Enhancement of the dark matter abundance before reheating: Applications to gravitino dark matter

Abstract

In the first stages of inflationary reheating, the temperature of the radiation produced by inflaton decays is typically higher than the commonly defined reheating temperature1/2 where Γ φ is the inflaton decay rate. We consider the effect of particle production at temperatures at or near the maximum temperature attained during reheating. We show that the impact of this early production on the final particle abundance depends strongly on the temperature dependence of the production cross section. For σv ∼ T n /M n+2 , and for n < 6, any particle produced at T max is diluted by the later generation of entropy near T RH . This applies to cases such as gravitino production in low scale supersymmetric models (n = 0) or NETDM models of dark matter (n = 2). However, for n ≥ 6 the net abundance of particles produced during reheating is enhanced by over an order of magnitude, dominating over the dilution effect. This applies, for instance to gravitino production in high scale supersymmetry models where n = 6.

Ultraviolet freeze-in and non-standard cosmologies

“…Whereas for n ≤ 6 the difference between the standard UV freeze-in calculations [1,3], which assume an instantaneous transition (i.e. employs the instantaneous decay approximation), differ only by an O(1) factor from calculations taking into account non-instantaneous reheating [4]. Subsequent papers [5-8, 37, 38] have explored the impact of this boost factor in specific models.…”

“…Additionally, it was recently highlighted that the initial value of ω impacts the DM relic density if it is established due to freeze-out or renormalisable (IR) freeze-in during the era of particle decays leading to the transition to radiation domination [19,23]. This paper is structured as follows: In Section 2 we outline the general framework in a model independent approach, in particular we derive the dependence of the critical dimension n c and the boost factor B on the equation of state prior to reheating ω for general operator dimension parameterised by n. We subsequently explore how the DM abundance varies for different choices of ω and n. In Section 3 we highlight four specific examples in which the DM abundance receives a significant enhancement, specifically we examine gravitino DM in High Scale Supersymmetry [4,39], the moduli portal [7], the vector Higgs portal, and the massive spin-2 portal [6]. In Section 4 we provide a summary and some concluding remarks.…”

A testable hidden-sector model for Dark Matter and neutrino masses

“…However constraints from direct and indirect detection have pushed the simplest models such as Higgs [15][16][17][18] or Z-portal [14,[19][20][21][22][23] towards corners of viable parameter space, implying the need to introduce extra states and jeopardize the simplicity of these constructions. Therefore simple alternative solutions to the DM conundrum such as the nonthermal DM freeze-in mechanism have been investigated in the context of very-weakly coupled scenarios [24][25][26][27] or by considering new high energy scales [28][29][30][31][32][33][34]. Aside from the theoretical motivations for such scenarios, they remain difficult to be probed by present and future experiments, only few specific cases lead to interesting signatures and detection prospects [35][36][37][38].…”

Gravitino decay in high scale supersymmetry with R -parity violation

“…6 We have assumed that μ 0 is flavor universal. 7 To be more precise, above the maximum temperature of the thermal bath T max which is different from T RH if one considers noninstantaneous reheating [31]. rate is doubly Planck suppressed, the abundance of dark matter produced from the bath is very limited [proportional to T 7 RH [8] as in Eq.…”

“…(26). In the weak-scale supersymmetry scenario, gravitinos are singly produced from the thermal bath and the relic abundance can be expressed as [31,35] …”