Charm decays
U. Nierste
Full text: pdf
Pre-published on: 2020 February 24
Published on:
Abstract
I discuss hadronic decays of $D$ mesons with emphasis on
the recent discovery of charm CP violation in $D^0\to K^+K^-,\pi^+\pi^-$
decays. The measured difference $\Delta a_{CP} \, \equiv \; a_{CP}^{\mathrm{dir}}(D^0\rightarrow K^+K^-) - a_{CP}^{\mathrm{dir}}(D^0\rightarrow\pi^+\pi^-) = \; (-15.4\pm 2.9)\cdot 10^{-4}$ of two direct CP asymmetries exceeds
the SM prediction by a factor of 7. A possible explanation is an enhancement
of the penguin amplitude entering $a_{CP}^{\mathrm{dir}}$ by QCD
effects which are not understood yet. Alternatively, $\Delta a_{CP}$
could be dominated by contributions from new physics. In order
to distinguish these two hypotheses further CP asymmetries
should be measured. To this end CP asymmetries resulting from
the interference of two tree-level amplitudes auch as
$a_{CP}^{\mathrm{dir}}(D^0\rightarrow K_SK_S)$ or
$a_{CP}^{\mathrm{dir}}(D^0 \to \bar{K}^{*0} K_S)$ are especially interesting.
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