Speaker
Dr
Johan Rathsman
(Uppsala University)
Description
We present a two-Higgs doublet model where only one of the doublets gets a vacuum expectation value
and there is a softly broken Z2 symmetry. In this "hidden doublet model", the CP-even states h and H mix,
and therefore they both couple to fermions, whereas the hidden states A0 and H+ only couple to fermions
via gauge boson-Higgs loops and thus these couplings are strongly suppressed. Our model shares some
features with the inert doublet model of Barbieri, Hall and Rychkov, in that it allows h and/or H to be heavy
and still satisfy the electroweak precision tests, but since the Z2 symmetry is softly broken, none of the
scalars is stable.
The model leads to a very interesting Higgs phenomenology. Apart from the possibility of having a
heavy h and/or H and thus improving the naturalness of the Higgs sector, the hidden states A0 and
H+ may predominantly decay into four fermions via off-shell gauge and Higgs bosons. On the one
hand this means that A0 and/or H+ can be very light, so that they may have been produced at LEP
but not detected due to the non-standard decay modes. Another possibility is that one of the CP-even
Higgs bosons, h or H, is light but has escaped detection because it decays to A0 A0 or H+ H-, which
decay in the four fermion modes already mentioned. We have calculated the decays of the hidden
states into four fermions at tree level and to two fermions at at one-loop level and also considered
electroweak and other experimental constraints on the parameter space of the model.
Primary author
Dr
Johan Rathsman
(Uppsala University)
Co-authors
Glenn Wouda
(Uppsala University)
Dr
Rikard Enberg
(Uppsala University)
