435 research outputs found
Nonperturbative QED Processes at ELI-NP
The present paper analyses the current results and pursuits the main steps
required for the design of SF-QED experiments at High-Power Laser System (HPLS)
of ELI-NP in Magurele, Romania. After a brief analysis of the first experiment
(E-144 SLAC), which confirmed the existence of non-linear QED interactions of
the high energy electrons with the photons of a laser beam, we went on to
present fundamental QED processes possible to be studied at ELI-NP in a
multi-photon regime. The kinematics and characteristic parameters of the laser
beam interacting with electrons were presented. In the preparation of an
experiment at ELI-NP, the analysis of the kinematics and dynamics of the
non-linear QED interaction processes with the physical vacuum are required.
Initially, the linear QED processes and the corresponding Feynman diagrams that
allow to determine the amplitude of these processes are reviewed. Based on
these amplitudes, the cross sections of the processes can be obtained. For
multi-photon interactions it is necessary to adapt the technique of Feynman
diagrams from linear QED processes to the non-linear ones, by moving to the
quantum field description with dressed Dirac-Volkov states, for particles in
intense EM field. They then allow evaluation of the amplitude of the physical
processes and ultimately the determination of the corresponding cross section.
The SF-QED processes of multi-photon interactions with strong laser fields, can
be done taking into account the characteristics of the existing facilities at
ELI-NP in the context of the experimental production of electron-positron-pairs
and of energetic gamma-rays. We show also some upcoming experiments similar to
ours, in various stages of preparation.Comment: Presented at Bucharest University Meeting 2023
https://ssffb.fizica.unibuc.ro/SSFFB/Section.php?SectID=22
Preliminary study of the 19F(7Li,7Be)19O reaction at 52 MeV with MAGNEX
The 19F(7Li,7Be)19O charge-exchange reaction at 52 MeV incident energy has been performed at INFN-LNS in Catania using the MAGNEX spectrometer. The use of an algebraic ray-reconstruction technique has allowed to extract the 19O excitation energy spectrum and the experimental angular distributions obtained with a single angular setting of the spectrometer
First measurements at the DAΦNE φ-factory with the DEAR experimental setup
The relevant background for the DEAR experiment } low-energy X rays and ionizing particles } present in the DEAR interaction region of the DA'NE e'e~ collider was investigated using the "rst-stage DEAR setup and CCD detectors. An extensive Monte Carlo simulation was performed for the present setup and beam conditions. Good quantitative agreement between measurements and simulation was achieved. This is a con"rmation that, with respect to the expected background, which gives an important contribution to the statistical precision of the experiment, the con"guration chosen to measure the strong interaction shift and width in kaonic hydrogen and kaonic deuterium can indeed reach the planned level of accuracy. ( 2000 Elsevier Science B.V. All rights reserved
The DEAR experiment on DAΦNE
DEAR is one of the first experiments at the new DAΦNE Ø-factory at the Laboratori Nazionali di Frascati dell'INFN. The objective of the DEAR experiment is to perform a precision measurement of the strong interaction shifts and widths of the K-series lines in kaonic hydrogen and the first observation of the same quantities in kaonic deuterium. The aim is to obtain a precise determination of the isospin-dependent kaon-nucleon scattering lengths which will represent a breakthrough in KN low-energy phenomenology and will allow us to determine the kaon-nucleon sigma terms. The sigma terms give a direct measurement of chiral symmetry breaking and are connected to the strangeness content of the proton. First results on background measurements with the DEAR NTP setup installed on DAΦNE are reported
First measurement of kaonic helium-3 X-rays
The first observation of the kaonic 3He 3d - 2p transition was made using
slow K- mesons stopped in a gaseous 3He target. The kaonic atom X-rays were
detected with large-area silicon drift detectors using the timing information
of the K+K- pairs of phi-meson decays produced by the DAFNE e+e- collider. The
strong interaction shift of the kaonic 3He 2p state was determined to be -2+-2
(stat)+-4 (syst) eV.Comment: Accepted for publication in Phys. Lett.
Measurements of the reaction of antiproton annihilation at rest at three hydrogen target densities
The proton-antiproton annihilation at rest into the final state
was measured for three different target densities: liquid hydrogen, gaseous
hydrogen at NTP and at a low pressure of 5 mbar. The yield of this reaction in
the liquid hydrogen target is smaller than in the low-pressure gas target. The
branching ratios of the channel were calculated on the basis of
simultaneous analysis of the three data samples. The branching ratio for
annihilation into from the protonium state turns out to be
about ten times smaller as compared to the one from the state.Comment: 10 pages, 3 Postscript figures. Accepted by Physics Letters
A New Measurement of Kaonic Hydrogen X rays
The system at threshold is a sensitive testing ground for low
energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we
have measured the -series x rays of kaonic hydrogen atoms at the DANE
electron-positron collider of Laboratori Nazionali di Frascati, and have
determined the most precise values of the strong-interaction energy-level shift
and width of the atomic state. As x-ray detectors, we used large-area
silicon drift detectors having excellent energy and timing resolution, which
were developed especially for the SIDDHARTA experiment. The shift and width
were determined to be eV and
eV, respectively. The new
values will provide vital constraints on the theoretical description of the
low-energy interaction.Comment: 5 figures, submitted to Physics Letters
New data on OZI rule violation in bar{p}p annihilation at rest
The results of a measurement of the ratio R = Y(phi pi+ pi-) / Y(omega pi+
pi-) for antiproton annihilation at rest in a gaseous and in a liquid hydrogen
target are presented. It was found that the value of this ratio increases with
the decreasing of the dipion mass, which demonstrates the difference in the phi
and omega production mechanisms. An indication on the momentum transfer
dependence of the apparent OZI rule violation for phi production from the 3S1
initial state was found.Comment: 11 pages, 3 PostScript figures, submitted to Physics Letter
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