Coherent Production of Pions and Rho Mesons in Neutrino Charged Current Interactions on Neon Nuclei at the Fermilab Tevatron

Abstract

The coherent production of single pions and $\rho$ mesons in charged current interactions of neutrinos and antineutrinos on neon nuclei has been studied. The data were obtained using the Fermilab 15-foot Bubble Chamber, filled with a heavy Ne- $H_2$ mixture and exposed to the Quadrupole Triplet neutrino beam produced by 800 Ge V protons from the Tevatron. The average beam energy was 86 Ge V. In a sample of 330 000 frames, 1032 two-prong $\nu_\mu + \nu\bar{\mu}$ charged current interactions were selected. The goal of this study was to investigate the low $Q^2$ high $\nu$ region where the hadron dominance model can be tested. In this model, the vector and axial-vector parts of the weak hadronic current are dominated by the $\nu$ and $\alpha_1$ mesons respectively. The coherent signal was extracted using the distributions in the variable [t], the square of the four-momentum transferred to the neon nucleus. The signal for single pion coherent production was found to be $52.1\pm9.4$ events at [t] < 0.1 $GeV^2$ • After correction for the experimental losses, the number of events was estimated to be $86.6 \pm 19.6$ events. This corresponds to a production rate with respect to the total number of charged current interactions of ${(}0.31 \pm 0.07{)} %$ The cross section for coherent single pion production was thus calculated to be ${(}313 \pm 72{)}$ x $10^{-40}$ $cm^2$ / neon nucleus. The cross section and kinematical characteristics of these events were found to be in good agreement with the predictions of a model based on the PCAC hypothesis and the hadron dominance model. The signal for coherent single $\rho$ meson production was found to be $19.2 \pm 6.8$ events at [t] < 0.1 $GeV^2$, i.e. $62.8 \pm 27.0$ events after correction for the experimental losses. The production rate with respect to the total number of charged current interactions was determined to be ${(}0.23 \pm 0.10{)}$%. The corresponding single $\rho$ meson coherent production was then calculated to be ($227 \pm 98$) x $10^{-40} cm^2$ /neon nucleus. The cross section and the kinematical characteristics of these events were found to be in reasonable agreement with the predictions based on the hadron dominance model. Moreover, the Partially Conserved Axial Current (PCAC) hypothesis can be tested by studying the coherent production of single pions.