The ${{\mathit d}}$-, ${{\mathit u}}$-, and ${{\mathit s}}$-quark masses are estimates of so-called “current-quark masses,” with ratios ${\mathit m}_{{{\mathit u}}}/{\mathit m}_{{{\mathit d}}}$ and ${\mathit m}_{{{\mathit s}}}/{\mathit m}_{{{\mathit d}}}$ extracted from pion and kaon masses using chiral symmetry. The estimates of ${{\mathit d}}$ and ${{\mathit u}}$ masses are not without controversy and remain under active investigation. Within the literature there are even suggestions that the ${{\mathit u}}~$quark could be essentially massless. The ${{\mathit s}}$-quark mass is estimated from SU(3) splitting in hadron masses.

VALUE (MeV) $\bf{ 4.70 \pm0.07}$    (CL = 90%) OUR EVALUATION