Axial U(1) symmetry at high temperatures in lattice QCD with chiral fermions

Aoki, Shinya*; Aoki, Yasumichi*; Fukaya, Hidenori*; Hashimoto, Shoji*; Kanamori, Issaku*; Kaneko, Takashi*; Nakamura, Yoshifumi*; Rohrhofer, C.*; Suzuki, Kei

Proceedings of Science (Internet), 396, p.332_1 - 332_7, 2022/07

https://doi.org/10.22323/1.396.0332

The axial U(1) anomaly in high-temperature QCD plays an important role to understand the phase diagram of QCD. The previous works by JLQCD Collaboration studied high-temperature QCD using 2-flavor dynamical chiral fermions such as the domain-wall fermion and reweighted overlap fermion. We extend our simulations to QCD with 2+1-flavor dynamical quarks, where the masses of the up, down, and strange quarks are near the physical point, and the temperatures are close to or higher than the pseudocritical temperature. In this talk, we will present the results for the Dirac spectrum, topological susceptibility, axial U(1) susceptibility, and hadronic collelators.

Role of the axial anomaly in the chiral susceptibility of QCD at high temperature

Aoki, Shinya*; Aoki, Yasumichi*; Fukaya, Hidenori*; Hashimoto, Shoji*; Rohrhofer, C.*; Suzuki, Kei

Progress of Theoretical and Experimental Physics (Internet), 2022(2), p.023B05_1 - 023B05_12, 2022/02

https://doi.org/10.1093/ptep/ptac001

The chiral susceptibility, or the first derivative of the chiral condensate with respect to the quark mass, is often used as a probe for the QCD phase transition since the chiral condensate is an order parameter of symmetry breaking. However, the chiral condensate also breaks the axial symmetry, which is usually not studied as it is already broken by the anomaly and apparently has little impact on the transition. We investigate the susceptibilities in the scalar and pseudoscalar channels in order to quantify how much the axial breaking contributes to the chiral phase transition. Employing a chirally symmetric lattice Dirac operator and its eigenmode decomposition, we separate the axial breaking effects from others. Our result in two-flavor QCD indicates that both of the connected and disconnected chiral susceptibilities are dominated by axial breaking at temperatures MeV after the quadratically divergent constant is subtracted.

High temperature gas-cooled reactors

Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

https://doi.org/10.1016/C2018-0-05383-9

As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.

Symmetries of the light hadron spectrum in high temperature QCD

Rohrhofer, C.*; Aoki, Yasumichi*; Cossu, G.*; Fukaya, Hidenori*; Gattringer, C.*; Glozman, L. Ya.*; Hashimoto, Shoji*; Lang, C. B.*; Suzuki, Kei

Proceedings of Science (Internet), 363, p.227_1 - 227_7, 2020/08

https://doi.org/10.22323/1.363.0227

Properties of QCD matter change significantly around the chiral crossover temperature, and the effects on and topological susceptibilities, as well as the meson spectrum have been studied with much care. Baryons and the effect of parity doubling in this temperature range have been analyzed previously by various other groups employing different setups. Here we construct suitable operators to investigate chiral and axial symmetries in the baryon spectrum. Measurements for different volumes and quark-masses are done with two flavors of chirally symmetric domain-wall fermions at temperatures above the critical one. The possibility of emergent and symmetries is discussed.

True Boundary for the formation of homoleptic transition-metal hydride complexes

Takagi, Shigeyuki*; Iijima, Yuki*; Sato, Toyoto*; Saito, Hiroyuki; Ikeda, Kazutaka*; Otomo, Toshiya*; Miwa, Kazutoshi*; Ikeshoji, Tamio*; Aoki, Katsutoshi*; Orimo, Shinichi*

Angewandte Chemie; International Edition, 54(19), p.5650 - 5653, 2015/05

https://doi.org/10.1002/anie.201500792

Density-functional study of perovskite-type hydride LiNiH and its synthesis; Mechanism for formation of metallic perovskite

Takagi, Shigeyuki*; Saito, Hiroyuki; Endo, Naruki; Sato, Ryutaro*; Ikeshoji, Tamio*; Matsuo, Motoaki*; Miwa, Kazutoshi*; Aoki, Katsutoshi; Orimo, Shinichi*

Physical Review B, 87(12), p.125134_1 - 125134_6, 2013/03

https://doi.org/10.1103/PhysRevB.87.125134

Identified charged hadron production in collisions at = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

https://doi.org/10.1103/PhysRevC.83.064903

Transverse momentum distributions and yields for , and in collisions at = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different collisions. We also present the scaling properties such as and scaling and discuss the mechanism of the particle production in collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

Measurement of neutral mesons in + collisions at = 200 GeV and scaling properties of hadron production

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03

https://doi.org/10.1103/PhysRevD.83.052004

The PHENIX experiment at RHIC has measured the invariant differential cross section for production of , , and mesons in collisions at = 200 GeV. The spectral shapes of all hadron transverse momentum distributions are well described by a Tsallis distribution functional form with only two parameters, and , determining the high and characterizing the low regions for the spectra, respectively. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.

Effect of the heat treatment conditions onto characteristics of Chromium-Zirconium Copper

Aoki, Shoji*; Wada, Masahiko*; Yamaji, Tetsuo*; Mori, Kensuke; Enoeda, Mikio; Hirose, Takanori; Suzuki, Kazuhiko

Do To Dogokin, 45(1), p.125 - 130, 2006/08

Chromium-zirconium copper (Cu-Cr-Zr) as precipitation hardened copper alloy is examined as one of the structural materials used for the ITER in vacuum vessel components (blanket and divertor etc.). The precipitation hardening in Cu-Cr-Zr is made by the solution treatment with rapid cooling to obtain the supersaturated solid solution of chromium and zirconium in copper, and the subsequent aging treatment to grow the refined precipitate consists of chromium and zirconium respectively. While the parts have been assembled and used by copper alloys already precipitation hardened in general use, the blanket parts will be done by the innovative method with the thermomechanical treatment set of the precipitation hardening at the same time as dissimilar material junction in the ITER blanket. In this research, the mechanical and electrical conductivity properties change was investigated under the wide range of thermomechanical treartment conditions in order to comprehend the conditions necessary to fulfill the excellent characteristics in Cu-Cr-Zr. Therefore, the influence of the quenching cooling rate condition after solution treatment and the other conditions on Cu-Cr-Zr was inspected by measuring electrical conductivity as the indication of the solution treatment state i.e. the supersaturated solid solution or the precipitation state and measuring the tensile test properties of the specimens that are prepared by the set of the solution treatments with some quenching cooling rate conditions and following aging treatments.

Desulfurization reaction of high sulfur content flue gas treated by electron beam

Hirosawa, Shojiro*; Kojima, Takuji; Hashimoto, Shoji; Suzuki, Ryoji*; Aoki, Shinji*

Radioisotopes, 51(8), p.285 - 295, 2002/08

https://doi.org/10.3769/radioisotopes.51.285

Experiments of flue gas treatment by electron beam were carried out, using simulated lignite-burning flue gas containing SO(5500ppm), NO(390ppm) and HO(22%). Removal efficiency of SO was more than 90% at a dose of 1-2kGy. It shows applicability of electron beam for treatment of lignite-burning flue gas. Another removal reaction besides the radiation-induced radical reaction and the thermal reaction occurring without irradiation was suggested by the facts that removal of SO by the radical reaction is only a few hundreds of ppm and the removal amounts by thermal reaction under irradiation is lower than a half of total desulfurization. The mechanism similar to thermal reaction was proposed, assuming simultaneous uptake reaction of SO and NH on the surface of liquid aerosol. It was suggested that ammonium nitrate having deliquescence relative humidity(DRH) of 60% at 25 plays an important role in producing liquid aerosols. Decrease of DRH of ammonium nitrate with increasing temperature and with formation of double salt of ammonium sulfate results in enhancement of formation of liquid aerosols.