# On-line “Newton 1665” seminars – phenomenology/theory/astro/cosmo

February 28, 2020 to March 31, 2021
On Zoom
Europe/Rome timezone

## Absence of CP violation in the strong interactions

Jul 17, 2020, 3:00 PM
30m
On Zoom

#### On Zoom

https://cern.zoom.us/j/5876144043

### Speaker

Bjorn Garbrecht (Munich, Tech. U.)

### Description

https://inspirehep.net/literature/1776674
The CP-odd theta-term that should be assumed to be nonzero in general requires an explanation why it does not lead to CP-violating observables in the strong interactions. Known approaches include vanishing quark masses or extensions of the Standard Model. Here, we construct the fermionic Green's and correlation functions in the background of an instanton gas. For these correlators, we find that the CP-odd phases in the terms that break chiral symmetry from the quark masses and from the instanton effects are aligned, such that there remain no CP-violating observables. Crucial for this conclusion is that in the calculation of the correlators, the spacetime volume has to be taken to infinity before summing over the topological sectors.

The absence of CP-violation in strong interactions is therefore explained within the Standard Model.

### Presentation materials

 seminar_bg_280720.pdf video