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Reheating after the Supercooled Phase Transitions with Radiative Symmetry Breaking

Francesco Rescigno, Alberto Salvio

TL;DR

This work analyzes how the universe reheats after long periods of supercooling in theories with radiative symmetry breaking (RSB). It develops a general framework for δχ decays into SM particles and dark‑sector states, deriving decay rates and the resulting reheating temperature $T_{rh}$, and it shows two distinct regimes: (i) $\chi_0 \gg v$, where SM reheating proceeds via perturbative decays of the flat-direction $\chi$; and (ii) $\chi_0$ not much larger than $v$, where preheating transfers energy to a dark photon that subsequently decays to SM fields. The paper also demonstrates sterile‑neutrino DM production from δχ decays, and presents a concrete gauged $B-L$ model where $m_{N_1} \sim 100$ MeV DM and EW symmetry breaking arise radiatively. In the dark‑sector case with $\chi_0\lesssim v$, preheating provides a robust path to fast reheating via the dark photon, with observational constraints (beam dumps, SN1987A, $(g-2)_e$, BBN/CMB) carefully considered. Overall, the results clarify post‑PT cosmology in RS B theories and connect reheating to DM production and observational signatures.

Abstract

Theories with radiative symmetry breaking (RSB) lead to first-order phase transitions and the production of gravitational waves as well as primordial black holes if the supercooling period lasted long enough. Here we explain how to efficiently reheat the universe after such period in the above-mentioned class of theories. Two cases are possible, depending on whether the RSB scale is much larger than the electroweak (EW) symmetry breaking scale or not. When it is, the dominant reheating mechanism can be the decays of the field responsible for RSB in the Standard Model (SM) sector. We point out that in a similar way dark matter (DM) can be produced and we analyze in some detail the case of a sterile-neutrino, finding that the full DM abundance is reproduced when this particle is at the $10^2$ MeV scale in a well-motivated SM completion. When the RSB scale is not much larger than the EW symmetry breaking scale, we find that efficient reheating always occurs when the energy density of the false vacuum is first entirely transferred to a dark photon and then to SM fermions via dark-photon decays.

Reheating after the Supercooled Phase Transitions with Radiative Symmetry Breaking

TL;DR

This work analyzes how the universe reheats after long periods of supercooling in theories with radiative symmetry breaking (RSB). It develops a general framework for δχ decays into SM particles and dark‑sector states, deriving decay rates and the resulting reheating temperature , and it shows two distinct regimes: (i) , where SM reheating proceeds via perturbative decays of the flat-direction ; and (ii) not much larger than , where preheating transfers energy to a dark photon that subsequently decays to SM fields. The paper also demonstrates sterile‑neutrino DM production from δχ decays, and presents a concrete gauged model where MeV DM and EW symmetry breaking arise radiatively. In the dark‑sector case with , preheating provides a robust path to fast reheating via the dark photon, with observational constraints (beam dumps, SN1987A, , BBN/CMB) carefully considered. Overall, the results clarify post‑PT cosmology in RS B theories and connect reheating to DM production and observational signatures.

Abstract

Theories with radiative symmetry breaking (RSB) lead to first-order phase transitions and the production of gravitational waves as well as primordial black holes if the supercooling period lasted long enough. Here we explain how to efficiently reheat the universe after such period in the above-mentioned class of theories. Two cases are possible, depending on whether the RSB scale is much larger than the electroweak (EW) symmetry breaking scale or not. When it is, the dominant reheating mechanism can be the decays of the field responsible for RSB in the Standard Model (SM) sector. We point out that in a similar way dark matter (DM) can be produced and we analyze in some detail the case of a sterile-neutrino, finding that the full DM abundance is reproduced when this particle is at the MeV scale in a well-motivated SM completion. When the RSB scale is not much larger than the EW symmetry breaking scale, we find that efficient reheating always occurs when the energy density of the false vacuum is first entirely transferred to a dark photon and then to SM fermions via dark-photon decays.

Paper Structure

This paper contains 14 sections, 105 equations, 3 figures.

Table of Contents

  1. Introduction
  2. General structure of the theory
  3. Interactions
  4. Scalar and vector interactions
  5. Fermion interactions
  6. Decay Rates
  7. Radiative electroweak symmetry breaking
  8. Reheating through the decays of the flat-direction field
  9. Compatibility between reheating and phase transition
  10. Sterile-neutrino dark matter from reheating
  11. A model of radiative EW and lepton symmetry breaking
  12. Preheating
  13. Conclusions
  14. Three-body phase space

Figures (3)

  • Figure 1: Relevant decay rates, $\Gamma$, in units of the SM VEV $v$, of $\delta \chi$ into SM particles as a function of the mixing angle $\alpha$ or, equivalently, the radiative symmetry breaking scale $\chi_0$.
  • Figure 2: The parameter space for sterile-neutrino dark matter production via $\delta \chi$ decays in the model of Sec. \ref{['Radiative electroweak and lepton symmetry breaking']}. $\beta/H_n$ has been computed with the method explained in Sec. 3.2.3 of Salvio:2023ext. We show in green the Lymann-$\alpha$ constraint on the mass of the non-thermal sterile neutrino DM, where we used the prescription presented in Cirelli:2024ssz, in purple the overproduction constraint, in dark gray the no-nucleation constraint and in dark green the region where the perturbation theory starts to be less accurate ($g>1$).
  • Figure 3: Region of the dark photon parameter space where fast reheating can occur. Here we set $g_*=100$ (only to report values of $T_{\rm eq}$, which, however, depend weakly on $g_*$) and the relevant constraints on dark photons are included. Di-lepton searches with experiments at collider/fixed target: A1 Merkel:2014avp, LHCb LHCb:2019vmc, CMS CMS:2019kiy, BaBar BaBar:2014zli, KLOE KLOE-2:2011hhjKLOE-2:2012liiKLOE-2:2014qxgKLOE-2:2016ydq, NA48/2 NA482:2015wmo, NA64 NA64:2018lsq. Old beam dump: E774 Bross:1989mp, E141 Riordan:1987aw, E137 Bjorken:1988asBatell:2014mgaMarsicano:2018krp, $\nu$-Cal Blumlein:2011mvBlumlein:2013cua, CHARM Gninenko:2012eq. Constraints from supernovae SN1987A Chang:2016ntp and $(g-2)_e$Pospelov:2008zw are also included. Constraints on low reheating coming from BBN and CMB deSalas:2015gljHasegawa:2019jsaAllahverdi:2020bys are represented by the gray area, where we applied the constraint directly to the equivalence temperature, $T_{\rm eq}\gtrsim 5$ MeV. The region where $T_{\rm rh}< T_{\rm eq}$ is the region where the reheating is not fast.