Tenth-order QED contribution to the lepton anomalous magnetic moment: Sixth-order vertices containing an internal light-by-light-scattering subdiagram
This paper reports the tenth-order QED contribution to the lepton g-2 from the gauge-invariant set, called Set III(c), which consists of 390 Feynman vertex diagrams containing an internal fourth-order light-by-light-scattering subdiagram. The mass-independent contribution of Set III(c) to the electron g-2 (a_e) is 4.9210(103) in units of (alpha/pi)^5. The mass-dependent contributions to a_e from diagrams containing a muon loop is 0.00370(37) (alpha/pi)^5. The tau-lepton loop contribution is negligible at present. Altogether the contribution of Set III(c) to a_e is 4.9247 (104) (alpha/pi)^5. We have also evaluated the contribution of the closed electron loop to the muon g-2 (a_mu). The result is 7.435(134) (alpha/pi)^5. The contribution of the tau-lepton loop to a_mu is 0.1999(28)(alpha/pi)^5. The total contribution of variousleptonic loops (electron, muon, and tau-lepton) of Set III(c) to a_mu is 12.556 (135) (alpha/pi)^5.

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

title: Complete tenth-order QED contribution to the muon g-2.
abstract: We report the result of our calculation of the complete tenth-order QED terms of the muon g-2. Our result is a(μ)((10))=753.29 (1.04) in units of (α/π)(5), which is about 4.5 s.d. larger than the leading-logarithmic estimate 663(20). We also improve the precision of the eighth-order QED term of a(μ), obtaining a(μ)((8))=130.8794 (63) in units of (α/π)(4). The new QED contribution is a(μ)(QED)=116,584,718,951 (80)×10(-14), which does not resolve the existing discrepancy between the standard-model prediction and measurement of a(μ).

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: Polarization of Electrons in Muon Decay with General Parity-Nonconserving Interactions
abstract: The polarization of electrons in muon decay is studied in the case of the four-component neutrino theory with general parity-nonconserving interactions. The spectrum for each of the two states of longitudinal polarization is described by a set of three parameters of which only two are independent By observing the electron polarization in arbitrary directions, one can determine ten parameters of which six are related to the two longitudinal polarizations and the rest to the transverse part. It is seen that the prediction of the two-component neutrino theory about the electron polarization in muon decay is quite specific and can be distinguished from that of the general case, if the latter involves the interactionB of the S, T, P types in charge-retention order. However, from the study of the polarization of electrons, it is impossible to distinguish the two-component theory from the four-component theory which involves only the vectortype interactions. It is noticed that the TCP theorem determines a detailed correspondence between the polarization provides us with an opportunity to determine experimentally whether weak interactions actually obey the TCP theorem or not.

title: Automated calculation scheme for alpha**n contributions of QED to lepton g-2: Generating renormalized amplitudes for diagrams without lepton loops
abstract: Among 12 672 Feynman diagrams contributing to the electron anomalous magnetic moment at the tenth order, 6354 are the diagrams having no lepton loops, i.e., those of quenched type. Because the renormalization structure of these diagrams is very complicated, some automation scheme is inevitable to calculate them. We developed an algorithm to write down FORTRAN programs for numerical evaluation of these diagrams, where the necessary counterterms to subtract out ultraviolet subdivergence are generated according to Zimmermann's forest formula. Thus far we have evaluated crudely integrals of 2232 tenth-order vertex diagrams which require vertex renormalization only. Remaining 4122 diagrams, which have ultraviolet-divergent self-energy subdiagrams and infrared-divergent subdiagrams, are being evaluated by giving small mass λ to photons to control the infrared problem.

title: S11(1535) Resonance in Nuclear Medium Observed with the (gamma, eta) Reactions

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.

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: Photoproduction of neutral kaons at LNS