1,787 research outputs found
Gravitational waves from phase transition in split NMSSM
We discuss gravitational wave signal from the strongly first order
electroweak phase transition in the split NMSSM. We find that for sets of
parameters predicting successful electroweak baryogenesis the gravitational
wave signal can be within the reach of future experiments LISA, BBO and
Ultimate DECIGO.Comment: 8 pages, 2 figures, published versio
The exact tree-level calculation of the dark photon production in high-energy electron scattering at the CERN SPS
Dark photon () that couples to the standard model fermions via the
kinetic mixing with photons and serves as a mediator of dark matter production
could be observed in the high-energy electron scattering off nuclei followed by the decay. We have
performed the exact, tree-level calculations of the production cross
sections and implemented them in the program for the full simulation of such
events in the experiment NA64 at the CERN SPS. Using simulations results, we
study the missing energy signature for the bremsstrahlung
invisible decay that permits the determination of the mixing
strength in a wide, from sub-MeV to sub-GeV, mass range. We refine and
expand our earlier studies of this signature for discovering by including
corrections to the previously used calculations based on the improved
Weizsaker-Williams approximation, which turn out to be significant. We compare
our cross sections values with the results from other calculations and find a
good agreement between them. The possibility of future measurements with
high-energy electron beams and the sensitivity to are briefly discussed.Comment: 11 pages, 6 figures, revised version, improved cross-section
integrator is used, comparison with bremsstrahlung spectrum is added, final
conclusions remain unchange
Missing energy signature from invisible decays of dark photons at the CERN SPS
The dark photon () production through the mixing with the bremsstrahlung
photon from the electron scattering off nuclei can be accompanied by the
dominant invisible decay into dark-sector particles. In this work we
discuss the missing energy signature of this process in the experiment NA64
aiming at the search for decays with a high-energy electron
beam at the CERN SPS. We show the distinctive distributions of variables that
can be used to distinguish the signal from background. The
results of the detailed simulation of the detector response for the events with
and without emission are presented. The efficiency of the signal event
selection is estimated. It is used to evaluate the sensitivity of the
experiment and show that it allows to probe the still unexplored area of the
mixing strength and masses up to
GeV. The results obtained are compared with the results
from other calculations. In the case of the signal observation, a possibility
of extraction of the parameters and by using the missing
energy spectrum shape is discussed. We consider as an example the with the
mass 16.7 MeV and mixing , which can explain an
excess of events recently observed in nuclear transitions of an excited state
of Be. We show that if such exists its invisible decay can be observed
in NA64 within a month of running, while data accumulated during a few months
would allow also to determine the and parameters.Comment: 12 pages, 15 figures. Revised versio
Resonant probing spin-0 and spin-2 dark matter mediators with fixed target experiments
We discuss the mechanism to produce electron-specific dark matter mediators
of spin-0 and spin-2 in the electron fixed target experiments such as NA64 and
LDMX. The secondary positrons induced by the electromagnetic shower can produce
the mediators via annihilation on atomic electrons. That mechanism, for some
selected kinematics, results in the enhanced sensitivity with respect to the
bounds derived by the bremsstrahlunglike emission of the mediator in the
specific parameter space. We derive the corresponding experimental reach of the
NA64 and LDMX.Comment: 12 pages, 7 figures. Typos are corrected, efficiencies are added, the
version is accepted for publication in PR
Constraints on CP-odd ALP couplings from EDM limits of fermions
We discuss constraints on soft CP-violating couplings of axion-like particles
with photon and fermions by using data on electric dipole moments of Standard
Model particles. In particular, for the ALP leptophilic scenario we derive
bounds on CP-odd ALP-photon-photon coupling from data of the {\tt ACME}
Collaboration on electron EDM. We also discuss prospects of the Storage Ring
experiment to constrain the ALP-photon-photon coupling from data on proton EDM
for the simplified hadrophilic interactions of ALP. The regarding constraints
from experimental bounds on the muon and neutron EDMs are weak. We set
constraint on the CP-odd ALP coupling with electron and derive bounds on
combinations of coupling constants, which involve soft CP-violating terms.Comment: 12 pages, 2 figures, journal reference correcte
Light-shining-through-wall cavity setups for probing ALPs
We discuss the aspects of axion-like-particles (ALPs) searches with
Light-Shining-through-Wall (LSW) experimental setups consisted of two
radio-frequency cavities. We compare the efficiencies of three setups which
involve the cavity pump modes and external magnetic fields. Additionally, we
discuss the sensitivity dependence both on the relative position of two
cylindrical cavities and on their radius-to-length ratio.Comment: 9 pages, 6 figures, 1 table. Revised version, accepted to JETP
Letter
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