Limits on new coloured fermions using precision jet data from the Large Hadron Collider

Abstract

This work presents an interpretation of high precision jet data from the ATLAS experiment in terms of exclusion limits for new coloured matter. To this end, the effect of a new coloured fermion with a mass m X on the solution of the renormalization group equation QCD is studied. Theoretical predictions for the transverse energy-energy correlation function and its asymmetry are obtained with such a modified solution and, from the comparison to data, 95% CL exclusion limits are set on such models.

Dark Matter in the Standard Model Extension with Singlet Quark

“…As the vector-like (non-chiral) singlet fermions do not receive their masses from a Higgs doublet, they are allowed by existing experimental data on Higgs physics. The last limits on new colored fermions follow from the jets data from the LHC [25]. The corresponding limits for effective colored factors n ef f = 2, 3, 6 are about 200 GeV, 300 GeV, 400 GeV.…”

LHC-friendly minimal freeze-in models

“…Last, but not least, one could have rare decays with invisible final states, for instance K + → π + ss; once again these diagrams would contribute proportional to (y f s ) 2 and we can safely neglect them 9 . Compared to the leptonic model, electroweak precision data considerations are replaced here by the running of the strong coupling, however the corresponding bounds are rather mild and in the range of a few hundred GeVs [80]. LHC searches for multi-jets plus missing energy are subdominant, as the jet requirements force them to be mostly prompt.…”

Extractions of the QCD coupling in ATLAS

“…They are in very good agreement with the renormalization group equation (RGE) dependence predicted in QCD. In fact, the goodness of this agreement has been used recently to put limits on new coloured fermions in a way which is independent of assumptions about their decay modes [7].…”