Penguin diagram

As a penguin diagrams ( engl. penguin diagram ) is a special class of Feynman diagrams, respectively, having the form of a penguin with a little goodwill ( see chart). Such graphs are used in particle physics to describe a wide variety of transformation processes of elementary particles. With penguin diagrams of the B -meson decay is specifically described, which accordingly is ( penguin decay german) also called Penguin decay.

Description

A penguin decay is a special type of decay in which, however, can occur "down -type " quarks as virtual particles all. This is important, for example, CP violation, since it can be explained by the presence of an imaginary phase in the CKM matrix element of the top quark in the standard model.

There are several "Penguin " species. If a gluon emitted in the decay of a B0, one speaks of a QCD penguin. If, instead of a photon or Z0 emitted, it is an electroweak penguin. In addition, there are double - penguins.

In 1993 was observed in a particle accelerator at particle CLEO II of the Cornell Electron Storage Ring of Cornell University in Ithaca for the first time a " penguin ".

The name of the chart goes to the British theoretical physicist John Ellis ( born 1946 ) back. According to his own description, he settled a bet that he, if he lost a game of darts, at its next trade publication the word " penguin " would need to use. Ellis lost the bet and called his diagram penguin diagram.