θ -dependence of light nuclei and nucleosynthesis

We explore whether the axion which solves the strong CP problem can naturally be much lighter than the canonical QCD axion. The $$ {Z}_{\mathcal{N}} $$ Z N symmetry proposed by Hook, with $$ \mathcal{N} $$ N mirror and degenerate worlds coexisting in Nature and linked by the axion field, is considered in terms of generic effective axion couplings. We show that the total potential is safely approximated by a single cosine in the large $$ \mathcal{N} $$ N limit, and we determine the analytical formula for the exponentially suppressed axion mass. The resulting universal enhancement of all axion interactions relative to those of the canonical QCD axion has a strong impact on the prospects of axion-like particle experiments such as ALPS II, IAXO and many others: experiments searching for generic axion-like particles have in fact discovery potential to solve the strong CP problem. The finite density axion potential is also analyzed and we show that the $$ {Z}_{\mathcal{N}} $$ Z N asymmetric background of high-density stellar environments sets already significant model-independent constraints: 3 ≤ $$ \mathcal{N} $$ N ≲ 47 for an axion scale fa ≲ 2.4 × 1015 GeV, with tantalizing discovery prospects for any value of fa and down to $$ \mathcal{N} $$ N ∼ 9 with future neutron star and gravitational wave data, down to the ultra-light mass region. In addition, two specific ultraviolet $$ {Z}_{\mathcal{N}} $$ Z N completions are developed: a composite axion one and a KSVZ-like model with improved Peccei-Quinn quality.

Section: Jhep05(2021)184mentioning

confidence: 99%

An even lighter QCD axion

Luzio

Gavela

Quílez

et al. 2021

“…Why does nature prefer absence of CP violation in the strong sector? There seem to be no anthropic arguments that motivate a small θ [65,66]. A popular way to dynamically remove the θ term is through the Peccei-Quinn mechanism that leads to a new field, the axion, which can potentially be linked to Dark Matter.…”

Section: Jhep11(2021)127mentioning

confidence: 99%

A low-energy perspective on the minimal left-right symmetric model

Dekens

Andreoli

Vries

et al. 2021

We perform a global analysis of the low-energy phenomenology of the minimal left-right symmetric model (mLRSM) with parity symmetry. We match the mLRSM to the Standard Model Effective Field Theory Lagrangian at the left-right-symmetry breaking scale and perform a comprehensive fit to low-energy data including mesonic, neutron, and nuclear β-decay processes, ∆F = 1 and ∆F = 2 CP-even and -odd processes in the bottom and strange sectors, and electric dipole moments (EDMs) of nucleons, nuclei, and atoms. We fit the Cabibbo-Kobayashi-Maskawa and mLRSM parameters simultaneously and determine a lower bound on the mass of the right-handed WR boson. In models where a Peccei-Quinn mechanism provides a solution to the strong CP problem, we obtain $$ {M}_{W_R} $$ M W R ≳ 5.5 TeV at 95% C.L. which can be significantly improved with next-generation EDM experiments. In the P-symmetric mLRSM without a Peccei-Quinn mechanism we obtain a more stringent constraint $$ {M}_{W_R} $$ M W R ≳ 17 TeV at 95% C.L., which is difficult to improve with low-energy measurements alone. In all cases, the additional scalar fields of the mLRSM are required to be a few times heavier than the right-handed gauge bosons. We consider a recent discrepancy in tests of first-row unitarity of the CKM matrix. We find that, while TeV-scale WR bosons can alleviate some of the tension found in the Vud,us determinations, a solution to the discrepancy is disfavored when taking into account other low-energy observables within the mLRSM.

“…in refs. [21,22]. In particular, it was shown in [22] that nuclear binding increases with θ and that θ 0.1 would not upset the world as we know it.…”

Section: Introductionmentioning

confidence: 99%

“…[21,22]. In particular, it was shown in [22] that nuclear binding increases with θ and that θ 0.1 would not upset the world as we know it. It is thus also of interest to study the reaction rate of the fundamental α-α scattering process as a function of θ, as will be done here.…”

Section: Introductionmentioning

confidence: 99%

Alpha-alpha scattering in the Multiverse

Elhatisari

Lähde²,

Lee

et al. 2022

Self Cite

We investigate the phase shifts of low-energy α-α scattering under variations of the fundamental parameters of the Standard Model, namely the light quark mass, the electromagnetic fine-structure constant as well as the QCD θ-angle. As a first step, we recalculate α-α scattering in our Universe utilizing various improvements in the adiabatic projection method, which leads to an improved, parameter-free prediction of the S- and D-wave phase shifts for laboratory energies below 10 MeV. We find that positive shifts in the pion mass have a small effect on the S-wave phase shift, whereas lowering the pion mass adds some repulsion in the two-alpha system. The effect on the D-wave phase shift turns out to be more pronounced as signaled by the D-wave resonance parameters. Variations of the fine-structure constant have almost no effect on the low-energy α-α phase shifts. We further show that up-to-and-including next-to-leading order in the chiral expansion, variations of these phase shifts with respect to the QCD θ-angle can be expressed in terms of the θ-dependent pion mass.