How should we interpret the two transport relaxation times in the   cuprates ?
  We observe that the appearance of two transport relaxation times in the various transport coefficients of cuprate metals may be understood in terms of scattering processes that discriminate between currents that are even, or odd under the charge conjugation operator. We develop a transport equation that illustrates these ideas and discuss its experimental and theoretical consequences. 
P. Coleman, A. J. Schofield and A. M. Tsvelik