Longitudinal and transverse forces on a vortex in superfluid 4He

We examine the transverse and longitudinal components of the drag force upon a straight vortex line due to the scattering of liquid He-4 excitations. For this purpose, we consider a recently proposed Hamiltonian that describes the dissipative motion of a vortex, giving an explicit expression for the vortex-quasiparticle interaction. The dissipative coefficients involved are obtained in terms of the reservoir correlation function. Most of our explicit calculations are concerned with the range of temperatures below 0.4 K, for which the reservoir is composed of phonon quasiparticle excitations. We also discuss some important implications for the determination of possible scattering processes leading to dissipation, on the basis of the values of the vortex mass found in the literature.