113 research outputs found
Temperature-induced reversal of magnetic interlayer exchange coupling
For epitaxial trilayers of the magnetic rare-earth metals Gd and Tb, exchange
coupled through a non-magnetic Y spacer layer, element-specific hysteresis
loops were recorded by the x-ray magneto-optical Kerr effect at the rare-earth
thresholds. This allowed us to quantitatively determine the strength of
interlayer exchange coupling (IEC). In addition to the expected oscillatory
behavior as a function of spacer-layer thickness , a temperature-induced
sign reversal of IEC was observed for constant , arising from
magnetization-dependent electron reflectivities at the magnetic interfaces.Comment: 4 pages, 4 figures; accepted version; minor changes and new Figs. 2
and 4 containing more dat
The quest for axions and other new light particles
Standard Model extensions often predict low-mass and very weakly interacting particles, such as the axion. A number of small-scale experiments at the intensity/precision frontier are actively searching for these elusive particles, complementing searches for physics beyond the Standard Model at colliders. Whilst a next generation of experiments will give access to a huge unexplored parameter space, a discovery would have a tremendous impact on our understanding of fundamental physics
Search for hidden-photon dark matter with the FUNK experiment
Many extensions of the Standard Model of particle physics predict a parallel
sector of a new U(1) symmetry, giving rise to hidden photons. These hidden
photons are candidate particles for cold dark matter. They are expected to
kinetically mix with regular photons, which leads to a tiny oscillating
electric-field component accompanying dark matter particles. A conducting
surface can convert such dark matter particles into photons which are emitted
almost perpendicularly to the surface. The corresponding photon frequency
follows from the mass of the hidden photons. In this contribution we present a
preliminary result on a hidden photon search in the visible and near-UV
wavelength range that was done with a large, 14 m2 spherical metallic mirror
and discuss future dark matter searches in the eV and sub-eV range by
application of different detectors for electromagnetic radiation.Comment: Contribution to the 35th International Cosmic Ray Conference
ICRC2017, 10 to 20 July, 2017, Bexco, Busan, Korea. arXiv admin note: text
overlap with arXiv:1711.0296
Search for dark photons as candidates for Dark Matter with FUNK
An additional U(1) symmetry predicted in theories beyond the Standard Model of particle physics can give rise to hidden (dark) photons. Depending on the mass and density of these hidden photons, they could account for a large fraction of the Dark Matter observed in the Universe. When passing through an interface of materials with different dielectric properties, hidden photons are expected to produce a tiny flux of photons. The wavelength of these photons is directly related to the mass of the hidden photons. In this contribution we report on measurements covering the visible and near-UV spectrum, corresponding to a dark photon mass in the eV range. The data were taken with the FUNK experiment using a spherical mirror of ~14m2 total area built up of 36 aluminum segments
Axion-like-particle search with high-intensity lasers
We study ALP-photon-conversion within strong inhomogeneous electromagnetic
fields as provided by contemporary high-intensity laser systems. We observe
that probe photons traversing the focal spot of a superposition of Gaussian
beams of a single high-intensity laser at fundamental and frequency-doubled
mode can experience a frequency shift due to their intermittent propagation as
axion-like-particles. This process is strongly peaked for resonant masses on
the order of the involved laser frequencies. Purely laser-based experiments in
optical setups are sensitive to ALPs in the mass range and can
thus complement ALP searches at dipole magnets.Comment: 25 pages, 2 figure
Search for Dark Matter Axions with CAST-CAPP
The CAST-CAPP axion haloscope, operating at CERN inside the CAST dipole
magnet, has searched for axions in the 19.74 eV to 22.47 eV mass
range. The detection concept follows the Sikivie haloscope principle, where
Dark Matter axions convert into photons within a resonator immersed in a
magnetic field. The CAST-CAPP resonator is an array of four individual
rectangular cavities inserted in a strong dipole magnet, phase-matched to
maximize the detection sensitivity. Here we report on the data acquired for
4124 h from 2019 to 2021. Each cavity is equipped with a fast frequency tuning
mechanism of 10 MHz/min between 4.774 GHz and 5.434 GHz. In the present work,
we exclude axion-photon couplings for virialized galactic axions down to
at the 90% confidence
level. The here implemented phase-matching technique also allows for future
large-scale upgrades.Comment: 24 pages, 5 figures, Published version available with Open Access at
https://www.nature.com/articles/s41467-022-33913-
Search for dark photons as candidates for Dark Matter with FUNK
An additional U(1) symmetry predicted in theories beyond the Standard Model of particle physics can give rise to hidden (dark) photons. Depending on the mass and density of these hidden photons, they could account for a large fraction of the Dark Matter observed in the Universe. When passing through an interface of materials with different dielectric properties, hidden photons are expected to produce a tiny flux of photons. The wavelength of these photons is directly related to the mass of the hidden photons. In this contribution we report on measurements covering the visible and near-UV spectrum, corresponding to a dark photon mass in the eV range. The data were taken with the FUNK experiment using a spherical mirror of 14m total area built up of 36 aluminum segments
Electrospun shape memory scaffolds for bone tissue engineering
Poster Topic: Biomaterials in constructing tissue substitutesINTRODUCTION: Emulsion electrospinning is extensively used to make tissue engineering scaffolds with the capability of delivering bioactive agents such as growth factors [1]. Bone morphogenetic protein-2 (BMP-2) is a potent growth factor for osteogenesis. On the other hand, shape memory polymers (SMPs) have attracted great attention in tissue engineering[2]. An SMP device can be packed into a temporary shape with a much reduced size. After implantation through a narrow path, the device may recover to its larger and permanent shape upon specific stimulus. Another important issue is electrospinning of thick, 3D scaffolds. This study investigated electrospinning of a shape memory polymer, poly(D,L-lactide-co-trimethylene carbonate) P(DLLA-co-TMC), into thermo-responsive scaffolds. An auxiliary process was studied for facilitating the formation of thick scaffolds ...postprin
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