Measurement of the asymmetry for π photoproduction from polarized protons between 300 and 900 MeV

The asymmetry of the cross section for π⁺ photoproduction from a polarized butanol target has been measured at a c.m. angle 90° and photon energies between 300 and 900 MeV by a single-arm spectrometer detecting positive pions. Our results indicate that the asymmetry has clear positive peaks at photon energies 400 and 700 MeV with a deep valley at about 600 MeV. The general feature of the results is well reproduced by the phenomenological analyses made by Walker and ourselves; however, the best fit to the polarized target asymmetry data seems to give a somewhat different set of parameters from that given by Walker.     

Multipole analysis of π+ and π0 photoproduction from threshold to Eγ = 330 MeV

We present results of an energy independent multipole analysis of π⁺ and π⁰ photoproduction on protons for photon energies between 160 MeV and 330 MeV. Each isospin part of the l ? 1 amplitudes has been parametrized; the 1 ? 2 amplitudes have been approximated by the Born terms. Unambiguous solutions for all the multipoles in the whole range of E_γ have been obtained. The continuity of the solutions as functions of the energy is very good.     

Experimental investigation of the reaction12C(γ, π0)X in the photon energy range between threshold and 450 MeV

The photoproduction of neutral pions on¹²C has been investigated between threshold and 450 MeV photon energy using the tagged photon beam at the Bonn 500 MeV synchrotron and a large acceptance detector. Theπ ⁰ detector consists of cylindrical wire chambers covering a solid angle of nearly 4π. Using a scintillation counter as an active¹²C target an attempt was made to separate coherent and incoherentπ ⁰ photoproduction. The measured total and differential cross sections are compared to corresponding theoretical calculations.     

Measurement of J/ψ production in 280 GeV/cμ+ iron interactions

Virtual photoproduction of J/ψ mesons has been measured for 280 GeV muon iron interactions in an iron/scintillator calorimeter target. The J/ψ's were identified by their decay into muon pairs. 315 events were observed, about half of which were elastic. The t, Q² and v distributions of these elastic events are presented. The v dependence is measured between 40 and 180 Mev and compared with lower energy photoproduction results. The Q² dependence is compared with the predictions of the vector dominance model.     

Evidence of the Non-Strange Partner of Pentaquark from the Elementary K +Λ Photoproduction

The existence of the J ^p  = 1/2⁺ narrow resonance predicted by the chiral soliton model has been investigated by utilizing the new kaon photoproduction data. For this purpose, we have constructed two phenomenological models, which are able to describe kaon photoproduction from threshold up to W = 1,730 MeV. By varying the resonance mass, width, and KΛ branching ratio in this energy range we found that the most convincing mass of this resonance is 1,650 MeV. Using this result we estimate the masses of other antidecuplet family members.     

π 0 and η Photoproduction on the Deuteron at ELPH, Tohoku University

Baryon spectroscopy is important to understand Quantum Chromodynamics at low energies. In this purpose, a series of π ⁰ and η photoproduction experiments was carried out with an electro-magnetic calorimeter FOREST at Research Center for Electron Photon Science, Tohoku University. The incident tagged bremsstrahlung photon energy ranges from 550 to 1,150 MeV. The differential and total cross sections obtained for π ⁰ and η photoproduction processes on the proton are consistent with the SAID and MAID calculations. The analysis of π ⁰ and η photoproduction on the neutron is underway.     

Study for the ω–N Interaction Through ω Photoproduction Near the Threshold

The total cross section has been measured for ω meson photoproduction on the proton for the center-of-mass energy ${\sqrt{s}}$ ranging from 1.69 to 1.75 GeV. Including the subthreshold region of ω photoproduction, a set of about 40 data points has been obtained with a fine energy step of 1–2 MeV. The data set enables us to deduce the ω-N scattering length.     

Symmetry properties of the pomeron for t≠0

We investigated the SU(3) character of vacuum exchange amplitudes for πN, KN elastic scattering and for vector-meson photoproduction. Support is found for the recently proposed view that the single component becomes increasingly dominant away from t = 0, and that the eikonal amplitude is the quantity to which the symmetry breaking predictions seem to apply.     

Coherent π0 photoproduction near threshold on closed-shell nuclei

Coherent π⁰ photoproduction is considered on closed-shell nuclei in the DWIA frame from threshold up to pion energies of 50 MeV. The elementary photoproduction operator is taken from Blomqvist and Laget and treated in the coordinate-space representation. It includes, besides the negligible Born terms, delta formation in the s-channel and ω⁰ exchange in the t-channel, two mechanisms which have comparable importance even near threshold. The emerging pion wave is distorted by optical-model potentials which give equally good fits both to pionic atom data and pion scattering data. In the considered energy range the DWIA cross section is enhanced with respect to the plane-wave case by an amount between 50% and 100% depending on the particular optical-model potential. Distortion is necessary to gain a satisfactory agreement with the available data.     

πp phase shifts from 88 to 310 MeV

Phase shift solutions are presented at pion kinetic energies from 88 to 292 MeV where new measurements of the differential elastic cross section are available, and at 310 MeV. The resulting phase shifts are fitted to effective-range formulae. The resonant P₃₃ phase shift is allowed to take different values for π⁺p and π^?p scattering. There are differences in mass and width between these charge states of the resonance of M⁰ ? M⁺⁺ = 1.4 ± 0.4 MeV/c² and Γ⁰ ? Γ⁺⁺ = 10.3 ± 1.3 MeV/c². The difference in width can be accounted for largely but not entirely by the Coulomb barrier, the channel π^?p → γn, and the difference in phase space between π^?p → π⁰n and π⁺p → π⁺p.     

Correction of the model of <Emphasis Type="Italic">η</Emphasis>′-meson photoproduction on protons at intermediate energies on the basis of new threshold data

The isobarmodel, which reproduced fairly well experimental data on η′-meson photoproduction at photon energies between 1500 and 3700 MeV, is refined with allowance for new experimental data in the vicinity of the reaction threshold.     

New evidence for the P11 (1470) resonance in π + p → n + π below 600 MeV

The differential cross section for π⁻p → nπ^o has been measured in detail from 150 to 600 MeV. The backward cross section has a previously unobserved dramatic dip at 425 MeV. We interpret this dip in terms of interference between the P₃₃(1236) and the P₁₁(1470) resonances. These data provide strong evidence for the adequacy of the phase shift solutions in this energy range.     

Isobaric Model of <Emphasis Type="Italic">η'</Emphasis>-Meson Photoproduction on Protons with Allowance of New Data on Σ Asymmetry

The isobaric model, which describes well the experimental cross sections for η'-meson photoproduction at photon energies between 1500 and 2300 MeV, is refined with allowance for new experimental data on the beam asymmetry for this reaction.     

Real-to-imaginary ratio of the pp forward elastic scattering amplitude in the momentum range between 180 and 590 MeV/c

The real-to-imaginary ratio of the $\text{p}\text{p}$ forward elastic scattering amplitude has been measured at the LEAR facility of CERN by the Coulomb-nuclear interference method at seven beam momenta between 181 and 590 MeV/c. The ratio is positive at 590 MeV/c, becomes negative below 500 MeV/c, reaches a minimum at 260 MeV/c and then crosses zero again at about 230 MeV/c.     

Phase-shift analysis of d-α elastic scattering between 3 and 17 MeV

Phase shifts for d-α elastic scattering have been extracted from differential cross sections and the vector and tensor analysing powers of ⁴He($\text{d}$, d)⁴He scattering in the energy range from 3 to 17 MeV. The angular momenta were restricted to L ≦ 4 and mixing parameters ε¹ and ε². Good fits could be obtained to nearly all the experimental data analysed. The total reaction cross section and polarization-transfer coefficients were predicted and compared with the measured data; satisfactory agreement was found within the experimental errors. Evidence for a new resonance was found between 11 and 15 MeV.     

Properties of the φ and f′ produced in the channel Kp → KpKK̄ at 10 GeV/c

Data are presented and cross sections given for ф and f′ production in the channel K⁺p → K⁺pKK? at 10 Gev/c. The resonance parameters obtained from a fit to the KK? effective mass distribution are M = (1020.4 ± 0.5) MeV/c² and Γ = (5.0 ± 1.3) MeV/c² for the ф meson and M = (1514 ± 4) MeV/c² and Γ = (28 ± 15) MeV/c² for the f′. The resonance widths are corrected for experimental resolution. The branching fraction for the rate (ф → K⁰₁K⁰₂)/(ф → K⁺K⁻) is determined to be 1.15 ± 0.15. The angular distributions for the decay of the f′ have unnormalized moments _H(2,0) and H(4,0) different from the values for the nearby background, indicating spin 2 or greater for the f′.     

Bremsstrahlung in α-α scattering

The bremsstrahlung cross section in α-α scattering has been determined for incident laboratory energies between 12.5 and 19.0 MeV. The experimental cross sections are compared with the theoretical calculations for external emission only.     

Two-nucleon T = 0 transfer reactions in the 0p shell

The ¹⁶O(d, α)¹⁴N, ¹⁴N(d, α)¹²C and ¹²C(d, α)¹⁰B reactions at E_d = 40MeV and the ¹²C(α d)1¹⁴N at E_α = 55 MeV were investigated. A total of seventeen transitions are analysed in terms of one-step, zero-range DWBA calculations, using the two-particle coefficients of fractional parentage obtained from the Cohen-Kurath Op shell wave functions. For most transitions, fair agreement is obtained between experiment and calculation, possible exceptions being the transition to the E_x = 4.43 MeV, J^π = 2⁺ state in ¹²C and to the E_x = 2.15 MeV, J^π = 1⁺ state in ¹⁰B, for which the calculations predict too much L = 0 strength. Where possible, a comparison with previous (p, ³He) results is made. In ¹⁴N a state at E_x = 11.04 MeV was observed for which the values (J_π; T) = (3⁺; 0) are suggested. In ¹²C we found, in addition to the well known T = 0 states, two relatively sharp T = 0 states at E_x = 19.50 ± 0.10 and 20.55 ± 0.10 MeV. The shape and strength of the angular distribution for the transitions to these states can be approximately accounted for by the calculations, although no one-to-one correspondence between observed and predicted levels could be established.     

Proton Compton effect in the Δ(1232) energy region

The proton Compton effectγ+p→γ+p in theΔ (1232) energy region has been thoroughly studied. At the Bonn 500 MeV synchrotron differential cross sections were measured covering a large range of the CM scattering angle (50°≦θ_γ≦130°) and an energy range from 240 to 440 MeV (LAB energy of the primary photon). A contribution to the counting rate from the competing process ofπ ⁰ photoproduction was strongly suppressed by detecting both particles in the final state and by a proper choice of the endpoint energy of the gamma ray beam. The remaining contribution was monitored experimentally. The measured data were complemented by cross sections at 0° which were computed from the totalγ p cross sections with an input from a multipole analysis of single pion photoproduction. Preliminary results of this experiment have been published in Lett. Nuovo Cimento. In the meantime the experimental data were reanalyzed. The final data presented here are larger than the preliminary ones by about 15%.     

Positive pion photoproduction from hydrogen at photon energies between 500 MeV and 1,400 MeV in forward direction

The differential cross section of the reactionγ+p→π ⁺ was measured at pion CM-angles of 20° and 30° for photon energies between 500 MeV and 1,400 MeV. The pions were detected in a magnetic spectrometer. By measuring each pion trajectory and by offline calculation of the initial pion parameters an energy resolution of about 2.5% FWHM was achieved. The results complete a set of data which were measured in recent years at the Bonn 2.5 GeV synchrotron. In comparison to photoproduction analyses two effects were revealed: The η cusp appears in the energy dependence of the cross section as a sharp drop atK _γ=710 MeV. In the region of the third resonance the data show a greater enhancement than predicted by most of the analyses.