The European Spallation Source neutrino Super Beam

TL;DR

This paper discusses the potential of the European Spallation Source to serve as a high-intensity neutrino beam facility aimed at discovering CP violation in the leptonic sector, leveraging its unique capabilities and upgrades.

Contribution

It proposes utilizing the ESS proton linac and upgrades to create the world's most intense neutrino Super Beam for CP violation studies and other physics applications.

Findings

Sensitivity at the 2nd oscillation maximum is three times higher than the 1st.

The proposed facility can also produce muons for additional physics research.

The ESS upgrades enable a versatile physics program including proton decay and astrophysics.

Abstract

After measuring in 2012 a relatively large value of the neutrino mixing angle $\theta_{13}$, the door is now open to observe for the first time a possible CP violation in the leptonic sector. The measured value of $\theta_{13}$ also privileges the 2nd oscillation maximum for the discovery of CP violation instead of the usually used 1st maximum. The sensitivity at this 2nd oscillation maximum is about three times higher, with a lower influence of systematic errors, than for the 1st maximum. Going to the 2nd oscillation maximum necessitates a very intense neutrino beam with the appropriate energy. The world's most intense pulsed spallation neutron source, the European Spallation Source, will have a proton linac with 5 MW power and 2 GeV energy. This linac, under construction, also has the potential to become the proton driver of the world's most intense neutrino beam with high probability to discover a neutrino CP violation. The physics performance of that neutrino Super Beam in conjunction with a megaton underground Water Cherenkov neutrino detector installed at a distance of about 500~km from ESS has been evaluated. In addition, the choice of such detector will extent the physics program to proton-decay and astrophysics searches. The ESS proton linac upgrades, the accumulator ring needed for proton pulse compression, the target station, the far detector and the physics potential are described. In addition to neutrinos, this facility will also produce at the same time a copious number of muons which could be used by a low energy neutrino facility for sterile neutrino searches, a future Neutrino Factory or a Muon Collider. The ESS neutron facility will be fully ready by 2023 at which moment the upgrades for the neutrino facility could start.