STRUCTURE FUNCTIONS FROM NEUTRINO-DEUTERIUM DEEP INELASTIC SCATTERING

Quantum chromodynamics (QCD) and the quark-parton model qualitatively explain a large body of high energy scattering data, but detailed quantitative predictions are hampered by calculational difficulties. The difference between the fractional momentum distributions of the u and d quarks in the proton (the non-singlet distribution) is particularly easy to study theoretically. Given an experimentally measured non-singlet distribution at one value of Q $\sp2$ (momentum transfer between a neutrino probe and a target nucleon) the same distribution at higher Q $\sp2$ can be calculated. Accurate measurements of the non-singlet distribution are therefore a good basis for tests of QCD and the quark-parton model.

The non-singlet distribution was extracted from data gathered in an exposure of the 16 ft. deuterium-filled bubble chamber at Fermilab to a high energy neutrino beam. The raw bubble chamber data consists of the tracks recorded on some 320,000 sets (three views) of photographs. The events which produced these tracks were reconstructed using computer techniques. Events which met certain acceptance criteria were defined as deep inelastic scattering events, an interaction in which the neutrino fragments its nucleon target to produce mesons and other baryons. Neutrino-neutron and neutrino-proton interactions were distinguished by counting the number of charged tracks made by the fragmentation products, whence double differential cross sections for neutrino-proton and neutrino-neutron scattering were deduced. Assuming isospin symmetry, the difference of the two cross sections is proportional to the non-singlet quark momentum distribution. A phenomenon called rescattering causes the mis-identification of neutron events as proton events about 9% of the time. As the rescattering fraction is known only approximately, the non-singlet distribution extracted according to the above procedure contains a systematic uncertainty.

The data support the general expectations of the quark-parton model within the limits of statistical and systematic uncertainty, and agree fairly well with the results of other experiments.