Heavy quark mass effects in the energy–energy correlation in the back-to-back region

We consider heavy quark mass (m) effects in the energy–energy correlation function in e+e-↦hadrons at high energy Q, in the back-to-back (two-jet) region. In the ultra-relativistic limit, Q≫m, the QCD Sudakov form factor S(b) in impact parameter (b-)space reads: (Formula presented.) The double-log function A(αS) describes the effects of soft gluons, quasi-collinear to the original heavy quark-antiquark pair, while the single-log functions B(αS) and D(αS) describe hard collinear radiation and soft radiation not log-collinearly enhanced, respectively. The usual logarithmic expansion of the low transverse momenta contribution to the form factor (k2[removed]