Preceding a core-collapse supernova (CCSN), various processes produce an increasing amount of neutrinos of all flavors characterized by mounting energies from the interior of massive stars. Among them, the electron antineutrinos are potentially detectable by terrestrial neutrino experiments such as KamLAND and Super-Kamiokande (SK) via inverse beta decay interactions. Once these pre-supernova (pre-SN) neutrinos are observed, an early warning of the upcoming CCSN can be provided. In light of this, KamLAND and SK, both located in the Kamioka mine in Japan, have been monitoring pre-SN neutrinos since 2015 and 2021, respectively. Recently, we performed a joint study between KamLAND and SK on pre-SN neutrino detection. A pre-SN alert system combining the KamLAND detector and the SK detector was developed and put into operation, which can provide a supernova alert to the astrophysics community. Fully leveraging the complementary properties of these two detectors, the combined alert is expected to resolve a pre-SN neutrino signal from a 15 M-circle dot star within 510 pc of the Earth at a significance level corresponding to a false alarm rate of no more than 1 per century. For a Betelgeuse-like model with optimistic parameters, it can provide early warnings up to 12 hr in advance.

The sensitivity of a joint oscillation analysis between the Tokai-to-Kamioka (T2K) accelerator and Super-Kamiokande (SK) atmospheric neutrinos is presented. The two experiments have been playing leading roles in the global constraints on neutrino oscillation parameters such as $\delta_{\mathrm{CP}}$, $\theta_{23}$, and neutrino mass ordering (MO). The atmospheric neutrinos observed in SK have a good sensitivity to the MO, meanwhile a precise measurement of the leptonic CP violation phase ($\delta_{\mathrm{CP}}$) can be achieved by the exclusive $\nu_\mu\rightarrow\nu_e$ and $\bar\nu_\mu\rightarrow\bar\nu_e$ oscillation measurements in accelerator neutrinos. However, possible degeneracy limits the measurement precision in each experiment. In this work, we perform a joint fit to overcome this obscurity with the correlation of systematic uncertainties taken into account. The impact of T2K near detector constraints on the fit of SK atmospheric neutrinos is tested, and an increase of sensitivity to $\delta_{\mathrm{CP}}$ and MO is demonstrated.

Before the 2018 Super-Kamiokande (SK) detector upgrade, a hundred and forty-five 50 cm Box and Line (B&L) photomultiplier tubes (PMTs) have been carefully checked and measured in a laboratory near to the SK tank. Through various investigations including charge and timing response, required voltage, dark rate, etc., we have concluded that all received B&L PMTs were of good quality to be installed inside SK. In total 136 B&L PMTs have been picked at random and installed to replace the old SK PMTs.

T2K (Tokai to Kamioka), the world's first off-axis long-baseline neutrino beam experiment, was built for the precision measurement of neutrino oscillations. T2K makes use of a highly intense and almost pure $\nu_{\mu}$/$\overline{\nu}_{\mu}$ beam produced at the J-PARC accelerator complex and sent 295 km across Japan to the far detector, Super-Kamiokande. After the $\nu_{\mu}\rightarrow \nu_e$ appearance was observed at T2K in 2013, confirming the non-zero mixing angle $\theta_{13}$, T2K started to search for the first time for experimental evidence of CP violation in neutrino oscillations. To enhance this search substantially, the T2K collaboration is proposing an extension of data taking until 2026 for an overall accumulation of $20\times10^{21}$ protons-on-target (POT). This amount of data, along with T2K hardware upgrades and analysis improvements, allows us to intensively explore CP violation in the lepton sector, to precisely measure neutrino oscillation parameters, and to positively search for unknown physics.

We describe how the main neutrino interaction generators (GENIE, NEUT and NuWro) used by current neutrino oscillation experiments treat the shallow and deep inelastic region. We then compare their predictions for charged current events in this region, in terms of transferred momentum as well as multiplicities for different types of hadrons. We present additional comparisons in the low hadronic invariant mass region, where the generators use different custom models.