English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We provide model-independent bounds on the rates of rare decays $\eta(\eta^\prime) \to \pi\pi$ based on experimental limits on the neutron electricdipole moment (nEDM). Starting from phenomenological $\eta(\eta^\prime) \pi\pi$couplings, the nEDM arises at two loop level. The leading-order relativisticChPT calculation with the minimal photon coupling to charged pions and a protoninside the loops leads to a finite, counter term-free result. This is animprovement upon previous estimates which used approximations in evaluating thetwo loop contribution and were plagued by divergences. While constraints on the$\eta(\eta^\prime) \pi\pi$ couplings in our phenomenological approach aresomewhat milder than in the picture with the QCD $\theta$-term, our calculationmeans that whatever the origin of these couplings, The decays $\eta (\eta') \to2 \pi$ will remain unobservable in the near future.

Bounds on rare decays of $\eta$ and $\eta^\prime$ mesons from the neutron EDM