With the establishment and maturation of the experimental programs searching for new
physics with sizeable couplings at the LHC, there is an increasing interest in the broader …

We review the landscape of QCD axion models. Theoretical constructions that extend the
window for the axion mass and couplings beyond conventional regions are highlighted and …

In the late 1970s, the axion was proposed as a solution to the strong CP problem, ie, the
puzzle why the strong interactions conserve parity P and the product CP of charge …

Axions and other very light axion-like particles appear in many extensions of the Standard
Model, and are leading candidates to compose part or all of the missing matter of the …

Four decades after its prediction, the axion remains the most compelling solution to the
strong-CP problem and a well-motivated dark matter candidate, inspiring a host of elegant …

This biennial Review summarizes much of particle physics. Using data from previous
editions, plus 2158 new measurements from 551 papers, we list, evaluate, and average …

Current upper bounds on the neutron electric dipole moment constrain the physically
observable quantum chromodynamic (QCD) vacuum angle| θ¯|≲ 10− 11. Since QCD …

Axion emission by hot and dense plasmas is a new energy-loss channel for stars.
Observable consequences include a modification of the solar sound-speed profile, an …

We have searched for solar axions or similar particles that couple to two photons by using
the CERN Axion Solar Telescope (CAST) set-up with improved conditions in all detectors …

▪ Abstract Low-mass particles, such as neutrinos, axions, other Nambu-Goldstone bosons,
and gravitons, are produced in the hot and dense interior of stars. Therefore, astrophysical …