121956246
Eighth-order magnetic moment of the electron. III. Sixth-order vertices containing a second-order vacuum polarization subdiagram
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.
3035381
Eighth-order magnetic moment of the electron. IV. Vertex diagrams containing photon-photon scattering subdiagrams.
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.
124063358
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.
120857356
Forward Scattering Amplitude and Univalent Functions
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.
119920938
Muon Decay with Parity Nonconserving Interactions and Radiative Corrections in the Two-Component Theory
121471667
Theory of Lepton g – 2: Improvement of QED Terms
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.
120952573
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.
95055312
Photoproduction of neutral kaons at LNS
121123072
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.
122810217
NEUTRAL KAON PHOTOPRODUCTION AT LNS, TOHOKU UNIVERSITY
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.
123400132
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.