A measurement of coherent neutral pion production in neutrino neutral current interactions in the NOMAD experiment

We present a study of exclusive neutral pion production in neutrino–nucleus Neutral Current interactions using data from the NOMAD experiment at the CERN SPS. The data correspond to 1.44×10(6) muon-neutrino Charged Current interactions in the energy range 2.5?E??300 GeV. Neutrino events with only one visible p(0) in the final state are expected to result from two Neutral Current processes: coherent p(0) production, ?+A??+A+p(0) and single p(0) production in neutrino–nucleon scattering. The signature of coherent p(0) production is an emergent p(0) almost collinear with the incident neutrino while p(0)'s produced in neutrino–nucleon deep inelastic scattering have larger transverse momenta. In this analysis all relevant backgrounds to the coherent p(0) production signal are measured using data themselves. Having determined the backgrounds, and using the Rein–Sehgal model for the coherent p(0) production to compute the detection efficiency, we obtain 4630±522(stat)±426(syst) corrected coherent-p(0) events with Ep(0)?0.5 GeV. We measure s(?A??Ap(0))=[72.6±8.1(stat)±6.9(syst)]×10(-40) cm(2)/nucleus. This is the most precise measurement of the coherent p(0) production to date.