Bilinear R Parity Violation at the ILC - Neutrino Physics at Colliders

Abstract

Supersymmetry (SUSY) with bilinearly broken R parity (bRPV) offers an attractive possibility to explain the origin of neutrino masses and mixings. In such scenarios, the study of neutralino decays at colliders gives access to neutrino sector parameters. The ILC offers a very clean environment to study the neutralino properties as well as its subsequent decays, which typically involve a $W$ or $Z$ boson and a lepton. This study is based on ILC beam parameters according to the Technical Design Report for a center of mass energy of $500\,\mathrm{GeV}$. A full detector simulation of the International Large Detector (ILD) was performed for all Standard Model backgrounds and for $\widetilde{\chi}_1^0$-pair production within a simplified model. The bRPV parameters are fixed according to current neutrino data. In this scenario, the $\widetilde{\chi}_1^0$ mass can be reconstructed with an uncertainty of $\delta m = (40(\text{stat.}) + 50(\text{syst.}))\,\mathrm{MeV}$ for an integrated luminosity of $500\,\mathrm{fb}^{-1}$ from direct $\widetilde{\chi}_1^0$-pair production, thus, to a large extent independently of the rest of the SUSY spectrum. The achievable precision on the atmospheric neutrino mixing angle $\sin^2 \theta_{23}$ from measuring the neutralino branching fractions $\mathrm{BR}(\widetilde{\chi}_1^0 \rightarrow W \mu)$ and $\mathrm{BR}(\widetilde{\chi}_1^0 \rightarrow W \tau)$ at the ILC is better than current uncertainties from neutrino experiments. Thus, the ILC could have the opportunity to unveil the mechanism of neutrino mass generation.