First Measurement of Coherent Production of Pions in Argon

New on the arXiv today is a paper submitted to PRL describing the first measurement of charged-current coherent production of pions on argon in a neutrino (and an antineutrino) beam. The paper is from the ArgoNeuT collaboration using a liquid argon time projection chamber. Measurements of cross sections in argon are very important, as liquid argon TPCs are the proposed technology to be used for the future LBNE experiment. This paper is measuring the cross section where a muon neutrino hits a nucleus, converting into a muon and creating a pion at the same time. In coherent interactions, very little momentum is transferred to the nucleus and the pion carries the charge to balance out the muon. The nucleus basically does not do anything other than provide a charge for the neutrino to interact with, whereas typically nucleons (protons and neutrons) are knocked out of the nucleus with some measurable amount of energy.