Abstract
Thermal pair annihilation of heavy particles, such as dark matter or its co-annihilation partners, can be strongly influenced by attractive interactions. We investigate the case that pair annihilation proceeds through a velocity-suppressed p-wave operator, in the presence of an SU(3) gauge force. Making use of a non-relativistic effective theory, the thermal average of the pair-annihilation rate is estimated both through a resummed perturbative computation and through lattice simulation, in the range M/T∼10...30. Bound states contribute to the annihilation process and enhancement factors of up to ∼100 can be found.
Highlights
Inelastic processes between a dilute ensemble of heavy particles moving slowly in a thermal environment are encountered in many physical situations
We may consider heavy dark matter particles pair-annihilating into Standard Model particles in the early universe, or a heavy quark and anti-quark pair-annihilating into light quarks and gluons in a quark-gluon plasma generated in heavy ion collision experiments
If we find ourselves in the non-relativistic regime, i.e. with dark matter masses M π T, the annihilations can be described by local operators [1], similar to those found in the NRQCD context [2]
Summary
Inelastic processes between a dilute ensemble of heavy particles moving slowly in a thermal environment are encountered in many physical situations. The theoretical treatment of slow annihilation processes is facilitated by noting that the average kinetic energy of the annihilating particles is small compared with their rest mass, M v2 ∼ T M. Such a scale separation permits for a factorized description of annihilation processes in terms of a series of long-distance matrix elements times short-distance Wilson coefficients [2]. We have developed a framework which permits to estimate the thermally averaged pair annihilation rate, including bound-state effects, beyond perturbation theory [16]. 2), we review thermally averaged pair annihilation rates within resummed perturbation theory Having introduced the lattice framework (cf. sec. 4), we present and discuss numerical results (cf. sec. 5), and conclude with a brief summary (cf. sec. 6)
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