QUARKS INSPIRE   JSON PDGID:
Q001

${\mathit {\mathit d}}$

$I(J^P)$ = $1/2(1/2^{+})$ 
Mass ${\mathit m}_{\mathrm {}}$ = $4.70$ $\pm0.07$ (MeV) Charge = $−{1\over 3}$ $\mathit e$ $\mathit I_{\mathit z}$ = $−{1\over 2}$
${\mathit m}_{{{\mathit s}}}/{\mathit m}_{{{\mathit d}}}$ = $\text{17 - 22}$   
${{\overline{\mathit m}}}$ = (${\mathit m}_{{{\mathit u}}}$ $+$ ${\mathit m}_{{{\mathit d}}})/$2 = $3.49 \pm0.07 (MeV)$   
${\mathit {\mathit d}}$-QUARK MASS [1] $4.70$ $\pm0.07$ MeV  CL=90%
 
[1] The ratios ${\mathit m}_{{{\mathit u}}}/{\mathit m}_{{{\mathit d}}}$ and ${\mathit m}_{{{\mathit s}}}/{\mathit m}_{{{\mathit d}}}$ are extracted from pion and kaon masses using chiral symmetry. The estimates of ${{\mathit u}}$ and ${{\mathit d}}$ 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) splittings in hadron masses.