Reducing Penguin Pollution

Understand

The most common decay used for measuring 2beta_s, the phase of Bs-Bsbar mixing, is Bs -> J/psi phi.

• This decay is dominated by the colour-suppressed tree diagram, but there are other contributions due to gluonic and electroweak penguin diagrams.
• These are often referred to as "penguin pollution" (PP) because their inclusion in the amplitude leads to a theoretical error in the extraction of 2beta_s from the data.
• In the standard model (SM), it is estimated that the PP is negligible, but there is some uncertainty as to its exact size.