Determination of the πN charge exchange scattering amplitude from the experimental data at high energies

The difference between theπ ⁺ p andπ ^? p diffraction peaks is used for an estimate of the imaginary part of the charge exchange scattering amplitude. The imaginary part has a narrow peak in the forward direction and passes over to negative values at a momentum transfert of about ?0.15(GeV/c)². If the charge exchange amplitude is dominated by the contribution of theρ Regge pole, the peak is mainly due to thet-dependence of the residue function and a narrow forward peak is expected in the charge exchange angular distribution.     

Electromagnetic effects and scattering lengths extraction from experimental data on K → 3π decays

The final state interactions in K ^± → π^±π⁰π⁰ decays are considered using the methods of nonrelativistic quantum mechanics. It is shown how to take into account the largest electromagnetic effect in the analysis of experimental data using the amplitudes calculated earlier. The relevant expressions for amplitude corrections valid both above and below the two charged pions production threshold , including the average effect for the threshold bin, are proposed. These formulae can be used in the procedure of pion scattering lengths measurement from spectrum. The text was submitted by the authors in English.     

Determination of the pattern of nuclear binding from the data on lepton–nucleus deep inelastic scattering

Nucleon structure function ratios measured in the range of atomic masses are analyzed with the aim of determining the pattern of the x and A dependence of modifications caused by the nuclear environment. It is found that the x and A dependence of the deviations of the from unity can be factorized in the entire range of x. The characteristic feature of the factorization is represented with the three cross-over points , i = 1–3 in which independently of A. In the range the pattern of is fixed with . The pattern of the x dependence is compared with theoretical calculations of Burov, Molochkov and Smirnov to demonstrate that the evolution of the nucleon structure as a function of A occurs in two stages: first for and second for . The long-standing problem of the origin of the EMC effect is understood as a modification of the nucleon structure in the field responsible for the binding forces in a three-nucleon system. Received: 28 January 1999 / Revised version: 1 April 1999 / Published online: 3 August 1999     

Lightest scalar resonances and the dynamics of the γγ → ππ reactions

The high-statistics Belle data on the γγ → π⁺π^? and γγ → π⁰π⁰ reactions have been jointly analyzed. The main dynamical mechanisms of these reactions for energies below 1.5 GeV have been revealed. It has been shown that the direct coupling constants of the σ(600) and f ₀(980) resonances with a γγ pair are small and that the σ(600) → γγ and f ₀(980) → γγ decays are four-quark transitions due primarily to π⁺π^? and K ⁺ K ^?-loop mechanisms, respectively. The role of the chiral shielding of the σ(600) resonance is emphasized. The widths of the f ₀(980) → γγ and σ(600) → γγ decays averaged over the resonance mass distributions, as well as the width of the f ₂(1270) → γγ decay, are estimated as \(\langle \Gamma _{f_0 \to \gamma \gamma } \rangle _{\pi \pi } \approx 0.19 keV, \langle \Gamma _{\sigma \to \gamma \gamma } \rangle _{\pi \pi } \approx 0.45 keV\), and \(\Gamma _{f_2 \to \gamma \gamma } (m_{f_2 }^2 ) \approx 3.8 keV\).     

Light scalar mesons in experimental data on the decay ϕ → π 0 π 0 γ and ππ scattering

Results of a simultaneous analysis of data from the KLOE detector (Italy) on the decay ? → π ⁰ π ⁰ γ and data on ππ scattering and on the reaction ππ → K $ \bar K Results of a simultaneous analysis of data from the KLOE detector (Italy) on the decay ϕ → π ⁰ π ⁰ γ and data on ππ scattering and on the reaction ππ → K are presented. These data are described with allowance for the chiral shielding of the σ(600) meson. The results favor the four-quark nature of the σ(600) and f ₀(980) mesons. Original Russian Text ? N.N. Achasov, A.V. Kiselev, 2007, published in Yadernaya Fizika, 2007, Vol. 70, No. 11, pp. 2005–2021.     

On equations solvable by the inverse scattering method for the Schrödinger operator

The new approach to deriving nonlinear evolution equations solvable by the inverse scattering method is proposed. In particular, this approach allows one to describe all equations solvable by the inverse scattering method for the Schrödinger operator.     

Study of fermilab data for the reaction π−p → π0n

Fermilab data for the angular distribution measurements of the reaction ^–p ⁰n are investigated and it is shown that a good fit with experiment is obtained by using a simple Regge pole model with phenomenological residue functions. The energy dependence in this case is found to be different from that for the d/dt data obtained at Serpukhov.Work supported by the Pakistan Science Foundation under contract No. P-PU-PHY(11/1).     

Analisis of inelastic scattering of π-mesons from nuclei within the microscopic optical potential

Cross sections of inelastic scattering of π-mesons from Si, Ni, and Pb nuclei at energy T _lab = 291 MeV are calculated using the distorted wave approximation. The microscopic direct and transition optical potentials are determined by specifying the pion-nucleon scattering amplitude and the nuclear density distribution, where we use the in-medium πN amplitude parameters obtained earlier by analyzing the elastic scattering data for the same nuclei. The cross sections are calculated on the basis of the relativistic wave equation. The deformation parameters of the nuclei are obtained by comparing inelastic scattering cross sections with the appropriate experimental data.     

Study of Fermilab data for the reaction π− p→ηn

Fermilab data for the angular distribution measurements of the reaction ^– p n are investigated and it is shown that a good fit with experiment is obtained by using a simple Regge pole model with phenomenological residue functions. The energy dependence in this case is found to be different from that for the d/dt/ data obtained at Serpukhov.Work supported by the Pakistan Science Foundation under contract No. P-PU-PHY(11/1).     

Formation of two pions on nuclei in A(γ, ππN)B reactions

A model is proposed for double pion photoproduction on nuclei that is accompanied by nucleon emission. Simple models that faithfully reproduce single-particle differential cross sections are used to describe photon interactions with intranuclear nucleons. The calculated cross sections for pion photoproduction on ¹²C nuclei are compared with inclusive pion spectra measured in the second resonance region of photon energies.     

Determination of the M-matrix in d-α elastic scattering from a complete set of experiments

Six polarization transfer coefficients of the d-α elastic scattering have been measured at an incident deuteron energy of 11.9 MeV and a scattering angle θlab = 37.3°. Together with earlier data on cross section and analyzing powers, a complete set of measurements allows to deduce the d-α M-matrix directly from experiment.     

Constraints on πN threshold parameters and the sigma term from measuring the polarization

We discuss N polarizations and cross sections at low energies. Presently two conflicting solutions for the low energy amplitudes exist. The first one is based on low energy scattering data and disagrees with the chiral sigma term while the second one, based on mesic atoms level shifts, is consistent with chiral expectations. We show that the ^±p polarization atT _R = 51 MeV is able to distinguish these solutions. We also illustrate the sensitivity to the small P waves.Contributed paper to the symposium on Mesons and Light and Nuclei IV, Bechyn, Czechoslovakia, September 5–10, 1988.We would like to thank J. Gasser and H. Leutwyler for the stimulating collaboration on which this note is based. G. Höhler, R. Koch and H. M. Staudenmaier from the Karlsruhe group have generously supplied all conceivable information on their analysis.     

Determination of the Galaxy age by the method of uranium–thorium–plutonium isotopic ratios

The dependence of the Galaxy age (Т _G), as determined by the method of uranium–thorium isotopic ratios, on the parameters of the nucleosynthesis model is studied within the theory of galactic nucleosynthesis. It is shown that ТG depends strongly both on the scenario of the production of nuclei in the r-process and those features of neutron-rich nuclei that are used in the respective analysis and on galactic-nucleosynthesis parameters. The effect of a sudden nucleosynthesis spike before the formation of a solar system on the Galaxy age is evaluated. The region of admissible values of the parameters of galacticnucleosynthesis theory is discussed. The method of uranium–thorium isotopic ratios is supplemented with the ²⁴⁴Pu/²³⁸U ratio for yet another cosmochronometer pair, and the Galaxy age is estimated on the basis of the model modified in this way.     

Determination of the CP properties of the Higgs boson from data on tau-lepton-decay products in the process e + e − → τ + τ − ν \bar \nu

The process e ⁺ e ^? → τ ⁺ τ ^? v $ \bar \nu $ , which is highly sensitive to anomalous Hττ interaction, is investigated within a model involving a new pseudoscalar Higgs boson. It is shown that the problem of separating the contributions of the scalar and pseudoscalar states of the Higgs boson can be solved via taking into account the polarizations of final-state particles. The inclusion of cascade tau-lepton decays makes it possible to determine reliably the CP state of the Higgs boson and to pinpoint the magnitude and sign of respective coupling constants.     

Analysis of data on proton-proton scattering in the energy range 100–1300 MeV

The results of a partial-wave analysis of data on proton-proton interaction in the energy range 100–1300 MeV are presented. The real parts of phase shifts were found for states of orbital angular momentum up to L = 9, while their imaginary parts were determined for states of orbital angular momentum up to L = 5. The sixth parameter of the S matrix was introduced in order to describe states of total angular momentum J = 2 and 4. The inelasticity thresholds were chosen individually for each state and were found to be substantially different from one another. The resulting solution was characterized by χ ² = 1.155 per point in the case where the number of experimental data was 12 841 and by a large imaginary part of the phase shift in the ³ P ₂-wave state at the edge of the energy range. Special features of the interaction in orbital states are discussed along with the energy dependence of integrated amplitudes and amplitudes of the scattering matrix at zero angle.     

Investigation of the mechanism of inelastic alpha-particle scattering on 28Si nuclei by the method of angular αγ correlations at E α = 30.3 MeV

The angular dependence of the differential cross sections for alpha-particle scattering on ²⁸Si nuclei and double-differential cross sections for the reaction ²⁸Si(α, αγ)²⁸Si at E _α = 30.3 MeV is measured for the case of alpha-particle emission angle between 20° and 160° and the excitation of low-lying states of the ²⁸Si nucleus (0⁺, ground state; 2⁺ state at 1.78 MeV; 4⁺ state at 4.62 MeV; 0⁺ state at 4.96 MeV; and 3^? + 4⁺, 6.88 MeV + 6.89 MeV). The spin-tensor components of the density matrix for the 2⁺ state at 1.78 MeV and the 4⁺ state at 4.62 MeV in the ²⁸Si* nucleus are reconstructed in a modelindependent way. Seven rank-6 components are reconstructed for the 3^? state at 6.88 MeV. Orientation features of ²⁸Si* are determined. The experimental data in question are compared with the results of the calculations performed under the assumption of the collective-excitation mechanism and by the coupled-channel method.