Constituent quark mass

The Konstituentenquarkmasse referred to QCD , the effective mass of the constituent quarks , in certain parts of the interaction between the quarks are already included. It is used to describe the hadrons in the low energy limit, where a perturbative analysis is not possible.

Scattering experiments show that hadrons are not only made up of bare quarks ( current quarks ), but also of gluons and so-called sea ​​quarks ( virtual quark- antiquark pairs as excitations of the quantum field theoretical vacuum ). The interaction with the sea quarks and gluons or the dynamic breaking of the chiral symmetry result in constituent quark masses that are much higher than the current quark masses. So z. B. explain the observed masses of protons and neutrons , which are significantly higher than the sums of the current quark masses of the light up and down quarks from which they are composed.

For the heavy quarks (c, b, t) the current quark mass is so dominant that there is hardly any difference to the constituent quark mass.

Masses of constituent and current quarks

	up	charm	Top
m KQ	${\displaystyle m_{u}}$≈ 300 MeV / c 2	${\displaystyle m_{c}}$= 1.0..1.6 GeV / c 2	${\displaystyle m_{t}}$= 168..192 GeV / c 2
m SQ	${\displaystyle m_{u}}$≈ 1.5..3 MeV / c 2	${\displaystyle m_{c}}$= 1.25 ± 0.09 GeV / c 2	${\displaystyle m_{t}}$= 174.2 ± 3.3 GeV / c 2
	down	strange	bottom
m KQ	${\displaystyle m_{d}}$≈ 300 MeV / c 2	${\displaystyle m_{s}}$= 450 MeV / c 2	${\displaystyle m_{b}}$= 4.1..4.5 GeV / c 2
m SQ	${\displaystyle m_{d}}$≈ 3..7 MeV / c 2	${\displaystyle m_{s}}$= 95 ± 25 MeV / c 2	${\displaystyle m_{b}}$= 4.2 ± 0.07 GeV / c 2

literature

• FE Close: An Introduction to quarks and partons . Academic Press, London 1979, ISBN 0-12-175150-3 .