The discovery of a charged Higgs boson (H ± ) would be a clear indication for physics beyond the Standard Model. Charged Higgs bosons are predicted in several extensions of the SM, such as models containing Higgs triplets and Two-Higgs-Doublet Models (2HDM).  Electroweak symmetry breaking through two complex Higgs doublets lead to five physical  states, out of which two are charged. Here, the type-II 2HDM is considered, which is also  the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM). For m_H± >  m_top, (200-600 GeV), the dominant production mode for charged Higgs bosons at the Large Hadron Collider (LHC) is via gb → tH± (in a five-flavour scheme, or 5FS) and gg → tbH±  (in a four-flavour scheme, or 4FS).

This analysis describes a search for a charged Higgs bosons with the ATLAS experiment at CERN’s LHC. The data collected during the LHC Run-1, collisions at √s = 8TeV corresponding to an integrated luminosity of 20.3 fb⁻¹  , is analysed, searching for a heavy charged Higgs boson, which decays predominantly into a top and bottom quarks. In this  mass range, the production of a charged Higgs boson in association with a top quark, gb → tH±  is searched for using complex multi-jet final states with one electron or muon.  The requirement of at least three b-tagged jets helps effectively reduce the Standard Model backgrounds, and further signal discrimination is achieved by employing multi-variate anal-  ysis techniques.

A moderate excess of data with respect to the predicted backgrounds is observed across a wide mass range. For H± masses between 200 and 400 GeV, except for small regions around 250 GeV and 300 GeV, the m _− modh scenario of the Minimal Supersymmetric Standard Model is excluded for tanβ ≤ 0.5. In this search channel, no significant deviations from the predictions of the Standard Model are observed. Upper limits at the 95% con- fidence level are placed on the qq → H± production cross section times the branching fraction BR(H± → tb).