81 research outputs found
New Preshower detector for DIRAC Experiment
The Preshower (PSh) detector is a component of the DIRAC setup. It is
designed to improve rejection efficiency of e-e+ pairs background in the
{\pi}{\pi} and K{\pi} pair measurement. To increase the overall efficiency, a
new two-layer structure scintillator Preshower detector has been realized in
the region where the Nitrogen Cherenkov detector has been shortened to
introduce new detectors. The new Preshower-Cherenkov combination ensures the
electron rejection efficiency better than 99.9% in momentum region 1-7 GeV/c.Comment: to be published in NIM
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
First atom lifetime and scattering length measurements
The results of a search for hydrogen-like atoms consisting of
mesons are presented. Evidence for atom production
by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen
in terms of characteristic pairs from their breakup in the same target
() and from Coulomb final state interaction (). Using
these results the analysis yields a first value for the atom lifetime
of fs and a first model-independent measurement of
the S-wave isospin-odd scattering length
( for isospin ).Comment: 14 pages, 8 figure
Determination of scattering lengths from measurement of atom lifetime
The DIRAC experiment at CERN has achieved a sizeable production of
atoms and has significantly improved the precision on its lifetime
determination. From a sample of 21227 atomic pairs, a 4% measurement of the
S-wave scattering length difference
has been attained, providing an important test of Chiral Perturbation Theory.Comment: 6 pages, 6 figure
DIRAC Experiment and Test of Low-Energy QCD
The low-energy QCD predictions to be tested by the DIRAC experiment are revised. The experimental method, the setup characteristics and capabilities, along with first experimental results are reported. Preliminary analysis shows good detector performance: alignment error via mass measurement with , relative momentum resolution , and evidence for $\pi^
Detection of Pionium with DIRAC
The aim of the DIRAC experiment at CERN is to provide an accurate determination of S-wave pion-pion scattering lengths from the measurement of the lifetime of the pi+ pi- atom. The measurement will be done with precision comparable to the level of accuracy of theoretical predictions, formulated in the context of Chiral Perturbation Theory. Therefore, the understanding of chiral symmetry breaking of QCD will be submitted to a stringent test
Detection of atoms with the DIRAC spectrometer at CERN
The goal of the DIRAC experiment at CERN is to measure with high precision
the lifetime of the atom (), which is of order
s, and thus to determine the s-wave -scattering
lengths difference . atoms are detected through the
characteristic features of pairs from the atom break-up
(ionization) in the target. We report on a first high statistics atomic data
sample obtained from p Ni interactions at 24 GeV/ proton momentum and
present the methods to separate the signal from the background.Comment: 19 pages, 12 figures, 1 tabl
Evidence for -atoms with DIRAC
We present evidence for the first observation of electromagnetically bound
-pairs (-atoms) with the DIRAC experiment at the CERN-PS.
The -atoms are produced by the 24 GeV/c proton beam in a thin Pt-target
and the and -mesons from the atom dissociation are analyzed in
a two-arm magnetic spectrometer. The observed enhancement at low relative
momentum corresponds to the production of 173 54 -atoms. The mean
life of -atoms is related to the s-wave -scattering lengths, the
measurement of which is the goal of the experiment. From these first data we
derive a lower limit for the mean life of 0.8 fs at 90% confidence level.Comment: 15 pages, 9 figure
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