First Measurement of Neutrino and Antineutrino Coherent Charged Pion Production on Argon

We report on the first cross section measurements for charged current coherent pion production by neutrinos and antineutrinos on argon. These measurements are performed using the ArgoNeuT detector exposed to the NuMI beam at Fermilab. The cross sections are measured to be 2.6+1.2−1.0(stat)+0.3−0.4(syst)×10−38  cm2/Ar for neutrinos at a mean energy of 9.6 GeV and 5.5+2.6−2.1(stat)+0.6−0.7(syst)×10−39  cm2/Ar for antineutrinos at a mean energy of 3.6 GeV.