524 research outputs found
Intermediate Scale Accidental Axion and ALPs
We discuss the problem of constructing models containing an axion and
axion-like particles, motivated by astrophysical observations, with decay
constants at the intermediate scale ranging from GeV to GeV. We
present examples in which the axion and axion-like particles arise accidentally
as pseudo Nambu-Goldstone bosons of automatic global chiral symmetries, in
models having exact discrete symmetries.Comment: 4 pages. To appear in the Proceedings of the 10th Patras Workshop on
Axions, WIMPs and WISPs, CERN, 29 June - 04 July 201
Grand Unification and Proton Stability Near the Peccei-Quinn Scale
We show that in an model with a DSF-like invisible axion
it is possible to obtain (i) the convergence of the three gauge coupling
constants at an energy scale near the Peccei-Quinn scale; (ii) the correct
value for ; (iii) the stabilization of the proton by
the cyclic symmetries which also stabilize the axion as a
solution to the strong CP problem. Concerning the convergence of the three
coupling constants and the prediction of the weak mixing angle at the -peak,
this model is as good as the minimal supersymmetric standard model with
. We also consider the standard model with six and seven
Higgs doublets. The main calculations were done in the 1-loop approximation but
we briefly consider the 2-loop contributions.Comment: 12 pages, 4 figure
The 750 GeV -cion: Where else should we look for it?
The resonance at GeV in the diphoton channel observed by ATLAS
and CMS, if it holds up, is almost certainly the ()cion of a larger dynasty
in a UV completion that may very well be connected to the hierarchy problem. At
this stage, however, an effective field theory framework provides a useful way
to parametrize searches for this resonance in other channels. Assuming that the
excess is due to a new scalar or pseudoscalar boson, we study associated
production of ("-strahlung") at the LHC and propose searches in several
clean channels like , \gamma\gamma\ell\eslash and
\ell\ell\ell\gamma\eslash to probe dimension-5 operators coupling to
Standard Model gauge bosons. We consider a range of widths for , from 5 GeV
to 45 GeV, and find that the three channels probe complementary regions of
parameter space and the suppression scale . The finding of most
immediate relevance is that with 3 fb, the LHC might already reveal new
excesses in the channel and a 5(3) discovery
may already be possible after collecting 65(25) fb of data with
\ell\ell\ell\gamma\eslash events if the scale of the new physics is within
9 TeV for couplings respecting 8 TeV LHC bounds and compatible with the
observed excess in diphotons for a wide resonance as suggested by the ATLAS
Collaboration. Beyond the EFT parametrization, we found realizations of models
with heavy vector-like quarks and leptons which can simultaneously fit the
diphoton excess and be discovered in the channels proposed here.Comment: 11 pages, 2 tables, 5 figures. References and comments added. Version
accepted for publication in Physics Letters
Maximum Entropy Inferences on the Axion Mass in Models with Axion-Neutrino Interaction
In this work we use the Maximum Entropy Principle (MEP) to infer the mass of
an axion which interacts to photons and neutrinos in an effective low energy
theory. The Shannon entropy function to be maximized is suitably defined in
terms of the axion branching ratios. We show that MEP strongly constrains the
axion mass taking into account the current experimental bounds on the neutrinos
masses. Assuming that the axion is massive enough to decay into all the three
neutrinos and that MEP fixes all the free parameters of the model, the inferred
axion mass is in the interval eV eV, which can be tested
by forthcoming experiments such as IAXO. However, even in the case where MEP
fixes just the axion mass and no other parameter, we found that eV eV in the DFSZ model with right-handed neutrinos. Moreover, a light
axion, allowed to decay to photons and the lightest neutrino only, is
determined by MEP as a viable dark matter candidate.Comment: 13 pages, 5 figures, typos corrected, figures update
Naturally light invisible axion in models with large local discrete symmetries
We show that by introducing appropriate local symmetries in
electroweak models it is possible to implement an automatic Peccei-Quinn
symmetry keeping at the same time the axion protected against gravitational
effects. Although we consider here only an extension of the standard model and
a particular 3-3-1 model, the strategy can be used in any kind of electroweak
model. An interesting feature of this 3-3-1 model is that if: {\it i)} we add
right-handed neutrinos, {\it ii)} the conservation of the total lepton number,
and {\it iii)} a symmetry, the and the chiral Peccei-Quinn
are both accidental symmetries in the sense that they are not
imposed on the Lagrangian but they are just the consequence of the particle
content of the model, its gauge invariance, renormalizability and Lorentz
invariance. In addition, this model has no domain wall problem.Comment: Some changes and a new reference added, 7 page
Naturally light invisible axion and local Z_{13} times Z_3 symmetries
We show that by imposing local symmetries in an
electroweak model we can implement an invisible axion in
such a way that (i) the Peccei-Quinn symmetry is an automatic symmetry of the
classical Lagrangian; and (ii) the axion is protected from semi classical
gravitational effects. In order to be able to implement such a large discrete
symmetry, and at the same time allow a general mixing in each charge sector, we
introduce right-handed neutrinos and enlarge the scalar sector of the model.
The domain wall problem is briefly considered.Comment: PQ charges and typos correcte
Inferences on the Higgs Boson and Axion Masses through a Maximum Entropy Principle
The Maximum Entropy Principle (MEP) is a method that can be used to infer the
value of an unknown quantity in a set of probability functions. In this work we
review two applications of MEP: one giving a precise inference of the Higgs
boson mass value; and the other one allowing to infer the mass of the axion. In
particular, for the axion we assume that it has a decay channel into pairs of
neutrinos, in addition to the decay into two photons. The Shannon entropy
associated to an initial ensemble of axions decaying into photons and neutrinos
is then built for maximization.Comment: Contributed to the 13th Patras Workshop on Axions, WIMPs and WISPs,
Thessaloniki, May 15 to 19, 201
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