Did something decay, evaporate, or annihilate during big bang nucleosynthesis?

Abstract

Results of a detailed examination of the cascade nucleosynthesis resulting from the putative hadronic decay, evaporation, or annihilation of a primordial relic during the Big Bang nucleosynthesis (BBN) era are presented. It is found that injection of energetic nucleons around cosmic time 10 3 sec may lead to an observationally favored reduction of the primordial 7 Li/H yield by a factor 2 − 3. Moreover, such sources also generically predict the production of the 6 Li isotope with magnitude close to the as yet unexplained high 6 Li abundances in low-metallicity stars. The simplest of these models operate at fractional contribution to the baryon density Ω b h 2 > ∼ 0.025, slightly larger than that inferred from standard BBN. Though further study is required, such sources, as for example due to the decay of the next-to-lightest supersymmetric particle into GeV gravitinos or the decay of an unstable gravitino in the TeV range of abundance ΩGh 2 ∼ 5 × 10 −4 show promise to explain both the 6 Li and 7 Li abundances in low metallicity stars.Big Bang nucleosynthesis has since long been known as one of the most precise and furthest back-reaching probes of cosmic conditions and the cosmic matter content of the early Universe. It thus, for example, has significantly contributed to the notion that a large fraction of matter in present-day galaxies is believed to be of non-baryonic nature as well as considerably limited some extensions of the standard model of particle physics. Paramount to having become such a useful tool of cosmology was and is, not only the examination of early synthesis of light elements in it's simplest standard version, but also in a variety of non-standard, alternative scenarios, relaxing a priori non-verified assumptions entering the calculations of a standard BBN (SBBN). Depending on the light element yields obtained in these latter scenarios, such calculations may then either favor a modified version of BBN, or strengthen the case for the SBBN. In either case, calculations of non-standard BBN may be used to place limits on the cosmic condition in the early Universe. In this spirit, technically advanced calculations of BBN including decaying particles during, or after BBN, an inhomogeneous baryon distribution, small-scale antimatter domains, neutrino degeneracy, or varying fundamental constants (for reviews cf.[1]), among others, have been performed over the years, rendering SBBN (also by the principle of Occam's razor) as our preferred scenario for BBN On the observational side significant advances have been made with the advent of high-resolution spectrographs on the Keck-and VLT-telescopes and the resulting capability to perform D/H abundance determinations of unprecedented accuracy in a few simple high-redshift quasar absorption line (QAL) systems. Furthermore an independent determination of the fractional contribution of baryons to the critical density, Ω b , from precision measurements of the cosmic microwave background radiation (CMB) by various balloon missions and the WMAP [2] sattelite has...

Gravitino or axino dark matter with reheat temperature as high as 1016 GeV

“…Highly relativistic axions are produced in NLSP decays, which make a negligible contribution to dark radiation. Furthermore, since the final products are the LSP and the axion, these decays are not subject to BBN limits [40][41][42]. As we will see in this section, the origin of the current dark matter abundance is typically due to either NLSP or LSP production, unless we consider peculiar parameter space regions.…”

Axino cold dark matter revisited

“…For axino DM, the lifetime of the NLSP, such as the neutralino or the stau, is typically around 1 sec, or less, and therefore constraints from the BBN are weak. However, for longer lifetimes such constraints become important [50][51][52]. This leads to an upper bound on the decay products of the NLSP for a given NLSP lifetime.…”

Path to metallicity: Synthesis of CNO elements in standard BBN

“…The only free parameter is the baryon fraction ω b , which can be presently determined by Cosmic Microwave Background (CMB) anisotropy [1]. Using the CMB value for ω b turns BBN into a parameter-free (and thus highly predictive) theory, which can be used to check the internal consistency of the standard cosmological model, to constrain astrophysical mechanisms like 7 Li and 3 He stellar reprocessing [2,3], to probe the cosmic neutrino background and/or constrain exotic physics, as for example in [4,5,6,7,8,9,10].…”