QED Contributions to Muon g−2: Tenth-order graphs
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: 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: 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: Improved Theory of the Muon Anomalous Magnetic Moment
abstract: A new theoretical value a/sub ..mu../ = 11 659 202(20) x 10/sup -10/ is reported for the muon anomalous moment, based on the first complete calculation of the ..cap alpha../sup 4/ QED term and improvements of the ..cap alpha../sup 3/ QED term and various hadronic contributions. The remaining error is mostly due to the experimental inputs needed for evaluation of the hadronic vacuum polarization effect. Further improvement of this error seems possible. Thus the electroweak theory may be tested at the one-loop level if measurement of a/sub ..mu../ is improved by an order of magnitude.

title: Proper Eighth-Order Vacuum-Polarization Function and its Contribution to the Tenth-Order Lepton g-2
abstract: This paper reports the Feynman-parametric representation of the vacuum-polarization function consisting of 105 Feynman diagrams of the eighth order, and its contribution to the gauge-invariant set called Set I(i) of the tenth-order lepton anomalous magnetic moment. Numerical evaluation of this set is carried out using FORTRAN codes generated by an automatic code generation system gencodevpN developed specifically for this purpose. The contribution of diagrams containing an electron loop to the electron g-2 is 0.017 47 . The contribution of diagrams containing a muon loop is 0.000 001 67 (3)({alpha}/{pi}){sup 5}. The contribution of a tau-lepton loop is negligible at present. The sum of all these terms is 0.017 47 . The contribution of diagrams containing an electron loop to the muon g-2 is 0.0871 (59)({alpha}/{pi}){sup 5}. This is to be compared with the unpublished asymptotic analytic result (0.252 37+O(m{sub e}/m{sub {mu}}))({alpha}/{pi}){sup 5}. The contribution of a tau-lepton loop to a{sub {mu}} is 0.000 237 (1)({alpha}/{pi}){sup 5}. The total contribution to a{sub {mu}}, the sum of these terms and the mass-independent term, is 0.1048 (59)({alpha}/{pi}){sup 5}.

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: 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: NEUTRAL KAON PHOTOPRODUCTION AT LNS, TOHOKU UNIVERSITY
abstract: The elementary photo-strangeness production process has been intensively studied based on the high-quality data of the charged kaon channel, γ + p → K+ + Λ(Σ0). However, there had been no reliable data for the neutral kaon channel γ + n → K0 + Λ(Σ0) and the theoretical investigations suffer seriously from the lack of the data. In order to have reliable data for the neutral kaon photo-production data, substantial effort has been made to measure the γ + n → K0 + Λ process in the π+π- decay channel, using a liquid deuterium target and a tagged photon beam (Eγ = 0.8-1.1 GeV) in the threshold region at the Laboratory of Nuclear Science (LNS), Tohoku University. We have taken exploratory data quite successfully with the use of Neutral Kaon Spectrometer (NKS) at LNS-Tohoku in 2003 and 2004. The data is compared to theoretical models and it indicates a hint that the K0 differential cross section has a backward peak in the energy region. The second generation of the experiment, NKS2, is designed to extend the NKS experiment by considerably upgrading the original neutral kaon spectrometer, fully replacing the spectrometer magnet, tracking detectors and all the trigger counters. The new spectrometer NKS2 has significantly larger acceptance for neutral kaons compared with NKS, particularly covering forward angles and much better invariant mass resolution. The estimated acceptance of NKS2 is three (ten) times larger for than that of NKS. The spectrometer is newly constructed and installed at the Laboratory of Nuclear Science, Tohoku University in 2005. The deuterium target data was taken with tagged photon beam in 2006-2007. We will report recent results of NKS2 in this paper. Additionally, a status of the upgrade project that gives us larger acceptance and capability of K0 + Λ coincidence measurement will be presented.

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: Study of double pion photoproduction on the deuteron
abstract: The π + π − photoproductions on the proton and deuteron have been studied in a photon energy range of 0.8–1.1 GeV at the Laboratory of Nuclear Science, Tohoku University. Charged pions and protons were detected using Neutral Kaon Spectrometer. We obtained the cross sections for the p ( γ , p π + π − ) and d ( γ , p π + π − ) n . The quasi-free process with a neutron spectator was extracted by the neutron momentum cut of p n > 0.3 GeV / c . The cross section for the Δ + + Δ − production was deduced in the non-quasi-free process of the γ d → p n π + π − . It was 13.4 ± 0.4 μb at E γ = 0.82 GeV .

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