J. Bell

Properties of K0 and Λ inclusive production in charged-current antineutrino-nucleon interactions☆

Abstract In this paper we discuss inclusive spectra of K0s and Λs produced in charged in charged-current ν μ N interactions in the Fermilab 15 ft bubble chamber filled with a 64% Ne-H2 mixture. Data presented in terms of the invariant cross section show, when compared with results from experiments with other incident beams, that the behavior of these distributions is approximately the same. The K0 and Λ fragmentation functions are presented and the shape of the K0 fragmentation function is found to be consistent with the parametrization of Field and Feynman. The average K0 and Λ transverse momentum squared as a function of Q2, W2, x and z is presented. Comparisons for the K0s produced in the current fragmentation region are in qualitative agreement with QCD predictions. The value of the Λ polarization is measured and a positive normal polarization PN = 0.34±0.18 is found.

Quark jets from antineutrino interactions (I). Net charge and factorization in the quark jets

Abstract We investigate properties of the hadron jets produced in deep inelastic antineutrino-nucleon charged current interactions in the Fermilab 15 foot bubble chamber. Our detailed analysis of the jet net charge provides evidence for the quark origin of the hadron jets. The factorization hypothesis for the inclusive one-particle cross section is found to be valid.

Charged current events with neutral strange particles in high-energy antineutrino interactions

The results of a study of strange particle production in charged current νμN interactions in the Fermilab 15 ft bubble chamber filled with a heavy NeH2 mixture are presented. Production rates and average multiplicities of K0s and Λs as functions of W2 and Q2 are given. The experimental data agree well with the quark-parton model predictions if a yield of 0.06 ± 0.02 of K0s and Λs from charm production is included. Upper limits for D-meson production are given and the shape of the charmed quark fragmentation function is discussed. Inclusive production of the K∗(890) and Σ(1385) resonances is measured and it is shown that only about 5% of the K0 mesons and Λ hyperons results from resonance decays. Relative production rates of neutral strange particles on proton and neutron targets are studied.

Net charge in deep inelastic antineutrino-nucleon scattering

Abstract We investigate the net change in the current fragmentation region in antineutrino-nucleon charged current interactions in the Fermilab 15 ft bubble chamber. Support is presented for the d-quark origin of the forward hadrons in the hadron center-of-mass system. An extrapolation of the net charge to infinite center-of-mass energy is performed giving as a result 〈Q〈 v =− (0.44 ± 0.09) . Combining this result with the result obtained using our v events in the same experiment we obtain the value 0.98 ± 0.15 for the charge difference between the fragmenting quarks in v and v charged current events.

Measurement of SU(3) symmetry violation in the quark jet

Abstract We have used the ratio between the production rates of K 0 s and π − s in antineutrino-nucleon interactions in the Fermilab 15 ft bubble chamber to measure the size of the SU (3) symmetry violation in the production of quark-antiquark pairs to be 0.27±0.04. This value is significantly larger than the value obtained from a recent ep experiment. There is no apparent dependence of the K 0 π − ratio with W 2 , Q 2 , x b or p T 2 .

Quark jets from antineutrino interactions: (II). Inclusive particle spectra and multiplicities in the quark jets

Abstract We present results on inclusive particle production in the antineutrino charged current induced hadron jets observed in the Fermilab 15 ft bubble chamber. Fractional energy distributions, particle ratios and average multiplicities of the hadrons in the jets are measured. Ratios between the inclusive production rates of different mesons in the jets are studied to seek evidence for the d-quark origin of the observed hadrons. Good over-all agreement with the hypothesis of d-quark fragmentation with universal fragmentation functions obeying isospin systematics is established.

Inclusive charged-current antineutrino-nucleon interactions at high energies

Abstract We present results on the experimental study of inelastic charged-current antineutrino-nucleon scattering in the energy range of 10–200 GeV. The data sample, consisting of about 6500 antineutrino-induced events, was obtained in the Fermilab 15 ft bubble chamber filled with a heavy neon-hydrogen mixture. The differential cross sections for ¯νμN interactions are presented in terms of scaling variables x and y. The structure functions F2ν and xF3¯ν have been evaluated as functions of x and E¯ν. A deviation from the scaling hypothesis, similar to those found in other experiments on inelastic lepton-nucleon scattering, has been observed. The data are interpreted in the framework of the quark-parton model. Quark and antiquark distributions and their energy dependences are presented.

Average transverse momentum behaviour of charged hadrons in charged current antineutrino-nucleon interactions

Abstract We have studied transverse momenta of charged hadrons in the current fragmentation region of charged current antineutrino- nucleon interactions observed in the Fermilab 15 ft bubble chamber. The measured momentum squared transverse to the v μ + plane (p out 2 ) of the negative hadrons varies as a function of Q2, W2 and x as expected from t he leading order perturbative QCD calculations. Positively charged hadrons show a different transverse momentum behaviour as a function of Q2.

Quark jets from antineutrino interactions: (III). Transverse structure of the quark jets

Abstract We extend our systematic study of the properties of hadron jets produced in antineutrino-nucleon charged current interactions to those observables which characterize the distribution of particles perpendicular to the jet axis. These antineutrino-induced jets are found to have properties similar to those of the jets observed in e + e − annihilation at comparable c.m. energies. No deviations from the simple quark-parton model predictions are found.

Observation of μ+e+ events in antineutrino-nucleon interactions

Abstract The first observation of μ + e + events produced in antineutrino interactions using the Fermilab 15 ft bubble chamber is reported. The relative yield of μ + e + events is (4.8 −3.2 +5.3 ) × 10 −4 of all charged-current events with antineutrino energy greater than 10 GeV. The observed V 0 rate is 1.0 −1.0 +1.2 per μ + e + event. Possible sources of these events are discussed.