Meson production in photon and neutrino experiments

The reaction γp→ρ⁰_fastpπ⁺π^- has been studied with the linearly polarized 20 GeV monochromatic photon beam at the SLAG Hybrid Facility, to test the prediction of s channel helicity conservation in inelastic diffraction for t < 0.4(GeV/c)². In a sample of 1934 events from this reaction, the ρ⁰ decay angular distributions and spin density matrix elements are consistent with s channel helicity conservation. The π⁺π^- mass shape displays the same skewing as seen in the reaction γp→pπ⁺π^-, and the pπ⁺π^- mass distribution compares well and scales according to the vector dominance model with that produced in π^±p→pπ⁺π^-.

Coherent production of the a₁ meson has been observed through the re action νFr → μ^-a₁Fr in the Tohoku 1m freon bubble chamber hybrid system. The bubble chamber was exposed to the Fermilab wide-band neutrino beam, generated by 800 GeV protons at the Tevatron. The observed rate from the final charged current sample of 1792 events was 1.1 ± 0.47%, and the a₁-W coupling is calculated to be f²_a/f²_ρ = 5.2 ± 2.2. A comparison of the cross section and the kinematical parameters with the theoretical predictions of the vector dominance model, gives reasonable agreement with the data.

A Monte-Carlo study was performed to check the possibility of detecting the radiative decay of the D; in our bubble chamber. Using the most favorable predicted rate through the φ branching ratio, it was determined that three times our data sample would be needed for a one σ effect above background