High Energy Physics Seminar

How many QCD axions can there be? Can the standard ma-fa relation be modified without extra sources of PQ breaking? Multiple axion-like fields arise naturally in string theory, extra-dimensional models, and other extensions of the Standard Model. In this talk we explore their implications for the strong CP problem, dark matter production, and experimental strategies to distinguish them. First, we study the possible masses and couplings of multiple QCD axions, obtaining a novel sum rule that links their individual signals as a rigorous consequence of the PQ symmetry.  Second, we show that axion dark matter production is significantly modified in multi-axion scenarios due to level-crossing effects, which we describe analytically via the Landau-Zener formalism. Finally, we address the question of whether a next-generation helioscope such as IAXO could tell one axion from two: by exploiting the spectral signatures of axion flavor oscillations over the Earth-Sun baseline, we identify the regions of parameter space where IAXO can discriminate a two-axion signal from the single-axion hypothesis.

The talk is in 469 Lauritsen.

Contact [email protected] for Zoom link.