Photoproduction of neutral kaons at LNS

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

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.

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: 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: 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: Automated calculation scheme for αn contributions of QED to lepton g−2: New treatment of infrared divergence for diagrams without lepton loops
abstract: We have developed an efficient algorithm for the subtraction of infrared divergences that arise in the evaluation of QED corrections to the anomalous magnetic moment of lepton ( g − 2 ). By incorporating this new algorithm, we have extended the automated code-generating system developed previously to deal with diagrams without internal lepton loops (called q-type ), which produced convergent integrals when applied to diagrams that have only ultraviolet-divergent subdiagrams of vertex type. The new system produces finite integrals for all q-type diagrams, including those that contain self-energy subdiagrams and thus exhibit infrared-divergent behavior. We have thus far verified the system for the sixth- and eighth-order cases. We are now evaluating 6354 vertex diagrams of q-type that contribute to the tenth-order lepton g − 2 .

title: An Ultra-Precise Storage Ring for the Muon g — 2 Measurement
abstract: An ultra precise 3 GeV/c storage ring with a 14.5 kG super-ferric magnet is under construction at the Brookhaven AGS for the measurement of the muon anomalous magnetic moment to 0.35 PPM accuracy. This requires a magnetic field which is constant to ≈ 1 PPM and is known sufficiently well that the magnetic field integral averaged over the muon orbits can be calculated to 0.1 PPM. First the magnetic field will be statically shimmed by various techniques. Pole face winding will be used for final small static and dynamic corrections. Very elaborate NMR field monitoring techniques are required. A “movable trolley” located inside the vacuum chamber and the electrostatic focusing quadrupoles will measure the field throughout the muon storage volume. The trolley “siding” is 180˚ from the injection point where no electric quadrupoles are located. Injection can be interrupted so the trolley can circle the ring. Also ≈ 200 NMR probes located outside the vacuum chamber monitor the field during physics running and control the pole face windings. The very large (≈ 15 m diameter) superconducting coils (SC) are designed. Test winding will soon commence. Orders for the magnet steel can now be placed. R and D on various pulsed and SC dc injection methods is ongoing.

title: Forward Scattering Amplitude and Univalent Functions
abstract: 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.

title: Eighth-order magnetic moment of the electron. I. Second-order vertex containing second-, fourth-, and sixth-order vacuum polarization subdiagrams
abstract: We have calculated the contribution to the eighth-order anomalous magnetic moment of the electron arising from 25 Feynman diagrams generated by inserting second-, fourth-, and sixth-order vacuum polarization loops in the photon line of the second-order vertex diagram. Our result is $0.0766(6){(\frac{\ensuremath{\alpha}}{\ensuremath{\pi}})}^{4}$. The theoretical error represents the estimated accuracy (90% confidence limit) of the numerical integrations.

title: Possible tests of anomalously large leptonic weak interactions in high-energy e+ e- collisions
abstract: 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 ${(\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{m}\mathrm{e}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{t}\mathrm{e}\ensuremath{-}\mathrm{b}\mathrm{o}\mathrm{s}\mathrm{o}\mathrm{n}\phantom{\rule{0ex}{0ex}}\mathrm{m}\mathrm{a}\mathrm{s}\mathrm{s})}^{2}$.