Carbon isotopic ratio as a function of stellar mass, color-coded by the metallicity. Left (right) panel considers RGB (HB) stars. Additionally, the locus of synthetic thin disk populations from Lagarde et al. (2017) are included in the panel for core He-burning giants. Solid lines are with thermohaline mixing and dashed line for giants with no extra mixing. Black lines inidicate the position of modeled stars of [Fe/H] ∼ 0.5, while gray lines are for stars of [Fe/H] ∼ −0.5.