Paper detail

Towards ruling out the charged Higgs interpretation of the $R_{D^{(*)}}$ anomaly

Motivated by the notorious anomaly in the lepton flavor universality ratios $R_{D^{(*)}}$, 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 $B_c\toτν$ decay, $B_{s}$ meson mixing data, tau sleptons and di-jet searches at the LHC allows to explain the $R_{D^{(*)}}$ anomaly at the $1\,σ$ 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 ($pp \to b+τ_h + ν$). 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 $R_{D^{(*)}}$ 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$^{-1}$.