A new search for the diffuse supernova neutrino background (DSNB) flux has been conducted at Super-Kamiokande (SK), with a 22.5 × 2970-kton•day exposure from its fourth operational phase IV. The new analysis improves on the existing background reduction techniques and systematic uncertainties and takes advantage of an improved neutron tagging algorithm to lower the energy threshold compared to the previous phases of SK. This allows for setting the world's most stringent upper limit on the extraterrestrial νe flux, for neutrino energies below 31.3 MeV. The SK-IV results are combined with the ones from the first three phases of SK to perform a joint analysis using 22.5 × 5823 kton•days of data. This analysis has the world's best sensitivity to the DSNB νe flux, comparable to the predictions from various models. For neutrino energies larger than 17.3 MeV, the new combined 90% C.L. upper limits on the DSNB νe flux lie around 2.7 cm −2 •sec −1 , strongly disfavoring the most optimistic predictions. Finally, potentialities of the gadolinium phase of SK and the future Hyper-Kamiokande experiment are discussed.

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MnP, a superconductor under pressure, exhibits a ferromagnetic order below TC~290 K followed by a helical order with the spins lying in the ab plane and the helical rotation propagating along the c axis below Ts~50 K at ambient pressure. We performed single crystal neutron diffraction experiments to determine the magnetic ground states under pressure. Both TC and Ts are gradually suppressed with increasing pressure and the helical order disappears at ~1.2 GPa. At intermediate pressures of 1.8 and 2.0 GPa, the ferromagnetic order first develops and changes to a conical or two-phase (ferromagnetic and helical) structure with the propagation along the b axis below a characteristic temperature. At 3.8 GPa, a helical magnetic order appears below 208 K, which hosts the spins in the ac plane and the propagation along the b axis. The period of this b axis modulation is shorter than that at 1.8 GPa. Our results indicate that the magnetic phase in the vicinity of the superconducting phase may have a helical magnetic correlation along the b axis.Comment: 5 pages, 4 figure

Abstract. The phase boundary between wadsleyite and ringwoodite in Mg2SiO 4 composition was determined by in situ observation using synchrotron X-ray and multi anvil apparatus in KEK, Tsukuba, Japan. An energy dispersive method was employed using the Ge solid state detector and the white X-ray beam from the synchrotron radiation source. The pressure was determined by the equation of state of NaCl. The stability field was identified by the change in intensities of diffraction lines of each phases. As a result, the phase boundary is expressed as a linear equation P=I0.32(28)+0.00691(9)xT, where P is pressure in gigapascals and T is temperature in degrees Celsius. IntroductionOlivine is the major constituent in the Earth's upper mantle, and the significant seismic discontinuities, which locate 400 km and 670 km deep, are considered to be caused by the phase transition of olivine to wadsleyite (modified spinel structure) and the decomposition of ringwoodite (spinel structure) to magnesiowustite and There are a number of quench experiments so far on the phase boundary between wadsleyite and ringwoodite [e.g., Kawada, 1977; $uito, 1977;Katsura and Ito, 1989], however, the in situ X-ray determination have not been conducted yet.In the quench experiments, pressure was estimated from the calibration curve, which is based on the fixed point at room and/or high temperatures, and the considerable uncertainty remains in pressure (e.g., +I.5GPa above 14 GPa