The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Looking for Physics Beyond the Standard Model: Searches for Charged Higgs Bosons at e+e Colliders

Ari Kiiskinen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Engineering Physics and Mathematics for public examination and debate in Auditorium F1 at Helsinki University of Technology (Espoo, Finland) on the 16th of April, 2004, at 12 o'clock noon.

Overview in PDF format (ISBN 952-10-1680-9)   [1077 KB]
Dissertation is also available in print (ISBN 952-10-1679-5)


This thesis describes direct searches for pair production of charged Higgs bosons performed in the data collected by the DELPHI detector at the LEP collider at CERN. In addition, the possibilities of discovering heavy charged Higgs bosons at possible future high-energy linear colliders are studied.

The existence of charged Higgs bosons is predicted by many extensions of the Standard Model. A possible discovery of these particles would be a solid proof for physics beyond the Standard Model. The discovery of charged Higgs bosons, and measurement of their properties, would also provide useful information about the structure of the more general theory.

New analysis methods were developed for the searches performed at LEP. A large, previously unexplored, mass range was covered but no evidence for the existence of the charged Higgs bosons was found. This allowed the setting of new lower mass limits for the charged Higgs boson within the framework of general two Higgs doublet models. Results have been interpreted and presented in many model hypotheses.

High-energy linear e+e colliders would provide an excellent environment for searches for charged Higgs bosons in future. New analysis methods were developed for the reconstruction and analysis of the decay processes of heavy charged Higgs bosons. The discovery potential and the ability to measure the mass and the decay rates of the charged Higgs boson were demonstrated.

This thesis consists of an overview and of the following 7 publications:

  1. DELPHI Collaboration (Abreu P. et al. with Kiiskinen A.), 1999. Search for charged Higgs bosons at LEP 2. Physics Letters B 460, numbers 3-4, pages 484-497. © 1999 Elsevier Science. By permission.
  2. Kiiskinen A., on behalf of the DELPHI Collaboration, 1999. Search for charged Higgs bosons and measurement of |Vcs| in quark and lepton flavour identified events at LEP2. Nuclear Instruments and Methods in Physics Research A 433, numbers 1-2, pages 332-337. © 1999 Elsevier Science. By permission.
  3. Kiiskinen A., Nomokonov V. and Orava R., 1998. Using colour portraits in identifying the quark-antiquark pairs in heavy boson decays. DELPHI 98-91 CONF 159 (ICHEP'98 CONF 159) (22 June 1998). HIP 1998-46/EXP. © 1998 by authors.
  4. DELPHI Collaboration (Abdallah J. et al. with Kiiskinen A.), 2002. Search for charged Higgs bosons in e+e collisions at √ = 189-202 GeV. Physics Letters B 525, numbers 1-2, pages 17-28. © 2002 Elsevier Science. By permission.
  5. DELPHI Collaboration (Abdallah J. et al. with Kiiskinen A.), 2003. Search for charged Higgs bosons at LEP in general two Higgs doublet models. CERN-EP/2003-064. The European Physical Journal C, accepted for publication. © 2003 by authors and © 2003 Springer-Verlag. By permission.
  6. Kiiskinen A., Battaglia M. and Pöyhönen P., 2001. Study of e+eH+H at a 800 GeV linear collider. In: Para A. and Fisk H. E. (editors), Physics and experiments with future linear e+e colliders. AIP Conference Proceedings 578, pages 237-240. © 2001 American Institute of Physics. By permission.
  7. Battaglia M., Ferrari A., Kiiskinen A. and Mäki T., 2001. Pair production of charged Higgs bosons at future linear e+e colliders. In: Proceedings of the Snowmass 2001, the Future of Particle Physics, edited by Norman Graf. Snowmass Village, CO, USA, 30 June - 21 July 2001, eConf C010630, SLAC-R-599, E3017. © 2001 Stanford Linear Accelerator Center (SLAC). By permission.

Keywords: charged Higgs bosons, two Higgs doublet models, Higgs boson searches, LEP, DELPHI, linear colliders

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© 2004 Helsinki University of Technology

Last update 2011-05-26