184 research outputs found
Results of a Search for Paraphotons with Intense X-ray Beams at SPring-8
A search for paraphotons, or hidden U(1) gauge bosons, is performed using an
intense X-ray beamline at SPring--8. "Light Shining through a Wall" technique
is used in this search. No excess of events above background is observed. A
stringent constraint is obtained on the photon--paraphoton mixing angle, for .Comment: 10 pages, 4 figure
Recoil effects of photoelectrons in a solid
High energy resolution C 1 photoelectron spectra of graphite were measured
at the excitation energy of 340, 870, 5950 and 7940eV using synchrotron
radiation. On increasing the excitation energy, i.e., increasing kinetic energy
of the photoelectron, the bulk origin C 1 peak position shifts to higher
binding energies. This systematic shift is due to the kinetic energy loss of
the high-energy photoelectron by kicking the atom, and is clear evidence of the
recoil effect in photoelectron emission. It is also observed that the
asymmetric broadening increases for the higher energy photoelectrons. All these
recoil effects can be quantified in the same manner as the M\"ossbauer effect
for -ray emission from nuclei embedded in crystals.Comment: 4 pages, 2 figure
Bulk screening in core level photoemission from Mott-Hubbard and Charge-Transfer systems
We report bulk-sensitive hard X-ray ( = 5.95 KeV) core level
photoemission spectroscopy (PES) of single crystal VCrO
and the high- cuprate BiSrCaCuO (Bi2212).
VCrO exhibits low binding energy "satellites" to the V
"main lines" in the metallic phase, which are suppressed in the
antiferromagnetic insulator phase. In contrast, the Cu spectra of Bi2212
do not show temperature dependent features, but a comparison with soft X-ray
PES indicates a large increase in the "satellites" or weight
in the bulk. Cluster model calculations, including full multiplet structure and
a screening channel derived from the coherent band at the Fermi energy, give
very satisfactory agreement with experiments
High efficiency and low absorption Fresnel compound zone plates for hard X-ray focusing
Circular and linear zone plates have been fabricated on the surface of
silicon crystals for the energy of 8 keV by electron beam lithography and deep
ion plasma etching methods. Various variants of compound zone plates with
first, second, third diffraction orders have been made. The zone relief height
is about 10 mkm, the outermost zone width of the zone plate is 0.4 mkm. The
experimental testing of the zone plates has been conducted on SPring-8 and ESRF
synchrotron radiation sources. A focused spot size and diffraction efficiency
measured by knife-edge scanning are accordingly 0.5 mkm and 39% for the first
order circular zone plate.Comment: 5 pages, 7 figure
Quantum enhanced X-ray detection
We present the first experimental demonstration of quantum-enhanced detection
at x-ray wavelengths. We show that x-ray pairs that are generated by
spontaneous down-conversion can be used for the generation of heralded x-ray
photons and measure directly the sub-Poissonian statistics of the single
photons by using photon number resolving detectors. We utilize the properties
of the strong time-energy correlations of the down converted photons to
demonstrate the ability to improve the visibility and the signal-to-noise ratio
of an image with a small number of photons in an environment with a noise level
that is higher than the signal by many orders of magnitude. In our work we
demonstrate a new protocol for the measurement of quantum effects with x-rays
using advantages such as background free measurements that the x-ray regime
offers for experiments aiming at testing fundamental concepts in quantum
optics.Comment: 12 page
Search for Axion like particles using Laue-case conversion in a single crystal
Axion Like Particles (ALPs) with a sub-keV range mass are searched by using
the light-shining-through-a-wall technique. A novel system is developed in
which injected X rays are converted and reconverted by the Laue-case conversion
within a silicon single crystal with dual blades. The resonant ALPs' mass of
the conversion is scanned by varying the X-ray injection angle to the crystal.
No significant signals are observed, and 90% C. L. upper limits on the ALP-two
photon coupling constant are obtained as follows, g_{a\gamma\gamma} < 4.2
\times 10^{-3} GeV^{-1} (m_a < 10 eV), g_{a\gamma\gamma} < 5.0 \times 10^{-3}
GeV^{-1} (46 eV < m_a < 1020 eV). These are the most stringent laboratorial
constraints on ALPs heavier than 300 eV.Comment: 13 pages, 5 figures, 1 tabl
Search for Photon-Photon Elastic Scattering in the X-ray Region
We report the first results of a search for real photon-photon scattering
using X rays. A novel system is developed to split and collide X-ray pulses by
applying interferometric techniques. A total of pulses (each
containing about photons) from an X-ray Free-Electron Laser are
injected into the system. No scattered events are observed, and an upper limit
of (95% C.L.) is obtained on the
photon-photon elastic scattering cross section at 6.5 keV
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