Increasing Neff with particles in thermal equilibrium with neutrinos

Abstract

Recent work on increasing the effective number of neutrino species (Neff) in the early universe has focussed on introducing extra relativistic species (`dark radiation'). We draw attention to another possibility: a new particle of mass less than 10 MeV that remains in thermal equilibrium with neutrinos until it becomes non-relativistic increases the neutrino temperature relative to the photons. We demonstrate that this leads to a value of Neff that is greater than three and that Neff at CMB formation is larger than at BBN. We investigate the constraints on such particles from the primordial abundance of helium and deuterium created during BBN and from the CMB power spectrum measured by ACT and SPT and find that they are presently relatively unconstrained. We forecast the sensitivity of the Planck satellite to this scenario: in addition to dramatically improving constraints on the particle mass, in some regions of parameter space it can discriminate between the new particle being a real or complex scalar.

10 pages, 5 figures v2 matches version to appear in JCAP

References in corpus (12)

• Primordial Nucleosynthesis: from precision cosmology to fundamental physics
• The Primordial Lithium Problem
• Probing cosmological parameters with the CMB: Forecasts from full Monte Carlo simulations
• A new cosmic microwave background constraint to primordial gravitational waves
• The primordial abundance of 4He: a self-consistent empirical analysis of systematic effects in a large sample of low-metallicity HII regions
• Signatures of a hidden cosmic microwave background
• Using BBN in cosmological parameter extraction from CMB: a forecast for Planck
• Dark Radiation Emerging After Big Bang Nucleosynthesis?
• A theory of extra radiation in the Universe
• Constraining Fundamental Physics with Future CMB Experiments
• Dark Radiation in extended cosmological scenarios
• Origin of Delta N_eff as a Result of an Interaction between Dark Radiation and Dark Matter

Cited by in corpus (66)

• In the Realm of the Hubble tension $-$ a Review of Solutions
• The trouble with $H_0$
• Feebly-Interacting Particles:FIPs 2020 Workshop Report
• Constraining the Self-Interacting Neutrino Interpretation of the Hubble Tension
• Neutrino Mass Ordering from Oscillations and Beyond: 2018 Status and Future Prospects
• Reducing the $H_0$ and ${\sigma }_8$ tensions with Dark Matter-neutrino interactions
• Limits on Neutrino-Neutrino Scattering in the Early Universe
• BBN And The CMB Constrain Neutrino Coupled Light WIMPs
• The completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Large-scale Structure Catalogues and Measurement of the isotropic BAO between redshift 0.6 and 1.1 for the Emission Line Galaxy Sample
• Dark Matter Annihilation to Neutrinos
• BBN And The CMB Constrain Light, Electromagnetically Coupled WIMPs
• New Light Species and the CMB
• Dark matter-neutrino interactions through the lens of their cosmological implications
• Let there be Light Dark Matter: The gauged $U(1{)}_{L_{\mu }-L_{\tau }}$ case
• Revisiting Neutrino Self-Interaction Constraints from $Z$ and $\tau$ decays
• Equivalent Neutrinos, Light WIMPs, and the Chimera of Dark Radiation
• Invisible and displaced dark matter signatures at Belle II
• Additional Light Sterile Neutrinos and Cosmology
• Neutrino Self-Interactions and Double Beta Decay
• Ruling out the light WIMP explanation of the galactic 511 keV line
• Neutrino experiments probe hadrophilic light dark matter
• Dirac neutrinos and $N_{\mathrm{eff}}$ II: the freeze-in case
• Joint CMB and BBN Constraints on Light Dark Sectors with Dark Radiation
• Dark Sector Equilibration During Nucleosynthesis
• Non-thermal WIMPs as "Dark Radiation" in Light of ATACAMA, SPT, WMAP9 and Planck
• Magnification bias in galaxy surveys with complex sample selection functions
• Cosmological Implications of Light Sterile Neutrinos produced after the QCD Phase Transition
• Cosmology-marginalized approaches in Bayesian model comparison: the neutrino mass as a case study
• Cosmological Constraints on Non-flat Exponential $f(R)$ Gravity
• What does cosmology tell us about the mass of thermal-relic dark matter?
• Dark Radiation and Decaying Matter
• Consistency of cosmic shear analyses in harmonic and real space
• Towards a full description of MeV dark matter decoupling: a self-consistent determination of relic abundance and $N_{\mathrm{eff}}$
• Dark matter origins of neutrino masses
• Inevitable imprints of patchy reionization on the cosmic microwave background anisotropy
• Concealing Dirac neutrinos from cosmic microwave background
• More Is Different: Reconciling eV Sterile Neutrinos with Cosmological Mass Bounds
• A null test to probe the scale-dependence of the growth of structure as a test of General Relativity
• Probing interactions within the dark matter sector via extra radiation contributions
• The ${\nu }_R$-philic scalar: its loop-induced interactions and Yukawa forces in LIGO observations
• Direct cosmological inference from three-dimensional correlations of the Lyman-$\alpha$ forest
• Minimising the impact of scale-dependent galaxy bias on the joint cosmological analysis of large scale structures
• A short survey of matter-antimatter evolution in the primordial universe
• A General Framework for Removing Point Spread Function Additive Systematics in Cosmological Weak Lensing Analysis
• CMB signature of non-thermal Dark Matter produced from self-interacting dark sector
• Linear Systematics Mitigation in Galaxy Clustering in the Dark Energy Survey Year 1 Data
• Cosmology and prospects for sub-MeV dark matter in electron recoil experiments
• Can Sterile Neutrino Explain Very High Energy Photons from GRB221009A?
• Exact joint likelihood of pseudo-$C_{\ell }$ estimates from correlated Gaussian cosmological fields
• Anomalous Ionization in the Central Molecular Zone by sub-GeV Dark Matter
• Constraining IGM enrichment and metallicity with the C IV forest correlation function
• Cosmological Fisher forecasts for next-generation spectroscopic surveys
• Measuring inflaton couplings via dark radiation as $\Delta N_{\mathrm{eff}}$ in CMB
• Constraints on dark energy from TDCOSMO & SLACS lenses
• A framework to mitigate patchy reionization contamination on the primordial gravitational wave signal
• Limit on the dark matter mass from its interaction with photons
• Dark Matter as a Solution to Muonic Puzzles
• Asymmetric dark matter and effective number of neutrinos
• $\Delta N_{\text{eff}}$ and entropy production from early-decaying gravitinos
• Probing Dark Sector Particles Coupling to Neutrinos with Double Beta Decay
• New Limits on Light Dark Matter-Nucleon Scattering
• Directional Neutrino Searches for Galactic Center Dark Matter at Large Underground LArTPCs
• Quarks to Cosmos: Particles and Plasma in Cosmological evolution
• Forecasting the potential of weak lensing magnification to enhance LSST large-scale structure analyses
• Cosmic Shear in Harmonic Space from the Dark Energy Survey Year 1 Data: Compatibility with Configuration Space Results
• Imprints of light dark matter on the evolution of cosmic neutrinos