5 research outputs found
Constraints on Axion Models
Two particular classes of axion models are presented, each one yielding a
lower bound on the axion decay constant, based though on different
considerations. In the first class only some, and not all, of the right-handed
quarks have PQ charges, whereas in the second one the left-handed sector of the
same quarks is taken into account as well. In the first case we find that
bounds coming from astrophysics are significantly relaxed compared with those
for the DFSZ. As for the second class, the astrophysical constraints proved to
be less severe (with one exception), than those coming from FCNC processes.Comment: Talk given at the 5th IFT Workshop: Axions, U. of Florida,
Gainesville, Florida, USA, 13-15 Mar 1998. Based on hep-ph/9708281 and
hep-ph/9807363. 5pp, 1 eps fig, uses espcrc2 and graphics style
Constraints on Axion Models from
We explore a new class of axion models in which some, but not all, of the
left-handed quarks have a Peccei-Quinn symmetry. These models are potentially
afflicted by flavour changing neutral currents. We derive the bounds on the
Peccei-Quinn symmetry-breaking scale from bounds on the
branching ratio, showing that in some cases they are even stronger than the
astrophysical ones, but still not strong enough to kill off the models.Comment: 15pp RevTeX, 1 eps fig, uses graphics style. Expanded discussion on
massive scalars and pseudoscalars, typos. To appear in Physical Review
Constraints on Variant Axion Models
A particular class of variant axion models with two higgs doublets and a
singlet is studied. In these models the axion couples either to the -quark
or -quark or both, but not to , , , or . When the axion couples
to only one quark the models possess the desirable feature of having no domain
wall problem, which makes them viable candidates for a cosmological axion
string scenario. We calculate the axion couplings to leptons, photons and
nucleons, and the astrophysical constraints on the axion decay constant
are investigated and compared to the DFSZ axion model. We find that the most
restrictive lower bound on , that from SN1987a, is lowered by up to a
factor of about 30, depending on the model and also the ratio of the vacuum
expectation values of the higgs doublets. For scenarios with axionic strings,
the allowed window for in the quark model can be more than two orders
of magnitude. For inflationary scenarios, the cosmological upper bound on
, where is the QCD anomaly factor, is unaffected: however, the
variant models have either 3 or 6 times smaller than the DFSZ model.Comment: 21pp RevTeX, 1 eps fig, uses graphics style, typo corrected, and
corrected file sent this time. To appear in Physical Review