New physics in singly Cabibbo-suppressed D decays

Abstract

A U-spin relation among four ratios of amplitudes for $D^0\to {\pi }^{+}{K}^{-}$, $K^{+}{\pi }^{-}$, $K^{+}{K}^{-},{\pi }^{+}{\pi }^{-}$, including first, second and third order U-spin breaking, has been derived recently with a precision of $10^{-3}$. We study effects of new $|\Delta C|=1$ operators on this relation. We find that it is not affected by U-spin scalar operators, including QCD penguin and chromomagnetic dipole operators occurring in supersymmetric and extra-dimensional models. The relation is modified by new $U=1$ operators with a sensitivity of a few percent characteristic of second order U-spin breaking. Combining this relation with CP asymmetries in $D^0\to K^{+}{K}^{-},{\pi }^{+}{\pi }^{-}$ leads to a more solid constraint on $U=1$ operators than from asymmetries alone.

Comments: References added, to be published in Physics Letters B