Axion-electron coupling from the RGB tip of Globular Clusters

Abstract

We present a preliminary study of the Globular Cluster RGB devoted to improve the available constraint for the axion-electron coupling. By means of multi-band IR photometry of the cluster M3 we obtain gae/10 −13 < 2.57 (95% C.L.).

More Axions from Strings

“…17 Defined as L ⊃ − 1 4 g aγγ aF F in the low energy theory, where F is the electromagnetic field strength. 18 The existing experimental and observational bounds shown are from ADMX [60,61], earlier cavity experiments "UF/RBF" [62,63], HAYSTACK [64], CAST [65], observations of horizontal branch starts "HB" [66], supernova 1987a "SN1987a" [67][68][69] (see however [70]) and red giants and white dwarf stars "RG/WD" [71][72][73][74]. The constraints on DSFZ axions from supernova 1987a, red giants and white dwarfs are model dependent via the mixing angle β.…”

Neutrino Masses and Hubble Tension via a Majoron in MFV

“…being f a the axion scale, that is connected to the Φ VEV in this model by the relation f a = v Φ /9. For QCD axions, the most stringent constraint on f a comes from the axion couplings to photons [97][98][99] and to electrons [100][101][102], which push its value to be larger than f a 1.2 × 10 7 GeV and f a 8 × 10 8 GeV, respectively.…”

The DFSZ axion in the CMB

“…Here we consider: the X1T excess in electron-recoil events [31] and observations of faster-than-expected cooling rates of white dwarfs (see e.g. [32,33]) and red giant stars (see [34][35][36]). Both observations can be interpreted in terms of an axion particle, with suggested coupling to electrons 4 , typically written in terms of g ae ≡ m e c e /f , given (at 1σ) by 5 Xenon-1T [31]: g ae 2.6 +0.7 −0.7 × 10 −12 , (16) Star Cooling [56]:…”

“…Second, on the astrophysical side, measurements of the cooling rates of certain white dwarfs (see e.g. [32,33]) and red giant stars (see [34][35][36]) appear to hint (at slightly more than 3σ) at a DFSZ axion 1 Recent works [24,25] fixed the axion-pion coupling according to the KSVZ scenario (and did not discuss production via leptons). Therefore, such bounds on the QCD axion mass cannot be applied to DFSZ scenarios (especially when correlating with the Xenon-1T excess).…”