Abstract
The European Spallation Source (ESS), currently under construction in Lund, Sweden, is a research center that will provide, by 2023, the world’s most powerful neutron source. The average power of the proton linac will be 5 MW. Pulsing this linac at higher frequency will make it possible to raise the average total beam power to 10 MW to produce, in parallel with the spallation neutron production, a very intense neutrino Super Beam of about 0.4 GeV mean neutrino energy. This will allow searching for leptonic CP violation at the second oscillation maximum where the sensitivity is about 3 times higher than at the first. The ESS neutrino Super Beam, ESSnuSB operated with a 2.0 GeV linac proton beam, together with a large underground Water Cherenkov detector located at 540 km from Lund, will make it possible to discover leptonic CP violation at 5σ significance level in 56% (65% for an upgrade to 2.5 GeV beam energy) of the leptonic CP-violating phase range after 10 years of data taking, assuming a 5% systematic error in the neutrino flux and 10% in the neutrino cross section. The paper presents the outstanding physics reach possible for CP violation with ESSnuSB obtainable under these assumptions for the systematic errors. It also describes the upgrade of the ESS accelerator complex required for ESSnuSB.
Highlights
The European Spallation Source (ESS), currently under construction in Lund, Sweden, is a research center that will provide, by 2023, the world’s most powerful neutron source
The ESS neutrino Super Beam, European Spallation Source neutrino Super Beam (ESSnuSB) operated with a 2.0 GeV linac proton beam, together with a large underground Water Cherenkov detector located at 540 km from Lund, will make it possible to discover leptonic CP violation at 5σ significance level in 56% (65% for an upgrade to 2.5 GeV beam energy) of the leptonic CP-violating phase range after 10 years of data taking, assuming a 5% systematic error in the neutrino flux and 10% in the neutrino cross section
In a first publication [9] the European Spallation Source neutrino Super Beam (ESSnuSB) collaboration proposes searching for leptonic CP violation by making use of the Super Beam described above and a Megaton water Cherenkov detector placed in the 1200 m deep Garpenberg mine located at a distance of 540 km from the neutrino source in Lund, near the second neutrino oscillation maximum
Summary
An ultimate goal of the long baseline neutrino experiments being planned is the discovery and high precision measurement of the leptonic CP violation through measurement of the ]μ → ]e oscillation probability. The European Spallation Source (ESS) [6] under construction in Lund, Sweden, since the fall of 2014, is a research center that will have the world’s most powerful neutron source It is based on a 2.0 GeV superconducting linac (with space available for an upgrade to the originally planned energy of 2.5 GeV), providing 2.86 ms long proton pulses at 14 Hz for the spallation neutron facility with 5 MW average power on target (Figure 1). In a first publication [9] the European Spallation Source neutrino Super Beam (ESSnuSB) collaboration proposes searching for leptonic CP violation by making use of the Super Beam described above and a Megaton water Cherenkov detector placed in the 1200 m deep Garpenberg mine located at a distance of 540 km from the neutrino source in Lund, near the second neutrino oscillation maximum. It is proposed that some of these modifications be made already during the current linac construction phase, such that it will later be possible to upgrade the linac with only minor interventions during the operation of the linac for
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