Physics potential of the ESS$$\nu $$SB

Abstract

The ESSνSB project proposes to base a neutrino "Super Beam" of unprecedented luminosity at the European Spallation Source. The original proposal identified the second peak of the oscillation probability as the optimal to maximize the discovery potential to leptonic CP violation. However this choice reduces the statistics at the detector and penalizes other complementary searches such as the determination of the atmospheric oscillation parameters, particularly the octant of θ 23 as well as the neutrino mass ordering. We explore how these shortcomings can be alleviated by the combination of the beam data with the atmospheric neutrino sample that would also be collected at the detector. We find that the combination not only improves very significantly these drawbacks, but also enhances both the CP violation discovery potential and the precision in the measurement of the CP violating phase, for which the facility was originally optimized, by lifting parametric degeneracies. We then reassess the optimization of the ESSνSB setup when the atmospheric neutrino sample is considered, with an emphasis in performing a measurement of the CP violating phase as precise as possible. We find that for the presently preferred value of δ ∼ −π/2, shorter baselines and longer running time in neutrino mode would be optimal. In these conditions, a measurement better than 14 • would be achievable for any value of the θ 23 octant and the mass ordering. Conversely, if present and next generation facilities were not able to discover CP violation, longer baselines and more even splitting between neutrino and neutrino modes would be preferable. These choices would allow a 5σ discovery of CP violation for around a 60% of the possible values of δ and to determine its value with a precision around 6 • if it is close to 0 or π . a

Exploring invisible neutrino decay at ESSnuSB

“…The topics, which we address in this work, are the following: (i) the capability of ESSnuSB to put bound on the decay parameter assuming there is no decay in Nature, (ii) the capability of ESSnuSB to discover neutrino decay assuming that neutrinos decay in Nature, (iii) how precisely ESSnuSB can measure the decay parameter if there exists neutrino decay in Nature, and (iv) the effect of neutrino decay on the measurement of δ CP . Since the sensitivity of ESSnuSB to measure the neutrino mass ordering, the octant of θ 23 , and the precision of θ 23 is weak [31][32][33][34], we will not address such potential measurements in this work.…”

Testing lepton flavor models at ESSnuSB

“…In our work, we use exactly the same configuration of ESSnuSB as was used to generate the results of ref. [66]. In the original experimental setup of ESSnuSB, the second peak of the neutrino oscillation probability was identified to be optimal to maximize the CP violation discovery potential.…”

“…The capability of ESSnuSB in measuring the unknown neutrino oscillation parameters within the standard three-flavor oscillation scenario has recently been studied in refs. [64][65][66]. Other future LBL facilities, which are also capable of measuring θ 23 and δ CP with very good precision, are DUNE [67,68] and T2HK [69] that are expected to become operational in the next decade.…”

“…This is due to the poor θ 23 measurement capability of ESSnuSB, which was discussed earlier. This may be mitigated by combining the LBL data with the sample of atmospheric neutrinos that the detector would collect[66].…”

Updated physics performance of the ESSnuSB experiment

“…In addition we will present its capability to precisely measure Δm 2 31 and θ 23 . Note that the physics performance of ESSnuSB within the three flavor scenario has been studied in the past [11][12][13][14][15]. However, in all these studies the configuration of ESSnuSB used was taken from an earlier project.…”