Beam test of a BSO calorimeter

title: Photoproduction of η-mesons off C and Cu nuclei for photon energies below 1.1 GeV
abstract: The η -meson photoproduction cross sections have been measured on C and Cu targets for the photon energies between 600 and 1100 MeV to investigate the behavior of the S 11 ( 1535 ) resonance in a nucleus. The excitation functions of the cross section as well as the angular and momentum distributions of η -mesons are in quantitative agreement with the Quantum Molecular Dynamics (QMD) model calculations in which the η -meson emission processes other than the S 11 ( 1535 ) resonance are also incorporated. It is shown that the η production in the γ N → π η N reaction and the D 15 ( 1675 ) resonance formation in the γ n → η n reaction play an important role for E γ > 900 MeV .

title: The 1.2 GeV photon tagging system at LNS-Tohoku
abstract: A tagged photon beam line has been constructed in the Stretcher–Booster ring (STB ring) at Tohoku University. The quasi-monochromatic photon beam is produced by the internal photon tagging system which consists of a solid fiber radiator and the compact tagging counter installed in a bending magnet of the STB ring. The energy range of the tagged photon is from 0.8 to 1.1 GeV with the electron energy of 1.2 GeV . The performance of the tagging system has been investigated. The system provides good quality of γ -rays for the nuclear and hadron physics experiments.

title: First beam test on a BSO electromagnetic calorimeter
abstract: A beam test has been performed on a prototype electromagnetic calorimeter of bismuth silicate BSO crystals for the first time using electrons of 0.5–3.0 GeV. The calorimeter consists of nine BSO crystals, 22 mm × 22 mm × 180 mm (15.6 radiation lengths), arranged in a 3 × 3 array. Each crystal is coupled to a small photomultiplier tube of 20 mm in diameter. The obtained energy resolution is σ E / E = ( 0.023 ± 0.003 ) / E ( GeV ) ⊕ ( 0.017 ± 0.002 ) for incident electrons of the energy E in GeV. The position information for an electron injected onto the center crystal of the calorimeter array is given with energy deposit signals from nine BSO crystals. The RMS position resolution σ x is parameterized as σ x = [ ( 3.2 ± 0.1 ) / E ( GeV ) ⊕ ( 1.3 ± 0.1 ) ] mm at the center of the crystal. Misidentification probability of pions to electrons is found to be ∼ 10 - 3 for the pion momentum ranging from 1.0 to 3.0 GeV/ c .

title: K0 photoproduction on 12C in the threshold region
abstract: The γ n → K 0 Λ process plays an important role in the study of strangeness production by the electromagnetic interaction. We have investigated the quasi-free production reaction on a 12 C target in the threshold region ( E γ = 0.8 – 1.1 GeV ) at the Laboratory of Nuclear Science, Tohoku University. Preliminary results are presented.

title: Photoproduction of neutral kaons on a liquid deuterium target in the threshold region
abstract: The photoproduction process of neutral kaons on a liquid deuterium target is investigated near the threshold region, E{sub {gamma}}=0.8-1.1 GeV. K{sup 0} events are reconstructed from positive and negative pions, and differential cross sections are derived. Experimental momentum spectra are compared with those calculated in the spectator model using a realistic deuteron wave function. Elementary amplitudes as given by recent isobar models and a simple phenomenological model are used to study the effect of the new data on the angular behavior of the elementary cross section. The data favor a backward-peaked angular distribution of the elementary n({gamma},K{sup 0}){lambda} process, which provides additional constraints on current models of kaon photoproduction. The present study demonstrates that the n({gamma},K{sup 0}){lambda} reaction can provide key information on the mechanism of the photoproduction of strangeness.

title: Radiative corrections to pi - e decay
abstract: An attempt is made to understand the reason why the radiative corrections to The effects of -e decay calculated by Berman are so large. The question is also discussed as to whether the pion decay agrees with the recently conjectured ''theorem'' that the radiative correction to the total probability of a decay process is finite in the limit where the mass of the secondary electron is assumed to be arbitrarily small, although corrections to partial probabilities may be divergent in such a limit.

title: High Precision Tests of Quantum Electrodynamics—An Overview

title: QED Contributions to Muon g−2: Tenth-order graphs
abstract: The QED contribution to muon g − 2 is known with sufficient precision for the current uncertainty of the muon g − 2 experiment. More accurate QED prediction, however, may be needed for the future experiment. We review the current status of QED contribution to muon g − 2 and report our on-going project about the tenth-order calculation.

title: Dominant colliding beam cross-sections at high-energies
abstract: We report on our calculation of the energy and angular dependence of the cross sections for the production of various particles by two-photon annihilation processes in ${e}^{+}{e}^{\ensuremath{-}}$ and ${e}^{\ensuremath{-}}{e}^{\ensuremath{-}}$ colliding beams. For beam energy $E$ of more than 1 GeV, these cross sections [$\ensuremath{\sigma}\ensuremath{\propto}{\ensuremath{\alpha}}^{4}{(\mathrm{ln}E)}^{3}$] become increasingly more important than the usual one-photon cross sections [$\ensuremath{\sigma}\ensuremath{\propto}{\ensuremath{\alpha}}^{2}{(E)}^{\ensuremath{-}2}$] for hadron production.

title: The two-photon process for particle production in colliding beam experiments
abstract: Cross sections for particle production by the two-photon process for the reactions ee→ee X with X = π 0 or η and X = π + π − or π + π − are calculated exactly by numerical techniques and are compared with predictions of the double equivalent photon approximation (DEPA). Implications of these results as to the validity of the DEPA are discussed and an attempt is made to summarize and clarify some of the earlier criticisms of this approximation.