Heavy neutral leptons at ANUBIS

Abstract

Recently Bauer et al. [arXiv:1909.13022] proposed ANUBIS, an auxiliary detector to be installed in one of the shafts above the ATLAS or CMS interaction point, as a tool to search for long-lived particles. Here, we study the sensitivity of this proposal for long-lived heavy neutral leptons (HNLs) in both minimal and extended scenarios. We start with the minimal HNL model where both production and decay of the HNLs are mediated by active-sterile neutrino mixing, before studying the case of right-handed neutrinos in a leftright symmetric model. We then consider a Uð1Þ B−L extension of the Standard Model (SM). In this model HNLs are produced from the decays of the mostly SM-like Higgs boson, via mixing in the scalar sector of the theory. In all cases, we find that ANUBIS has sensitivity reach comparable to the proposed MATHUSLA detector. For the minimal HNL scenario, the contributions from W's decaying to HNLs are more important at ANUBIS than at MATHUSLA, extending the sensitivity to slightly larger HNL masses at ANUBIS.

Quasi-Dirac neutrinos in the linear seesaw model

“…This feature will imply a different mass range for the Quasi-Dirac regime: in the linear seesaw scenario, which we study here, R takes values different from 0 or 1 at lower M N , including a few GeV. Therefore, sterile neutrino searches at current and nearfuture experiments such as SHiP, ANUBIS, MATUSHLA and DUNE [38][39][40], set interesting constraints on the parameter space of the linear seesaw scenario. It is worth to highlight that a measurement of R requires both leptons to be detected and their charge to be identified.…”

“…For some values of g 20 the model remains unconstrained by the low energy experimental bounds. A value of g = 1, where Y D = Y , corresponds to the traditional seesaw mechanism [5,6,61] where the heavy-light neutrino mixing is given by U [39,40,62,63], while the already excluded values (grey shaded region) are taken from refs. [38,63].…”

An allowed window for heavy neutral leptons below the kaon mass

“…HNL searches are an important part of the physics program of many proposed experiments, see, e.g. [70][71][72][73][74][75][76][77][78][79]. In the absence of positive results, one establishes upper limits on the mixing angles.…”

MoEDAL, FASER and future experiments targeting dark sector and long-lived particles

“…3, it is evident that MAPP-2, due to take data in HL-LHC, will fill the gap left by CMS, LHCb, MATHUSLA, FASER2 and CODEX-b [20]. Numerous studies have compared the physics reach of LLP experiments for different scenarios of heavy neutral leptons [18,[21][22][23]].…”