Hadronic decay of late-decaying particles and big-bang nucleosynthesis

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Light scalars may be ubiquitous in nature, and their quantum fluctuations can produce large non-Gaussianity in the cosmic microwave background temperature anisotropy. The non-Gaussianity may be accompanied with a small admixture of isocurvature perturbations, which often have correlations with the curvature perturbations. We present a general method to calculate the non-Gaussianity in the adiabatic and isocurvature perturbations with and without correlations, and see how it works in several explicit examples. We also show that they leave distinct signatures on the bispectrum of the cosmic microwave background temperature fluctuations.

“…Here ǫ X reads the fraction of the nonthermally produced LSP to the total LSP abundance. The gravitino number-to-entropy ratio (Y 3/2 ) is given by [35,37] …”

Section: A 'Realistic' Examplementioning

confidence: 99%

A general analysis of non-gaussianity from isocurvature perturbations

Kawasaki

Nakayama

Sekiguchi

et al. 2009

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“…Let us specify some representative values of this constraint, taking into account the most up-to-date analysis of Ref. [33]. In particular, if G decays mainly to photon and photino, from We observe that for B h = 1, the upper bound on Y G (T NS ) does not exclusively increase with an increase of m G , as in the case for B h = 0.001.…”

Section: Unstable Gravitinomentioning

confidence: 99%

Quintessential kination and thermal production of gravitinos and axinos

Gómez

Lola

Pallis

et al. 2009

The impact of a kination-dominated phase generated by a quintessential exponential model on the thermal abundance of gravitinos and axinos is investigated. We find that their abundances become proportional to the transition temperature from the kination to the radiation era; since this temperature is significantly lower than the initial ("reheating") temperature, the abundances decrease with respect to their values in the standard cosmology. For values of the quintessential energy-density parameter close to its upper bound, on the eve of nucleosynthesis, we find the following: (i) for unstable gravitinos, the gravitino constraint is totally evaded; (ii) If the gravitino is stable, its thermal abundance is not sufficient to account for the cold dark matter of the universe; (iii) the thermal abundance of axinos can satisfy the cold dark matter constraint for values of the initial temperature well above those required in the standard cosmology. A novel calculation of the axino production rate by scatterings at low temperature is also presented.

“…[28,29]. These constraints were extracted with the following observational values of the light element abundances (1σ error):…”

Section: Primordial Nucleosynthesis and Effects Of Late Nlsp Decaysmentioning

confidence: 99%

Gravitino dark matter and cosmological constraints

Steffen¹

2006

171

147

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.