The ATLAS discovery potential for a heavy charged Higgs boson in   gg->tbH^{+-} with H^{+-}->tb
  The feasibility of detecting a heavy charged Higgs boson, m(H^{+-})>m(t)+m(b), decaying in the H^{+-}->tb channel is studied with the fast simulation of the ATLAS detector. We study the gg->H^{+-}tb production process at the LHC which together with the aforementioned decay channel leads to four b-quarks in the final state. The whole production and decay chain reads gg->H^{+-}tb->t\bar{t}b\bar{b}->b\bar{b}b\bar{b}l\nu\bar{q}q'. Combinatorial background is a major difficulty in this multi-jet environment but can be overcome by employing multivariate techniques in the event reconstruction. Requiring four b-tagged jets in the event helps to effectively suppress the Standard Model backgrounds but leads to no significant improvement in the discovery potential compared to analyses requiring only three b-tagged jets. This study indicates that charged Higgs bosons can be discovered at the LHC up to high masses (m(H^{+-})>400 GeV) in the case of large tan(beta). 
K. A. Assamagan, N. Gollub