Boxing with neutrino oscillations - art. no. 113007

We develop a characterization of neutrino oscillations based on the coeffic ients of the oscillating terms. These coefficients are individually observa ble; although they are quartic in the elements of the unitary mixing matrix , they are independent of the conventions chosen for the angle and phase pa rametrization of the mixing matrix. We call these reparametrization-invaria nt observables "boxes" because of their geometric relation to the mixing ma trix, and because of their association with the Feynman hox diagram that de scribes oscillations in field theory. The real parts of the boxes are the c oefficients for the CP- or T-even oscillation modes, while the imaginary pa rts are the coefficients for the CP- or T-odd oscillation modes. Oscillatio n probabilities are linear in the boxes, so measurements can straightforwar dly determine values for the boxes (which can then be manipulated to yield magnitudes of mixing matrix elements). We examine the effects of unitarity on the boxes and discuss the reduction of the number of boxes to a minimum basis set. Far the three-generation case, we explicitly construct the basis . Using the box algebra, we show that CP violation may be inferred from mea surements of neutrino flavor mixing even when the oscillatory factors have averaged. The framework presented here will facilitate general analyses of neutrino oscillations among n greater than or equal to 3 flavors. [S0556-28 21(99)03009-X].