Two-Photon Mechanism of Particle Production by High-Energy Colliding Beams
We report on the calculation of the cross sections for the production of positive-charge-conjugation states such as ${\ensuremath{\pi}}^{0}$, $\ensuremath{\eta}$, ${e}^{+}{e}^{\ensuremath{-}}$, ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$, and ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ by a two-photon mechanism in ${e}^{\ensuremath{-}}{e}^{+}$ and ${e}^{\ensuremath{-}}{e}^{\ensuremath{-}}$ collisions. We give the precise relationship of the process $e+e\ensuremath{\rightarrow}e+e+X (X \mathrm{is}\mathrm{any} C=+ \mathrm{state})$ to the corresponding two-photon annihilation process $\ensuremath{\gamma}+\ensuremath{\gamma}\ensuremath{\rightarrow}X$, as well as a careful derivation of the equivalent-photon approximation. In the case of the ${\ensuremath{\pi}}^{0}$ production, we have found that, for the beam energy $E$ in the 1-3 GeV range, the exact total cross section is 20-30% larger than the one calculated previously in the equivalent-photon approximation. However, the introduction of form factors cuts down the exact total cross section, reducing it to within 10% of the equivalent-photon-approximation result. For $\ensuremath{\eta}$ production the agreement is even better. Thus it appears that the use of the equivalent-photon approximation is justified in most cases. We discuss detailed angular distributions in this approximation for the case of ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ production. One important problem which cannot be adequately studied in the equivalent-photon approximation is the degree of noncoplanarity of the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ (and the ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$) pair. We have studied this problem using the exact formula and found that, for $E=1$ GeV, typically 40-50% of pion pairs will be produced with the noncoplanarity angle greater than 12\ifmmode^\circ\else\textdegree\fi{}. We discuss the general structure of the $\ensuremath{\gamma}+\ensuremath{\gamma}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}}$ amplitude as well as a simple model incorporating the $\ensuremath{\sigma}$ meson. We also give a rough estimate of multihadron production cross sections.

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

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: S(11) resonance in nuclei observed with the STB Tagger at LNS Sendai

title: Photoproduction of neutral kaons at LNS

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: Photoproduction of neutral kaons on C in the threshold region
abstract: The measurement of neutral kaon photoproduction in the threshold region is in progress at Laboratory of Nuclear Science, Tohoku University. One of the purpose of the experiment is to study electromagnetic strangeness production mechanism, which is necessary for hypernuclear spectroscopy by electromagnetic probes. We have observed K 0 's produced on a carbon target in a commissioning run. Data taking will start in 2003.

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.