CP-symmetry

CP-symmetry is a symmetry obtained by a combination of the C-symmetry and the P-symmetry. When it was found that both these symmetries were violated individually, it looked plausible that a combination of the two would be preserved by all physical laws. Simply stated, the preservation of CP-symmetry by all physical phenomena would mean that all physical laws preserve form when a charge-inversion transformation (positive to negative and vice-versa inversion of electric charges) and a parity-inversion transformation ('left' to 'right' and vice versa; inversion; or, simply the reversal of the coordinate axis in a Cartesian coordinate system used to describe the system under consideration) are done simultaneously. But to the dismay of physicists, it was discovered in 1964 by the group of Cristenson, Cronin, Fitch and Turlay in a kaon decay experiment that this symmetry too was violated, and only a weaker version of the symmetry could be preserved by physical phenomena, which was CPT-symmetry. Because of the CPT-symmetry, a violation of the CP-symmetry is equivalent to a violation of the T-symmetry.

Related Topics:
C-symmetry - P-symmetry - Charge - Transformation - Parity - Cartesian coordinate system - 1964 - Kaon - CPT-symmetry

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Recently, a new generation of experiments, including the BaBar Experiment at the Stanford Linear Accelerator Center (SLAC) and the Belle Experiment at the High Energy Accelerator Research Organisation (KEK), Japan, have observed CP violation using B mesons. Before these experiments, it was a logical possibility that all CP violation was confined to kaon physics. These experiments dispelled any doubt that the interactions of the Standard Model violated CP.

Related Topics:
BaBar Experiment - SLAC - Belle Experiment - KEK - Meson - Standard Model

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The CP violation of the Standard model is incorporated by including a complex phase in the CKM matrix. A necessary condition for the appearance of the complex phase, and thus for CP-violation, is the presence of at least three generations of quarks.

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There is no experimentally known violation of the CP-symmetry in Quantum Chromodynamics. The strong CP problem is the question of why no such violation is detected even though the theory in principle allows for it.

Related Topics:
Quantum Chromodynamics - Strong CP problem

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CP violation is also necessary to explain why our universe contains vastly different amounts of matter and anti-matter. It seems unlikely that the CP violation observed in the Standard Model is sufficient to explain this difference. On-going experiments hope to uncover additional sources of CP violation.

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