Regge pole analysis of inelastic e - p scattering data

Based on the Regge pole fit to the high energy data on the e-p structure functions the q²-dependence of the Pomeranchuk and A₂ residues is determined in the non-scaling region. A FESR for vW₂ together with knowledge of these Regge residues is employed to confirm the existence of the J = 0 fixed pole in the virtual Compton amplitude.     

李模型中极点的运动

本文指出,在李模型中,不论有否左方割线和非弹性割线,只要不引入CDD极点,第二叶不具有代表共振态的极点。当CDD极点被引入后,第二叶极点可能在偶合常数增加时穿过正常割线而走入第一叶,但在这以前,另有一极点自左方(或穿过左方割线,或在-∞)走入第一叶。文中画出了一种情形下的二叶的全部极点的运动。     

Non-diffractive production of meson resonances

We study the peripheral cross sections of resonances that cannot be produced by π-exchange. In particular, we concentrate on the four meson nonets expected as L = 1 quark states (i.e., the J^P = 0⁺π_N(980); J^P = 1⁺ A₁, B; J^P = 2⁺ A₂). We use SU(3), Regge poles, factorization, exchange degeneracy, pole extrapolation, and the vector-meson-photon analogy. We predict the cross sections in both photoproduction and non-diffractive hadronic reactions. In passing, we discuss the large unnatural-parity (B, K?Q_B) exchange contributions and even the possibility of studying ππ → πω while avoiding the B production background.     

Threshold Behaviour of Simple and Double Regge Pole Trajectories

The threshold behaviour of simple and double Regge pole trajectories is studied. It is shown that for a number of cases two particle unitarity gives rise to moving J-plane zeros, colliding at threshold with Regge poles. Conditions are found for which Regge trajectories near the threshold S = S₀ have square-root behaviour independent of the value of α(S₀).     

Factorization and the couplings of the vacuum trajectory

The decoupling theorems associated with an isolated factorizable pomeron pole of unit intercept are re-examined. It is found that the coupling of three such poles, Γ(t, t, 0), need not vanish, precisely at the point t = 0. This is demonstrated by summing only over states in the appropriate unitarity sum, and sum rule, which are consistent with the M², s/M² → ∞ limit. The triple-Regge region then makes a constant contribution to σ_total, insteadsb of the ln lns result obtained if the isolated pole is assumed to couple also to states such that s/M² = constant. The physical implications regarding factorization and the pole-cut relationship are discussed. The relationship between higher order optical theorems (Mueller discontinuities) and particular terms in the unitarity sum for the two → two absorptive part A₂₂ is exploited. Consistent contributions to the triple-Regge region contribute constant vertex corrections to pure pole behaviour in A₂₂. There is no cut contribution and the magnitude of the vertex corrections reflects the relative amount of diffractive production. The analysis is extended to multiple fireball production where pure multipole structures emerge. The series naturally terminates if the diffractive component is sufficiently small. The implications for the behaviour of the total cross section at machine energies are discussed.     

P-Matrix analysis of the dibaryon1 D 2 resonance

We study the relation between intermediate energy nucleon-nucleon scattering and the eigenstates of the bag model using theP-matrix formalism. Data of existing phase-shift analyses are employed to calculate theP-matrix for the coupled¹ D ₂(pp) and⁵ S ₂(NΔ) channels in the energy region above the Δ-isobar production threshold. TheP-matrix calculated for the equivalent hadronic bag radiib=1.4?1.5 fm is shown to have a pole in the mass range 2.31–2.34 GeV in agreement with the MIT bag model prediction of theI=1,J ^P =2⁺ 6-quark state with the mass 2.34 GeV. The hadronic shift of this state is shown to be ≈200 MeV; the dibaryon pole of theS-matrix is located at the energy 2.15–2.17 GeV with the width ≈100–200 MeV.     

Scattering of charged particles by atoms

A closed variant of the Born approximation for calculating differential scattering cross sections in ion-atom collisions is developed. An expression in terms of the matrix elements J _ij with respect to the single-electron states of the atom is found for the matrix element describing the target atom in the formula for the differential cross section. The matrix elements J _ij are averaged over the relative orientation of the momentum transferred in the collision and the symmetry axis of the electronic orbitals of the target atom, using the single-electron Rutaan-Hartree-Fock wave functions. The algebraic representation of the matrix elements J _ij makes it possible to perform calculations for atoms with any value of Z. The model developed is used to calculate the cross sections σ_Σ and characteristic scattering angles θ_c for the process of electron loss by H^? ions with energy E = 0.1–100 MeV in targets consisting of atoms with Z = 2–54. It is shown that σ_Σ ∝ E ^?1 and θ_c ∝ E ^?1/2 for all Z, and for fixed E the behavior of σ_Σ(Z) and θ_c(Z) is determined by the order of filling of the electronic shells of the target atoms (the ionization potential). The computational results are analyzed and compared with the experimental data and the results of other calculations.     

Dynamically generated resonances from the vector octet-baryon octet interaction

We study the interaction of vector mesons with the octet of stable baryons in the framework of the local hidden gauge formalism using a coupled-channels unitary approach. We examine the scattering amplitudes and their poles, which can be associated to known J ^P = 1/2^-, 3/2^- baryon resonances, in some cases, or give predictions in other ones. The formalism employed produces doublets of degenerate J ^P = 1/2^-, 3/2^- states, a pattern which is observed experimentally in several cases. The findings of this work should also be useful to guide present experimental programs searching for new resonances, in particular in the strange sector where the current information is very poor.     

Determination of the coupling constants 3Hdn, 3Hπ and 3He3Heπ from data on the differential cross sections OF n3H and n3He elastic scattering

A determination of the coupling constants ³Hdn, ³H³H_π and ³He³He_π from existing differential cross section data for n³H and n³He elastic scattering has been carried out. The method is based on the extrapolation of dσ/dΩ to the deuteron and pion poles, exploiting conformal mapping techniques. Calculations result in a value of the ³Hdn coupling constant which is ≈ 20% smaller than dispersion relation predictions. A comparison of the value obtained with predictions based on nuclear models allows one to discriminate between different potentials. The residue at the pion pole turns out to be too weak and the conclusion is drawn that it is impossible to determine the coupling constants ³H³H_π and ³He³Heπ on the basis of existing data.     

General results on glueball masses in QCD

A number of authors have investigated mass inequalities for mesons and baryons in QCD. These provide rigorous non-perturbative constraints on the mass spectrum. Similar inequalities for glueballs are investigated. For nonzero spin J, in the large-N_c approximation, m_J⁻⩾m_J⁺ is found. (For J = 0, the existence of a gluon condensate can modify this statement.) There are also constraints on how fast m_J can grow with J. For example, for m_J = a + bJ^α, 0 ⩽ α ⩽ 1 is found, a result consistent with Regge behaviour.     

Line shape and excitation strength of the first excited state in9Be

The line shape and the excitation strength of the very weak first excited J ^π =1/2⁺ state at E_x=1.684 MeV in Zeitschrift für Physik Zeitschrift für Physik⁹Be has been investigated with high-resolution inelastic electron scattering at E₀=45 and 49 MeV and scattering angles θ=105°, 117°, 129° and 165°, and with high-resolution inelastic proton scattering at E₀=13MeV and θ=15° and 18°. Due to lying just above the neutron threshold the level has a strongly asymmetric line shape which in both experiments can be described consistently with a Breit-Wigner expression modified on the low energy side by the threshold behaviour of the cross section. The resonance energy is E_R=1.684 ± 0.007 MeV and the width T=217± 10 keV in thec.m. system. A single particle potential model calculation reproduces the line shape and the resonance parameters fairly well. In addition, the inelastic electron scattering form factor has been measured. In the range of momentum transfersq =0.24-0.46 fm^?1 it is dominated by a 0p_3/2→ 1s_1/2 particle-hole transition. The transition is mainly longitudinal and of isoscalar nature with a strength of B (E1)↑ =0.027 + 0.002 e² fm², but a small M2 contribution ofB(M2)↑=8.8 ±1.5 μ _N ² fm² has also been detected.     

Geometrical description of binary reactions and large p⊥ phenomena

We study consequences of defining the impact parameter as being the variable conjugate to transverse relative c.m. momentum, p_⊥. This coincides with a proposal originally made by Chang and Raman. The dynamical information carried by these are intimately connected to the behaviour of 90° scattering. In particular, impact parameter dynamics is a priori qualitatively different from direct channel angular momentum dynamics. A phenomenological study of elastic π^±p and pp data at fixed values of longitudinal momentum, p₆, leads to a generalized geometrical scaling hypothesis. In contrast with the power behaviour predicted by parton models, the data suggest exponential behaviour of the scaling amplitudes at fixed p₆ of the type e^Rp⊥ with R ? 1 fm. Correspondingly these amplitudes are described by a pair of complex conjugate singularities on the imaginary axis in the impact parameter plane.     

Electromagnetic scattering as a radiation reaction problem

Electromagnetic scattering is treated as a dynamical problem, by equating the external torque exerted by the incident wave on the sphere to the self torque due to the radiated (scattered) wave. ForI _mech=0,our scattering amplitude is equal to the usualP-wave amplitude of the electromagnetic scattering on an infinitely conducting sphere. The poles of the scattering amplitude, in particular their dependence onI _mech, are studied. For example, a pole on the positive imaginary axis, which usually corresponds to a bound state, corresponds to a runaway solution in our case. Non-decaying resonances are also discussed.     

Description of the low-energy doublet neutron-deuteron scattering in terms of parameters characterizing bound and virtual triton states

Low-energy doublet neutron-deuteron scattering is described in terms of the energies of the bound and virtual triton states and the nuclear vertex constants for these states. For the first time, the van Oers-Seagrave formula is derived from the Bargmann representation of the S matrix for a system having two states. The presence of a pole in this formula is shown to be a direct corollary of the existence of a low-energy virtual triton state. Simple explicit expressions for the nd scattering length and for the pole of the function kcotδ are obtained in terms of the parameters of the bound and virtual triton states. The low-energy parameters of nd scattering are calculated numerically, whereby it is shown that these parameters are highly sensitive to variations in the asymptotic normalization constant C _v ² for the virtual state. The C _v ² value fitted in our model to the experimental result for the nd scattering length is 0.0592.     

Experimentelle untersuchung der 5d6s6pz 2 F 5/2,7/2-Terme im Lanthan I-Spektrum unter Verwendung von Levelcrossing-Spektroskopie

The hyperfinestructure-interaction-constantsA/g _J andB/g _J of the 5d 6s6p z ² F _5/2,7/2 terms in the La I-spectrum were measured by levelcrossing technique. Using a La-atomic beam many levelcrossings between magnetic sublevels with ¦Δm¦=2 were detected in both terms by resonance scattering. Values for the lifetime of each state were deduced from the widths of Hanle-effect- and levelcrossing-signals.     

Effective-range function for doublet nd scattering from an analysis of modern data

The parameters of the generalized effective-range function K(k ²) having a pole are found by using the results that were obtained by calculating the S-wave phase shift δ(E) for doublet nd scattering and the triton binding energy on the basis of Faddeev equations and within the N/D method and which were presented in the literature. The convergence of the expansion of K(k ²) in powers of momentum is studied. The binding energy of the virtual triton and the residues of the partial-wave scattering amplitudes at the poles corresponding to the bound and virtual states are calculated. Correlations between the binding energies of the bound and virtual states of the triton, on one hand, and the doublet scattering length for nd interaction, on the other hand, are considered. The function K(k ²) is also calculated within a two-body model featuring various potentials.     

Reggeized symmetry models and pion-nucleon scattering in forward and backward directions

A Reggeization procedure is developed for higher symmetry schemes and its relationship with the SU(6) × SU(6) Reggeization is exhibited. The kinematic singularities arising from SU(6)_W-invariant vertex functions are removed with the help of fixed cuts and the resulting scattering amplitudes are extrapolated to hadron poles. The essentially parameter free theory thus obtained is shown to lead to reasonable forward and backward differential cross sections in pion-nucleon scattering at high energies.     

Triple differential cross section for angle,atomic number and energy (or angular momentum transfer) calculated for the 280MeV40Ar+58Ni (or 365MeV63Cu+197Au) system in a simple model

Highly excited levels of³³S populated by α-particle capture in²⁹Si have been investigated forE _α=1.962 MeV to 4.287 MeV. Excitation curves measured with Ge(Li) and BF₃ detectors are reported. More than fifty resonances can be identified with levels in³³S. (α, γ) angular distributions measured on five strong resonances have yieldedJ ^π values 1/2+, 3/2 +, 5/2?, 5/2?, 5/2? and 3/2+ respectively, for theE _x =10.054, 10.466, 10.523, 10.721, 10.758 and 10.776 MeV levels in³³S. Elastic scattering experiments have been performed and theJ ^π assignments are found to be consistent with thel-values inferred from the elastic scattering data. Decay schemes from the above³³S levels have been proposed. A new level at 9.245 MeV is also suggested and theJ ^π values for the 4.425 and 2.87 MeV states are shown to be consistent with 7/2+ and 3/2+ assignment, respectively. Nuclear Reactions²⁹Si(α, γ) and²⁹Si(α, α),E _α=1.962-4.287 MeV. Measured relative σ(E). DeducedJ ^π andE _γ of³³S levels. New³³S level atE _x =9.245 MeV. Enriched targets.     

Raman scattering from electronic excitations of samarium in semiconducting and metallic Sm1−xYxS

The Raman spectra of Sm_1?xY_xS for $\text{x?0.4}$ have been measured. Electronic scattering between the J = 0 ground state and the J = 1 and 2 excited states of Sm²⁺ is observed. The singlet-triplet transition is observed on both sides of the black to gold phase transition in Sm_1?xY_xS.