Determining the neutrino mass ordering and oscillation parameters with KM3NeT/ORCA

Abstract

The next generation of water Cherenkov neutrino telescopes in the Mediterranean Sea are under construction offshore France (KM3NeT/ORCA) and Sicily (KM3NeT/ARCA). The KM3NeT/ORCA detector features an energy detection threshold which allows to collect atmospheric neutrinos to study flavour oscillation. This paper reports the KM3NeT/ORCA sensitivity to this phenomenon. The event reconstruction, selection and classification are described. The sensitivity to determine the neutrino mass ordering was evaluated and found to be 4.4$$\sigma $$ σ if the true ordering is normal and 2.3$$\sigma $$ σ if inverted, after 3 years of data taking. The precision to measure $$\varDelta m^2_{32}$$ Δ m 32 2 and $$\theta _{23}$$ θ 23 were also estimated and found to be $$85 . 10^{-6}~{\mathrm{eV}^{2}}$$ 85 . 10 - 6 eV 2 and $$(^{+1.9}_{-3.1})^{\circ }$$ ( - 3.1 + 1.9 ) ∘ for normal neutrino mass ordering and, $$75 . 10^{-6}~{\mathrm{eV}^{2}}$$ 75 . 10 - 6 eV 2 and $$(^{+2.0}_{-7.0})^{\circ }$$ ( - 7.0 + 2.0 ) ∘ for inverted ordering. Finally, a unitarity test of the leptonic mixing matrix by measuring the rate of tau neutrinos is described. Three years of data taking were found to be sufficient to exclude "Equation missing" event rate variations larger than 20% at $$3\sigma $$ 3 σ level.

Combined sensitivity of JUNO and KM3NeT/ORCA to the neutrino mass ordering

“…The same is done for ORCA in section 3, based on the updated detector configuration, and simulation and reconstruction tools used for the latest NMO sensitivity study following ref. [38]. In this case, special attention is paid to the treatment of systematic uncertainties, in particular with the introduction of a systematic error on the measured energy scale at the detector level (not considered in ref.…”

“…The resulting trigger rate is about 54 kHz for noise events, 50 kHz for atmospheric muons and about 8 mHz for atmospheric neutrinos. The total simulated sample includes more than 15 years of atmospheric neutrinos, 1.4 days of noise events, and 14 days of atmospheric muons, which proves sufficient to probe the background contamination at a percent level [38].…”

“…The MC neutrino sample and event selection adopted in this study are identical to those used in the latest ORCA NMO sensitivity study and are extensively described in ref. [38]. From the detected signals, the energy and direction of the events are reconstructed using dedicated algorithms developed for shower-like [57] and track-like [58] event topologies.…”

Neutrino Tagging, a new tool for accelerator based neutrino experiments

“…The performances of the KM3NeT/ORCA detector in terms of energy response, effective mass and particle identification (PID) are assumed to be identical to the ones obtained on atmospheric neutrinos [38]. This hypothesis is conservative as new reconstruction and triggering algorithms could be developed to exploit the fact that the direction and energy of the beam neutrinos are known a-priori.…”

“…For what concerns the tagger, the energy resolution on the tagged neutrino is assumed to be 1% which is also a conservative hypothesis. 4.5 Tagged P2O Sensitivity to δ CP With the assumptions described above, the sensitivity of tagged P2O to δ CP is derived with a method similar to the one employed in [38] and using the oscillation parameters from [35]. The analysis is performed Figure 7: (a) Probability for νµ to oscillate to νe versus the probability for ν µ to oscillate to ν e .…”