VIOLATION OF THE POMERANCHUK THEOREM AND ZEROS OF THE SCATTERING AMPLITUDES.

title: Eighth-order magnetic moment of the electron. III. Sixth-order vertices containing a second-order vacuum polarization subdiagram
abstract: We have calculated the contribution to the eighth-order anomalous magnetic moment of the electron arising from 150 Feynman diagrams, each generated by inserting a second-order vacuum polarization loop in the photon lines of sixth-order vertices of the three-photon-exchange type. Our result is 1.419(16)(..cap alpha../..pi..)/sup 4/. The theoretical error represents the estimated accuracy (90% confidence limit) of the required numerical integrations.

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: Forward Scattering Amplitude and Univalent Functions
abstract: Starting with the relativistic crossing-symmetric forward scattering amplitude, we constructed previously a function $g(E)$ of energy $E$ which is both analytic and univalent (schlicht) in the upper-half energy plane. In this paper we exploit the univalence of $g(E)$ to obtain information on the analytic properties of the forward-scattering amplitude. Various inequalities satisfied by $g(E)$ are derived, making use of powerful theorems on univalent functions. In particular, we have established several theorems which relate the asymptotic behavior of the phase of $g(E)$ to that of $|g(E)|$ itself. We have also obtained several inequalities for $g(E)$ which may be useful in an experimental test of the consequences of local field theory. We start with only those properties of the forward scattering amplitude that have already been proved in axiomatic local field theory. The only extra assumption used that has not yet been proved in field theory is the physical assumption that the forward scattering amplitude does not become relatively real in the high-energy limit.

title: Eighth-order magnetic moment of the electron. IV. Vertex diagrams containing photon-photon scattering subdiagrams.
abstract: We have evaluated the contribution to the eighth-order term of the anomalous magnetic moment of the electron arising from a class of 144 vertex diagrams all of which contain a photon- photon scattering subdiagram with various further radiative corrections. Our result is (-0.473 +- 0.015)(..cap alpha../..pi..)/sup 4/. The theoretical error represents the estimated accuracy (90% confidence limit) of the required numerical integration. This result is obtained from approximately 6000 CPU hours of computation on various large-scale (scalar and vector) computers and replaces our earlier preliminary result for this group of diagrams.

title: Theory of Lepton g – 2: Improvement of QED Terms
abstract: This paper reports the current status of evaluation of QED terms of lepton g – 2. All terms of order α 4 contributing to a μ − a e have been evaluated by at least two independent methods. Leading terms of order α 5 contributing to a μ have been evaluated.

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: Narrow resonance at E(gamma) = 1020-MeV in the d (gamma, eta) p n reaction
abstract: Differential and total cross sections of the D(γ, η)pn reaction have been measured for photon energies between 600 and 1150 MeV. The data provide the information of the γn → ηn reaction above Eγ ≥ 800 MeV. The total cross section shows a narrow resonance structure peaked at Eγ = 1020 MeV. The angular distribution coefficients together with the total cross section are compared with the calculation of the isobar model by using the impulse approximation. Although the spin and parity of the resonance cannot be determined unambiguously, a negative parity assignment gives better fit to the data.

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: 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: 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.