1,214 research outputs found
Neutron EDM from Electric and Chromoelectric Dipole Moments of Quarks
Using QCD sum rules, we calculate the electric dipole moment of the neutron
d_n induced by all CP violating operators up to dimension five. We find that
the chromoelectric dipole moments of quarks \tilde d_i, including that of the
strange quark, provide significant contributions comparable in magnitude to
those induced by the quark electric dipole moments d_i. When the theta term is
removed via the Peccei-Quinn symmetry, the strange quark contribution is also
suppressed and d_n =(1\pm 0.5)[1.1e(\tilde d_d + 0.5\tilde
d_u)+1.4(d_d-0.25d_u)].Comment: 4 pages, revtex, v2: missing overall factor of two reinstate
Lorentz Violating Supersymmetric Quantum Electrodynamics
Theory of Supersymmetric Quantum Electrodynamics is extended by interactions
with external vector and tensor backgrounds, that are assumed to be generated
by some Lorentz-violating (LV) dynamics at an ultraviolet scale perhaps related
to the Planck scale. Exact supersymmetry requires that such interactions
correspond to LV operators of dimension five or higher, providing a solution to
the naturalness problem in the LV sector. We classify all dimension five and
six LV operators, analyze their properties at the quantum level and describe
observational consequences of LV in this theory. We show that LV operators do
not induce destabilizing D-terms, gauge anomaly and the Chern-Simons term for
photons. We calculate the renormalization group evolution of dimension five LV
operators and their mixing with dimension three LV operators, controlled by the
scale of the soft-breaking masses. Dimension five LV operators are constrained
by the low-energy precision measurements at 10^{-10}-10^{-5} level in units of
the inverse Planck scale, while the Planck-scale suppressed dimension six LV
operators are allowed by observational data.Comment: 37 pages LaTeX, minor revisions, and typos correcte
PAMELA Positron Excess as a Signal from the Hidden Sector
The recent positron excess observed in the PAMELA satellite experiment
strengthens previous experimental findings. We give here an analysis of this
excess in the framework of the Stueckelberg extension of the standard model
which includes an extra gauge field and matter in the hidden sector.
Such matter can produce the right amount of dark matter consistent with the
WMAP constraints. Assuming the hidden sector matter to be Dirac fermions it is
shown that their annihilation can produce the positron excess with the right
positron energy dependence seen in the HEAT, AMS and the PAMELA experiments.
Further test of the proposed model can come at the Large Hadron Collider. The
predictions of the flux ratio also fit the data.Comment: 9 pages,3 figures; Breit-Wigner enhancement emphasized; published in
PR
Probing CP Violation with the Deuteron Electric Dipole Moment
We present an analysis of the electric dipole moment (EDM) of the deuteron as
induced by CP-violating operators of dimension 4, 5 and 6 including theta QCD,
the EDMs and color EDMs of quarks, four-quark interactions and the Weinberg
operator. We demonstrate that the precision goal of the EDM Collaboration's
proposal to search for the deuteron EDM, (1-3)\times 10^{-27} e cm, will
provide an improvement in sensitivity to these sources of one-two orders of
magnitude relative to the existing bounds. We consider in detail the level to
which CP-odd phases can be probed within the MSSM.Comment: 5 pages, 4 figures; precision estimates clarified, to appear in Phys.
Rev.
How do you know if you ran through a wall?
Stable topological defects of light (pseudo)scalar fields can contribute to
the Universe's dark energy and dark matter. Currently the combination of
gravitational and cosmological constraints provides the best limits on such a
possibility. We take an example of domain walls generated by an axion-like
field with a coupling to the spins of standard-model particles, and show that
if the galactic environment contains a network of such walls, terrestrial
experiments aimed at detection of wall-crossing events are realistic. In
particular, a geographically separated but time-synchronized network of
sensitive atomic magnetometers can detect a wall crossing and probe a range of
model parameters currently unconstrained by astrophysical observations and
gravitational experiments.Comment: 5 pages, 2 figure; to appear in the PR
Solar Gamma Rays Powered by Secluded Dark Matter
Secluded dark matter models, in which WIMPs annihilate first into metastable
mediators, can present novel indirect detection signatures in the form of gamma
rays and fluxes of charged particles arriving from directions correlated with
the centers of large astrophysical bodies within the solar system, such as the
Sun and larger planets. This naturally occurs if the mean free path of the
mediator is in excess of the solar (or planetary) radius. We show that existing
constraints from water Cerenkov detectors already provide a novel probe of the
parameter space of these models, complementary to other sources, with
significant scope for future improvement from high angular resolution gamma-ray
telescopes such as Fermi-LAT. Fluxes of charged particles produced in mediator
decays are also capable of contributing a significant solar system component to
the spectrum of energetic electrons and positrons, a possibility which can be
tested with the directional and timing information of PAMELA and Fermi.Comment: 22 pages, 3 figure
CP-odd static electromagnetic properties of the W gauge boson and the t quark via the anomalous tbW coupling
In the framework of the electroweak chiral Lagrangian, the one-loop induced
effects of the anomalous coupling, which includes both left- and
right-handed complex components, on the static electromagnetic properties of
the boson and the quark are studied. The attention is focused mainly on
the CP-violating electromagnetic properties. It is found that the
anomalous coupling can induce both CP-violating moments of the boson,
namely, its electric dipole () and magnetic quadrupole
() moments. As far as the quark is concerned, a potentially
large electric dipole moment can arise due to the anomalous
coupling. The most recent bounds on the left- and right-handed parameters from
meson physics lead to the following estimates e-cm and e-cm, which
are 7 and 14 orders of magnitude larger than the standard model (SM)
predictions, whereas may be as large as e-cm, which is about 8
orders of magnitude larger than its SM counterpart.Comment: This paper has been merged with hep-ph/0612171 for publication in
Physical Review
Neutrino Physics with Dark Matter Experiments and the Signature of New Baryonic Neutral Currents
New neutrino states \nu_b, sterile under the Standard Model interactions, can
be coupled to baryons via the isoscalar vector currents that are much stronger
than the Standard Model weak interactions. If some fraction of solar neutrinos
oscillate into \nu_b on their way to Earth, the coherently enhanced elastic
\nu_b-nucleus scattering can generate a strong signal in the dark matter
detectors. For the interaction strength a few hundred times stronger than the
weak force, the elastic \nu_b-nucleus scattering via new baryonic currents may
account for the existing anomalies in the direct detection dark matter
experiments at low recoil. We point out that for solar neutrino energies the
baryon-current-induced inelastic scattering is suppressed, so that the possible
enhancement of new force is not in conflict with signals at dedicated neutrino
detectors. We check this explicitly by calculating the \nu_b-induced deuteron
breakup, and the excitation of 4.4 MeV \gamma-line in ^{12}C.
Stronger-than-weak force coupled to baryonic current implies the existence of
new abelian gauge group U(1)_B with a relatively light gauge boson.Comment: 20 pages, 5 figures. References added, inconsistent treatment of
neutrino oscillations corrected, conclusions unchange
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