REDUCING PENGUIN POLLUTION

Abstract

The most common decay used for measuring 2βs, the phase of [Formula: see text] mixing, is [Formula: see text]. This decay is dominated by the color-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 2βsfrom 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. Now, [Formula: see text] (the measured value of 2βs) is small, in agreement with the SM, but still has significant experimental errors. When these are reduced, if one hopes to be able to see clear evidence of new physics (NP), it is crucial to have the theoretical error under control. In this paper, we show that, using a modification of the angular analysis currently used to measure [Formula: see text] in [Formula: see text], one can reduce the theoretical error due to PP. Theoretical input is still required, but it is much more modest than entirely neglecting the PP. If [Formula: see text] differs from the SM prediction, this points to NP in the mixing. There is also enough information to test for NP in the decay. This method can be applied to all [Formula: see text] decays.