Updated physics performance of the ESSnuSB experiment

Abstract

In this paper, we present the physics performance of the ESSnuSB experiment in the standard three flavor scenario using the updated neutrino flux calculated specifically for the ESSnuSB configuration and updated migration matrices for the far detector. Taking conservative systematic uncertainties corresponding to a normalization error of $$5\%$$ 5 % for signal and $$10\%$$ 10 % for background, we find that there is $$10\sigma $$ 10 σ $$(13\sigma )$$ ( 13 σ ) CP violation discovery sensitivity for the baseline option of 540 km (360 km) at $$\delta _\mathrm{CP} = \pm 90^\circ $$ δ CP = ± 90 ∘ . The corresponding fraction of $$\delta _\mathrm{CP}$$ δ CP for which CP violation can be discovered at more than $$5 \sigma $$ 5 σ is $$70\%$$ 70 % . Regarding CP precision measurements, the $$1\sigma $$ 1 σ error associated with $$\delta _\mathrm{CP} = 0^\circ $$ δ CP = 0 ∘ is around $$5^\circ $$ 5 ∘ and with $$\delta _\mathrm{CP} = -90^\circ $$ δ CP = - 90 ∘ is around $$14^\circ $$ 14 ∘ $$(7^\circ )$$ ( 7 ∘ ) for the baseline option of 540 km (360 km). For hierarchy sensitivity, one can have $$3\sigma $$ 3 σ sensitivity for 540 km baseline except $$\delta _\mathrm{CP} = \pm 90^\circ $$ δ CP = ± 90 ∘ and $$5\sigma $$ 5 σ sensitivity for 360 km baseline for all values of $$\delta _\mathrm{CP}$$ δ CP . The octant of $$\theta _{23}$$ θ 23 can be determined at $$3 \sigma $$ 3 σ for the values of: $$\theta _{23} > 51^\circ $$ θ 23 > 51 ∘ ($$\theta _{23} < 42^\circ $$ θ 23 < 42 ∘ and $$\theta _{23} > 49^\circ $$ θ 23 > 49 ∘ ) for baseline of 540 km (360 km). Regarding measurement precision of the atmospheric mixing parameters, the allowed values at $$3 \sigma $$ 3 σ are: $$40^\circ< \theta _{23} < 52^\circ $$ 40 ∘ < θ 23 < 52 ∘ ($$42^\circ< \theta _{23} < 51.5^\circ $$ 42 ∘ < θ 23 < 51 . 5 ∘ ) and $$2.485 \times 10^{-3}$$ 2.485 × 10 - 3 eV$$^2< \varDelta m^2_{31} < 2.545 \times 10^{-3}$$ 2 < Δ m 31 2 < 2.545 × 10 - 3 eV$$^2$$ 2 ($$2.49 \times 10^{-3}$$ 2.49 × 10 - 3 eV$$^2< \varDelta m^2_{31} < 2.54 \times 10^{-3}$$ 2 < Δ m 31 2 < 2.54 × 10 - 3 eV$$^2$$ 2 ) for the baseline of 540 km (360 km).

Improving CP Measurement with THEIA and Muon Decay at Rest

“…As shown in the left figure of Fig. 3, once the π + , µ + , and e + energies are considered, the ν e CC-RES event rate is suppressed to negligible level with just around 8 × 10 −4 events/year for E vis ∈ [30,55] MeV at the THEIA-25 detector. Fig.…”

“…The upgrade from existing experiments includes: (1) Intensity Upgrade: the beam intensity is significantly enhanced, such as T2K-II [50]; (2) Detector Upgrade: T2HK [40] has a much larger detector Hyper-K than Super-K; (3) Spectrum Upgrade: DUNE [41] adopts wider on-axis spectrum than the off-axis one of NOνA; and (4) Baseline Upgrade with longer baseline such as T2HKK [51][52][53] and DUNE. In addition, there are also several new proposals: (5) the accelerator experiments such as P2O [54], ESSνSB [55], and MOMENT [56]; (6) CP measurement with sub-GeV atmospheric neutrino oscillation such as Super-PINGU [57,58], Super-ORCA [59], and even at JUNO [60] or DUNE [61]. Comparison among various experimental configurations can be found in [62][63][64][65].…”

“…For the atmospheric ν e with higher energies, 30% of the CC-QES scattering process can kick out a neutron and a proton from the nuclei via ν e + 16 O → e − + n + 15 O * + p. Since energy is needed to kick out n and p, the primary electron energy is much smaller than the neutrino energy. Mainly E ν ∈ [80,130] MeV will produce electrons with energy reconstructed in the µDAR range [30,55] MeV. In addition, roughly half of the single neutron events are also accompanied by a monoenergetic photon (∼6.2 MeV) due to the de-excitation of 15 O * , which can also serve as background veto.…”

“…Both electron (T e ) and proton (T p ) kinetic energies deposit as visible energy E vis . Requiring E vis ∈ [30,55] MeV, only 0.07 events per year at THEIA-25 can survive, which is a negligible amount.…”

“…The atmospheric νe (left) and νe (right) background event rate spectrum from CC-RES (solid) and CC-DIS (dashed) interactions as a function of the visible energy Evis at THEIA-25. With energy deposits from the primary electron (Te, red), charged π + (+Tπ, blue), µ + (+Tµ, green), the Michel electron (+T e + , yellow), and proton (+Tp, purple) gradually added up, the νe event spectrum moves out of the IBD energy window [30,55] MeV to higher energy. Similarly, the νe spectrum has the same feature with the primary electron (Te, red), charged π − (+Tπ, blue) or with Cherenkov cut (w/ Cher.…”