Heavy neutrinos from gluon fusion

Abstract

Heavy neutrinos, a key prediction of many standard model extensions, remain some of the most searched-for objects at collider experiments. In this context, we revisit the premise that the gluon fusion production mechanism, $gg \to Z^*/h^* \to N\nu_\ell$, is phenomenologically irrelevant at the CERN LHC and report the impact of soft gluon corrections to the production cross section. We resum threshold logarithms up to next-to-next-to-next-to-leading logarithmic accuracy (N$^3$LL), thus capturing the dominant contributions to the inclusive cross section up to next-to-next-to-leading order (N$^2$LO). For $m_N > 150$ GeV and collider energies $\sqrt{s} = 7 - 100$ TeV, corrections to the Born rates span $+160$ to $+260\%$. At $\sqrt{s}$=14 TeV, the resummed channel is roughly equal in size to the widely-believed-to-be-dominant charged current Drell-Yan process and overtakes it outright at $\sqrt{s} \gtrsim 20-25$ TeV. Results are independent of the precise nature/mixing of $N$ and hold generically for other low-scale seesaws. Findings are also expected to hold for other exotic leptons and broken axial-vector currents, particularly as the $Z^*$ contribution identically reduces to that of a pseudoscalar.