# X (charge)

In particle physics, the X-charge (or simply X) is a conserved quantum number associated with the SO(10) grand unification theory. It is thought to be conserved in strong, weak, electromagnetic and gravitational and Higgs interactions. Because the X-charge is related to the weak hypercharge, it varies depending on the helicity of a particle. For example, a left-handed quark has an X-charge of +1, whereas a right-handed quark can have either an X-charge of -1 (for up, charm and top quarks), or -3 (for down, strange and bottom quarks).

X is related to the difference between the baryon number B and the lepton number L (that is BL), and the weak hypercharge YW via the relation:

${\displaystyle X=5(B-L)-2Y_{W}.\,}$

The following table lists the X-charge values for the standard model particles and their antiparticles.

Particle Name Left-Handed X-charge Right-Handed X-charge
Up Quark 1 -1
Down Quark 1 -3
Charm Quark 1 -1
Strange Quark 1 -3
Top Quark 1 -1
Bottom Quark 1 -3
Electron -3 -1
Muon -3 -1
Tau -3 -1
Electron Neutrino -3 -5
Muon Neutrino -3 -5
Tau Neutrino -3 -5
Photon 0 0
W Boson 0 0
Z Boson 0 0
Gluon 0 0
Higgs Boson -2 -2
Up Antiquark 1 -1
Down Antiquark -3 -1
Charm Antiquark 1 -1
Strange Antiquark -3 -1
Top Antiquark 1 -1
Bottom Antiquark -3 -1
Positron 1 3
Antimuon 1 3
Antitau 1 3
Electron Antineutrino 5 3
Muon Antineutrino 5 3
Tau Antineutrino 5 3