Charmed quark component of the photon wave function

We determine the $c\bar c$ component of the photon wave function on the basis of (i) the data on the transitions e ⁺ e ^? → J/ψ(3096), ψ(3686), ψ(4040), ψ(4415), (ii) partial widths of the two-photon decays η _c0(2979), χ _c0(3415), χ _c2(3556) → γγ, and (iii) wave functions of the charmonium states obtained by solving the Bethe-Salpeter equation for the $c\bar c$ system. Using the obtained $c\bar c$ component of the photon wave function, we calculate the γγ-decay partial widths for radial excitation of the 2S state, η _c0(3594) → γγ, and 2P states χ _c0(3849), χ _c2(3950) → γγ.     

Photoproduction of eta mesons off protons for 0.75 GeV<E(gamma)<3 GeV

Total and differential cross sections for the reaction p(gamma,eta)p have been measured for photon energies in the range from 750 MeV to 3 GeV. The low-energy data are dominated by the S11 wave which has two poles in the energy region below 2 GeV. Eleven nucleon resonances are observed in their decay into peta. At medium energies we find evidence for a new resonance N(2070)D15 with (M,Gamma)=(2068+/-22, 295+/-40) MeV. At gamma energies above 1.5 GeV, a strong peak in the forward direction develops, signaling the exchange of vector mesons in the t channel.     

Photoproduction of π 0 ω off protons for E γ ≤3 GeV

Differential and total cross-sections for photoproduction of γp→pπ ⁰ ω and γp→Δ ⁺ ω were determined from measurements of the CB-ELSA experiment, performed at the electron accelerator ELSA in Bonn. The measurements covered the photon energy range from the production threshold up to 3GeV.     

Baryon-baryon and baryon-antibaryon interaction amplitudes in the spin-momentum operator expansion method

Partial-wave scattering amplitudes in baryon-baryon and baryon-antibaryon collisions and amplitudes for the production and decay of baryon resonances are constructed in the framework of the spin-momentum operator expansion method. The approach is relativistically invariant and it allows us to perform combined analyses of different reactions imposing analyticity and unitarity directly. The role of final-state interactions (triangle and box diagrams) is discussed.     

Quasifree photoproduction of eta mesons off the neutron

Quasifree photoproduction of eta mesons off nucleons bound in the deuteron has been measured with the CBELSA/TAPS detector for incident photon energies up to 2.5 GeV at the Bonn ELSA accelerator. The eta mesons have been detected in coincidence with recoil protons and recoil neutrons, which allows a detailed comparison of the quasifree n(gamma,eta)n and p(gamma,eta)p reactions. The excitation function for eta production off the neutron shows a pronounced bumplike structure at W=1.68 GeV (E{gamma} approximately 1 GeV), which is absent for the proton.     

Taking into Account the Centre-of-Mass Correlations in the Cross Sections for Elastic Scattering of Intermediate Energy Protons on the Exotic Nuclei <Superscript>6</Superscript>He and <Superscript>8</Superscript>He

We calculate the differential cross sections for proton elastic scattering on the exotic halo nuclei ⁶He and ⁸He at energies around ~0.7 GeV at the momentum transfers squared up to 0.30 (GeV/c)² and investigate the influence of the nucleon centre-of-mass correlations on the calculated cross sections. In particular, we show that the approximate account of the centre-of-mass correlations used previously considerably overestimates the cross sections at high values of the momentum transfer.     

Determination of the Average Energy of Iron Ions in the Axial Direction of a Micropinch Discharge Using an Ion Collector

The paper is devoted to determining the average ion energy for plasma propagating in the axial direction of a high-current low-inductance vacuum spark discharge in the Pion facility. The measurements have been carried out using an ion collector. The average energy of singly of singly charged iron ions depending on the voltage across the interelectrode gap is determined.     

Study of the reaction γp → pπ0η

The reaction γp → pπ⁰η has been studied with the CBELSA detector at the tagged photon beam of the Bonn electron stretcher facility. The reaction shows contributions from Δ⁺(1232)η , N(1535)⁺π⁰ and pa ₀(980) as intermediate states. A partial-wave analysis suggests that the reaction proceeds via formation of six Δ -resonances, Δ(1600)P ₃₃ , Δ(1920)P ₃₃ , Δ(1700)D ₃₃ , Δ(1940)D ₃₃ , Δ(1905)F ₃₅ , Δ(2360)D ₃₃ , and two nucleon resonances N(1880)P ₁₁ and N(2200)P ₁₃ , for which pole positions and decay branching ratios are given.     

Study of the Production of Positively Charged Pions in Proton–Proton Collisions in the Range of Primary Momenta between 1345 and 1536 MeV/ $$c$$

Physics of Atomic Nuclei - Differential cross sections obtained for the reaction $$pp\to pn\pi^{+}$$ at five incident proton momenta of 1345, 1393, 1439, 1486, and 1536 MeV/c are presented. The...