ABSTRACT
In this work we present PRyMordial: A package dedicated to efficient computations of observables in the Early Universe with the focus on the cosmological era of Big Bang Nucleosynthesis (BBN). The code offers fast and precise evaluation of BBN light-element abundances together with the effective number of relativistic degrees of freedom, including non-instantaneous decoupling effects. PRyMordial is suitable for state-of-the-art analyses in the Standard Model as well as for general investigations into New Physics active during BBN. After reviewing the physics implemented in PRyMordial, we provide a short guide on how to use the code for applications in the Standard Model and beyond. The package is written in Python, but more advanced users can optionally take advantage of the open-source community for Julia. PRyMordial is publicly available on GitHub.
ABSTRACT
The recent measurement of helium-4 from the near-infrared spectroscopy of extremely metal-poor galaxies by the Subaru Survey may point to a new puzzle in the early Universe. We exploit this new helium measurement together with the percent-level determination of primordial deuterium, to assess indications for a nonvanishing lepton asymmetry during the big bang nucleosynthesis era, paying particular attention to the role of uncertainties in the nuclear reaction network. A cutting-edge Bayesian analysis focused on the role of the newly measured extremely metal-poor galaxies, jointly with information from the cosmic microwave background, suggests the existence of a nonzero lepton asymmetry at around the 2σ level, providing a hint for cosmology beyond lambda cold dark matter. We discuss conditions for a large total lepton asymmetry to be consistently realized in the early Universe.
ABSTRACT
Within the standard approach of effective field theory of weak interactions for Δ B = 1 transitions, we look for possibly unexpected subtle New Physics effects, here dubbed "flavourful Easter eggs". We perform a Bayesian global fit using the publicly available HEPfit package, taking into account state-of-the-art experimental information concerning these processes, including the suggestive measurements from LHCb of R K and R K ∗ , the latter available only very recently. We parametrise New Physics contributions to b â s transitions in terms of shifts of Wilson coefficients of the electromagnetic dipole and semileptonic operators, assuming CP-conserving effects, but allowing in general for violation of lepton flavour universality. We show how optimistic/conservative hadronic estimates can impact quantitatively the size of New Physics extracted from the fit. With a conservative approach to hadronic uncertainties we find nonzero New Physics contributions to Wilson coefficients at the level of â¼ 3 σ , depending on the model chosen. Furthermore, given the interplay between hadronic contributions and New Physics effects in the leptonic vector current, a scenario with nonstandard leptonic axial currents is comparable to the more widely advocated one with New Physics in the leptonic vector current.
