T violation in neutrino oscillations in matter

We consider the interplay of fundamental and matter-induced T violation eff ects in neutrino oscillations in matter. After discussing the general featu res of these effects we derive a simple approximate analytic expression for the T-violating probability asymmetry DeltaP(ab)(T) for three-flavour neut rino oscillations in a matter with an arbitrary density profile in terms of the two-flavour neutrino amplitudes. Explicit examples are given for the c ases of a two-layer medium and for the adiabatic Emit in the general case. We then discuss implications of the obtained results for long baseline expe riments. We show, in particular, that asymmetric matter effects cannot hind er the determination of the fundamental CP- and T-violating phase delta (CP ) in the long baseline experiments as far as the error in this determinatio n is larger than 1% at 99% CL. Since there are no T-violating effects in th e two-flavour case, and in the limits of vanishing theta (13) or Deltam(21) (2) the three-flavour neutrino oscillations effectively reduce to the two-f lavour ones, studying the T-violating asymmetries ApT ab can in principle p rovide us with a complementary means of measuring theta (13) and Deltam(21) (2). (C) 2001 Elsevier Science B.V. All rights reserved.