Gravitino dark matter and cosmological constraints

Abstract

The gravitino is a promising candidate for cold dark matter. We study cosmological constraints on scenarios in which the gravitino is the lightest supersymmetric particle and a charged slepton the next-to-lightest supersymmetric particle (NLSP). We obtain new results for the hadronic nucleosynthesis bounds by computing the 4-body decay of the NLSP slepton into the gravitino, the associated lepton, and a quark-antiquark pair. The bounds from the observed dark matter density are refined by taking into account gravitinos from both late NLSP decays and thermal scattering in the early Universe. We examine the present free-streaming velocity of gravitino dark matter and the limits from observations and simulations of cosmic structures. Assuming that the NLSP sleptons freeze out with a thermal abundance before their decay, we derive new bounds on the slepton and gravitino masses. The implications of the constraints for cosmology and collider phenomenology are discussed and the potential insights from future experiments are outlined. We propose a set of benchmark scenarios with gravitino dark matter and long-lived charged NLSP sleptons and describe prospects for the Large Hadron Collider and the International Linear Collider.

Soft RPV through the baryon portal

“…Similarly, "Collective RPV" [8] only allows RPV in particular combinations of couplings, so their overall effect yields the requisite suppression. Other models with similar features are found in [9][10][11][12][13][14].…”

“…In this mass range m 3/2 < m p , so the process G → qqq is kinematically forbidden and the gravitino is stable. Since sparticles rarely decay to gravitinos and their annihilation rate is suppressed by the SUSY breaking scale, the present day abundance is thermally generated [13] 19) where T R is the reheating temperature, so the RPV gravitino is a viable dark matter candidate. Although the scenario in [13] assumes R-parity conservation, the analysis is applicable so long as thermal gravitino production in the early universe is not upset by additional decays or annihilation processes.…”

Thermal relic abundances of long-lived staus

“…12 (100 GeV ≤ m e τ 1 ≤ 10 TeV) of Ref. [22] and Figs. 14 (m e τ 1 = 100 GeV) and 15 (m e τ 1 = 300 GeV) of Ref.…”

“…11 of Ref. [22]. For a sizable admixture of τ L in τ 1 , this Y e τ constraint can become more restrictive in particular with the enhanced stau-Higgs couplings allowing for exceptionally small Y e τ values.…”

“…[22]-is respected for m e G 500 GeV even if only a small fraction f = 0.01 of dark matter is assumed to originate from τ 1 decays; cf. Fig.…”