Constraints on |Ue3|2 from a three-neutrino oscillation analysis of the CHOOZ data

Results of a new analysis of the CHOOZ data, performed in the framework of three-neutrino mixing, are presented. Both the cases of normal and inverted neutrino mass hierarchy are considered. The parameters characterizing the solar neutrino oscillations, Deltam(circle dot)(2) and tan(2)theta(circle dot), are assumed to lie in the region of the large mixing angle (LMA) MSW solution of the solar neutrino problem, which is favored by the current solar neutrino data. At Deltam(circle dot)(2) less than or similar to 10(-4) eV(2) the new CHOOZ exclusion plane practically coincides with the exclusion curve obtained in the two-neutrino mixing analysis. curve in the Deltam(31)(2)-\U-e3\(2) For Deltam(circle dot)(2) greater than or similar to 2 x 10(-4) eV(2), the constraints of the CHOOZ data on \U-e3\(2) are more stringent. For, e.g., sin(2)theta(circle dot) = 0.50 and Deltam(circle dot)(2) = 6 x 10(-4) eV(2), and at Deltam(31)(2) = 2.5 x 10(-3) eV(2) (the Super-Kamiokande best fit-point) we find that (at 90% C.L.) \U-e3\(2) < 1.7 x 10(-2), which is by more than a factor of 2 smaller than the upper bound obtained in the original two-neutrino mixing analysis of the CHOOZ data (\U-e3\(2) < 3.7 x 10(-2)). (C) 2002 Elsevier Science B.V. All rights reserved.