Search for Charged Higgs Bosons in e+e- Collisions at sqrt(s)=189-202 GeV

TL;DR

This study searched for charged Higgs bosons in high-energy electron-positron collisions at LEP II, using advanced methods for jet pairing and tau identification, but found no evidence and set a lower mass limit of 71.5 GeV/c^2.

Contribution

The paper introduces new techniques for jet pairing and tau identification in charged Higgs searches at LEP II.

Findings

No excess of events observed over Standard Model expectations.

Charged Higgs bosons with mass below 71.5 GeV/c^2 are excluded.

Enhanced methods improved background rejection and tau detection.

Abstract

A search for pair-produced charged Higgs bosons was performed in the high energy data collected by the DELPHI detector at LEP II at centre-of-mass energies from 189 GeV to 202 GeV. The three different final states, \tau \nu \tau \nu, c \bar s \bar c s and c \bar s \tau \nu were considered. New methods were applied to reject wrong hadronic jet pairings and for the tau identification, where a discriminator based on tau polarisation and polar angles was used. No excess of data compared to the expected Standard Model processes was observed and the existence of a charged Higgs boson with mass lower than 71.5 GeV/c^2 is excluded at the 95% confidence level.