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

title: Beam test of a BSO calorimeter

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: In Search of the Breakdown of QED: Study of Lepton g − 2 from 1947 to Present

title: Status of G‐2 calculation for the electron and muon
abstract: The electron anomalous magnetic moment provides the most precise test of QED. The present precision is such that one must begin to seriously question the validity of theories of condensed‐matter physics underlying the determination of α. The muon anomalous magnetic moment will play a very important role in testing gauge theories of electroweak interaction at the one loop level. Electron and muon moments may also provide useful information on the possible internal structure of leptons. Experimental and theoretical works are under way to improve the precision of these tests. Here I report on the present status of theoretical progress.

title: Eighth-order magnetic moment of the electron. II. Fourth-order vertices containing second- and fourth-order vacuum polarization subdiagrams
abstract: We have calculated the eighth-order contribution to the anomalous magnetic moment of the electron arising from 54 Feynman diagrams obtained by inserting second- and fourth-order vacuum polarization loops in the fourth-order vertex diagrams. Our result is -0.5238(10)(..cap alpha../..pi..)/sup 4/. The theoretical error represents the estimated accuracy (90% confidence limit) of the required numerical integrations.

title: Muon g-2 and Muonium Hyperfine Structure: Theory Update

title: New approach to the singularities of Feynman amplitudes in the zero-mass limit
abstract: We present an improved method for studying the behavior of Feynman amplitudes in the limit in which some or all of the masses of the internal lines vanish. Feynman amplitudes develop singularities in such a limit for certain configurations of external momenta. Our method enables us to determine these configurations, be they Euclidean or Minkowskian, on or off the mass shell. They are worked out explicitly in a few relatively simple cases which include most of the physically interesting singularities. Power-counting rules for these singularities are briefly discussed.