Search for Charged Higgs bosons: Preliminary Combined Results Using LEP data Collected at Energies up to 209 GeV
ALEPH Collaboration, DELPHI Collaboration, L3 Collaboration, OPAL Collaboration, the LEP Higgs Working Group
TL;DR
This work presents a preliminary combined LEP analysis of charged Higgs bosons predicted by two-Higgs-doublet models, aggregating data from ALEPH, DELPHI, L3, and OPAL collected up to 209 GeV. Using the hzha framework, MC simulations, and a CLs-based statistical approach, the study explores decays H+ -> cs and H+ -> τν across all branching ratios, covering the final states from pair production e+e- -> H+H-. The main result is a 95% CL lower bound m_H± > 78.6 GeV/c^2, independent of BR, with systematic uncertainties (notably the W mass) shifting limits by small amounts; no significant charged Higgs signal is observed, though an isolated L3 excess near 68 GeV is not supported by the other experiments. The analysis demonstrates a robust, BR-averaged constraint on the charged Higgs mass within 2HD/MSSM contexts and highlights the impact of WW background on sensitivity near the W mass.
Abstract
In the year 2000 the four LEP experiments have collected 870 pb-1 of data at energies between 200 and 209 GeV, with about 510 pb-1 above 206 GeV. These data have been combined with data sets collected earlier at lower energies. %The following 95% confidence level bounds have been obtained. For charged Higgs bosons predicted by two-doublet extensions of the Standard Model and decaying only into the channels H+->csbar and tau+nutau, a lower mass bound of 78.6 GeV is obtained, at the 95% confidence level.