Nonstandard top substructure

Abstract

The top quark, being the heaviest particle of the Standard Model (SM), is a prime candidate of where physics beyond the SM (BSM) might currently hide before our eyes. There are many natural extensions of the SM that rely on top compositeness, and the top quark could follow the paradigm of revealing a substructure when it is probed at high enough momentum transfers. Observing high pT top final states naturally drives us toward boosted hadronic analyses that can be tackled efficiently with jet substructure techniques. In this paper we analyze the prospects of constraining exemplary nonstandard QCD top interactions in this kinematical regime. We correctly include QCD modifications to additional gluon emission off the boosted top quark and keep track of the modified top tagging efficiencies. We conclude that nonstandard top QCD interactions can be formidably constrained at the LHC 14 TeV. Experimental systematic uncertainties are a major obstacle of the described measurement. Unless significantly improved for the 14 TeV run, they will saturate the direct sensitivity to nonresonant BSM top physics at luminosities of around 100/fb.