Can FCNC transition $c\to ul^+l^-$ be seen in $D\to Vl^+l^-$ decays?

TL;DR

This paper investigates the potential to observe the rare FCNC transition c→ul+ l− in D→V l+ l− decays, finding that long-distance effects dominate and that certain Cabibbo suppressed decays could reveal new physics beyond the Standard Model.

Contribution

The study provides a detailed analysis of D→V l+ l− decays within the Standard Model, highlighting the dominance of long-distance effects and identifying specific decays where new physics signals could be observed.

Findings

Short distance FCNC contribution is three orders of magnitude smaller than long distance.

Branching ratios for certain decays are above 10^{-7}, indicating potential for new physics detection.

Predicted branching ratios for key decays are close to current experimental limits.

Abstract

The decays $D\to Vl^+l^-$ present in principle the opportunity to observe the short distance FCNC transition $c\to ul^+l^-$, which is sensitive to the physics beyond the Standard Model. We analyze the $D \to V l^+ l^- $ decays within the Standard Model, where in addition to the short distance dynamics also the long distance dynamics is present. The short distance contribution due to $c\to ul^+l^-$ transition, which is present only in the Cabibbo suppressed decays, is found to be three orders of magnitude smaller than the long distance contribution. The branching ratios well above $10^{-7}$ for Cabibbo suppressed decays could signal new physics. The most frequent decays are the Cabibbo allowed decays $D_s^+\to\rho^+\mu^+\mu^-$ and $D^0\to\bar K^{*0}\mu^+\mu^-$, which are expected at the branching ratios of $3\cdot 10^{-5}$ and $1.7\cdot 10^{-6}$, respectively. These rates are not much lower than the present experimental upper limit.