New physics decaying into metastable particles: impact on cosmic neutrinos

Abstract

We investigate decays of hypothetical unstable new physics particles into metastable species such as muons, pions, or kaons in the Early Universe, when temperatures are in the MeV range, and study how they affect cosmic neutrinos. We demonstrate that the non-trivial dynamics of metastables in the plasma alters the impact of the new physics particles on the neutrino population, including the effective number of neutrino degrees of freedom, $N_{\mathrm{eff}}$, modifies neutrino spectral distortions, and may induce asymmetries in neutrino and antineutrino energy distributions. These modifications have important implications for observables such as Big Bang Nucleosynthesis and the Cosmic Microwave Background, especially in light of upcoming CMB observations aiming to reach percent-level precision on $N_{\mathrm{eff}}$. We illustrate our findings with a few examples of new physics particles and provide a computational tool available for further exploration.

Version accepted for the publication in PRL. Companion paper of "Dynamics of metastable Standard Model particles from long-lived particle decays in the MeV primordial plasma"

References in corpus (10)

• Big Bang Nucleosynthesis as a Probe of New Physics
• BBN for the LHC: constraints on lifetimes of the Higgs portal scalars
• Metastable GeV-scale particles as a solution to the cosmological lithium problem
• Baryogenesis from Oscillations of Charmed or Beautiful Baryons
• Cosmological beam dump: constraints on dark scalars mixed with the Higgs boson
• Cosmological Constraints on Neutrino Injection
• Cosmic Neutrino Background Detection in Large-Neutrino-Mass Cosmologies
• What can CMB observations tell us about the neutrino distribution function?
• Effects of an Intermediate Mass Sterile Neutrino Population on the Early Universe
• Dynamics of metastable Standard Model particles from long-lived particle decays in the MeV primordial plasma

Cited by in corpus (8)

• Dynamics of metastable Standard Model particles from long-lived particle decays in the MeV primordial plasma
• Fast and Flexible Neutrino Decoupling Part I: The Standard Model
• Primordial neutrinos fade to gray: constraints from cosmological observables
• No Hiding in the Dark: Cosmological Bounds on Heavy Neutral Leptons with Dark Decay Channels
• Precision calculation of $N_{\text{eff}}$ with Neutrino Direct Simulation Monte Carlo
• Neutrino Emission and Plasma Heating from Primordial Black Holes: An Improved Approach to $N_{\mathrm{eff}}$ Constraints
• Nucleosynthesis and CMB bounds on photophilic ALPs: a fresh look
• Loop-Level Lepton Flavor Violation and Diphoton Signals in the Minimal Left-Right Symmetric Model