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Modern theories of physics tell that the vacuum is not an empty space. Hidden in the vacuum is a structure of anti-quarks $\bar{q}$ and quarks $q$. The $\bar{q}$ and $q$ pair has the same quantum number as the vacuum and condensates in it since the strong interaction of the quantum chromodynamics (QCD) is too strong to leave it empty. The $\bar{q}q$ condensation breaks the chiral symmetry of the vacuum. The expectation value $$ is an order parameter. For higher temperature or higher matter-density, $||$ decreases reflecting the restoration of the symmetry. In contrast to these clear-cut arguments, experimental evidence is so far limited. First of all, the $\bar{q}q$ is nothing but the vacuum itself. It is neither visible nor perceptible. In this article, we unravel this invisible existence by high precision measurement of pionic atoms, $π^-$-meson-nucleus bound systems. Using the $π^-$ as a probe, we demonstrate that $||$ is reduced in the nucleus by a factor of 58 $\pm$ 4% compared with that in the vacuum. This reduction indicates that the chiral symmetry is partially restored due to the extremely high density of the nucleus. The present experimental result clearly exhibits the existence of the hidden structure, the chiral condensate, in the vacuum., Nat. Phys. (2023)

Intensive research from the 1970's to 1990's towards geochemical detection of solar neutrinos using 205 Tl, 98 Mo and 81 Br has left 205 Tl the only viable candidate. LOREX (LORandite EXperiment ) is based on determining the solar (pp) neutrino flux for the period of 4.3 Ma from the reaction 205 Tl+v e → 205 Pb+e - , the lowest threshold (52 keV) for neutrino capture. The ratio of 205 Pb/ 205 Tl in lorandite (TlAsS 2 ) depends also on contributions from fast muon cosmic radiation. The latter is a function of paleo - depth, including the eroded layer over 4.3 Ma, determined using cosmogenic nuclides ( 26 Al, 36 Cl, 3 He and 21 Ne) in the ore body Crven Dol (Tl - As - Sb - S) in Allchar (Macedonia). The results give a l ower limit of paleo - depth of 490mwe and an upper limit of 2300mwe. From this the ratios 205 Pb ve / 205 Pb tot are estimated as 2:8 and 6:4, respectively. Identification of the 205 Pb nuclei in the lead sample extracted from the lorandite mineral requires 10 - 10 to 10 - 11 overall detection sensitivity for 205 Pb/Pb and comparable suppression of the 205 Tl isobar. This is proposed by full stripping of 205 Pb at high energy (345MeV/u) at the RIKEN - RIBF ion - beam facility. 205 Tl isobar separation is already largely achiev ed by chemical Pb - Tl separation by the overall sample preparation. Samples with a higher concentration ( 205 Tl/natPb=1%) are necessary for a guide - beam and initial accelerator tuning. A sample with a considerably lower level of about 10 - 8 is needed for cont rol of the beam analysis system with 205 Tl ions, in the presence ultimately of a lighter guide beam, to limit the in - beam production of 205 Pb by the (p,n) reaction on 205 Tl in the energy - loss and ion - stripping steps in the accelerator and the subsequent Bi gRIPS/Mass - Ring experimental apparatus. The relative cross sections between full stripping of 205 Pb and (p,n) on 205 Tl is estimated as 10 5 . Test experiments to verify the various aspects of the proposed approach at the RIBF are under preparation.

Excited states in the N=102 isotones 166Gd and 164Sm have been observed following isomeric decay for the first time at RIBF, RIKEN. The half-lives of the isomeric states have been measured to be 950(60) and 600(140) ns for 166Gd and 164Sm, respectively. Based on the decay patterns and potential energy surface calculations, including β6 deformation, a spin and parity of 6- has been assigned to the isomeric states in both nuclei. Collective observables are discussed in light of the systematics of the region, giving insight into nuclear shape evolution. The decrease in the ground-band energies of 166Gd and 164Sm (N=102) compared to 164Gd and 162Sm (N=100), respectively, presents evidence for the predicted deformed shell closure at N=100.