CP-violation reach of an electron capture neutrino beam

Abstract

This article extends the work of Bernabeu and Espinoza by examining the CP-violation reach of a $^{150}$Dy electron capture beam through the variation of the two Lorentz boosts, the number of useful electron capture decays, the relative run time of each boost and the number of atmospheric backgrounds. The neutrinos are assumed to be sourced at CERN with an upgraded SPS and are directed towards a 440 kton Water Cerenkov detector located at the Canfranc laboratory. Two large `CP-coverage' choices for the boost pairings are found; a $\delta$-symmetrical coverage for $(\gamma_{1}, \gamma_{2})$ = (280, 160) and an $\delta$-asymmetric coverage for $(\gamma_{1}, \gamma_{2})$ = (440,150). With a nominal useful decay rate of $N_{\rm ions} = 10^{18}$ ions per year, the $\delta$-symmetric setup can rule out CP-conservation down to $\sin^{2}2\theta_{13} = 3\cdot 10^{-4}$. To reach $\sin^{2}2\theta_{13} = 1\cdot 10^{-3}$ for both $\delta < 0$ and $\delta > 0$ requires a useful decay rate of $N_{\rm ions} = 6\cdot 10^{17}$ ions per year.