Resummed mass distribution for jets initiated by massive quarks

We resum the invariant mass distribution of jets initiated by massive quarks in next-to-leading logarithmic approximation and beyond in heuristic way. We find that the inclusion of mass terms, in the N-moment space, results in the universal factor delta(N) (Q(2); m(2)) = exp [integral(1)(0) dz z(Q2/m2 (N-1))-1/1-z {- integral(m2(1-z))(m2(1-z)2) dk(perpendicular to)(2)/k(perpendicular to)(2) A[alpha(S)(k(perpendicular to)(2))] - B[alpha(S)(m(2)(1-z))] + D[alpha(S)(m(2)(1-z)(2))]}], taking into account dead-cone effects and soft radiation characteristic of massive charges. This factor multiplies the massless jet distribution function J(N) (Q(2)). In the above equation the variable N is rescaled by the mass correction parameter m(2)/Q(2) <<1 with respect to the standard massless case, being in the quark mass and Q the hard scale. The functions A (alpha(S)) and B(alpha(S)) appear with a minus sign suppressing collinear effects at very large N greater than or similar to Q(2)/m(2), as expected. In the same region, soft radiation not collinearly enhanced, characteristic of on-shell massive charges, makes its appearance with the function D(alpha(S)). Phenomenological applications, such as the resummation of b -> c/v decay spectra or the inclusion of beauty mass effects in t -> bW decays, are briefly sketched. (c) 2007 Elsevier B.V. All rights reserved.