Search for CP violation in D⁰→π^-π⁺π⁰decays with the energy test

A search for time-integrated CP violation in the Cabibbo-suppressed decay D ⁰→π ^-π ⁺π ⁰is performed using for the first time an unbinned model-independent technique known as the energy test. Using proton-proton collision data, corresponding to an integrated luminosity of 2.0fb ^-1collected by the LHCb detector at a centre-of-mass energy of s=8TeV, the world's best sensitivity to CP violation in this decay is obtained. The data are found to be consistent with the hypothesis of CP symmetry with a p-value of (2.6±0.5)%.