The muon g-2 and lattice QCD hadronic vacuum polarization may point to new, long-lived neutral hadrons

The experimental value of g-2 of the muon is larger by $4.2\sigma$ than the Standard Model prediction based on the hadronic vacuum polarization contribution (HVP) determined from the measured R-ratio, $\sigma (e^{+}{e}^{-}\text{\hspace{0.17em}⁣}\to \text{\hspace{0.17em}⁣}hadrons)\mathrm{/}\sigma (e^{+}{e}^{-}\text{\hspace{0.17em}⁣}\to \text{\hspace{0.17em}⁣}{\mu }^{+}{\mu }^{-})$; the HVP calculated in lattice QCD also significantly exceeds the measured R-ratio value. We show here that these discrepancies can be explained by an undetected contribution to $e^{+}{e}^{-}\text{\hspace{0.17em}⁣}\to \text{\hspace{0.17em}⁣}hadrons$ as could arise from production of neutral, long-lived hadrons which have not previously been identified. We suggest two candidates for the new hadrons and propose several experimental tests.