CP violation

In <a href="/facts/Particle_physics/YgIuyj2t">particle physics</a>, CP violation is a violation of CP-symmetry (or charge conjugation parity symmetry): the combination of <a href="/facts/C-symmetry/YJ1vjdfD">C-symmetry</a> (<a href="/facts/Charge_(physics)/jnQEDBI3">charge conjugation</a> symmetry) and <a href="/facts/Parity_(physics)/emSbJ4hD">P-symmetry</a> (<a href="/facts/Parity_(physics)/emSbJ4hD">parity</a> symmetry). CP-symmetry states that the laws of physics should be the same if a particle is interchanged with its <a href="/facts/Antiparticle/7Ic43ThI">antiparticle</a> (C-symmetry) while its spatial coordinates are inverted ("mirror" or P-symmetry). 
CP violation is only observed in the <a href="/facts/Weak_interaction/f6upmKMs">weak interaction</a>. The discovery of CP violation in 1964 in the decays of neutral <a href="/facts/Kaon/Yn2w4QlQ">kaons</a> resulted in the <a href="/facts/Nobel_Prize_in_Physics/o6w1nCbr">Nobel Prize in Physics</a> in 1980 for its discoverers <a href="/facts/James_Cronin/gMGryPaJ">James Cronin</a> and <a href="/facts/Val_Fitch/Mtz5Wub0">Val Fitch</a>. CP violation was subsequently discovered in many other <a href="/facts/Meson/9R0kIc1q">meson</a> decays. In 2025, the <a href="/facts/LHCb_experiment/PAlpBtnl">LHCb experiment</a> discovered CP violation in baryons. There is some evidence CP violation may occur in neutrino interactions.
It is important to the <a href="/facts/Matter-antimatter_asymmetry/kfUEYG4F">matter-antimatter asymmetry</a> problem, the <a href="/facts/Strong_CP_problem/swnszaLf">strong CP problem</a>, and in the study of weak interactions in particle physics. Under the <a href="/facts/CPT_Theorem/JCH2z2j2">CPT theorem</a>, every CP violation is also a time-symmetry violation.

CP violation open-in-new

CP violation