Running in the ALPs

148

163

Axions and axion-like particles (ALPs) are well-motivated low-energy relics of high-energy extensions of the Standard Model, which interact with the known particles through higher-dimensional operators suppressed by the mass scale Λ of the new-physics sector. Starting from the most general dimension-5 interactions, we discuss in detail the evolution of the ALP couplings from the new-physics scale to energies at and below the scale of electroweak symmetry breaking. We derive the relevant anomalous dimensions at two-loop order in gauge couplings and one-loop order in Yukawa interactions, carefully considering the treatment of a redundant operator involving an ALP coupling to the Higgs current. We account for one-loop (and partially two-loop) matching contributions at the weak scale, including in particular flavor-changing effects. The relations between different equivalent forms of the effective Lagrangian are discussed in detail. We also construct the effective chiral Lagrangian for an ALP interacting with photons and light pseudoscalar mesons, pointing out important differences with the corresponding Lagrangian for the QCD axion.

mentioning

confidence: 99%

The low-energy effective theory of axions and ALPs

Bauer

Neubert

Renner

et al. 2021

148

163

“…The renormalization-group (RG) evolution of the dimension-5 ALP couplings in the effective Lagrangian L SM+ALP has recently been studied in [43,44]. Here we point out the important fact that the existence of an ALP with couplings to the SM necessarily induces non-zero Wilson coefficients of the dimension-6 SMEFT operators contained in L SMEFT , which produce effects across a wide variety of observables.…”

Section: Jhep06(2021)135mentioning

confidence: 96%

“…In recent work, a detailed study of the RG evolution of the ALP couplings to SM particles in the effective ALP Lagrangians (2.1) and (2.2) from the new-physics scale Λ down to low energies has been performed [43,44]. We summarize the one-loop RG equations in JHEP06(2021)135 appendix B.…”

Section: Jhep06(2021)135mentioning

confidence: 99%

“…A detailed study of the RG evolution of the ALP couplings to SM particles in the effective ALP Lagrangians (2.1) and (2.3) has been performed in [43,44]. In order to meaningfully derive the one-loop approximations to the RG equations, one needs to make an assumption about the relative size of the ALP-boson and ALP-fermion couplings.…”

Section: Jhep06(2021)135 B Rg Evolution Of Alp Couplingsmentioning

confidence: 99%

See 1 more Smart Citation

ALP — SMEFT interference

Galda

Neubert

Renner

2021

The Standard Model Effective Field Theory (SMEFT) offers a powerful theoretical framework for parameterizing the low-energy effects of heavy new particles with masses far above the scale of electroweak symmetry breaking. Additional light degrees of freedom extend the effective theory. We show that light new particles that are weakly coupled to the SM via non-renormalizable interactions induce non-zero Wilson coefficients in the SMEFT Lagrangian via renormalization-group evolution. For the well-motivated example of axions and axion-like particles (ALPs) interacting with the SM via classically shift-invariant dimension-5 interactions, we calculate how these interactions contribute to the one-loop renormalization of the dimension-6 SMEFT operators, and how this running sources additional contributions to the Wilson coefficients on top of those expected from heavy new states. As an application, we study the ALP contributions to the magnetic dipole moment of the top quark and comment on implications of electroweak precision constraints on ALP couplings.

“…For the intermediate regime between the MeV and the GeV scales, reactors [66], rare decay [59,60,63,64,[67][68][69][70][71], beam dump/fixed target [72][73][74][75][76][77][78][79][80] experiments and long-lived particle detectors at the LHC [69,81,82] compete with supernovae [83][84][85] as the most favourable environments for probing axions (see [69] for a recent review). Of particular interest is the interplay between the various axionic couplings in different experiments and observations [85,86] in these mass regimes -see [87][88][89] for the renormalization group (RG) equations that allow for a consistent comparison of constraints at different energy scales.…”

Section: Jhep07(2021)059mentioning

confidence: 99%

Leading logs in QCD axion effective field theory

Alonso-Álvarez

Ertas

Jaeckel

et al. 2021

The axion is much lighter than all other degrees of freedom introduced by the Peccei-Quinn mechanism to solve the strong CP problem. It is therefore natural to use an effective field theory (EFT) to describe its interactions. Loop processes calculated in the EFT may however explicitly depend on the ultraviolet cutoff. In general, the UV cutoff is not uniquely defined, but the dimensionful couplings suggest to identify it with the Peccei-Quinn symmetry-breaking scale. An example are K+ → π+ + a decays that will soon be tested to improved precision in NA62 and KOTO and whose amplitude is dominated by the term logarithmically dependent on the cutoff. In this paper, we critically examine the adequacy of using such a naive EFT approach to study loop processes by comparing EFT calculations with ones performed in complete QCD axion models. In DFSZ models, for example, the cutoff is found to be set by additional Higgs degrees of freedom and to therefore be much closer to the electroweak scale than to the Peccei-Quinn scale. In fact, there are non-trivial requirements on axion models where the cutoff scale of loop processes is close to the Peccei-Quinn scale, such that the naive EFT result is reproduced. This suggests that the existence of a suitable UV embedding may impose restrictions on axion EFTs. We provide an explicit construction of a model with suitable fermion couplings and find promising prospects for NA62 and IAXO.