Professor Amanda Cooper-Sarkar

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.

Abstract:

A novel and efficient kinematic method is used to estimate the number of ντ charged current interactions with Eν > 20 GeV in the BEBC beam dump experiment. The result, -14±12 ντ events, is consistent with zero. The ratio of Ds to D meson production in 400 GeV proton interactions in copper is estimated to be below 0.65 at 90% c.l. The oscillation probability P(νe→ντ) averaged over the electron-(anti)neutrino spectrum is found to be below 18%. The hypothesis that νe and ντ are identical is excluded by about 6 standard deviations. A remarkable event is described: it contains a muon, a high pT photon and a high pT hadron. © 1987.

Abstract:

The prompt electron neutrino and muon neutrino fluxes from proton copper interactions at 400 GeV/c proton momentum have been measured. The asymmetry between the prompt electron (anti) neutrino and the prompt muon (anti) neutrino event rates above 20 GeV is Aeμ = (Ne - Nμ (Nc + Nμ) = 0.07 ± 0.08 corresponding to an Ne/Nμ ratio of 1.14-0.16-0.19. The cross section weighted charge asymmetry for electrons and muons combined is Aνν = 0.15 ± 0.08. The number of D decays into νe and νμ is (4.1 ± 0.9) × 10-4 per incident proton. No evidence for ντ interactions was found. © 1986.

Abstract:

BEBC filled in turn with hydrogen, and with a neon-hydrogen mixture, was exposed to the CERN SPS wide band neutrino and antineutrino beams. The ratios of the charged-current cross sections per nucleon, σ(νH2) σ(νNe) and σ(νH2) σ(νNe), between 20 and 300 GeV were found to be 0.656 ± 0.020 and 1.425 ± 0.052, respectively. Multiplying these ratios by the revised cross sections in neon, σ(νNe) E = (0.723 ± 0.038) × 10-38 cm2/GeV per nucleon and σ(νNe) E = (0.351 ± 0.019) × 10-38 cm2/GeV per nucleon, and their ratio, σ(νNe) σ(νNe) = 0.485 ± 0.020,, yields values for the total charged-current cross sections on protons, σ(νp)/E and σ(νp) E, of (0.474 ± 0.029) × 10-38 cm2/GeV and (0.500 ± 0.032) × 10-38 cm2/GeV. respectively, and a value for the ratio σ(νp) σ(νp) of 1.053 ± 0.066. © 1986.