Inclusive strange particle production in π+p interactions at 16 GeV/c

The production of $\text{K}{}_{\mathrm{S}}{}^0\text{, Λ}\text{and}\text{Λ}$ is measured in π⁺p reactions at 16 GeV/c. The total strange particle cross section is found to be 4.0 ± 0.3 mb, about 20% of the inelastic cross section. Cross sections for single strange particles and for strange particle pairs are determined, both inclusively and as functions of the charged multiplicity. Relative production rates for different strange particle combinations are compared with the prediction of the isospin statistical model. Inclusive spectra for single particles are studied and it is found the K_S⁰ are produced mostly in the forward hemisphere, most probably by fragmentation of the incident pion into $\text{K}\text{K}\text{π}$. The Λ are mostly backwards, probably deriving from fragmentation of the proton into ΛK pairs. The $\text{Λ}$ tend to be produced forwards, but evidence is found for central $\text{Λ}\text{Λ}$ production. Distributions in rapidity of the Λ particles from π⁺p interactions are compared in terms of the factorisation hypothesis. Results are given on the Λ transversal polarisation.     

Differential cross sections for the charge exchange process π+p → π0 (π+p) at 8, 16 and 23 GeV/c

The differential cross section $\text{d}\text{σ}\text{d}\text{t′}$ for the charge-exchange process π⁺p → π⁰ (π⁺p) at 8, 16 and 23 GeV/c is presented for several regions of the π⁺p effective mass. It is found that the dip at t′ ≈ 0.6 (GeV/c)² which is observed in the Δ(1236) mass band becomes a less pronounced structure in the higher mass regions. However, while the slope of the $\text{d}\text{σ}\text{d}\text{t′}$ distributions in the near-forward direction decreases strongly with increasing π⁺p mass, there is no evidence that the observed structure moves to higher values of t′ as the π⁺p mass increases. These results are consistent with a Regge-exchange picture where the position of the dip is determined by the exchanged trajectory, but are inconsistent with a simple geometrical picture.     

A many-body calculation of the hyperfine interaction in the lowest2S and2P states of li-like systems

A non-relativistic perturbation method of Brueckner-Goldstone type is used to calculate the hyperfine interactions in the lowest² S and² P states of the Li-like systems, Li, Be⁺, B²⁺, C³⁺, N⁴⁺, O⁵⁺ and F⁶⁺. The effect of the polarization of the closed shell is treated to all orders of perturbation, while the correlation effect is calculated in the lowest order, i.e. in the third order of the perturbation expansion. Experimental data are at present available only for Li, Be⁺ and F⁶⁺, and the agreement with the calculated values is in these cases very good, usually within the experimental uncertainties. This implies that the predictions made in the remaining cases should be quite reliable, which may simplify the experimental determination of these quantities. Theoretical values are also given for the quadrupole interaction, which can be used to determine the nuclear quadrupole moments, when accurate experimental information becomes available.     

Multiplicities of secondary hadrons produced in vp and vp charged current interactions

In an experiment with the hydrogen bubble chamber BEBC at CERN multiplicities of hadrons produced in νp and $\text{v}\text{p}$ interactions have been investigated. Results are presented on the multiplicities of charged hadrons and neutral pions, forward and backward multiplicities of charged hadrons and correlations between forward and backward multiplicities. Comparisons are made with hadronic reactions and e⁺e^? annihilation. In the framework of the quark-parton model the data imply similar charged multiplicities for the fragments of a u- and a d-quark, and a larger multiplicities for the fragments of a uu- than for a ud-diquark. The correlation data suggest independent fragmentation of the quark and diquark for hadronic masses above ～ 7 GeV and local charge compensation within an event.     

Comments on the three-photon structure function

Using the simple quark parton model, estimates for the three-photon structure function, V(x), of the proton are given. This function, which is proportional to the interference between inelastic Compton scattering and wide angle bremsstrahlung, is shown to have an upper bound of $\text{2}\text{3}\text{vW}{}_2\text{(x)/x}$. Using SLAC inelastic electron scattering data from the proton this implies that V(x) is not dominated by a quasielastic peak, and therefore the sum rule, $\text{∝}{}_0{}^1\text{V(x)}\text{d}\text{x =}\text{5}\text{9}$, will be difficult to check at SLAC energies. Using electron scattering data from both the neutron and the proton, a more restrictive upper limit on V(x) is given which, at intermediate and large values of x, is nearly the same as values determined from two different sets of quark distributions. We conclude that the experiment still provides a new test of the proton model and a method for determining the quark charge.     

A study of the C(p, p′) reactions at 135 MeV

A relativistic mean field approach is used to determine and compare the single-particle Dirac potentials for nuclei and hypernuclei (Λ, Σ, Ξ). A simple model is used and the Dirac-Hartree-Fock equations are reduced to a Schrödinger-like equation. The subsequent central and spin-orbit shell-model potentials are compared to those of phenomenological approach and other recent microscopic approaches. In the case of hypernuclei the Hartree approximation works already quite well without any need of taking into account the strangeness exchange part coming from strange mesons. The influence of the anomalous magnetic moment of the baryon on the spin-orbit term is found to be rather important for both Λ- and Σ-hyperons.     

Observation of leading particles in pp interactions with large transverse momentum secondaries at the CERN-ISR

Events with a positive particle of large transverse momentum emitted at medium angles have been studied using the split field magnet spectrometer at the CERN-ISR at a c.m. energy of √s = 52.5 GeV. Positive particles with large longitudinal momentum, |x| > 0.5, i.e., leading particles, associated to large p_T events, are analysed.     

Study of transverse momenta of charged hadrons produced in νp and\bar vp charged current interactions

Data from a neutrino and antineutrino hydrogen experiment with BEBC are used to investigate transverse properties of the produced charged hadrons. Measurements are presented on average transverse momenta of charged pions as functions of Feynman-x and the hadronic mass, on the transverse momentum flow within an event and on jet-related quantities. The main features of the data are well described by the LUND model. The data favour a version of the model in which soft gluon effects are included and the primordial transverse momentum of the quarks in the proton is small. Effects from 1^st order QCD (hard gluon emission) are negligible.     

A semi-automated method for fluorimetric determination of epinephrine and norepinephrine, without mutual interference, in single brain samples

A method is described for the separation and automated fluorimetric determination of epinephrine and norepinephrine in brain tissue extracts without mutual interference. The catecholamines are isolated and purified by extraction from activated alumina. Oxidation and rearrangement to their fluorescent lutines is carried out on two separate AutoAnalyzer manifolds and fluorescence is read in an Aminco-Bowman spectrophotofluorimeter. The interference by one amine with the determination of the other is less than 1% for determination of epinephrine in the presence of an equimolar concentration of norepinephrine, and, conversely, less than 4% for determination of norepinephrine. This eliminates the need for solution of simultaneous equations, the results of which are often misleading when the ratio of one amine to the other in brain exceeds 10:1. This method can be useful for rapid screening of psychoactive compounds affecting central and peripheral adrenergic stores.