Novel model-marginalized cosmological bound on the QCD axion mass

• Published in: Physical Review D
• Main Authors: Di Valentino, Eleonora, Gariazzo, Stefano, Giarè, W., Melchiorri, Alessandro, Mena, Olga, Renzi, F.
• Other Authors: European Commission, Ministerio de Ciencia e Innovación (España), Generalitat Valenciana, Agencia Estatal de Investigación (España)
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Physical Society 2023
• Subjects: Sheffield; South Pole; South pole
• Online Access: http://hdl.handle.net/10261/335903; https://doi.org/10.1103/PhysRevD.107.103528

We present model-marginalized limits on mixed hot dark matter scenarios, which consider both thermal neutrinos and thermal QCD axions. A novel aspect of our analyses is the inclusion of small-scale cosmic microwave background (CMB) observations from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT), together with those from the Planck satellite and baryon acoustic oscillation (BAO) data. After marginalizing over a number of well-motivated nonminimal background cosmologies, the tightest 95% Confidential Level (CL) upper bound we obtain is 0.21 eV, both for ∑mν and ma, from the combination of ACT, Planck and BAO measurements. Restricting the analyses to the standard ΛCDM picture, we find ∑mν<0.16 eV and ma<0.18 eV, both at 95% CL Interestingly, the best background cosmology is never found within the minimal ΛCDM plus hot relics, regardless of the datasets exploited in the analyses. The combination of Planck with either BAO, SPT or ACT prefers a universe with a nonzero value of the running in the primordial power spectrum with strong evidence. Small-scale CMB probes, both alone and combined with BAO, either prefer, with substantial evidence, nonflat universes (as in the case of SPT) or a model with a time varying dark energy component (as in the case of ACT). E. D. V. is supported by a Royal Society Dorothy Hodgkin Research Fellowship. This article is based upon work from COST Action CA21136 addressing observational tensions in cosmology with systematics and fundamental physics (CosmoVerse) supported by COST (European Cooperation in Science and Technology). A. M. andW. G. are supported by the TASP INFN initiative. We acknowledge IT Services at The University of Sheffield for the provision of services for High Performance Computing. This work has been partially supported by the MCIN/AEI/10.13039/501100011033 of Spain under Grant No. PID2020–113644 GB-I00, by the Generalitat Valenciana of Spain under Grant No. PROMETEO/2019/ 083 and by the European Union’s Framework Programme for ...