonance at the CMS Experiment

Searches for Beyond Standard Model (BSM) physics are a key focus of experiments conducted at the LHC, with one promising candidate being the ultra-heavy diquark S_uu, which can be explored in 13-13.6 TeV proton-proton collisions at the LHC using the CMS detector. The s-channel production of S_uu can have a significantly large enough cross-section compared to other diquark candidates due to the large PDF of up quarks in proton. If S_uu is the only BSM particle within LHC reach, it can decay via two up-type SM quarks, i.e. uu, ut, and tt, resulting in a narrow final state, with a small width-to-mass ratio below 4%. For our analysis, we concentrate on S_uu decaying into ut, with a leptonic decay of the top quark, resulting in a unique final state with collimated positively charged lepton and b-quark jet, a high-pT light-quark jet, and missing transverse momentum. Notably, there are no corresponding final states with a negatively charged lepton. The peculiarity of the decay products makes this channel almost QCD-free, and the major background comes from SM top quarks, which are well-studied.