Waseda University

About: Waseda University is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Large Hadron Collider & Catalysis. The organization has 24220 authors who have published 46859 publications receiving 837855 citations. The organization is also known as: Waseda daigaku & Sōdai.

Measurement of the W-boson mass in pp collisions at s=7TeV with the ATLAS detector.

Abstract: A measurement of the mass of the $W$ boson is presented based on proton-proton collision data recorded in 2011 at a centre-of-mass energy of 7 TeV with the ATLAS detector at the LHC, and corresponding to 4.6 fb$^{-1}$ of integrated luminosity. The selected data sample consists of $7.8 \times 10^6$ candidates in the $W\rightarrow \mu u$ channel and $5.9 \times 10^6$ candidates in the $W\rightarrow e u$ channel. The $W$-boson mass is obtained from template fits to the reconstructed distributions of the charged lepton transverse momentum and of the $W$ boson transverse mass in the electron and muon decay channels, yielding \begin{eqnarray} m_W &=& 80370 \pm 7 \, (\textrm{stat.}) \pm 11 \, (\textrm{exp. syst.}) \pm 14 \, (\textrm{mod. syst.}) \, \textrm{MeV} &=& 80370 \pm 19 \, \textrm{MeV}, \end{eqnarray} where the first uncertainty is statistical, the second corresponds to the experimental systematic uncertainty, and the third to the physics-modelling systematic uncertainty. A measurement of the mass difference between the $W^+$ and $W^-$ bosons yields $m_{W^+}-m_{W^-} = -29 \pm 28$ MeV.

Ferroelectric Behavior in the Copolymer of Vinylidenefluoride and Trifluoroethylene

Abstract: The linear and nonlinear dielectrical and depolarization processes of the copolymer of vinylidene fluoride and trifluoroethylene have been measured. The D vs. E hysteresis loop below room temperature indicates the ferroelectricity of this copolymer. The dielectric anomaly and the disappearance of remnant polarization at T0=70°C suggest that T0 is the phase transition temperature from the ferroelectricity to the paraelectricity phase. Results are analyzed on the basis of Weiss-type semimolecular theory.

Improvement of low energy atmospheric neutrino flux calculation using the JAM nuclear interaction model

Abstract: We present the calculation of the atmospheric neutrino fluxes with an interaction model named JAM, which is used in PHITS (Particle and Heavy-Ion Transport code System) [K. Niita et al., Radiation Measurements 41, 1080 (2006).]. The JAM interaction model agrees with the HARP experiment [H. Collaboration, Astropart. Phys. 30, 124 (2008).] a little better than DPMJET-III [S. Roesler, R. Engel, and J. Ranft, arXiv:hep-ph/0012252.]. After some modifications, it reproduces the muon flux below $1\text{ }\text{ }\mathrm{GeV}/c$ at balloon altitudes better than the modified DPMJET-III, which we used for the calculation of atmospheric neutrino flux in previous works [T. Sanuki, M. Honda, T. Kajita, K. Kasahara, and S. Midorikawa, Phys. Rev. D 75, 043005 (2007).][M. Honda, T. Kajita, K. Kasahara, S. Midorikawa, and T. Sanuki, Phys. Rev. D 75, 043006 (2007).]. Some improvements in the calculation of atmospheric neutrino flux are also reported.

Global stability of the rarefaction wave of a one-dimensional model system for compressible viscous gas

Abstract: This paper is concerned with the asymptotic behavior toward the rarefaction wave of the solution of a one-dimensional barotropic model system for compressible viscous gas. We assume that the initial data tend to constant states atx=±∞, respectively, and the Riemann problem for the corresponding hyperbolic system admits a weak continuous rarefaction wave. If the adiabatic constant γ satisfies 1≦γ≦2, then the solution is proved to tend to the rarefaction wave ast→∞ under no smallness conditions of both the difference of asymptotic values atx=±∞ and the initial data. The proof is given by an elementaryL 2-energy method.

Discovery of high-energy gamma-ray emission from the binary system PSR B1259–63/LS 2883 around periastron with Fermi

Abstract: We report on the discovery of 100 MeV γ -rays from the binary system PSR B1259−63/LS 2883 using the Large Area Telescope (LAT) on board Fermi. The system comprises a radio pulsar in orbit around a Be star. We report on LAT observations from near apastron to ∼128 days after the time of periastron, tp, on 2010 December 15. No γ -ray emission was detected from this source when it was far from periastron. Faint γ -ray emission appeared as the pulsar approached periastron. At ∼tp + 30 days, the 100 MeV γ -ray flux increased over a period of a few days to a peak flux 20-30 times that seen during the pre-periastron period, but with a softer spectrum. For the following month, it was seen to be variable on daily timescales, but remained at ∼(1-4) × 10−6 cm−2 s−1 before starting to fade at ∼tp +57 days. The total γ -ray luminosity observed during this period is comparable to the spin-down power of the pulsar. Simultaneous radio and X-ray observations of the source showed no corresponding dramatic changes in radio and X-ray flux between the pre-periastron and post-periastron flares. We discuss possible explanations for the observed γ -ray-only flaring of the source.