Old and new anomalies in charm

Abstract: 

The recent LHCb determination of the direct CP asymmetries in the decays D0→K+K−,π+π− hints at a sizeable breaking of two approximate symmetries of the SM: CP and U-spin. We aim at explaining the data with BSM physics and use the framework of flavorful Z′ models. Interestingly, experimental and theoretical constraints very much narrow down the shape of viable models: Viable, anomaly-free models are electron- and muon-phobic and feature a light Z′ of 10-20 GeV coupling only to right-handed fermions. The Z′ can be searched for in low mass dijets or at the LHC as well as dark photon searches. A light Z′ of ∼ 3 GeV or ∼ 5-7 GeV can moreover resolve the longstanding discrepancy in the J/ψ,ψ′ branching ratios with pion form factors from fits to e+e−→π+π− data, and simultaneously explain the charm CP asymmetries. Smoking gun signatures for this scenario are Υ and charmonium decays into pions, taus or invisbles.

Link zum paper:

https://arxiv.org/abs/2309.04513