Dimensionless physical constant
Standard model
The original standard model of particle physics from the 1970s contained 19 fundamental dimensionless constants describing the masses of the particles and the strengths of the electroweak and strong forces.

Dimensionless physical constant

Section Title: Standard model
Table Section Text: The original standard model of particle physics from the 1970s contained 19 fundamental dimensionless constants describing the masses of the particles and the strengths of the electroweak and strong forces.

Dimensionless constants of the Standard Model

Symbol	Description	Dimensionless value	Alternative value representation

mu / mP	up quark mass	1.4 × 10−22 – 2.7 × 10−22	1.7 – 3.3 MeV/c2

md / mP	down quark mass	3.4 × 10−22 – 4.8 × 10−22	4.1 – 5.8 MeV/c2

mc / mP	charm quark mass	1.04 × 10−19	1.27 GeV/c2

ms / mP	strange quark mass	8.27 × 10−21	101 MeV/c2

mt / mP	top quark mass	1.41 × 10−17	172.0 GeV/c2

mb / mP	bottom quark mass	3.43 × 10−19	4.19 GeV/c2

θ12,CKM	CKM 12-mixing angle	0.23	13.1°

θ23,CKM	CKM 23-mixing angle	0.042	2.4°

θ13,CKM	CKM 13-mixing angle	0.0035	0.2°

δCKM	CKM CP-violating Phase	0.995	57°

me / mP	electron mass	4.18546 × 10−23	511 keV/c2

mνe / mP	electron neutrino mass	below 1.6 × 10−28	below 2 eV/c2

mμ / mP	Muon mass	8.65418 × 10−21	105.7 MeV/c2

mνμ / mP	muon neutrino mass	below 1.6 × 10−28	below 2 eV/c2

mτ / mP	tau mass	1.45535 × 10−19	1.78 GeV/c2

mντ / mP	tau neutrino mass	below 1.6 × 10−28	below 2 eV/c2

θ12,PMNS	PMNS 12-mixing angle	0.5973±0.0175	34.22°±1°

θ23,PMNS	PMNS 23-mixing angle	0.785±0.12	45°±7.1°

θ13,PMNS	PMNS 13-mixing angle	≈0.077	≈4.4°

δPMNS	PMNS CP-violating Phase	Unknown

α	fine-structure constant	0.00729735	1/137.036

αs	strong coupling constant	≈1	≈1

mW± / mP	W boson mass	(6.5841 ± 0.0012) × 10−18	(80.385 ± 0.015) GeV/c2

mZ0 / mP	Z boson mass	(7.46888 ± 0.00016) × 10−18	(91.1876 ± 0.002) GeV/c2

mH / mP	Higgs boson mass	≈1.02 × 10−17	(125.09 ± 0.24) GeV/c2

Sentence(s)

The fine-structure constant α has a value of ​¹⁄137.036.

final_sentence: The fine-structure constant α has a value of ​¹⁄137.036.