Open charm production and spectroscopy at CMS and ATLAS

The central and general purpose experiments at the LHC have contributed to open charm physics, complementing LHCb in ${\rm B}_{\rm c}$ property studies, and ATLAS has discovered a ${\rm B}_{\rm c}$ excitation that is consistent with ${\rm B}_{\rm c}$(2S). ATLAS has studied charged D$_{\rm (s)}$ meson production, while CMS has studied D$^0$ production. In particular, CMS measured the nuclear modification factor $R_{\rm AA}$ in PbPb collisions at 5.02 TeV, finding strong medium suppression in PbPb compared with pp collisions over a broad range of $p_T$, and consistent with the ALICE result scaled to similar energy. An important tool has been developed to identify charm jets, complementing b-tagging algorithms. CMS has developed a 2D c-tagger to discriminate c-jet from light jet and b-jet, respectively. After training on simulated data, the c-tagger has been validated with W$+$c and t$\bar {\rm t}$ events using 2015 data at 13 TeV, with extracted scale factor $SF_{\rm c}$ close to 1. A similar c-tagger has been developed by ATLAS, but the 2D version for Run 2 is not yet publicly available.