1,951 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
A Study of the Mechanism of Action of Zervamicin IIB Peptide Antibiotic by Molecular Dynamics Simulation
We model mechanism of action of a channel-forming peptide antibiotic, zervamicin IIB, by molecular dynamics (MD) simulation. Interaction of this peptide with neutral and negatively charged lipid bilayers is investigated. It is found that charge of membrane surface influences the orientation of zervamicin IIB molecule, that may in turn effect its permeation into the membrane. On this basis we propose modifications to ZrvIIB structure that may increase its affinity towards the prokaryotic cellular membrane. Zervamicin IIB transmembrane channels are modeled as bundles consisting of 4, 5 and 6 individual peptide monomers. Our results suggest that four monomers don’t form a stable water-filled ion channel. Thus the channel with the least number of monomers (and the lowest conductance level by literature data) is a pentamer
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