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Landau–Yang theorem

A photon here is any particle with spin 1, without mass and without internal degrees of freedom. The photon is the only known particle with these properties.

Consequences[edit]

The theorem has several consequences in particle physics. For example:

• The meson ρ cannot decay into two photons, differently from the neutral pion, that almost always decays into this final state (98.8% of times).^[1]
• The boson Z cannot decay into two photons.
• The Higgs boson, whose spin was not measured before 2013, but whose decay into two photons was observed in 2012^[2][3] cannot have spin 1 in models that assume the Landau–Yang theorem.

Original references[edit]

Additional references[edit]