Survival probabilities of charmonia as a clue to measure transient magnetic fields

Iwasaki, Sachio*; Jido, Daisuke*; Oka, Makoto; Suzuki, Kei

Physics Letters B, 820, p.136498_1 - 136498_6, 2021/09

https://doi.org/10.1016/j.physletb.2021.136498

We investigate time evolution of -wave charmonium populations under a time-dependent homogeneous magnetic field and evaluate survival probabilities of the low-lying charmonia to the goal of estimating the magnetic field strength at heavy-ion collisions. Our approach implements mixing between different spin eigenstates and transitions to radially excited states. We show that the survival probabilities can change even by an extremely short magnetic field. Furthermore, we find that the survival probabilities depend on the initial spin states. We propose the sum of the survival probabilities over spin partners as an observable insensitive to the initial states. We also find that the sum can be approximately given as a function of with a duration time and the maximum strength of the magnetic field .

Microscopic theory of electrically induced spin torques in magnetic Weyl semimetals

Kurebayashi, Daichi*; Araki, Yasufumi; Nomura, Kentaro*

Journal of the Physical Society of Japan, 90(8), p.084702_1 - 084702_9, 2021/08

https://doi.org/10.7566/JPSJ.90.084702

We theoretically study current- and charge-induced spin torque in magnetic Weyl semimetals. In magnetic Weyl semimetals (WSM), topologically nontrivial band structure mediates anomalous coupling between magnetization and transport, making WSMs preferable for spintronics systems. In this paper, we determine all current-induced spin torques including spin-orbit torque and spin-transfer torque, up to first order with respect to spatial and temporal derivatives and electrical currents. We also calculate the charge-induced spin torque microscopically. We find the charge-induced spin torque originates from the chiral anomaly due to the correspondence between spin operators and axial current operators in our model.

Gamma-ray observations at the coastal area of Japan Sea in winter seasons

Tsuchiya, Harufumi; Enoto, Teruaki*; Wada, Yuki*; Furuta, Yoshihiro; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; Umemoto, Daigo*; Makishima, Kazuo*; GROWTH collaboration*

Proceedings of Science (Internet), 358, 6 Pages, 2021/07

http://dx.doi.org/10.22323/1.358.1163

Meteorological aspects of gamma-ray glows in winter thunderstorms

Wada, Yuki*; Enoto, Teruaki*; Kubo, Mamoru*; Nakazawa, Kazuhiro*; Shinoda, Taro*; Yonetoku, Daisuke*; Sawano, Tatsuya*; Yuasa, Takayuki*; Ushio, Tomoo*; Sato, Yosuke*; et al.

Geophysical Research Letters, 48(7), 11 Pages, 2021/04

https://doi.org/10.1029/2020GL091910

During three winter seasons from November 2016 to March 2019, 11 gamma-ray glows were detected at a single observation site of our ground-based gamma-ray monitoring network in Kanazawa, Japan. These events are analyzed with observations of an X-band radar network, a ceilometer, a disdrometer, and a weather monitor. All the detected glows were connected to convective high-reflectivity regions of more than 35 dBZ, developed up to an altitude of 2 km. They were also accompanied by heavy precipitation of graupels. Therefore, graupels in the lower layer of thunderclouds that correspond to high-reflectivity regions can form strong electric fields producing gamma-ray glows. Also, these events are compared with a limited sample of nondetection cases, but no significant differences in meteorological conditions were found between detection and nondetection cases in the present study.

Study of the axial anomaly at high temperature with lattice chiral fermions

Aoki, Sinya*; Aoki, Yasumichi*; Cossu, G.*; Fukaya, Hidenori*; Hashimoto, Shoji*; Kaneko, Takashi*; Rohrhofer, C.*; Suzuki, Kei

Physical Review D, 103(7), p.074506_1 - 074506_18, 2021/04

https://doi.org/10.1103/PhysRevD.103.074506

We investigate the axial anomaly of two-flavor QCD at temperatures 190-330 MeV. In order to preserve precise chiral symmetry on the lattice, we employ the Mbius domain-wall fermion action as well as overlap fermion action implemented with a stochastic reweighting technique. Compared to our previous studies, we reduce the lattice spacing to 0.07 fm, simulate larger multiple volumes to estimate finite size effect, and take more than four quark mass points, including one below physical point to investigate the chiral limit. We measure the topological susceptibility, axial susceptibility, and examine the degeneracy of partners in meson/baryon correlators. All the data above the critical temperature indicate that the axial violation is consistent with zero within statistical errors. The quark mass dependence suggests disappearance of the anomaly at a rate comparable to that of the symmetry breaking.

Two relativistic Kondo effects; Classification with particle and antiparticle impurities

Araki, Yasufumi; Suenaga, Daiki*; Suzuki, Kei; Yasui, Shigehiro*

Physical Review Research (Internet), 3(1), p.013233_1 - 013233_12, 2021/03

https://doi.org/10.1103/PhysRevResearch.3.013233

We investigate two different types of relativistic Kondo effects, distinguished by heavy-impurity degrees of freedom, by focusing on the energy-momentum dispersion relations of the ground state with condensates composed of a light Dirac fermion and a nonrelativistic impurity fermion. Heavy fermion degrees of freedom are introduced in terms of two types of heavy-fermion effective theories, in other words, two heavy-fermion limits for the heavy Dirac fermion, which is known as the heavy-quark effective theories (HQETs) in high-energy physics. While the first one includes only the heavy-particle component, the second one contains both the heavy-particle and heavy-antiparticle components, which are opposite in their parity. From these theories, we obtain two types of Kondo effects, in which the dispersions near the Fermi surface are very similar, but they differ in the structure at low momentum. We also classify the possible forms of condensates in the two limits. The two Kondo effects will be examined by experiments with Dirac/Weyl semimetals or quark matter, lattice simulations, and cold-atom simulations.

Thundercloud project; Exploring high-energy phenomena in thundercloud and lightning

Yuasa, Takayuki*; Wada, Yuki*; Enoto, Teruaki*; Furuta, Yoshihiro; Tsuchiya, Harufumi; Hisadomi, Shohei*; Tsuji, Yuna*; Okuda, Kazufumi*; Matsumoto, Takahiro*; Nakazawa, Kazuhiro*; et al.

Progress of Theoretical and Experimental Physics (Internet), 2020(10), p.103H01_1 - 103H01_27, 2020/10

https://doi.org/10.1093/ptep/ptaa115

Charmed baryon spectrum from lattice QCD near the physical point

Bahtiyar, H.*; Can, K. U.*; Erkol, G.*; Gubler, P.; Oka, Makoto; Takahashi, Toru*

Physical Review D, 102(5), p.054513_1 - 054513_18, 2020/09

https://doi.org/10.1103/PhysRevD.102.054513

Spectrum of the ground state and excited states of charmed baryons was evaluated in the lattice QCD, the first principle of hadronic interaction. We deliver the spectrum of the positive and negative parity baryons with one, two or three charmed quarks. A variational approach was employed by the use of multiple operators with different Dirac matrix configurations and the smearings.

Axial U(1) symmetry and mesonic correlators at high temperature in lattice QCD

Suzuki, Kei; Aoki, Sinya*; Aoki, Yasumichi*; Cossu, G.*; Fukaya, Hidenori*; Hashimoto, Shoji*; Rohrhofer, C.*

Proceedings of Science (Internet), 363, 7 Pages, 2020/08

https://doi.org/10.22323/1.363.0178

We investigate the high-temperature phase of QCD using lattice QCD simulations with dynamical Mbius domain-wall fermions. On generated configurations, we study the axial symmetry, overlap-Dirac spectra, screening masses from mesonic correlators, and topological susceptibility. We find that some of the observables are quite sensitive to lattice artifacts due to a small violation of the chiral symmetry. For those observables, we reweight the Mbius domain-wall fermion determinant by that of the overlap fermion. We also check the volume dependence of observables. Our data near the chiral limit indicates a strong suppression of the axial anomaly at temperatures 220 MeV.

Study on optical properties of metallic sodium by vacuum ultra violet in UVSOR, 2

Kawaguchi, Munemichi; Saito, Junichi; Daido, Hiroyuki*; Suemoto, Toru*

UVSOR-47, P. 85, 2020/08

https://www.uvsor.ims.ac.jp/eng/activity/2019/page_02.html

To elucidate theoretically the transparent metallic sodium in the vacuum ultraviolet (VUV) spectral range, the aim of this research is to obtain the accurate spectrum using UVSOR. We confirmed the validity for the transmittance measurement in UVSOR by the measurement of transmittance of CaF windows. However, the transparency phenomenon of VUV in the metallic sodium has never been confirmed by our group. In the future, we will improve the sodium sample and conduct the measurement again.