Current quark mass

The mass of the current quark (engl. Current quark mass ) is the mass of the bare quark , as shown in the Lagrangian of quantum (QCD, the quantum field theory of the strong interaction ) to calculate Feynman diagrams is used.

detection

Since quarks were never observed freely ( confinement ), but always bound as pairs in mesons or as three-way configurations in baryons , the masses of free quarks cannot be determined experimentally, but have to be extrapolated from theoretical models . For example, lattice theory calculations or calculations with effective theories ( chiral perturbation theory ) result in relationships between the masses of different mesons and so-called sum rules, from which conclusions can be drawn about the masses of the bare quarks:

Masses of the current quarks
${\displaystyle m_{u}}$= 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
${\displaystyle m_{d}}$= 3 .. 7 MeV / c 2	${\displaystyle m_{s}}$= 95 ± 25 MeV / c 2	${\displaystyle m_{b}}$= 4.2 ± 0.07 GeV / c 2

Comparison with constituent quark masses

The current quark masses are much smaller than the constituent quark masses ; H. than the masses of the bound quarks; This can be obtained by dividing the observed mass of protons and neutrons between the three quarks that make them up. The largest part of the mass of protons and neutrons is therefore formed by the QCD field energy .

literature

• Gasser, Heinrich Leutwyler Quark Masses , Physics Reports 1982

source

1. ^ Gasser, Leutwyler Physics Reports 1982
2. ↑ Particle Data Group, Yao et al. a. Journal of Physics G 33, 2006, p. 1, online