This paper presents the expected sensitivity to the neutrino oscillation parameters of the Hyper-Kamiokande long-baseline program. The Hyper-Kamiokande experiment, currently under construction in Japan, will measure the oscillations of accelerator-produced neutrinos with thousands of selected events per sample: this corresponds to an increase of statistics of a factor 25–100 with respect to recent results from the currently-running long-baseline neutrino oscillation experiment in Japan, T2K. In the most favorable scenario we will achieve the discovery of Charge-Parity (CP) violation in neutrino oscillation at $$5\sigma $$ 5 σ C.L. in less than 3 years. With 10 years of data-taking, and assuming a neutrino : antineutrino beam running ratio of 1:3, a CP violation discovery at $$5\sigma $$ 5 σ C.L. is possible for more than 60% of the actual values of the CP-violating phase, $$\delta _{CP}.$$ δ CP . Moreover, we will measure $$\delta _{CP}$$ δ CP with a precision ranging from 20 $$^{\circ },$$ ∘ , in the case of maximal CP violation, to 6 $$^{\circ },$$ ∘ , in the case of CP conservation. We aim to achieve a 0.5% resolution on the $$\Delta m^2_{32}$$ Δ m 32 2 parameter, and a resolution between 3% and 0.5% on the $$\sin ^2\theta _{23}$$ sin 2 θ 23 parameter, depending on its true value. These results are obtained by extending the analysis methods of T2K with dedicated tuning to take into account the Hyper-Kamiokande design: the larger far detector, the more powerful beam, the upgraded near detector ND280, and the planned additional Intermediate Water Cherenkov Detector.

Underground locations can be used in various ways for scientific and economic purposes. One of the main factors influencing the safety level in the underground mine workings is natural radioactivity. The article presents research carried out on the natural radioactivity in shallow mine workings at the GIG Experimental Mine ‘Barbara’. The description of the natural radiation includes radon determination in the air, in situ gamma spectrometry, neutron flux measurements, and laboratory measurements of ^226,228Ra, ⁴⁰K, and ^234,238U isotopes using gamma and alpha spectrometry techniques. In the measurement chamber at the depth 46 m (122 m w.e.) in the sandstone layer, the photon flux registered at the 7–3150 keV energy range is equal to 17.6 ± 1.9 cm⁻²s⁻¹, the gamma-ray dose rate is 0.200 ± 0.029 µSv/h, and the thermal neutron flux is equal to (8.6 ± 1.1) × 10⁻⁶ cm⁻²s⁻¹. After closing the measurement chamber and turning off ventilation, a significant ingrowth of ²²²Rn content was observed, reaching the value of 4040 ± 150 Bq/m³. An increased gamma-ray flux and thermal neutron flux were observed in the investigated location.

Natural radioactivity in underground locations is the main parameter for the safety of work (occupational hazards) and for the success of experiments in physics or biology requiring unique conditions. The characterization of natural prominence was carried out in the Conceptual Lab development in one of KGHM deep copper mines co-ordinated by KGHM Cuprum R&D. Natural radioactivity studies were performed and included in situ gamma spectrometry, neutron flux measurements, radon concentration, and alpha and gamma laboratory spectrometry measurements of rock samples. At a depth of 1014.4 m (2941.8 m w.e.) within the anhydrite layer, a neutron flux of 2.0 ± 0.2 × 10⁻⁶ cm⁻² s⁻¹, a gamma-ray dose of 0.008 ± 0.001 μSv/h, a photon flux density of 0.64 ± 0.20 cm⁻² s⁻¹, and a radon concentration of 6.6 Bq/m³ were determined. Laboratory analyses of ^226,228Ra, ⁴⁰K, and ^238,234U concentrations in collected rock samples showed low values. The exceptionally low level of natural radioactivity in the Polkowice-Sieroszowice mine makes this location a unique place for scientific research.

There has been growing interest in using underground locations for applications in various fields, including research. In Poland, for several years, attempts have been made to build an underground laboratory. For this purpose, selecting an appropriate location requires a detailed analysis of the level of natural radioactivity. The present study presents detailed characteristics of the natural background radiation in close vicinity to shaft L-VI of the Lubin mine, at the depth of 910 m (2275 m w.e.). The in situ measurement of the photon flux in the 7–3150 keV energy range was equal to 8.08 ± 0.90 cm⁻²s⁻¹, and the gamma-ray dose rate of 0.070 ± 0.010 µSv/h with the highest contribution from ⁴⁰K and ²¹⁴B isotopes. The thermal neutron flux measured using helium counters was equal to 4.2 ± 0.9 × 10⁻⁶ cm⁻²s⁻¹. The radon concentration in the air measured with the RAD7 monitor showed low values ranging from 0 to 15.3 Bq/m³. Laboratory measurements of rocks using alpha and gamma spectrometry techniques showed a significant variation in the concentration of ²²⁶Ra and ^234,238U isotopes, and the highest concentration values were recorded for shales. The ⁴⁰K, ^234,238U and ²²⁶Ra isotopes make the greatest contribution to the natural radioactivity of analyzed rocks.