MICROSCOPE limits on the strength of a new force, with comparisons to gravity and electromagnetism

Understand

Extremely weak new forces could lead to apparent violations of the Equivalence Principle.

• The MICROSCOPE experiment implies that the relative strength of a new long-range force, compared with gravity, is constrained to $|\bar\alpha_g|<3.2\ 10^{-11},2.3\ 10^{-13},2.2\ 10^{-13},6.7\ 10^{-13}$ and $1.5\ 10^{-12}$ at $2\sigma$, for a coupling to $B,\ L,\ B-L,\ B+L$ or $3B+L$; or, for a coupling to isospin, $|\alpha_g|<8.4\ 10^{-12}$.
• This is a gain in sensitivity $\simeq 3$ for a coupling to $B$, to $\approx$ 15 in the other cases, including $B-L$ as suggested by grand unification.
• This requires paying attention to the definition of $\bar\alpha_g$.