QCD Corrections to Pair Production of Type III Seesaw Leptons at Hadron Colliders

Abstract

If kinematically accessible, hadron collider experiments provide an ideal laboratory for the direct production of heavy lepton partners in Seesaw models. In the context of the Type III Seesaw Mechanism, the $\mathcal{O}(\alpha_s)$ rate and shape corrections are presented for the pair production of hypothetical, heavy $SU(2)_L$ triplet leptons in $pp$ collisions at $\sqrt{s}=$ 13, 14, and 100 TeV. The next-to-leading order (NLO) $K$-factors span, approximately, $K^{NLO}=1.1 - 1.4$ for both charged current and neutral current processes over a triplet mass range $m_T = 100~\text{GeV}-2~\text{TeV}$. Total production cross sections exhibit a $^{+5\%}_{-6\%}$ scale dependence at 14 TeV and $\pm1\%$ at 100 TeV. The NLO differential $K$-factors for heavy lepton kinematics are largely flat, suggesting that na\"ive scaling by the total $K^{NLO}$ is reasonably justified. The resummed transverse momentum distribution of the dilepton system is presented at leading logarithmic (LL) accuracy. The effects of resummation are large in TeV-scale dilepton systems. Discovery potential to heavy lepton pairs at 14 and 100 TeV is briefly explored: At the High-Luminosity LHC, we estimate a $4.8-6.3\sigma$ discovery potential maximally for $m_T = 1.5-1.6~\text{TeV}$ after 3000 fb$^{-1}$. With 300 (3000) fb$^{-1}$, there is $2\sigma$ sensitivity up to $m_T = 1.3-1.4~\text{TeV}~(1.7-1.8~\text{TeV})$ in the individual channels. At 100 TeV and with 10 fb$^{-1}$, a $5\sigma$ discovery can be achieved for $m_T=1.4-1.6~\text{TeV}$. Due to the factorization properties of Drell-Yan-type systems, the fixed order and resummed calculations reduce to convolutions over tree-level quantities.