Results are reported from an improved measurement of ?µ??e transitions by the NOvA experiment. Using an exposure equivalent to 6.05×1020 protons on target, 33 ?e candidates are observed with a background of 8.2±0.8 (syst.). Combined with the latest NOvA ?µ disappearance data and external constraints from reactor experiments on sin22?13, the hypothesis of inverted mass hierarchy with ?23 in the lower octant is disfavored at greater than 93% C.L. for all values of dCP
