Effective interactions of axion supermultiplet and thermal production of axino dark matter

Abstract

We discuss the effective interactions of axion supermultiplet, which might be important for analyzing the cosmological aspect of supersymmetric axion model. Related to axino cosmology, it is stressed that three seemingly similar but basically different quantities, the Wilsonian axino-gluino-gluon coupling, the 1PI axino-gluino-gluon amplitude, and the PQ anomaly coefficient, should be carefully distinguished from each other for correct analysis of the thermal production of axinos in the early Universe. It is then noticed that the 1PI axino-gluino-gluon amplitude at energy scale p in the range M Φ < p < v P Q is suppressed by M 2 Φ /p 2 in addition to the well-known suppression by p/16π 2 v P Q , where M Φ is the mass of the heaviest PQ-charged and gauge-charged matter supermultiplet in the model, which can be well below the PQ scale v P Q . As a result, axino production at temperature T > M Φ is dominated by the production by matter supermultiplet, not by the production by gauge supermultiplet. Still the axino production rate is greatly reduced if M Φ ≪ v P Q , which would make the subsequent cosmology significantly altered. This would be most notable in the supersymmetric DFSZ model in which M Φ corresponds to the Higgsino mass which is around the weak scale, however a similar reduction is possible in the KSVZ model also. We evaluate the relic axino density for both the DFSZ and KSVZ models while including the axino production in the processes involving the heaviest PQ-charged and gauge-charged matter supermultiplet.

Axino cold dark matter revisited

“…The same as figure 4 but showing as well in magenta the yield suppression found in ref. [58] for different values of the heavy quark masses.…”

“…[58] appeared which discusses in details axino couplings and finds a non-trivial momentum dependence in the one-particle irreducible one-loop axino-gluon-gluino couplings. The coefficient C 1P I of these interactions is suppressed when the external particle momentum is much larger than the mass M of the PQ-charged fermions in the loop.…”

“…In the DFSZ models, there is also a tree-level axino-Higgs-higgsino coupling [58]; compare the second term in eq. (2.13),…”

“…Similar figures in the DFSZ model are presented in figures 6 and 7, which can be compared to the figures in ref. [58].…”

Axino dark matter in moduli-induced baryogenesis

“…As it is mentioned in refs. [34,[38][39][40], the scattering process via strong interaction is suppressed in high temperature regime. Instead, the production due to axino interaction with Higgs and Higgsino or stop and top is effective.…”