# 17th International Conference on Topics in Astroparticle and Underground Physics (TAUP 2021)

26 August 2021 to 3 September 2021

## Thermal axions with multi-eV masses are possible in low-reheating scenarios

30 Aug 2021, 17:10
50m
Talk in parallel session Cosmology and particle physics

### Speaker

Pierluca Carenza (Bari University & INFN Bari)

### Description

We revise cosmological mass bounds on hadronic axions in low-reheating cosmological scenarios, with a reheating temperature $T_{\rm RH}\le 100$ MeV, in light of the latest cosmological observations. In this situation, the neutrino decoupling would be unaffected, while the thermal axion relic abundance is suppressed. Moreover, axions are colder in low-reheating temperature scenarios, so that bounds on their abundance are possibly loosened. As a consequence of these two facts, cosmological mass limits on axions are relaxed. Using state-of-the-art cosmological data and characterizing axion-pion interactions at the leading order in chiral perturbation theory, we find in the standard case an axion mass bound $m_a < 0.26$ eV. However, axions with masses $m_a \simeq 1$ eV, or heavier, would be allowed for reheating temperatures $T_{\rm RH}<80$ MeV. Multi-eV axions would be outside the mass sensitivity of current and planned solar axion helioscopes and would demand new experimental approaches to be detected.

 Reference to paper (DOI or arXiv) 2104.04

### Primary authors

Pierluca Carenza (Bari University & INFN Bari) Massimiliano Lattanzi (Universita' di Ferrara) Alessandro MIRIZZI (Bari University) Francesco Forastieri (IFN Ferrara)

### Presentation Materials

 Pres_TAUP2021.pdf Thermal axions with eV-scale mass in low-reheating scenarios
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