Towards ruling out the charged Higgs interpretation of the R D ∗ $$ {R}_{D^{\left(\ast \right)}} $$ anomaly

Motivated by the notorious anomaly in the lepton flavor universality ratios $$ {R}_{D^{\left(\ast \right)}} $$ , we study the sensitivity of the Large Hadron Collider (LHC) to a low-mass charged Higgs boson H− lighter than 400 GeV in a generic two Higgs doublet model. A combination of current constraints from the Bc → τν decay, Bs meson mixing data, tau sleptons and di-jet searches at the LHC allows to explain the $$ {R}_{D^{\left(\ast \right)}} $$ anomaly at the 1σ level by a low-mass charged Higgs. In this context, we estimate the reach of an LHC search for resonant H− production, where the final state contains an energetic τ lepton decaying hadronically, a neutrino with large transverse momentum, and an additional b-jet (pp → b + τh + ν). Requiring the additional b-tagged jet in the τν resonance search profits from the suppression of the Standard Model background, and therefore it allows us to judge the low-mass H− interpretation of the $$ {R}_{D^{\left(\ast \right)}} $$ anomaly. To demonstrate this, we perform a fast collider simulation for the τν resonance search with an additional b-tagged jet, and find that most of the interesting parameter region of the whole mass range can already be probed with the current integrated luminosity of 139 fb−1.