Title     : Theoretical upper bounds for Higgs boson masses 
Author    : Miroslav Kladiva                             
Department: Institute of Theoretical Physics         
Supervisor: Prof. Jiri Horejsi, DrSc.          
Supervisor's e-mail address: horejsi@ipnp.troja.mff.cuni.cz
Abstract  : 

In this work we examine, the perturbative (tree-level) unitarity bound, also
called Lee-Quigg-Thacker (LQT) bound, for Higgs boson masses. First it is  done
in the case of the electroweak Standard Model (SM), for which this method has
been originally invented.  We summarize briefly the basic concepts and
properties of SM with emphasis on high-energy behaviour of scattering
amplitudes. We recover the original result 1 TeV and improved result 707 GeV
for the Higgs mass upper bound.  Next we employ this method to find upper
bounds for Higgs boson masses within Two Higgs Doublet Model (THDM). Two
possibilities are distinguished: first,  the model without flavour-changing
neutral processes in leading order, where we obtain the upper bounds for all
Higgs boson masses involved in THDM with smallest bound being 411 GeV;  second,
a model admitting in general flavour-changing neutral processes in lowest
order,  where we obtain the dependence of upper bounds on a parameter  related
to such type of processes.

Keywords: Standard Model, Electroweak interactions, Unitarity bound, Higgs boson mass, Two Higgs Doublet Model