Professor Amanda Cooper-Sarkar

Abstract:

The average multiplicities of charged hadrons and of π⁺, π^- and π⁰ mesons, produced in {Mathematical expression}Ne and νNe charged current interactions in the forward and backward hemispheres of the W^±-nucleon center of mass system, are studied with data from BEBC. The dependence of the multiplicities on the hadronic mass (W) and on the laboratory rapidity (yLab) and the energy fraction (z) of the pion is also investigated. Special care is taken to determine the π⁰ multiplicity accurately. The ratio of average π multiplicities {Mathematical expression} is consistent with 1. In the backward hemisphere {Mathematical expression} is positively correlated with the charged multiplicity. This correlation, as well as differences in multiplicities between {Mathematical expression} and {Mathematical expression}, {Mathematical expression} scattering, is attributed to reinteractions inside the neon nucleus of the hadrons produced in the initial {Mathematical expression} interaction. © 1988 Springer-Verlag.

Abstract:

Nearly 40000 neutrino and antineutrino interactions in BEBC are compared to measure the differences between neon and deuterium in the quark and antiquark distributions and in the nucleon structure functions. The ratio of Ne to D cross sections indicates some decrease between x∼0.2 and x∼0.6. The y distributions show there is no significant increase in the neon sea, but prefer a small decrease. Taken altogether, the x and y distributions and the measured total cross-sections indicate some change in the shape of the valence distributions. No significant dependence on A is observed for either the shape of the sea or the ratio of longitudinal to transverse cross-sections. © 1987 Springer-Verlag.

Abstract:

Coherent production of ρ- mesons in charged current antineutrino interactions on neon nuclei is studied in the BEBC bubble chamber exposed to the CERN SPS wide band beam. The cross section is measured to be (95±25)·10-40 cm2 per neon nucleus, averaged over the beam energy spectrum. The distributions of kinematical variables and the absolute value of the cross section are in agreement with theoretical predictions based on the CVC hypothesis and the vector meson dominance model. © 1987 Springer-Verlag.

Abstract:

In a bubble chamber experiment with BEBC the spin alignment parameter η= 1 2 (2ρ{variant}00 - ρ{variant}11 - ρ{variant}-1-1) is measured for ρ{variant}0 mesons produced in deep inelastic charged-current antineutrino and neutrono interactions on neon. In the current fragmentation region η is found to be ηv=0.48±0.27 (stat.)±0.15 (syst.) for vNe and ηv=0.12±0.20 (stat.)±0.10 (syst.) for vNe interactions. © 1987.

Abstract:

The isoscalar nucleon structure functions F2(x, Q²) and xF3(x, Q²) are measured in the range 02<64 GeV², 1.72<250 GeV², x<0.7 using ν and {Mathematical expression} interactions on neon in BEBC. The data are used to evaluate possible higher twist contributions and to determine their impact on the evaluation of the QCD parameter Λ. In contrast to previous analyses reaching to such low W² values, it is found that a low {Mathematical expression} value in the neighbourhood of 100 MeV describes the data adequately and that the contribution of dynamical higher twist effects is small and negative. © 1987 Springer-Verlag.