The quest for an intermediate-scale accidental axion and further ALPs

Abstract

Abstract:The recent detection of the cosmic microwave background polarimeter experiment BICEP2 of tensor fluctuations in the B-mode power spectrum basically excludes all plausible axion models where its decay constant is above 10 13 GeV. Moreover, there are strong theoretical, astrophysical, and cosmological motivations for models involving, in addition to the axion, also axion-like particles (ALPs), with decay constants in the intermediate scale range, between 10 9 GeV and 10 13 GeV. Here, we present a general analysis of models with an axion and further ALPs and derive bounds on the relative size of the axion and ALP photon (and electron) coupling. We discuss what we can learn from measurements of the axion and ALP photon couplings about the fundamental parameters of the underlying ultraviolet completion of the theory. For the latter we consider extensions of the Standard Model in which the axion and the ALP(s) appear as pseudo Nambu-Goldstone bosons from the breaking of global chiral U(1) (Peccei-Quinn (PQ)) symmetries, occurring accidentally as low energy remnants from exact discrete symmetries. In such models, the axion and the further ALP are protected from disastrous explicit symmetry breaking effects due to Planck-scale suppressed operators. The scenarios considered exploit heavy right handed neutrinos getting their mass via PQ symmetry breaking and thus explain the small mass of the active neutrinos via a seesaw relation between the electroweak and an intermediate PQ symmetry breaking scale. For a number of explicit models, we determine the parameters of the low-energy effective field theory describing the axion, the ALPs, and JHEP06 (2014)037 their interactions with photons and electrons, in terms of the input parameters, in particular the PQ symmetry breaking scales. We show that these models can accommodate simultaneously an axion dark matter candidate, an ALP explaining the anomalous transparency of the universe for γ-rays, and an ALP explaining the recently reported 3.55 keV gamma line from galaxies and clusters of galaxies, if the respective decay constants are of intermediate scale. Moreover, they do not suffer severely from the domain wall problem.

Axion predictions in SO(10) × U(1)PQ models

“…As anticipated earlier, the θ k parameter for a given group (see (3.1)) and the axion enter the low-energy Lagrangian in the combination θ k + 1/f A,k A. The above effective interactions can also be recovered by rotating the scalar phases away from the Yukawa couplings [48]. The PQ-invariant Yukawa couplings induce contributions to the Lagrangian of the form…”

ALPs at colliders

“…The initial model for the axion, the so-called PQWW axion [1,7,8], is linked to a solution to the QCD θ-problem, and is very constrained by data [9]. In the category of invisible axions, we find two popular axion models, DSFZ [10,11] and KSVZ [12][13][14]. Besides these archetypical examples, axion-like particles abound in the model-building bestiarum, e.g.…”

“…Besides these archetypical examples, axion-like particles abound in the model-building bestiarum, e.g. axions as Dark Matter mediators [15], axion Dark Matter [16][17][18], axions from the compactification of extra-dimensions [19] or more general situations with multi-axion sectors [14].…”

A couplet from flavored dark matter

“…Nevertheless, a large number of DM models have been proposed to explain this signal. The ideas that have been proposed include sterile neutrinos , axions [70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85], supersymmetry [86][87][88][89][90][91][92] and a number of other mechanisms . We now show that the 3.5 keV line, if confirmed, can be easily accommodated within the framework of the minimal model.…”