Fig. 5: Exclusion plot for the proton coupling (mean limits).

Other laboratory (solid lines) and astrophysical (dashed lines) constraints are shown for reference and extracted from ref. ⁵⁶: CASPEr-ZULF^44,53, ChangE³¹, K-³He (rescaled from g_aNN constraints)³⁰ and neutron-star cooling⁶².