120479135
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 .
120762412
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 .
116485131
S11(1535) Resonance in Nuclear Medium Observed with the (gamma, eta) Reactions
106402542
Photoproduction of neutral kaons on a liquid deuterium target in the threshold region
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.
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.
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.
118235292
Eighth-Order Anomalous Magnetic Moment of the Electron
A very preliminary value $(\ensuremath{-}0.8\ifmmode\pm\else\textpm\fi{}2.5){(\frac{\ensuremath{\alpha}}{\ensuremath{\pi}})}^{4}$ is reported for the complete eighth-order QED contribution to the electron anomalous magnetic moment. The large error reflects the difficulty in evaluating the huge integrals involved and will be reduced in the future. Theory and experiment agree within 2 standard deviations. The current result enables us to determine, in a manner based solely upon elementary-particle physics, the fine-structure constant $\ensuremath{\alpha}$ to an accuracy of 0.08 ppm.
119405933
Improved alpha**4 term of the muon anomalous magnetic moment
We have completed the evaluation of all mass-dependent {alpha}{sup 4} QED contributions to the muon g-2, or a{sub {mu}}, in two or more different formulations. Their numerical values have been greatly improved by an extensive computer calculation. The new value of the dominant {alpha}{sup 4} term A{sub 2}{sup (8)}(m{sub {mu}}/m{sub e}) is 132.6823 (72), which supersedes the old value 127.50 (41). The new value of the three-mass term A{sub 3}{sup (8)}(m{sub {mu}}/m{sub e},m{sub {mu}}/m{sub {tau}}) is 0.0376 (1). The term A{sub 2}{sup (8)}(m{sub {mu}}/m{sub {tau}}) is crudely estimated to be about 0.005 and may be ignored for now. The total QED contribution to a{sub {mu}} is 116 584 719.58(0.02)(1.15)(0.85)x10{sup -11}, where 0.02 and 1.15 are uncertainties in the {alpha}{sup 4} and {alpha}{sup 5} terms and 0.85 is from the uncertainty in {alpha} measured by atom interferometry. This raises the standard model prediction by 13.9x10{sup -11}, or about 1/5 of the measurement uncertainty of a{sub {mu}}. It is within the noise of current uncertainty ({approx}100x10{sup -11}) in the estimated hadronic contributions to a{sub {mu}}.
18177406
New approach to the separation of ultraviolet and infrared divergences of Feynman-parametric integrals
A scheme for systematically separating ultraviolet divergences of Feynman amplitudes in parametric space is developed. It is summarized by an explicit formula which enables us to incorporate readily the ultraviolet-finite remainders thus constructed into the usual renormalization scheme. It is shown further that infrared divergences can be treated in a very similar way. Our method is particularly suitable for numerical integration.
121452688
Possible tests of anomalously large leptonic weak interactions in high-energy e+ e- collisions
Some consequences of two possible mechanisms of a breakdown in $V\ensuremath{-}A$ theory leading to anomalously large weak vertices in hitherto untested leptonic reactions are discussed. We consider the processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{e}{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\nu}}}_{e}\ensuremath{\gamma}$ with total c.m. energies around 10 GeV. A purely leptonic neutral current can cause a measurable forward-backward muon asymmetry and a muon polarization in the first reaction. Expressions are computed for these effects in terms of the most general nonderivative coupling. On the other hand, some intrinsic anomaly in diagonal weak vertices can make the cross section for the second process large and measurable; in that case, study of the $\ensuremath{\gamma}$ spectrum can reveal information about the structure of such an anomalous vertex. The angular distribution and the energy spectrum of the photon are computed for the $V\ensuremath{-}A$ and $S\ensuremath{-}P$ theories up to terms that are first order in ${(\mathrm{total}\mathrm{c}.\mathrm{m}.\mathrm{energy})}^{2}$/2 ${(\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{m}\mathrm{e}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{t}\mathrm{e}\ensuremath{-}\mathrm{b}\mathrm{o}\mathrm{s}\mathrm{o}\mathrm{n}\phantom{\rule{0ex}{0ex}}\mathrm{m}\mathrm{a}\mathrm{s}\mathrm{s})}^{2}$.
122743760
Real Part of the Scattering Amplitude and the Behavior of the Total Cross Section at High Energies
Abstract : Certain theorems first pointed out by Meiman are used to include the information contained in analyticity in energy and crossing symmetry in the derivation of upper bounds for the forward scattering amplitude. Theorems are obtained relating the asymptotic behavior of the ratio of the real part to the imaginary part of the forward amplitude on the one hand, to that of the total cross section on the other. Except for the special case where Ref/Imf=pi/lnE as the incident laboratory energy E approaches infinity, it is found that the Froissart bound can be improved. It is found that the GreenbergLow bound which follows from axiomatic field theory can always be improved by a fractional power of E under the physical assumption that the amplitude does not become purely real as E approaches infinity. It is found that the asymptotic behavior Ref=cE is not allowed. This sheds light on the question of the 'elementary' nature of vector mesons. An inequality is given which, in principle, could lead to an experimental check of analyticity and crossing with data obtained only from a finite range of energy. (Author)