Revival of $H^-$ interpretation of $R_{D^{(*)}}$ anomaly and closing low mass window

Abstract

Thanks to the recent careful revisit of the theoretical prediction of the B c meson lifetime, the conservative upper bound on the branching ratio (BR) of τν mode is found to be 63% due to the large charm quark mass uncertainty. Although it is well known that a charged Higgs (H − ) interpretation of the R D ( * ) anomaly is excluded by the previously proposed bounds, BR(B c → τν) ≤ 30% and ≤ 10%, H − can still explain the anomaly within 1σ if we adopt the 63% one. The scalar contribution is also favored by the polarization data F D * L measured at the Belle. Since the implied NP scale is within the reach of the Large Hadron Collider (LHC), collider searches are powerful tools to test the scenario. For instance, the τν resonance search has already put the more stringent bound for m H − ≥ 400 GeV. In this work we revisit the further lighter mass range, 180 GeV≤ m H − ≤ 400 GeV which has not been covered yet. We will see that a combination of the conventional stau search and low mass flavor inclusive and bottom flavored di-jet resonance searches can place a new limit on the interpretation. We summarize the current status of the low mass region and discuss the future sensitivity in the high luminosity (HL)-LHC based on the existent collider constraints.

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

“…It is noted that the charged-Higgs scenario with larger mass is excluded by the τν resonance search at the LHC [38,39] #1 , and the low-mass bottom flavored di-jet search [40,41] and a conventional search for tau sleptons [42] constrain the available parameter region. The result clearly shows the importance of the improvement in τν resonance searches [36], which is the main subject of this paper. From the results obtained in Refs.…”

“…According to the findings in Ref. [36], the charged-Higgs solution to the R D ( * ) anomaly can directly be probed at the LHC, once the experimental sensitivity to low-mass charged Higgs bosons in τν resonance searches is improved. In this section we discuss the strategy to achieve this goal, as well as our procedure for the generation of signal and relevant SM BG events.…”

“…-2 -Following Ref. [36], we introduce the simplified interaction Lagrangian for a charged scalar H − entering R D ( * ) as…”

“…[36] since the constraint from B c → τν is significantly relaxed [23,24,37]. The revision [36] found that a charged scalar can still explain the R D ( * ) anomaly within the 1 σ region when m H − ≤ 400 GeV holds. It is noted that the charged-Higgs scenario with larger mass is excluded by the τν resonance search at the LHC [38,39] #1 , and the low-mass bottom flavored di-jet search [40,41] and a conventional search for tau sleptons [42] constrain the available parameter region.…”

“…The model has widely been discussed in the literature [25][26][27][28][29][30][31][32][33][34][35], and recently been revisited in Ref. [36] since the constraint from B c → τν is significantly relaxed [23,24,37]. The revision [36] found that a charged scalar can still explain the R D ( * ) anomaly within the 1 σ region when m H − ≤ 400 GeV holds.…”