899 research outputs found

### Lepton Electric Dipole Moment and Strong CP Violation

Contribution of the strong CP angle, $\bar\theta$, to the Wilson Coefficients
of electron and muon electric dipole moment (EDM) operators are discussed.
Previously, $\bar\theta$ contribution to the electron EDM operator was
calculated by Choi and Hong. However, the effect of CP-violating three meson
coupling was missing there. We include this missing contribution for the first
time in the literature, and reevaluate the Wilson coefficients of the lepton
EDM operator. We obtain $d_e = - (2.2-8.6) \times 10^{-28} \bar\theta$ e-cm
which is 15 - 70 % of the result obtained in Choi and Hong. We also estimated
the muon EDM as $d_\mu = - (0.5-1.8) \times 10^{-25} \bar\theta$ e-cm. Using
$|\bar\theta| \lesssim 10^{-10}$ suggested by the neutron EDM measurements, we
obtain $|d_e| \lesssim 8.6 \times 10^{-38}$ e-cm and $|d_\mu| \lesssim 1.8
\times 10^{-35}$ e-cm. The $\bar\theta$ contribution to the muon EDM is much
below the sensitivities of the current and near future experiments. Our result
shows that the $\bar\theta$ contribution to $d_{e,\mu}$ can be larger than the
CKM contributions by many orders of magnitude.Comment: 10 pages, 2 figures; v3: version published, reference adde

### LHC Future Prospects of the 750 GeV Resonance

A quantitative discussion on the future prospects of the 750 GeV resonance at
the LHC experiment is given using a simple effective field theory analysis. The
relative size of two effective operators relevant to diphoton decays can be
probed by ratios of diboson signals in a robust way. We obtain the future
sensitivities of $Z\gamma$, $ZZ$ and $WW$ resonance searches at the high
luminosity LHC, rescaling from the current sensitivities at $\sqrt{s}=13$ TeV.
Then, we show that a large fraction of parameter space in the effective field
theory will be covered with 300 fb$^{-1}$ and almost the whole parameter space
will be tested with 3000 fb$^{-1}$. This discussion is independent of
production processes, other decay modes and total decay width.Comment: version published, reference added, 4 pages, 3 figure

### Composite Accidental Axions

We present several models where the QCD axion arises accidentally. Confining
gauge theories can generate axion candidates whose properties are uniquely
determined by the quantum numbers of the new fermions under the Standard Model.
The Peccei-Quinn symmetry can emerge accidentally if the gauge theory is
chiral. We generalise previous constructions in a unified framework. In some
cases these models can be understood as the deconstruction of 5-dimensional
gauge theories where the Peccei-Quinn symmetry is protected by locality but
more general constructions are possible.Comment: 24 pages, 3 figure

### Quantum corrections to the spin-independent cross section of the inert doublet dark matter

The inert Higgs doublet model contains a stable neutral boson as a candidate
of dark matter. We calculate cross section for spin-independent scattering of
the dark matter on nucleon. We take into account electroweak and scalar quartic
interactions, and evaluate effects of scattering with quarks at one-loop level
and with gluon at two-loop level. These contributions give an important effect
for the dark matter mass to be around m_h/2, because a coupling with the
standard model Higgs boson which gives the leading order contribution should be
suppressed to reproduce the correct amount of the thermal relic abundance in
this mass region. In particular, we show that the dark matter self coupling
changes the value of the spin-independent cross section significantly.Comment: 38 pages, 18 figure

### Neutrinoful Universe

The Standard Model of particle physics fails to explain the important pieces
in the standard cosmology, such as inflation, baryogenesis, and dark matter of
the Universe. We consider the possibility that the sector to generate small
neutrino masses is responsible for all of them; the inflation is driven by the
Higgs field to break $B-L$ gauge symmetry which provides the Majorana masses to
the right-handed neutrinos, and the reheating process by the decay of the $B-L$
Higgs boson supplies the second lightest right-handed neutrinos whose CP
violating decays produce $B-L$ asymmetry, a la, leptogenesis. The lightest
right-handed neutrinos are also produced by the reheating process, and remain
today as the dark matter of the Universe. In the minimal model of the inflaton
potential, one can set the parameter of the potential by the data from CMB
observations including the BICEP2 and the Planck experiments. In such a
scenario, the mass of the dark matter particle is predicted to be of the order
of PeV. We find that the decay of the PeV right-handed neutrinos can explain
the high-energy neutrino flux observed at the IceCube experiments if the
lifetime is of the order of $10^{28}$ s.Comment: 21 pages, 9 figures; v2: added reference and fixed typ

### Muon specific two-Higgs-doublet model

We investigate a new type of a two-Higgs-doublet model as a solution of the
muon $g-2$ anomaly. We impose a softly-broken $Z_4$ symmetry to forbid tree
level flavor changing neutral currents in a natural way. This $Z_4$ symmetry
restricts the structure of Yukawa couplings. As a result, extra Higgs boson
couplings to muons are enhanced by a factor of $\tan\beta$, while their
couplings to all the other standard model fermions are suppressed by
$\cot\beta$. Thanks to this coupling property, we can avoid the constraint from
leptonic $\tau$ decays in contrast to the lepton specific two-Higgs-doublet
model, which can explain the muon $g-2$ within the 2$\sigma$ level but cannot
within the $1\sigma$ level due to this constraint. We find that the model can
explain the muon $g-2$ within the 1$\sigma$ level satisfying constraints from
perturbative unitarity, vacuum stability, electroweak precision measurements,
and current LHC data.Comment: 24 pages, 3 figure

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