Abstract
A search for the single production of doubly-charged Higgs bosons is performed using e+e− collision data collected by the OPAL experiment at centre-of-mass energies between 189 GeV and 209 GeV. No evidence for the existence of H±± is observed. Upper limits are derived on hee, the Yukawa coupling of the H±± to like-signed electron pairs. A 95% confidence level upper limit of hee< 0.071 is inferred for M(H±±)<160 GeV assuming that the sum of the branching fractions of the H±± to all lepton flavour combinations is 100%. Additionally, indirect constraints on hee from Bhabha scattering at centre-of-mass energies between 183 GeV and 209 GeV, where the H±± would contribute via t-channel exchange, are derived for M(H±±)<2 TeV. These are the first results both from a single production search and on constraints from Bhabha scattering reported from LEP.
Highlights
Some theories beyond the Standard Model predict the existence of doubly-charged Higgs bosons, H±±, including in Left-Right Symmetric models [1], Higgs Triplet models [2], and little Higgs models [3]
The pair production of doubly-charged Higgs bosons has been considered in a previous OPAL publication [6], where masses less than 98.5 GeV are excluded for doubly-charged Higgs bosons in Left-Right Symmetric models
For comparison with the experimental data, QED radiative corrections are applied to the Born level terms for doubly-charged Higgs boson exchange and interference with Standard Model processes given in [5] using the program MIBA [30]
Summary
Some theories beyond the Standard Model predict the existence of doubly-charged Higgs bosons, H±±, including in Left-Right Symmetric models [1], Higgs Triplet models [2], and little Higgs models [3]. The pair production of doubly-charged Higgs bosons has been considered in a previous OPAL publication [6], where masses less than 98.5 GeV are excluded for doubly-charged Higgs bosons in Left-Right Symmetric models. The Yukawa coupling of the H±± to the charged leptons hll is model dependent, and is not generally determined directly by the lepton mass, so decays to all lepton flavour combinations need to be considered. Collision data with centre-of-mass Since the production cross-section energies depends only on hee, the Yukawa coupling of the H±± to like-signed electron pairs, the search is sensitive to this quantity. In addition to the direct search results introduced above, we derive indirect constraints on hee, the Yukawa Bhabha scattering coupling of H±± to electrons, measured by OPAL in 688.4 using pb−1 otfhedadtiaffecroelnletciatledcroasts√-sesc=tio1n8o3f–2w0i9deG-aenVg.le
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