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Unitarity Triangle containing angle β describes CP violation in the weak interaction. If there is CP violation in the strong interaction, is it also described by a Unitarity Triangle containing the CP violating angle θ?
I guess that this depends a bit on how one counts, but you can put either of those contributions to zero by a chiral transformation - but generally not both simultaneously (or rather, the strong CP problem is that it does seem possible to do so). In some sense similar to how you can get rid of the Majorana phases in the CKM but not the Dirac phase - you do end up with a physical phase and thus CP violation. Exactly where the phase enters will depend on how one chooses to parameteise the theory.vanhees71 said:In case of the strong interaction you have two terms, the socalled Θ-term and in the mass term of the quarks, related to chiral symmetry.
My familiarity is only with the graphical unitary triangle, and they contain the β, α, and γ angles.Orodruin said:Now here’s a little brain teaser for you: What happened to the theta terms of the electroweak interactions?
Save it for later. It is an interesting puzzle that tends to confuse people.Ranku said:My familiarity is only with the graphical unitary triangle, and they contain the β, α, and γ angles.
Standard Model QCD assumes as an axiom that the CP violating angle θ of the strong force is zero, and there is no experimental evidence that disagrees in a statistically significant way with this conclusion.Ranku said:Unitarity Triangle containing angle β describes CP violation in the weak interaction. If there is CP violation in the strong interaction, is it also described by a Unitarity Triangle containing the CP violating angle θ?
Three hard problems!
In this talk I investigate the long-distance properties of quantum chromodynamics in the presence of a topological theta term. This is done on the lattice, using the gradient flow to isolate the long-distance modes in the functional integral measure and tracing it over successive length scales.
Gerrit Schierholz, "Strong CP problem, electric dipole moment, and fate of the axion" arXiv:2201.12875 (January 30, 2022) (invited talk at XXXIII International Workshop on High Energy Physics "Hard Problems of Hadron Physics: Non-Perturbative QCD and Related Quests", November 2021).It turns out that the color fields produced by quarks and gluons are screened, and confinement is lost, for vacuum angles theta > 0, thus providing a natural solution of the strong CP problem. This solution is compatible with recent lattice calculations of the electric dipole moment of the neutron, while it excludes the axion extension of the Standard Model.
The Unitarity Triangle is a graphical representation of the complex phase structure of the Standard Model of particle physics. It is used to describe the relationship between the three quark families and their interactions, including CP violation angle β and θ.
CP violation angle β and θ are important because they provide insight into the asymmetry between matter and antimatter in the universe. This is a fundamental question in particle physics and understanding CP violation is crucial in developing a more complete understanding of the universe.
CP violation angle β and θ are measured through experiments that study the decay of particles, particularly those containing b-quarks. By analyzing the decay products and their properties, scientists can determine the values of β and θ and test the predictions of the Standard Model.
The current understanding of CP violation angle β and θ is that they are non-zero, meaning that CP symmetry is violated in the interactions of quarks. This has been confirmed through numerous experiments, including those at the Large Hadron Collider at CERN.
The value of CP violation angle β and θ is an important test of the predictions of the Standard Model. Any deviation from the expected values could indicate the presence of new physics beyond the Standard Model. Therefore, precise measurements of these parameters help to refine and improve our understanding of the fundamental forces and particles in the universe.