Updated constraints on new physics in rare charm decays

TL;DR

This paper examines how recent experimental constraints impact new physics models in rare charm meson decays, finding limited effects due to dominant long-distance physics and current bounds.

Contribution

It provides updated constraints on new physics contributions in rare charm decays, analyzing MSSM, vector-like quarks, and R-parity violating SUSY effects with current experimental data.

Findings

MSSM effects are negligible in D→Vγ decays due to long-distance dominance.

Heavy up vector-like quarks can slightly increase decay rates at high dilepton mass.

R-parity violating SUSY can modestly modify differential decay distributions within current bounds.

Abstract

Motivated by recent experimental results on charm physics we investigate implications of the updated constraints of new physics in rare charm meson decays. We first reconsider effects of the MSSM in $c\to u \gamma$ constrained by the recent experimental evidence on $\Delta m_D$ and find, that due to the dominance of long distance physics, $D \to V \gamma$ decay rates cannot be modified by MSSM contributions. Then we consider effects of the extra heavy up vector-like quark models on the decay spectrum of $D^+ \to \pi^+ l^+ l^-$ and $D_s^+ \to K^+ l^+ l^-$ decays. We find a possibility for the tiny increase of the differential decay rate in the region of large dilepton mass. The R-parity violating supersymmetric model can also modify short distance dynamics in $c \to u l^+ l^-$ decays. We constrain relevant parameters using current upper bound on the $D^+ \to \pi^+ l^+ l^-$ decay rate and investigate impact of that constraint on the $D_s^+ \to K^+ l^+ l^-$ differential decay dilepton distribution. Present bounds still allow small modification of the standard model differential decay rate distribution.