A feasibility study of the measurement of Higgs pair creation at a Photon Linear Collider

We studied the feasibility of the measurement of Higgs pair creation at a Photon Linear Collider (PLC). From the sensitivity to the anomalous self-coupling of the Higgs boson, the optimum $\gamma \gamma$ collision energy was found to be around 270 GeV for a Higgs mass of 120 GeV/$c^2$. We found that large backgrounds such as $\gamma \gamma \rightarrow W^+W^-, ZZ,$ and $b\bar{b}b\bar{b}$, can be suppressed if correct assignment of tracks to parent partons is achieved and Higgs pair events can be observed with a statistical significance of $\sim 5 \sigma$ by operating the PLC for 5 years.Comment: 7 pages, 8 figures, 5 table

Distinct cellular pathways select germline-encoded and somatically mutated antibodies into immunological memory

One component of memory in the antibody system is long-lived memory B cells selected for the expression of somatically mutated, high-affinity antibodies in the T cell–dependent germinal center (GC) reaction. A puzzling observation has been that the memory B cell compartment also contains cells expressing unmutated, low-affinity antibodies. Using conditional Bcl6 ablation, we demonstrate that these cells are generated through proliferative expansion early after immunization in a T cell–dependent but GC-independent manner. They soon become resting and long-lived and display a novel distinct gene expression signature which distinguishes memory B cells from other classes of B cells. GC-independent memory B cells are later joined by somatically mutated GC descendants at roughly equal proportions and these two types of memory cells efficiently generate adoptive secondary antibody responses. Deletion of T follicular helper (Tfh) cells significantly reduces the generation of mutated, but not unmutated, memory cells early on in the response. Thus, B cell memory is generated along two fundamentally distinct cellular differentiation pathways. One pathway is dedicated to the generation of high-affinity somatic antibody mutants, whereas the other preserves germ line antibody specificities and may prepare the organism for rapid responses to antigenic variants of the invading pathogen

Fundamental study on functionality of synthetic sulfides : Evaluation of metal sulfides as solid lubricant

Replacement of exhaustible and harmful resources used as solid lubricants is required for sliding elements such asplain bearings. In particular, the substitution of lead containing in the lead bronze is considered an urgent task. Therefore, in this study, attention was focused on metal sulfides (Cu2S, Cu5FeS4, SnS, TiS2, etc) as a substitute material for lead. After synthesis of sulfide and preparation of sintered body, friction and abrasion test was carried out and applicability as solid lubricant was investigated. The tribological properties of the dry conditions were evaluated by a journal type high speed tester. As a result, the friction coefficient of the bronze specimen without sulfide was about 0.3, whereas the bronze specimen containing sulfide showed a friction coefficient of about 0.1, indicating that the sulfide reducedthe frictional resistance. Among them, the specimens containing Cu2S and Cu5FeS4 exhibited a lower friction coefficient. It is considered that this is influenced not onlyby the effect of hardness but also by film formation by sulfide

MOLECULAR DYNAMICS SIMULATION OF LI-ION COORDINATION STRUCTURE AND TRANSPORT PROPERTIES IN LIB ELECTROLYTES: INFLUENCE OF MOLECULAR SIZE

Lithium-ion batteries (LIBs) are currently attracting much attention because electric vehicles and large storage batteries are becoming widespread. For lightweight and efficient usability, LIB performance for safety, capacity, charge/discharge cycle characteristics, and electric current must be improved. Development of high performance LIB relies mostly on progress of materials used for electrolytes and electrodes. In particular, electrolytes are an important factor because they play a role in carrying charged substances, i.e. ions, between separated electrodes. The ion-carrying performance depends on the choice of electrolyte, and thus, in this study, we discuss the relationship between the geometric shape of molecules used as electrolytes and their physical properties, using molecular dynamics (MD) simulations. We showed that, as the smaller solvent is used, ionic conductivity of the system is further enhanced. MD simulations showed that there are two main reasons for this behavior. First, a smaller radius allows the solvent molecule to diffuse easily. Consequently, when solvent molecules frequently surround a lithium ion, and the diffusion coefficient of the lithium ion becomes larger. Second, because small solvent molecules naturally come close to ions, salt (composed of cations and anions) is forced to be dissociated because of the solvent molecules, and the degree of salt dissociation increases

On the thermal sunset diagram for scalar field theories

We study the so-called `` sunset diagram'', which is one of two-loop self-energy diagrams, for scalar field theories at finite temperature. For this purpose, we first find the complete expression of the bubble diagram, the one-loop subdiagram of the sunset diagram, for arbitrary momentum. We calculate the temperature independent part and dependent part of the sunset diagram separately. For the former, we obtain the discontinuous part first and the finite continuous part next using a twice-subtracted dispersion relation. For the latter, we express it as a one-dimensional integral in terms of the bubble diagram. We also study the structure of the discontinuous part of the sunset diagram. Physical processes, which are responsible for it, are identified. Processes due to the scattering with particles in the heat bath exist only at finite temperature and generate discontinuity for arbitrary momentum, which is a remarkable feature of the two-loop diagrams at finite temperature. As an application of our result, we study the effect of the diagram on the spectral function of the sigma meson at finite temperature in the linear sigma model, which was obtained at one-loop order previously. At high temperature where the decay $\sigma\to\pi\pi$ is forbidden, sigma acquires a finite width of the order of $10 {\rm MeV}$ while within the one-loop calculation its width vanishes. At low temperature, the spectrum does not deviate much from that at one-loop order. Possible consequences with including other two-loop diagrams are discussed.Comment: 30 page

Synthesis and Functional Evaluation of Sulfides : Application of Solid Lubricant and Thermoelectric Material

Sufides as MoS2 are known as solid lubricants. These materials are also known as thermoelectric materials. However, there is no material satisfying both functions at the same time. In this study, sulfides powders such as Cu2S (chalcocite), TiS2, SnS, Cu5FeS4 (bornite) were synthesized under vacuum condition. Some specimens of sintered sulfides were evaluated by friction tester and their lubricity. As a result it was found that SnS had indicated better friction properties. Other specimens were evaluated in terms of Seebeck coefficients, which is one of the thermoelectric properties. Experimental results of the Seebeck coefficients were compared with simulation results. For thermoelectric properties, the　Seebeck coefficient of Cu2S had matched with experiments and simulation. Totally, Cu2S (chalcocite) and SnS has superior properties both, as solid lubricant as well as thermoelectric material.This is a product of research which was financially supported in part by the Kansai University Subsidy for Supporting Young Scholars, 2016 – \u27Study on sulfide synthesis of superior solid lubricity and thermoelectric properties\u2