K^＋ Scattering with the Nuclear Pion from Chiral Effective Lagrangian

The K^ scattering cross section with the in-medium virtual pion is evaluated in the lowest-order chiral perturbation theory with the density-dependent pion decay constant and mass.The contribution of nuclear pions to the total K^ -nucleus cross section is found to be about 5% and 12% when the excess pion numbers per nucleon nπ=0.057 and 0.13 are used.The inclusion of the off-mass-shell behavior of the K^ π amplitude produced a significant improvement in the K^ -nucleus cross section.     

Search for coherent charged pion production in neutrino-carbon interactions

We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed, and an upper limit of is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV.     

AN ESTIMATION OF PION YIELDS

Using the spectrum of bremsstrahlung obtained by solving shower equation of electrons in matter and the differential cross section of photoproduction of pions in OPE approximation, we calculate by PDp-11/23 the pion yields results from 1.2 GeV electrons bombarding on different targets, Be, C, Al, Cu and Pt. The optimization is made for pion yields to find the optimistic production angle. In order to choose the thickness of the target, the curves of pion yields vs. Target thickness are given.     

Antikaon production in nucleon- nucleon reactions near threshold

The antikaon production cross section from nucleon-nucleon reactions near threshold is studied in a meson exchange model. We include both pion and kaon exchange, but neglect the interference between the amplitudes. In case of pion exchange the antikaon production cross section can be expressed in terms of the antikaon production cross section from a pion-nucleon interaction, which we take from the experimental data if available. Otherwise, a K* -resonance exchange model is introduced to relate the different reaction cross sections. In case of kaon exchange the antikaon production cross section is related to the elastic KN and K?N cross sections, which are again taken from experimental measurements. We find that the one-meson exchange model gives a satisfactory fit to the available data for the NN → NN KK? cross section at high energies. We compare our predictions for the cross section near threshold with an earlier empirical parameterization and that from phase space models.     

Correlation and polarization characteristics of the 40Ca(p, dπ+)39K reaction

The ⁴⁰Ca(p, dπ⁺)³⁹K reaction was studied theoretically at a proton energy of 650 MeV within the distorted wave impulse approximation (DWIA) and under the assumption of a quasi-free mechanism of the elementary process pp → dπ⁺ of pion production. The peripheral nature of the reaction on the nucleus was shown. The influence of the effects of distortions in the initial and final states of the reaction on the differential cross section and other spin-dependent characteristics are discussed.     

Emission in the final state in processes with the production of charged pions and light leptons

The Drell-Yan form is proposed for the decay widths of heavy quarks and cross sections for high-energy scattering with the production of charged pions and light leptons including radiative corrections in the final state in the leading logarithmic approximation. The corresponding spectral distributions are given in terms of the convolution of the cross section (decay width) in the Born approximation with the structure functions of pions and leptons. The pion structure function is given in the explicit form.     

Mean field approach to pion production in intermediate energy heavy ion collisions

The pion production in intermediate-energy heavy ion collisions is studied in the mean field approximation. Pion spectra are calculated in the slab geometry for various incident energies. It is found that the one-nucleon process cannot explain the observed cross section and that two-nucleon processes are important.     

Inelastic Pion Scattering from 12C at 800 MeV/c

The differential cross section of the inelastic scattering of pion at 800 MeV/c fir the 3^- excited states of ¹²C is calculated by making use of eikonal approximation and the collective coordinate. The calculation indicates that the 3_- state of ¹²C is octupole vibrational state.The results are in agreement with experimental data.     

Inclusive (p, π) reactions at 201 and 180 MeV

Inclusive proton-induced charged pion production was studied on ¹²C, ⁸⁹Y and ^natPb at 201 and 180 MeV. A QQD spectrometer was used for forward angles and a plastic scintillator range spectrometer for backward angles. The angular dependence, variation with the pion energy, and total cross sections are deduced from doubly differential cross section measurements.     

Coherent pion electroproduction on the deuteron in the Δ(1232) resonance region

Coherent pion electroproduction on the deuteron is studied in the ((1232) resonance region in the impulse approximation, i.e., neglecting pion rescattering and two-body effects. The elementary reaction on the nucleon is described in the framework of an effective Lagrangian approach including the dominant P₃₃(1232) resonance and the usual background terms of the Born contributions for ?⁰ production. We have studied the influence of these different contributions on the various structure functions which determine the unpolarized exclusive differential cross section in a variety of kinematic regions.     

Measurement of R at VEPP-2000

The new e^＋e^- storage ring, VEPP-2000, is being commissioned at Budker Institute of Nuclear Physics, Novosibirsk. Measurement of the total cross section e^＋e^- → hadrons in the whole VEPP-2000 energy range is one of the main goals of the new experiments. We discuss the goals of the measurement and the expected systematic errors.     

Pionic disintegration of the deuteron

Pionic disintegration of the deuteron between threshold and the 3,3 resonance region is described by a model containing one- and two-body absorption. The two-body absorption mechanism is due to pion and ?-meson rescattering calculated from phenomenological Lagrangians. The role of the ?-meson is crucial in reducing the cross section due to pion exchange. The role of the mass distribution of the ρ-meson, hadronic form factors and final state interactions are investigated. Good agreement with empirical results for the total cross section is obtained with a set of currently accepted values for the meson-nucleon coupling constants and the ρ-mass distribution.     

Coupled-channel calculations of positron-atom scattering at intermediate energies

We present the cross sections for positron collisions with the alkali atoms Li, Na and K in the close-coupling approximation within the framework of a single-active-electron model. Our target basis sets are represented by Li(2s, 3s, 2p, 3p), Na(3s, 4s, 3p, 4p), and K(4s, 5s, 4p, 5p) respectively. The effects of coupling to the lowest lying Ps channels have been investigated by augmenting the target basis sets with the Ps(1s, 2s, 2p) eigenstates. The calculations have been made for impact energies below 50 eV. The interaction between the positron and the alkali target atom is represented by a model potential obtained using a single-active-electron approximation. The effect on elastic scattering and excitation due to the coupling between the direct and the Ps formation channels is found to be of great significance at low impact energies. The case of K is of particular interest. The inclusion of the Ps channels quantitatively reproduces the maximum in the total cross section at about 6 eV as reported in a recent experiment by Parikh et al. We find that the calculated total cross sections for Na and K are in good agreement with the experimental data of Parikh et al. and Kwan et al. respectively in the energy range of 2–50 eV provided allowance is made for the incomplete elastic discrimination in the experiment. The Ps formation reduces the K(4s4p) cross section at all energies below 30 eV and a reduction is also seen in the elastic cross section for energies below about 7 eV. Similar effects are observed in the case of Li. In the case of Na for impact energies between 2 and 20 eV Ps formation significantly reduces the Na(3s3p) excitation cross section, while the elastic scattering cross section increases. The calculated total Ps formation cross sections for Na and K are in good agreement with the preliminary experimental data of Kwan, Stein and co-workers.     

Measurement of the pion form factor for Mππ^2 between 0.1 and 0.85 GeV2 with the KLOE detector

The KLOE experiment at the φ-factory DAФPNE has measured the pion form factor in the range between 0.1 〈 Mππ^2 〈 0.85 GeV^2 using events taken at √s = 1 GeV with a photon emitted at large polar angles in the initial state. This measurement extends the Mππ^2 region covered by KLOE ISR measurements of the pion form factor down to the two pion production threshold. The value obtained in this measurement of the dipion contribution to the muon anomalous magnetic moment of △αμ^ππ= （478.5±2-0stat±4.8syst±2.9theo）·10^-10 further confirms the discrepancy between the Standard Model evaluation for αμ and the experimental value measured by the （g-2） collaboration at BNL.     

Tensor polarized γ-deuteron Compton scattering in effective field theory

The differential cross section for γ-deuteron Compton scattering from a tensor polarized deuteron is computed in an effective field theory. The first non-vanishing contributions to this differential cross section are the interference terms between the leading electric coupling diagrams and the subleading single potential pion exchange diagrams or the subleading magnetic moment coupling diagrams. At 90° photon scattering angle, only the pion term contributes at this order to the tensor polarized differential cross section. This provides a clean way to study the photon pion dynamics in the two nucleon sector. The effect is measurable for photon energies between 40 and 80 MeV provided the uncertainty in the measured cross sections are ≲ 7%.     

Subthreshold η production on nuclei by protons

A simple expression for the inclusive cross section of η production on light nuclei by protons has been obtained in the first collision approximation in the framework of the intranuclear cascade approach. An intranuclear cascade model which takes into account η production by primary proton and secondary pion, elastic scattering of η on intranuclear nucleons and absorption of η in nuclear matter has been developed. The calculated cross sections are found to be in satisfactory agreement with the experimental data.     

Inclusive charged pion photoproduction on12C using tagged photons in the energy range (200–390) MeV

The photoproduction of charged pions on¹²C has been investigated using the tagged photon beam facility at the Bonn 500 MeV synchrotron. Pions were detected in a broad range magnetic spectrometer. Double differential cross sections for pion emission at fixed photon energies are presented. The integration of the measured distributions yields the total cross section for inclusive pion production. The data are compared to the predictions of a simple model that takes the quasifree production of pions and their subsequent scattering and reabsorption into account.     

Al原子K壳层光电离的理论研究

基于多组态Dirac-Fock理论方法及其相应的GRASP2K和修改后的RATIP2012程序包,计算了极化光子入射Al原子K壳层光电离截面,并利用最新发展的RPI-E计算程序研究了K壳层光电子角分布,重点讨论了辐射场的非偶极项对光电离截面和光电子角分布的影响.结果表明,在入射光子5000 e V能量范围内,辐射场的非偶极效应对光电离总截面的影响可以忽略不计.随着入射光子能量的增加,辐射场的非偶极效应对光电子角分布的影响越来越大,入射光子能量在5000 eV,一级非偶极参数γ的数值达到1.5.     

Electron excitation cross sections of Li,Na and K

The Vainshtein approximation with exchange via the Ochkur-Rudge method and Ochkur's modified first Born approximation are used to calculate electron excitation cross sections of Li, Na and K. The results are compared with experiments and the frozen core Glauber cross sections.