Proton-proton elastic scattering and nucleon resonance production at high energies

Angular distributions of proton-proton elastic scattering have been measured for incident beam momenta of 10.0, 12.0, 14.2 and 24.0 GeV/c over a range of lab scattering angles from 12 to 152 mrad. This is equivalent to a range of four-momentum transfer squared from about 0.1 to 6.7 GeV² at the highest momentum. Nucleon resonance production in the two-body reaction p + p → p + X has been studied at 24.0 GeV/c incident momentum from 13.5 to 112 mrad by measuring the proton momentum spectra from the elastic peak down to a momentum corresponding to a missing mass of about 2.6 GeV. The new data are compared with previous results and theoretical models.     

Pion small-angle multiple scattering at energies spanning the (3,3) resonance

The small-angle multiple scattering of positive and negative pions has been measured for C, Al, Cu and Pb targets throughout an energy range spanning the (3, 3) resonance. The measurements were made using two-dimensional multiwire proportional counters placed in the pion beam. All previous multiple scattering data for electrons and protons as well as these new data for pions are used to recalculate the empirical terms in the Moliere theory of multiple scattering. A second-order Born approximation multiple scattering theory has been devised for spin zero particles. Modified Moliere theory gives a better fit to the experimental data than the second-order Born calculation. Because the updated Moliere theory contains much simpler equations and gives closer agreement with experiment, it is recommended in place of the more sophisticated theory for the interpretation of new experimental data.     

DWBA approach to inelastic scattering at medium energies

Medium energy proton elastic and inelastic scattering to states of ⁵⁸Ni and ²⁰⁸Pb, and ⁴He elastic and inelastic scattering to states of ⁴⁰Ca, are analyzed using the partial wave approach, by solving the Schrödinger equation with relativistic kinematics and using the distorted wave Born approximation. Our results can be compared with results of several previous analyses of the nucleon inelastic data using the Glauber approximation. Our calculations are absolute, using nuclear collective parameters obtained from a survey of a large number of low-energy analyses of inelastic scattering of electrons, nucleons and nuclei from ⁴⁰Ca, ⁵⁸Ni and ²⁰⁸Pb.     

Neutrino scattering bound on intrinsic charm of nucleon

The uudc$\text{c}$ five-quark Fock component of the proton, recently proposed by Brodsky et al., is compatible with the CDHS upper bound on wrong-sign ν → μ⁺ events if the integrated charm probability per nucleon is at the suggested level λ = 0.01. With various realistic assumptions, the CDHS bound may be interpreted as λ < 0.025 with 90% confidence.     

Lepton scattering off few-nucleon systems at medium and high energies

The interpretation of recent JLab experimental data on the exclusive process A(e,e′p)B off few-nucleon systems is analyzed in terms of realistic nuclear wave functions and the Glauber multiple scattering theory, both in its original form and within a generalized eikonal approximation. The relevance of the exclusive process ⁴He(e,e′p)³H for possible investigations of QCD effects is illustrated.     

On the parametrization of pion nucleon scattering amplitude at energies less than 2 GeV

It is shown that 0⁺ pairing vibrations are associated with rather large mean square values of the quadrupole moment, indicating a pronounced intrinsic deformation. This deformation is demonstrated using a two level model, where the pairing vibration can be treated analytically within the quasi boson approximation. The results are compared with the data for the 6.06 MeV state in O¹⁶.     

On proton-deuteron backward elastic scattering at medium energies (II)

We examine rescattering corrections to the single nucleon exchange model of backward p-d elastic scattering and find them to be important at all energies. Using realistic deuteron wave functions we conclude that the rise at E_p (lab) ～ 400–600 MeV results from another mechanism, possibly the opening of the $\text{p}\text{+}\text{d}\text{→}\text{NNN}{}_{33}{}^1$ channel.     

“Spin-orbit deformation” in inelastic scattering of protons at medium energies

Distorted-wave Born-approximation calculations for medium-energy proton inelastic scattering to collective states, which use microscopic, spin-dependent optical potentials that properly describe proton elastic analyzing powers, show that inclusion of the deformation or collectivity of the spin-orbit term in the inelastic transition matrix element has an important effect on predictions for the available inelastic angular distributions and analyzing powers.     

Antiproton-hydrogen scattering at low-eV energies

In the scattering of negative particles other than the electron by atoms at lab-frame energies around 10 eV, an elastic process termed “brickwall scattering” might lead to a high probability for scattering angles around 180°. For an antiproton slowing in hydrogen, this backward scattering would result in the loss of nearly all of its energy in a single collision, since it and a hydrogen atom have nearly the same mass. Such energy loss would have a significant effect on the energy distribution of antiprotons at energies where capture by the protons of hydrogen is possible and might, thereby, affect the capture rate and the distribution of capture states. In the semiclassical treatment of the problem with an adiabatic potential energy, brickwall scattering is indeed present, and with a substantial cross section. However, this model appears to underestimate inelastic processes. Based on calculations for negative muons on hydrogen atoms, these processes appear to occur for about the same impact parameters as brickwall scattering and thus substantially reduce its effect.     

Pion bound states in nuclei

Bound π-nuclear states can appear under certain realistic conditions in finite nuclei. The best prospects are certain medium-weight nuclei with dense central regions and large neutron excess. Numerical illustrations are given for ¹⁶O, ²⁸Si, ³²Na and ²⁰⁸Pb with realistic parameters for the interaction. Further, we show that the usual low-energy π nuclear potential develops pathological features like an infinity of bound states beyond a certain critical strength. The natural remedies are indicated.     

Interferometry from a scattering medium

A two-beam random interferometer is demonstrated where coupling is facilitated by a scattering medium. A modulation observed in the normalized second-order intensity frequency correlation of the transmitted light is attributed to the relative temporal delay of the two beams and is insensitive to beam alignment and spacing.     

Pion cloud and the sea of the nucleon

I review recent progress in understanding the structure of the nucleon sea and the role of the nucleon’s pion cloud. In particular, I discuss the consequences of the pion cloud for the ƌ−ū asymmetry in the proton, the neutron’s electric form factor, and the proton’s electric to magnetic form factor ratio.     

Microscopic study on proton elastic scattering of light exotic nuclei at energies below than 100 MeV/nucleon

The proton elastic scattering data on some light exotic nuclei, namely, ^{6, 8}He, ^{9, 11}Li, and ^{10, 11, 12}Be, at energies below than 100MeV/nucleon are analyzed using the single folding optical model. The real, imaginary, and spin-orbit parts of the optical potential (OP) are constructed only from the folded potentials and their derivatives using M3Y effective nucleon-nucleon interaction. These OP parts, their renormalization factors and their volume integrals are studied. The surface and spin-orbit potentials are important to fit the experimental data. Three model densities for halo nuclei are used and the sensitivity of the cross-sections to these densities is tested. The imaginary OP within high-energy approximation is used and compared with the single folding OP. This OP with few and limited fitting parameters, which have systematic behavior with incident energy, successfully describes the proton elastic scattering data with exotic nuclei.     

Relativistic double differential cross sections for Compton scattering by bound electrons: Test at low photon energies and predictions at intermediate photon energies

Cross section profiles d²σ/dΩdω′ for Compton scattering of photons by bound electrons are calculated for all subshells of the atom. Results obtained from the form factor approximation and from a relativistic version of the impulse approximation are compared with experimental data for Cu and Pb at a scattering angle ofθ=145° and a photon energy of 662 keV. The impulse approximation proves to be superior to the form factor approximation and is used to predict cross section profiles for a primary energy of 50 MeV and different scattering angles and charge numbers. It is shown that only for the heaviest atoms and scattering angles belowθ=5° there is a non-negligible contribution of Compton scattering to the elastic peak.     

Hadron-nucleon elastic scattering at high energies

A review of experiments on high energy hadron-nucleon elastic scattering is given. Emphasis is placed on the most recent experiments at FNAL and CERN/ISR. Results (mostly preliminary) are discussed and compared with earlier experiments.Presented at the Symposium on Hadron-Hadron Scattering at High Energies, Liblice, Czechoslovakia, June 16–21, 1975.I like to thank the Czechoslovakian Academy of Sciences and the Organizing Committee of the Symposium, especially Dr. J.Fischer, for their invitation and hospitality. I am indebted to D. D.Jovanovitch of the Michigan-Argonne-Fermilab-Indiana collaboration for sending me their data prior to publication.