Yu Nakahama

Study on New Phenomena beyond the Standard Model of Particle Physics

　Unification of the forces and understanding of the vacuum are the targets of elementary particle physics. Super-symmetric theory (SUSY) has been a strong candidate of the unified theory due to its theoretical simpleness. On the other hand, dark matter has been established from cosmological observations and is commonly thought as yet-unknown elementary particles which SUSY can provide. Discovery of Higgs particle is a clue to understand the vacuum, and precise investigation of Higgs field including Higgs self-coupling is thought to be a direction of next particle physics efforts.
　Verification of the SUSY or beyond the standard particle theory is widely pursued by looking for a production of new particles and/or a discrepancy from the standard theory in precise measurements and rare phenomena. Dr. Nakahama introduced new method to measure CP asymmetries in neutral current decay of B mesons at the BELLE experiment and concluded no discrepancy from the standard theory. Then, in the ATLAS experiment, she led the search for SUSY gluino and squark inclusively and rejected many SUSY and dark matter models. It had a strong impact on both elementary particle and cosmology fields. She is pioneering to use Deep Learning tools in the verification of the Higgs field. Improvement of the ATLAS trigger performance is indispensable in upgrading the luminosity of LHC. It is highly praised that she realized the Run 2 operation of LHC as a person in charge of the ATLAS trigger selection project.
　Dr. Nakahama studied in the BELLE experiment, frontier of precise measurements. Then, she proceeded her study in the big ATLAS experiment, high energy frontier, and made various achievements. Consequently, she is promoted to important posts in the group and is a good role model of researchers in particle experiments using an accelerator. She is serving as a committee member of future planning of high energy physics community. She is contributing to activate the field and will continue to propel the field. As described above, she deserves to receive the Fumiko Yonezawa Memorial Prize as the young female leader in experimental particle physics.

　Dr. Emi Minamitani has been theoretically studying magnetism and phonon physics in nanoscale systems by employing cutting-edge computational-science approaches. In particular, she uncovered novel quantum phenomena emerging on solid surfaces by intimate collaborations with experimentalists.
　One of her important achievements is the study of the Kondo effect for molecules adsorbed on surfaces. Recently it has become possible to observe the Kondo effect of atoms/molecules on solid surfaces by STM experiments. Focusing on flexibility of shape of molecules as well as their orbital degrees of freedom, she developed a theory incorporating the Kondo effect and the interference effect between different channels in STM currents. Applying this theory, she found the SU(4) Kondo effect with spin/orbital degrees of freedom in a single iron phthalocyanine molecule, and further proposed the possibility for reversible control of quantum phase transitions due to competition between the Kondo effect and the magnetic anisotropy. These phenomena were confirmed experimentally.
　As another important achievement, she developed a theory of "STM-inelastic electron tunneling spectroscopy (STM-IETS)". In this method, one can detect phonon excitations which are induced by the electron tunneling from an STM tip to a surface. She clarified that the characteristic profile of the tunneling spectrum is determined by the strong momentum/energy dependence of the electron-phonon interaction, thereby explaining the peculiar experimental spectrum observed for the Cu(110) surface. She also succeeded in applying this theory to the graphen/SiC interface. These systematic studies have paved the way to explore phonon excitations on surfaces with the STM-IETS.
　These observations lead us to conclude that Dr. Minamitani's scientific achievements deserve the Fumiko Yonezawa Memorial Prize of the Physical Society of Japan.

Nano-heterostructures in ferroics and new functionalities appeared at their boundaries

　　Dr. Yokota has been studying the phase- and domain-boundaries in ferroic materials. First, for the piezoelectric solid solution system PbZr_1-xTi_xO₃, she has revealed the coexistence of multiple crystal structures by high resolution neutron diffraction experiment. Moreover, based on the precise analysis of the structure data with PDF method, she experimentally confirmed the rotation of polarization which had been theoretically proposed to cause a giant effect. Second, for inherently non-polar ferroelastic compounds, she successfully observed with the use of optical 2^nd harmonic generation microscope that the domain boundaries show polarization. These results indicate that the physical properties at domain- or heterostructure boundaries are different from bulk properties, which contributes to the establishment of a new field in solid state physics.
　　Dr. Yokota's continuous research activity is proved by many publications, invited talks and various awards. She is expected to be a role model for young female researchers, and thus deserves to be a winner for Fumiko Yonezawa Memorial Prize.

Assistant Professor, Research Center for Neutrino Science, Tohoku University

Measuring the Earth's neutrino flux and constraining its composition

Neutrino detections in Kamioka Mine, which originally started to aim at proton decay search, have achieved a significant progress in size and precision since Kamiokande (from 1983), Super-Kamiokande (from 1996), KamLAND (from 2002) and to Hyper-Kamiokande (expected from 2027). Their prominent results which brought two Nobel prizes to Japan are in super-nova neutrino, solar neutrino, atmospheric neutrino oscillation etc. Amongst those, an especially conspicuous outcome is geo-neutrino detections done by KamLAND, which is the major achievement performed by Prof. Hiroko Watanabe to be honored for the 2021 Fumiko Yonezawa Memorial Prize of the Physical Society of Japan. Geo neutrinos are produced by radioactive decays of thorium and uranium in the crust and the mantle of the earth, and one of important heat sources of the earth. The heat balance of the earth had been one of the long-standing puzzles in earth science over two centuries. Prof. Watanabe and her collaborators has determined geo-neutrino flux, and were able to put stringent constraints on heat models of the earth through detailed comparison between reactor neutrinos and geo neutrinos. While the first detection of the geo-neutrino by KamLAND was made in 2005, her result established a new interdisciplinary field, "neutrino earth science", which integrated neutrino physics and earth science. Prof. Watanabe is the corresponding author of this publication and has presented related works in many invited talks and plenary talks internationally. She is and will continue to be the leading scientist of "neutrino earth science" and presently promoting the separation of crust-origin neutrinos and mantle-origin neutrinos with a directionally sensitive neutrino-detection technology. Prof. Hiroko Watanabe thus deserves to receive the Fumiko Yonezawa Memorial Prize.