Particle Name

Mass Formula

Theoretical Value A of Mass (MeV)

Experimental Value B of Mass (MeV)

Error Rate = (A/B − 1)*%

$\eta$

$m_{\eta }=2\left(m_{\pi \pm }+m_{\pi 0}\right)$

549.09

$547.75\pm 0.12$

0.24%

${\eta }^{\prime }\left(958\right)$

$m_{\eta }=3m_{\pi \pm }+4m_{\pi 0}$

958.61

$958.78\pm 0.14$

−0.017%