Gamma and π0 production by 4 GeV/cπ+p interactions

Inclusive data for the production of γ rays and π⁰ are presented from an experiment with a 4 GeV/cπ⁺ beam, using a track-sensitive target. The results are compared with data at other energies and with π⁺and π^? distributions.     

An inclusive study of π-, K0 and a production from pn reactions at 11.6 GeV/c

Cross sections, multiplicities and particle inclusive spectra are presented for π^-, K⁰ and Λ produced in pn reactions at 11.6 GeV/c beam momentum. The results are compared with the data from pp interactions in the same energy range. Correlations between two π^- are also discussed. The main results are: the π^-, K⁰ and Λ all behave similarly as a function of transverse momentum squared; π^- in the forward c.m. hemisphere have spectra in x and y consistent with that of pp interactions, whereas the spectra of π^- in the backward hemisphere fall off more slowly with ∥x∥ and ∥y∥ than those in the forward hemisphere, suggesting n-fragmentation effects. The K⁰ and Λ have x and y distribution roughly similar to those in pp interactions. The K⁰ and Λ are consistent with a modified form of KNO scaling.     

Production and decay of the π−π−π+ system in the reaction π−d → dπ−π−π+ at 9 GeV/c

In this paper we present a study of the reaction π^?d → π^?π^?π⁺d at 9 GeV/c. The mass spectra are in fair agreement with the predictions of a reggeized pion-exchange Deck model. However, the s-channel azimuthal angular distribution indicates a ?-exchange Deck contribution. The results of the partial-wave analysis of the (3π)^? system are compared with those obtained in a hydrogen target: the J^P = 2⁺ contribution is very small (at most 1.5 ± 1.2)% in our data, which are dominated by J^P = 1⁺ for low mass, whereas the J^P = 0^?, 1⁺, 2^? have comparable importance in the higher mass region.     

High-resolution Fourier spectrometry of 15N2 infrared emission spectrum: Extensive analysis of the B3Πg-A3Σu+ system

The emission spectrum of the B³Π_g-A³Σ_u⁺ system of the ¹⁵N₂ molecule was recorded between 3500 and 12 500 cm⁻¹ with a high-resolution Fourier spectrometer. Twelve bands with 0 < v′ < 5 and 0 < v″ < 9 are analyzed. The molecular parameters of the B³Π_g and A³Σ_u⁺ states are obtained by a complete fitting procedure. Derived values of equilibrium constants are deduced; the Franck-Condon factors are calculated for the B-A system of ¹⁵N₂.     

First measurement of the exclusive (p,e+e−) reaction

We present the first data on the exclusive (p,e⁺e⁻) reaction in a nucleus. Cross sections for populating the ground state and first excited state in the residual nucleus are presented for the reaction ¹¹B(p, e⁺e⁻)¹²C at 98 MeV. The e⁺e⁻ momentum vectors were measured with a high-resolution magnetic pair spectrometer. The distributions of the virtual photon invariant mass and of the direction of the electron in the virtual photon rest system are compared with a simple single-nucleon model. The (p,e⁺e⁻) cross sections are compared with corresponding data for the (p, γ) reaction obtained with the same apparatus. The (p,e⁺e⁻) cross sections show substantial enhancement over what is expected from the simple model.     

The reaction γp → pπ+π−π+π− for photon energies from 25 to 70 GeV

Measurements of the reaction γp → pπ⁺π^?π⁺π^? are presented, in which π⁺π^?π⁺π^? systems with masses up to 3 GeV are produced from fragmentation of the incident photon. The reaction is dominated by production of the large peak of the ?′(1600) meson and, at higher masses ?2 GeV, y production of jet-like 4π systems. The ?′(1600) meson is produced by a predominantly s-channel helicity conserving mechanism. At higher masses there are also indications of ?π peaks, of masses 1.3 GeV (the A₂ meson) and 1.75 GeV, produced with a recoiling π meson by a mechanism consistent with the Deck effect.     

Study of the reactions K−p → Λ0+ neutrals in the C.M. energy range from 1580 to 1750 MeV

Results on the channels K^?p → Λ⁰η⁰, Λ⁰π⁰, Σ⁰π⁰, Λ⁰π⁰π⁰ and Σ⁰π⁰π⁰ are obtained in a K^?p formation experiment using 1 million photographs taken in a heavy liquid bubble chamber filled with a CF₃BrC₃H₈ mixture. The results are compared with hydrogen bubble chamber (HBC) experiments and with experiments having full or partial gamma-ray detection. Our Λ⁰π⁰ and Λ⁰ + neutral cross section agree with HBC results. Our Σ⁰π⁰ cross section does not exhibit a bump at 1670 MeV as previously seen in HBC experiments. Our Λ⁰π⁰π⁰ data are dominated by a Σ(1385)π⁰ production. Our Σ⁰π⁰π⁰ data is consistent with the presence of some Σ(1405)π⁰ production.     

Exchange,production and decay of the Z meson (JPC = 2−−)

Recent high-statistics data for π^?p→ω⁰n indicate the presence of an amplitude with exchange quantum numbers in the series J^PC = 2^?? 4^??,… Previous phenomenological and theoretical estimates of reggeised Z exchange J^PC = 2^??) are shown to be in good agreement with data. Implications for observing the exchange of its EXD partner (the much sought A₁) and other unnatural parity states are discussed with reference to a with a quark model estimate of its branching ratio, we predict the cross section for production of the Z and its subsequent decay into ωπ. The prospects for a partial-wave analysis of the ωπ enhancement observed at 1700 MeV are discussed.     

Phenomenological model for describing pion-pair production on a proton by virtual photons in the energy region of nucleon-resonance excitation

A phenomenological model is developed for describing the production of π ⁺ π ^? pairs on a proton by virtual photons in the energy region of nucleon-resonance excitation.The cross sections are calculated for the channels γp → π ^?Δ⁺⁺, γp → π ⁺Δ⁰, and γp → ρp, which make a dominant contribution to pion-pair production, and the results are compared with available experimental data.The contributions of nucleon resonances to the cross section for the reaction γp → π ^?Δ⁺⁺ are predicted within the developed approach.     

A study of final state deuteron events in 1.825 GeV/c pd interactions

The study of pd → ndπ⁺ and pd → pdπ^O reactions shows that the “slow deuteron” inelastic events are dominated by peripheral processes. Box diagrams are presented for the production mechanism of the 2.2 GeV/c² dπ enhancements. Evidence is presented that for ‘fast deuteron’ events d¹⁺⁺ and d¹⁺ resonances at 2.375 ± 0.010 GeV/c² with a width of 0.075 ± 0.015 GeV/c² are produced via baryon exchange. The elastic events have been compared with Glauber multiple scattering theory with reasonable agreement.     

The stability boundary of four-particle mesomolecules

Multiparametric variational calculations of the ground-state energy of symmetric four-particle mesomolecules of the type X ⁺ Y ⁺ X ^? Y ^? as a function of masses M and m of particles X and Y are carried out. A basis consisting of 3200 Gaussian functions depending on all six interparticle distances is used. Calculations are carried out with the optimization of 1200 nonlinear parameters of the first 200 basis functions. As opposed to mesomolecules of the type X ⁺ X ⁺ Y ^? Y ^?, which are stable for all values of masses M and m in X ⁺ Y ⁺ X ^? Y ^? systems, are stable with respect to dissociation if the ratio of the masses of particles X and Y in them satisfies the condition 0.472≤M/m≤2.12. Hence it follows that four symmetric mesomolecules of the type considered (π⁺μ ⁺π^?μ^?, t ⁺ d ⁺ t ^? d ^?, p ⁺ K ⁺ p ^? K ^?, and d ⁺ p ⁺ d ^? p ^?) and 84 various asymmetric mesomolecules of the type X ⁺ Y ⁺ Z ^? T ^? are knowingly stable with respect to dissociation. For mesomolecules of the type X ⁺ Y ⁺ X ^? Y ^?, which are stable with respect to dissociation, mathematical expectations of their physical quantities depending on interparticle distances that specify averaged geometrical structures of these systems are calculated and their dependence on the masses of particles M and m is studied.     

Spin-dependent level density in interacting boson-fermion-fermion model

Yield curves for the production of^117g In,^117m In,^116m1In,^115m In,^113m In,¹¹¹In,^110h In,^110l In,¹⁰⁹In,^108hIn and^108lIn from enriches¹¹⁸Sn have been measured by the activation method in the energy region 75–800 MeV. The cross sections have been deduced and for¹¹⁷In,¹¹⁰In and¹⁰⁸In isomeric cross section ratios have been determined. The experimental cross sections are compared to calculations with a cascade-evaporation model and to cross sections calculated with a semi-empirical formula. The isomeric ratios are compared to calculations based on the statistical formalism by Huizenga and Vandenbosch together with cascade-evaporation theory. The (γ, p) cross section and isomeric ratio are also compared to calculations based on a direct knock-out formalism.     

A study of 80,82,84Sr by (α, 2nγ) reactions

The ^AKr(α, 2nγ)^A+2Sr reactions have been studied by in-beam γ-ray spectroscopy for A = 78, 80, and 82. States with spins up to 10⁺ in ^82,84Sr and 6⁺ in ⁸⁰Sr are identified. The Sr nuclei undergo a transition from spherical to deformed ground states as neutrons are removed from the N = 50 shell. The systematics of these nuclei are compared with calculations based upon the shell model and interacting boson model.     

Tunable laser Stark-difference spectra of CD3OH

We present Doppler resolution limited spectra of the P(J) and R(J) multiplets for J ≦ 10 of the 10-μm CO stretch band of ¹²CD₃¹⁶OH using a tunable diode laser. Relative frequencies within the multiplets accurate to ±0.0002–0.0005 cm^?1 are obtained, but no absolute frequencies are given. We are able to assign most of the hindered rotation and K substructure in these multiplets. The assignments are based on analyses of Stark-difference spectra combined with the ground-state microwave data and the intensity variations which are expected theoretically. The ground and excited state A, K = 1 asymmetry splitting parameters are measured to be δ₁″ = (8.5450 ± 0.0080) × 10^?3cm^?1 and δ₁′ = (9.7706 ± 0.0080) × 10^?3cm^?1, respectively. The ground-state value agrees well with the microwave results. A rapid-scan system for recording data and a computer-aided technique for calibrating and plotting the spectra are described.     

Levels of 234U and 236U excited by the (d,d') reaction

The energy levels of ²³⁴U and ²³⁶U have been studied through the inelastic scattering of 16 MeV douterons. A magnetic spectrograph was used to momentum-analyse the scattered deuterons at θ = 90° and 125°. Excited in both ²³⁴U and ²³⁶U were the ground state bands up to and including the 8⁺ members, the K^π = 0⁺β-vibrations, the K^π = 2⁺γ-vibrations, and the K^π = 0^? octupole vibrational bands. In ²³⁴U, additional levels at 1023 and 1126 keV are ascribed to a K^π = 2^? band, levels at 1238, 1312, and 1446 keV are identified as members of either a K^π = 0^? or 1^? configuration, and other tentative assignments are made for members of K^π = 1^? and 3^? configurations. Relative reduced transition probabilities, B(E2), to the 2⁺ rotational and γ-vibrational states are generally found to be in good agreement with Coulomb excitation measurements. Relative B(E3) values for the 3^? states excited are slightly higher than the predictions of a microscopic theory of octupole vibrations.     

N2-broadening coefficients in the ν2 and ν4 bands of PH3

N₂-broadening coefficients are measured for 61 transitions of PH₃ in the ^QR branch of the ν₂ band and the ^PP, ^RP, ^SP, and ^PQ branches of the ν₄ band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 1 to 16 and K from 0 to 11 are located between 1008 and 1106 cm⁻¹. The collisional widths are determined by fitting each spectral line with a Voigt profile, a Rautian profile, and a speed-dependent Rautian profile. The latter models provide larger broadening coefficients than the Voigt model. These coefficients have also been calculated on the basis of a semiclassical model of interacting linear molecules by considering an atom-atom Lennard-Jones potential in addition to the electrostatic contributions. The theoretical results are in good agreement with the experimental data and reproduce the J dependence of the broadenings, but their decrease at high J values is overestimated for the ^QR (J, K) transitions.     

Absorption spectrum of Cr3+ in calcium tartrate tetrahydrate

Calcium tartrate tetrahydrate single crystals doped with Cr³⁺ ions are grown from silica gel. The optical absorption spectrum is studied at the laboratory and liquid nitrogen temperatures. From the analysis of the unpolarised and polarised spectra, the site symmetry of the Cr³⁺ ion is attributed to octahedral with a small tetragonal distortion. The following crystal field parameters are evaluated.B = 655 cm^-1C = 2948 cm^-1Dq = 1800 cm^-1Dt = 40 cm^-1     

Algebraic aspects of crystallography

Taking into account the fact that space groups are groups of transformations of Euclideann-dimensional space, non-equivalent systems of non-primitive translations are defined. They can be brought into one-to-one correspondence with the elements of the groupH ¹ (K, R ⁿ /Z ⁿ ) or with those of the groupH ¹ (K, Z ⁿ /kZ ⁿ )/H ¹ (K, Z ⁿ ). (K is a point group of orderk.) The consistency of these findings with the results of Part I is given by the isomorphisms $$H^2 (K,Z^n ) \cong H^1 (K,R^n /Z^n ) \cong H^1 (K,Z^n /kZ^n )/H^1 (K,Z^n ).$$ Theorems are proved giving the conditions for cohomology groupsH ^q (K, A) to be zero. These conditions are fulfilled in particular ifA=R ⁿ andK is a subgroup ofGL (n, R) that either is compact (thenq>0) or has a finite normal subgroup leaving no element ofR ⁿ invariant (thenq≧0). This implies that the affine, the Euclidean and the inhomogeneous Lorentz groups are the only extensions ofR ⁿ by the corresponding homogeneous groups. By way of illustration, the theory of this paper is applied to two 2-dimensional space groups.     

Lepton charge and model of weak interactions with μ-e transitions

The gauge model of weak interactions is proposed and μ^±?e^? transitions predicted by the model are discussed. Estimates are given for μ^±→e^? transitions on hadrons like K⁺→π^?μ⁺e⁺ with Γ (K⁺→π^?μ⁺e⁺) ? 10^?11Γ(K⁺ and μ^? capture on nuclei with W(μ^?→e⁺) ? 10^?12W(μ^? → ν). Single μ^± production in e^? beams with a cross section δ ～ 10^?42?10^?41 cm² is predicted.