Electron Identification in Belle

We report on electron identification methods and their performance in the Belle experiment at the KEK-B asymmetric B-Factory $e^{+} e^{-}$ storage ring. Electrons are selected using a likelihood approach that takes information from the electromagnetic calorimeter, the central drift chamber, and the silica aerogel Cherenkov counters as input. We achieve an electron identification efficiency of $(92.4 \pm 0.4)$ with a $\pi^{\pm}$ fake rate of $(0.25 \pm 0.02)$ for the momentum range between 1.0 GeV/$c$ and 3.0 GeV/$c$ in laboratory frame.Comment: 20 page

Spin and spin-spin correlations in chargino pair production at future linear e+e- colliders

A possibility to measure the spin and spin-spin correlations of a chargino pair is investigated in the process electron positron -> chargino_1 anti-chargino_1 -> (neutralino_1 quark anti-quark) (neutralino_1 quark anti-quark) at future linear-collider energies. The total and the differential cross sections are calculated by the GRACE system which allows for the full spin correlation. Experimental sensitivity of the measurements are examined by assuming the limited detector resolution, the initial state radiation and the beam-beam effect (beamstrahlung). It is found that generally the spin-spin correlation can only be measured with a lower sensitivity than the chargino spin itself. The dependence of the correlation measurements on the relevant SUSY parameters can be seen for a light sneutrino case, but the situation becomes worse for a heavier sneutrino.Comment: 23 pages, 7 figures, 6 tables; added reference for section

First-principles study on atomic configuration of electron-beam irradiated C60 film

Density functional calculations of the atomic configuration of electron-beam irradiated C-60 thin films were implemented. By examining the electronic structure and electron-transport properties of C-60 clusters, we found that a rhombohedral C-60 polymer with sp(3)-bonded dumbbell-shaped connections at the molecule junction is a semiconductor with a narrow band gap. In addition, the polymer changes to exhibit metallic behavior by forming sp(2)-bonded peanut-shaped connections. Conductance below the Fermi level increases and the peak of the conductance spectrum arising from the t(u1) states of the C-60 molecule becomes obscure after the connections are rearranged. The present rhombohedral polymer, including the [2 + 2] four-membered rings and peanut-shaped connections, is a candidate for representing the structure of the metallic C-60 polymer at the initial stage of electron-beam irradiation

Formation of Protoplanets from Massive Planetesimals in Binary Systems

More than half of stars reside in binary or multiple star systems and many planets have been found in binary systems. From theoretical point of view, however, whether or not the planetary formation proceeds in a binary system is a very complex problem, because secular perturbation from the companion star can easily stir up the eccentricity of the planetesimals and cause high-velocity, destructive collisions between planetesimals. Early stage of planetary formation process in binary systems has been studied by restricted three-body approach with gas drag and it is commonly accepted that accretion of planetesimals can proceed due to orbital phasing by gas drag. However, the gas drag becomes less effective as the planetesimals become massive. Therefore it is still uncertain whether the collision velocity remains small and planetary accretion can proceed, once the planetesimals become massive. We performed {\it N}-body simulations of planetary formation in binary systems starting from massive planetesimals whose size is about 100-500 km. We found that the eccentricity vectors of planetesimals quickly converge to the forced eccentricity due to the coupling of the perturbation of the companion and the mutual interaction of planetesimals if the initial disk model is sufficiently wide in radial distribution. This convergence decreases the collision velocity and as a result accretion can proceed much in the same way as in isolated systems. The basic processes of the planetary formation, such as runaway growth and oligarchic growth and final configuration of the protoplanets are essentially the same in binary systems and single star systems, at least in the late stage where the effect of gas drag is small.Comment: 26pages, 11 figures. ApJ accepte

Uniqueness of static spherically symmetric vacuum solutions in the IR limit of Ho\v{r}ava-Lifshitz gravity

We investigate static spherically symmetric vacuum solutions in the IR limit of projectable nonrelativistic quantum gravity, including the renormalisable quantum gravity recently proposed by Ho\v{r}ava. It is found that the projectability condition plays an important role. Without the cosmological constant, the spacetime is uniquely given by the Schwarzschild solution. With the cosmological constant, the spacetime is uniquely given by the Kottler (Schwarzschild-(anti) de Sitter) solution for the entirely vacuum spacetime. However, in addition to the Kottler solution, the static spherical and hyperbolic universes are uniquely admissible for the locally empty region, for the positive and negative cosmological constants, respectively, if its nonvanishing contribution to the global Hamiltonian constraint can be compensated by that from the nonempty or nonstatic region. This implies that static spherically symmetric entirely vacuum solutions would not admit the freedom to reproduce the observed flat rotation curves of galaxies. On the other hand, the result for locally empty regions implies that the IR limit of nonrelativistic quantum gravity theories does not simply recover general relativity but includes it.Comment: 10 pages, accepted for publication in International Journal of Modern Physics

Energy Loss Function and Source Function for Au 4f Photoelectrons Derived by Monte Carlo Analysis of Reflection Electron Energy Loss Spectroscopy (REELS) and X-Ray Photoelectron Spectroscopy (XPS) Spectra

We have derived the energy loss function of Au for 1 keV electrons by Monte Carlo analysis of the reflection electron energy loss spectroscopy (REELS) spectra. This energy loss function was significantly different from the optical loss function widely used and has revealed that the surface excitation affects the energy loss spectrum of keV electrons. X-ray photoelectron spectroscopy (XPS) background subtraction has been recently developed by using the energy loss function derived from the transmission electron energy loss spectroscopy (TEELS). We have demonstrated that the energy loss function derived from REELS has enabled a more accurate Au 4f XPS spectrum to be obtained after subtraction of the inelastic background