Majorana neutrinos in same-sign <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>W</mml:mi></mml:mrow><mml:mrow><mml:mo>±</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>W</mml:mi></mml:mrow><mml:mrow><mml:mo>±</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> scattering at the LHC: Breaking the TeV barrier

Abstract

We revisit the sensitivity to nonresonant, heavy Majorana neutrinos $N$ in same-sign ${W}^{\ifmmode\pm\else\textpm\fi{}}{W}^{\ifmmode\pm\else\textpm\fi{}}$ scattering at the $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$ 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 $pp\ensuremath{\rightarrow}{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}jj$ 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 $|{V}_{\ensuremath{\mu}N}{|}^{2}$ can be probed down to about 0.06--0.3(0.03--0.1) for ${m}_{N}=1--10\text{ }\text{ }\mathrm{TeV}$ with $\mathcal{L}=300\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}(3\text{ }\text{ }{\mathrm{ab}}^{\ensuremath{-}1})$. For heavier masses of ${m}_{N}=20\text{ }\text{ }\mathrm{TeV}$, we report sensitivity for $|{V}_{\ensuremath{\mu}N}{|}^{2}\ensuremath{\gtrsim}0.5(0.3)$. The ${W}^{\ifmmode\pm\else\textpm\fi{}}{W}^{\ifmmode\pm\else\textpm\fi{}}$ 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.

Topics & Concepts