Abstract
We investigate the pair production of right-handed neutrinos from the decay of an additional neutral ${Z}^{\ensuremath{'}}$ boson in the gauged $B\ensuremath{-}L$ model. Taking into account current constraints on the ${Z}^{\ensuremath{'}}$ mass and the associated gauge coupling ${g}_{1}^{\ensuremath{'}}$, we analyse the sensitivity of proposed experiments at the lifetime frontier, FASER 2, CODEX-b, MATHUSLA as well as a hypothetical version of the MAPP detector to a long lived heavy neutrino $N$ originating in the decays of the ${Z}^{\ensuremath{'}}$. We further complement this study with determining the reach of LHCb and a CMS-type detector for the high-luminosity LHC run. We demonstrate that in a backgroundfree scenario with ${g}_{1}^{\ensuremath{'}}={10}^{\ensuremath{-}3}$ near the current limit, FASER 2 is sensitive to the active-sterile neutrino mixing down to ${V}_{\ensuremath{\mu}N}\ensuremath{\approx}{10}^{\ensuremath{-}4}$, while a reach of ${V}_{\ensuremath{\mu}N}\ensuremath{\approx}{10}^{\ensuremath{-}5}$ can be obtained for CODEX-b and LHCb, in a mass regime of ${m}_{N}\ensuremath{\approx}5--20\text{ }\text{ }\mathrm{GeV}$ and ${m}_{{Z}^{\ensuremath{'}}}\ensuremath{\approx}20--70\text{ }\text{ }\mathrm{GeV}$. Finally, MATHUSLA can probe ${V}_{\ensuremath{\mu}N}\ensuremath{\approx}{10}^{\ensuremath{-}7}$ and cover the mixing regime expected in a canonical seesaw scenario of light neutrino mass generation.
Highlights
The observation of light neutrino mass from neutrino oscillation experiment shows the existence of physics beyond the Standard Model (SM)
Taking into account current constraints on the Z0 mass and the associated gauge coupling g01, we analyse the sensitivity of proposed experiments at the lifetime frontier, FASER 2, CODEX-b, MATHUSLA as well as a hypothetical version of the MAPP detector to a long lived heavy neutrino N originating in the decays of the Z0
In this work we have explored the potential to probe the B − L gauge boson Z0 decaying to two RH neutrinos in the Uð1ÞB−L model
Summary
The observation of light neutrino mass from neutrino oscillation experiment shows the existence of physics beyond the Standard Model (SM). In the small active-sterile neutrino mixing limit, this leads to distinctive displaced vertex signatures at the LHC Such a process is controlled by the B − L coupling g01, the mass of the heavy gauge boson (Z0) and that of the heavy neutrinos (Ni). In the regime of suppressed active-sterile neutrino mixing the decays of the righthanded neutrinos can lead to a displaced vertex signal at colliders This distinct signal can be regarded as background free for large decay lengths, even under the highly constrained parameter space, the channel pp → Z0 → NN leading to displaced vertices is a promising channel to search for at the proposed far detectors such as MATHUSLA [21], MAPP [22], CODEX-b [23], FASER [24] as well as LHCb [25] and CMS [15,16].
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