Majorana neutrinos in same-sign W±W± scattering at the LHC: Breaking the TeV barrier

We revisit the sensitivity to nonresonant, heavy Majorana neutrinos N in same-sign W+W+ scattering at the root s = 13 TeV LHC and its high-luminosity upgrade. As a benchmark scenario, we work in the context of the phenomenological type I seesaw model, relying on a simulation up to next-to-leading order in QCD with parton shower matching. After extensively studying the phenomenology of the pp -> mu(+/-)mu(+/-) jj process at the amplitude and differential levels, we design a simple collider analysis with remarkable signal-background separation power. At 95% confidence level we find that the squared muon-heavy neutrino mixing element vertical bar V-mu N vertical bar(2) can be probed down to about 0.06-0.3(0.03-0.1) for m(N) = 1-10 TeV with L = 300 fb(-1) (3 ab(-1)). For heavier masses of m(N) = 20 TeV, we report sensitivity for vertical bar V-mu N vertical bar(2) greater than or similar to 0.5(0.3). The (WW +/-)-W-+/- scattering channel can greatly extend the mass range covered by current LHC searches for heavy Majorana neutrinos and particularly adds invaluable sensitivity above a few hundred GeV. We comment on areas where the analysis can be improved as well as on the applicability to other tests of neutrino mass models.

Automated summary

This study revisits the sensitivity to heavy Majorana neutrinos in same-sign W+W+ scattering at the LHC, showing that a simple collider analysis can achieve remarkable signal-background separation power for detecting heavy neutrinos in a specific mass range. The (WW +/-)-W-+/- scattering channel greatly extends the mass range covered by current LHC searches for heavy Majorana neutrinos and adds invaluable sensitivity above a few hundred GeV. There is potential for improvement in the analysis and the applicability to other tests of neutrino mass models.