Soft gluons in semi-inclusive deep inelastic experiments

The longitudinal and transverse properties of the QCD contribution to semi-inclusive deep inelastic scattering is worked out within the soft gluon resummation procedure. The Λ parameter needed to reproduce the data is in agreement with the value extracted from scaling violations. The intrinsic transverse momentum squared of a quark inside a proton is around 0.45 GeV². Predictions for the transverse correlations $\text{〈}\text{p}{}_{\mathrm{1\perp }}\text{·}\text{p}{}_{\mathrm{2\perp }}\text{〉}$ of two outgoing pions are guven.     

Pion production and the higher resonances in pion-nucleon scattering

The reaction π + N → 2π + N has been studied in the vicinity of the higher resonances in the pion-nucleon cross section. The Low equation for the production amplitude is transformed into an integral equation by isolating the true one-meson intermediate states and discarding higher order contributions. The only part kept in the inhomogeneous term corresponds to the collision of a pion in the nucleon cloud with the incident pion in the resonant T = J = 1 state, which is simulated by an unstable vector Boson. Crossed terms are neglected and the 2π-N state is described by the static model. The terms kept in the sum over states describe the rescattering (off the nucleon) of one of the outgoing pions. The required off-the-energy-shell elastic scattering amplitude is approximated by the 3-3 resonance formula of Chew and Low. With these simplifications the Low equation for the production amplitude reduces to an easily soluble linear integral equation. The rescattering amplitude, which dominates the inhomogeneous term in the resonance region, is proportional to the 3-3 scattering amplitude of one of the outgoing pions. Although the result provides some support for the conventional isobar model, it is important to note that the largeness of the rescattering term arises from scattering far off the energy shell, rather than by “real” excitation as in the phenomenological isobar model. Quantitative calculations for the $\text{D}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ channel leading to a p-wave ($\text{J =}\text{3}\text{2}$) and an s-wave pion produce a maximum in the cross section near 600 Mev incident pion lab energy. For a π-π resonance energy squared S = 10, agreement with experiment is obtained with a width about one third that suggested by nucleon electromagnetic structure. In our approximation, the well known 600 Mev $\text{D}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ isospin $\text{1}\text{2}$ resonance occurs at the same energy as the 800 Mev $\text{D}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ isospin $\text{3}\text{2}$ resonance. It is assumed, but not proved, that the neglected terms are responsible for the splitting of the resonance energies. When this splitting is taken into account, the predicted charge state ratios near the second resonance agree well with existing data. The “third” resonance occurs for the state having two p-wave pions, according to the present theory, although no numerical calculations were made for this case. This point of view suggests that the $\text{F}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$, $\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$, and $\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ incident channels contribute to the third resonance.     

Resonant-Raman scattering from quasi-localized excitons in semiconductor quantum wells

Large polarization-dependent resonance enhancement is observed in first and second order Raman scattering in multiple quantum well $\text{GaAs}\text{(Al}{}_{\mathrm{x}}\text{Ga}{}_{\mathrm{1-x}}\text{)As}$ and $\text{GaAs}\text{AlAs}$ semiconductor heterostructures. Resonance enhancement is much stronger in the forbidden polarization than in the allowed and shows double resonance behaviour at incoming and outgoing photon energies. The resonance is stronger at incoming photon energies for one-phonon scattering and at outgoing photon energies for two-phonon scattering.     

Classical many-body model for heavy-ion collisions incorporating the Pauli principle

A classical model for heavy-ion collisions, introduced previously, has been extended to include certain effects of the Pauli principle. All nucleons are treated equally. They obey classical dynamics and interact through an ordinary two-body force and through a momentumdependent two-body “Pauli core” which satisfies, approximately, that $\text{p}{}_{\mathrm{ij}}\text{r}{}_{\mathrm{ij}}\text{≧ξ}\text{h}\text{?}$, where ξ is a dimensionless constant. A form for the Pauli core is presented. The ordinary two-body force has been adjusted to fit bulk properties of nuclei and to reproduce that moment of nucleon nucleon scattering cross sections which is relevant to hydrodynamics. The parameters of the forces are given.     

QCD effects in νN scattering above the threshold of W-boson production

The QCD effects are shown to result at $\text{s}\text{m}{}_{\mathrm{<mtext>w</mtext>}}{}^2\text{? 1}$ in a considerable increase of the νN cross section and modification of $\text{d}\text{σ}\text{d}\text{y}$ in comparison with scaling. At $\text{s}\text{m}{}_{\mathrm{<mtext>w</mtext>}}{}^2\text{≈ 3 × 10}{}^3$ the QCD cross section is twice that of scaling. At $\text{s}\text{m}{}_{\mathrm{<mtext>w</mtext>}}{}^2\text{? 1}$ the QCD structure functions of the nucleon acquire effective scaling behaviour.     

Transition magnetic moments of hadrons and sidewise dispersion relations

Systems of linear relations for the magnetic moments of the nucleon and transition moments μ_ωπγ, μ_?πγ and ${}^{\mathrm{\mu }}\text{N}{}^1{}_{1470}\text{N}\text{γ}$ are obtained on the basis of sidewise dispersion relations in the one-pion approximation. In such an approach the magnetic moments of the transition ω(?)→ πγ and $\text{N}{}^1{}_{1470}\text{→Nγ}$ are expressed in terms of the anomalous magnetic moments of the nucleon and the strong interaction coupling constants.     

f72 neutron occupancies in the Ca isotopes

Methods of obtaining nucleon occupancies from total energy-weighted sum rules for spectroscopic factors are described and applied to $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ neutron transfer data for Ca isotopes. The $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ neutron occupancies obtained are consistent with shell model expectations and, for ⁴¹Ca and ⁴³Ca, with values previously obtained from an analysis using non-energy-weighted sum rules.     

Some aspects of the quark parton model

A modified Kuti-Weisskopf model which satisfies the Feynman threshold constraints is considered further. Detailed predictions for the sum of neutrino and anti-neutrino differential cross sections on nucleon (which can be readily compared with forthcoming NAL data), the shapes of the structure functions $\text{?}{}_2{}^{\mathrm{\nu p,\nu n}}$ and the ratio $\text{?}{}_2{}^{\mathrm{\nu p}}\text{/?}{}_2{}^{\mathrm{\nu n}}$, and spin-dependence of inelastic electron-nucleon scattering versus scaling variable x are delineated. We also compare in some detail the general features of our model with the “model independent” approach of Feynman for quark parton theory.     

Gluon exchange corections to the nucleon magnetic moment in the mit bag model

We have calculated gluon exchange corrections to the nucleon magnetic moment predictions of the MIT bag model. The sizeable coupling constant $\text{g}{}^2{}_{\mathrm{c}}\text{/}\text{4π=0.5}$ does not produce an enormous correction (≈10%), but it is in the wrong direction to ameliorate the present 30% disagreement with experiment.     

Dynamical rescaling and universality of hadron structure functions

We argue that pion and nucleon structure functions differ principally due to their different numbers of quarks and different scales of confinement. The former generates an x rescaling while the latter, in QCD, gives rise to a Q² rescaling. Together these lead to the relation

with $\text{ξ}{}_{\mathrm{<mtext>N</mtext><mtext>\pi </mtext>}}\text{? 0.16}$, for x values away from the end points. This relation is in good agreement with data.     

Valence quark dominance in inelastic neutrino interactions

Scaling observed in neutrino nucleon interactions at relatively low energies and not too small , is attributed to elastic $\text{v(}\text{v}\text{)}$ scattering off three point-like, handed Zweig-Gell-Man valence quarks with low effective mass. The model predicts total inelastic cross sections all in agreement with available experiments.     

The pair correlations down to r = 0 in a fully ionized dilute and homogeneous hydrogen plasma in equilibrium

The pair correlations in a fully ionized dilute and homogeneous hydrogen plasma in equilibrium are calculated down to r = 0 on the basis of the equilibrium hierarchy of statistical mechanics and the linear superposition approximation. Thereby the Coulomb potential between electron and proton is modified by a damped potential with finite value at r = 0 which is due to quantum corrections given by Hagenow and Koppe. The solution of the hierarchy equations is quite simple: For $\text{r > γ}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{l}{}_{\mathrm{D}}\text{(γ = 5 × plasma parameter, l}{}_{\mathrm{D}}\text{= Debye-length)}$ one obtains the well-known result by Debye and Hückel, for $\text{r < γ}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{l}{}_{\mathrm{D}}$ the pair distribution functions are simply given by the corresponding Boltzmann factors. The calculation of the energy of the system leads to the result that the nonideal part is coming from the Debye-Hückel part of the pair correlations only.     

Nucleon-nucleus optical potential in a relativistic theory of nuclear matter

From a relativistic model of nuclear matter the optical potentials for nucleon scattering from ⁴⁰Ca and ⁹⁰Zr are obtained. These potentials are derived from the properties of the target nucleus and are essentially universal. This means that the integrated strength of the optical potential $\text{J}{}_{\mathrm{A}}\text{= (}\text{1}\text{A}\text{) ∫}\text{d}{}^3\text{r U}{}_{\mathrm{<mtext>op</mtext>}}\text{(r)}$ is very weakly dependent on A. The optical potential for antiparticle-nucleus scattering is also computed.     

Theoretical analysis of the centrifugal distortion contributions to the rotational spectra of 2Π diatomics

The centrifugal distortion contributions to the rotational energies of diatomic molecules are derived from the resolution of the vibration-rotation wave equation. The unknown radial dependence of the fine structure constants is taken into account by means of a Taylor expansion around the equilibrium distance. Hence, one obtains the expressions of the centrifugal corrections associated with each fine structure constant in terms of the equilibrium values of its radial derivatives. The case of ²Π states is examined in detail. The dependence of the centrifugal distortion effects upon the choice of the coupling scheme representation is exhibited and a ²Π energy matrix containing the centrifugal constants of any order is proposed. Such a matrix is appropriate to fit the data for any value of the rotational quantum number. The theoretical expressions of the energy levels are related to the experimental data and the correlations between the spin-orbit centrifugal and spin-rotation contributions are put in evidence. It is shown that very compact formulas can be derived allowing a straightforward evaluation of the successive radial derivatives of the spin-orbit function in terms of the spectroscopic data $\text{A}{}^{\mathrm{(1)}}\text{? ?α}{}_{\mathrm{A}}\text{(}\text{w}{}_{\mathrm{e}}\text{B}{}_{\mathrm{e}}\text{)}$; $\text{A}{}^{\mathrm{(2)}}\text{? ?(1 +}\text{α}{}_{\mathrm{B}}\text{w}{}_{\mathrm{e}}\text{2B}{}_{\mathrm{e}}{}^2\text{)A}{}^{\mathrm{(1)}}$; …. Application of these results to the case of several molecules is considered and discussed.     

π+-Electroproduction of hydrogen near threshold at four-momentum transfers of 0.2, 0.4 and 0.6 GeV2

The reaction e + p → e′ + π⁺ + n was measured near the one pion threshold, detecting the final electron and neutron in coincidence for values of q² = 0.2, 0.4 and 0.6 GeV². The normalized axial vector form factor to the nucleon $\text{F}{}_{\mathrm{<mtext>A</mtext>}}\text{(q}{}^2\text{)}\text{F}{}_{\mathrm{<mtext>A</mtext>}}\text{(0)}$ was determined from the data within a theoretical framework based on PCAC and current algebra.     

Combination tones in the response of single degree of freedom systems with quadratic and cubic non-linearities

The method of multiple scales is used to analyze the response of a single-degree-of-freedom system to either the combination resonance of the additive type $\text{Ω}{}_2\text{+ Ω}{}_1\text{≈ ω}{}_0$ or the combination resonance of the difference type $\text{Ω}{}_2\text{? Ω}{}_1\text{≈ ω}{}_0$, where $\text{Ω}{}_1$ and $\text{Ω}{}_2$ are the frequencies of the excitation and ω₀ is the linear undamped natural frequency of the system. To the second approximation, the combination resonance of the additive type has three effects on the steady state response. First, it produces terms having the frequencies $\text{Ω}{}_1\text{, Ω}{}_2$ and $\text{Ω}{}_2\text{+ Ω}{}_1$ at first order and terms having the frequencies 0, $\text{2Ω}{}_1\text{, 2Ω}{}_2\text{, Ω}{}_2\text{? Ω}{}_1$, $\text{2(Ω}{}_2\text{+ Ω}{}_1\text{), Ω}{}_2\text{+ 2Ω}{}_1$ and $\text{2Ω}{}_2\text{+ Ω}{}_1$ at second order. Second, it produces a shift in the natural frequency of the system. Third, it produces a virtual primary-resonant excitation having the frequency $\text{Ω}{}_2\text{+ Ω}{}_1\text{≈ ω}{}_0$ that makes the component having the frequency $\text{Ω}{}_2\text{+ Ω}{}_1$ be of first rather than second order. Similar effects are produced by a combination resonance of the difference type or a superharmonic resonance of order two.     

Spin dynamics in the quasi-1 dimensional spin-glass FeMgBo4

The results of an inelastic neutron scattering investigation performed on the insulating title compound are presented. The spin dynamic is well described by a relaxation model leading to a quasi-elastic Lorentzian neutron-scattering line. The relaxation rate $\text{1}\text{τ}{}_{\mathrm{R}}$ is a linear temperature function for T>20 K, which is ascribed to the isotropic and 1-D character of the spin correlations. At T = 20 ? 5 K a drastic drop in $\text{1}\text{τ}{}_{\mathrm{R}}$ is observed reflecting a “crossover” to a highly frustrated 3D-spin glass state.     

Baryon asymmetry and nucleon decay in supersymmetric guts

In a class of supersymmetric GUTs with a coloured Higgs sector of an intermediate mass, we study nucleon decay and the generation of baryon assymmetry. We find that: (a) a non-vanishing baryon asymmetry can be generated by the decay of coloured Higgs bosons and Higgs fermions into quarks and squarks; (b) nucleons decay at a rate 10^?31 yr^?1 preferably to $\text{μ}{}^{\mathrm{+}}\text{K}{}^0\text{,}\text{ν}{}_{\mathrm{\mu }}\text{K}{}^{\mathrm{+}}$ while decay involving dimension-five operators is kinematically excluded.     

Proton pole contribution in proton decay

We show that nucleon pole terms contribute significantly to proton decay, increasing the branching ratio for e⁺π⁰ and $\text{ν}{}_{\mathrm{<mtext>R</mtext>}}\text{π}{}^{\mathrm{+}}$ modes. The total lifetime is decreased to the point where keeping the SU(5) value of the lifetime below the experimental upper bound forces us to the choice of QCD scale parameter and proton radius parameter which are near the edge of the allowed region.     

Theory of kaonic atoms

A nonlocal energy-dependent self-consistent kaon-nucleus optical potential is derived for kaonic atoms. Energy level shifts and widths are calculated for several light nuclei, and the results are compared with experiment. The sensitivity of the results to changes in parameters of the nuclear matter distribution is studied. Nonlocality and off-energy-shell effects are examined.The optical potential is derived by means of a Brueckner-type many-body theory with the independent pair approximation for the kaon and the nucleon. The two-body interaction on which the optical potential depends is represented by separable potentials of the Yamaguchi form. Coupled channels ($\text{K}\text{N}$ and Σπ) are used for the I = 0 states, which are dominated by the $\text{Y}{}_0{}^1$ resonance, and only a single channel ($\text{K}\text{N}$) is used for the I = 1 state.Calculations are carried out in three levels of approximation of the nonlocal energy-dependent optical potential. In no approximation is the potential found to be proportional to the nuclear density. Indeed, the real part of the potential changes sign in the nuclear surface. Sensitivity of the results to variations in the nuclear matter distribution is investigated and found to be on the order of experimental error. Nonlocality and off-energy-shell effects are estimated to be at least as large as this error, so that these effects must be included if one wishes to extract information about the nuclear surface from the existing experimental data. The use of correct nucleon wavefunctions and binding energies is similarly found to be essential in the calculation.