Space Like Correlation of Feynman Propagator and Virtually Exchanged Neutrino Mass

The process such as π⁺ + n → p + μ⁺ + μ⁻ may occur through the virtually exchanged neutrino and anti-neutrino. The neutrino exchanged between two vertices, one of them is related to and the other is related to the neutrino absorption by the neutron leading to where denotes the virtual neutrino exchanged between the two vertices. The two vertices are connected by Feynman propagator of the neutrino and it can be non-vanishing even when the space time distance of two vertices is space like x² < 0 and they reside outside the light cone each other. The implication of the virtual exchanged neutrino is discussed.