Penguin diagram

Example of a penguin diagram. An incoming bottom quark (b) and an outgoing strange quark (s) are drawn, a top quark (t) in the loop, W is a W boson and the interaction at the bottom is an exchange of photons with another quark

A penguin diagram is a special class of Feynman diagrams which, with a little good will, have the shape of a penguin (see graphic ). Such diagrams are used in particle physics to describe the various transformation processes of elementary particles . Penguin diagrams specifically describe the B meson decay, which is accordingly also called penguin decay .

description

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

There are different types of "penguin". If a gluon is emitted when a B ⁰ decays, one speaks of a QCD penguin. If a photon or Z ^{0 is} emitted instead , it is an electroweak penguin. There are also double penguins.

In 1993, the particle CLEO II of Cornell Electron Storage ring of Cornell University in Ithaca for the first time a B-mesons decay, which includes a "Penguin" in a particle accelerator observed.

The name of the diagram goes back to the British theoretical physicist John Ellis . According to his own account, he made a bet that if he lost playing darts , he would have to use the word "penguin" in his next specialist publication. Ellis lost the bet and called the chart "Penguin Chart" in the paper he was working on. The first such diagram came from Arkady Vainshtein , Valentin Ivanovich Sakharov, and Mikhail Schifman .

literature

Hartmut Machner: Introduction to nuclear and elementary particle physics . Wiley-VCH, Weinheim 2005, ISBN 3-527-40528-3 , pp. 384 .
Uwe Reichert: Penguins in the particle zoo . In: Spectrum of Science . No. 4 , 1994, pp. 24 ( preview ).
P. Koppenburg, Z. Dolezal, M. Smizanska: Rare decays of b hadrons . In: Scholarpedia . tape 11 , no. 6 , 2016, p. 32643. , Doi : 10.4249 / scholarpedia.32643 ( scholarpedia.org ).

Web links

Kelly Izlar, The march of the penguin diagrams , Symmetry 2013

Individual evidence

^ J. Ellis, MK Gaillard, DV Nanopoulos, S. Rudaz: The phenomenology of the next left-handed quarks . In: Nuclear Physics B . tape 131 , 1977, pp. 285-307 , doi : 10.1016 / 0550-3213 (77) 90374-1 .
^ Nico Serra, Tom Blake ,: Chasing new physics with electroweak penguins . In: CERN Courier . May 22, 2013 ( cerncourier.com ).
↑ Mikhail A. Shifman: Foreword to ITEP lectures in particle physics . In: Mikhail A. Shifman (Ed.): ITEP Lectures in Particle Physics and Field Theory . tape 1 . World Scientific, Singapore 1999, pp. v-xi , arxiv : hep-ph / 9510397 .

[1] J. Ellis, MK Gaillard, DV Nanopoulos, S. Rudaz: The phenomenology of the next left-handed quarks . In: Nuclear Physics B . tape 131 , 1977, pp. 285-307 , doi : 10.1016 / 0550-3213 (77) 90374-1 .

[2] Nico Serra, Tom Blake ,: Chasing new physics with electroweak penguins . In: CERN Courier . May 22, 2013 ( cerncourier.com ).

[3] Mikhail A. Shifman: Foreword to ITEP lectures in particle physics . In: Mikhail A. Shifman (Ed.): ITEP Lectures in Particle Physics and Field Theory . tape 1 . World Scientific, Singapore 1999, pp. v-xi , arxiv : hep-ph / 9510397 .