SPECTATOR EFFECTS IN THE HEAVY-QUARK EFFECTIVE THEORY

We present a complete analysis of the Heavy Quark Effective Theory Lag rangian at order 1/m(2) in the leading logarithmic approximation, incl uding effects induced by spectator quarks. At this order new correctio n terms appear in the effective Lagrangian, as four-quark operators co ntaining both heavy and light quark fields. We compute the coefficient s of these operators to one-loop order and in the leading logarithmic approximation. Two of them break the heavy quark spin symmetry and we estimate their contribution to the hyperfine splitting of the heavy me sons in the factorization approximation. We find that they make a posi tive contribution to the hyperfine splitting of about 5% of the measur ed splittings. (C) 1997 Elsevier Science B.V.