234 research outputs found
Development Of Innovating Na Leak Detector On Pipes
International audienceWithin the ASTRID reactor project, CEA, EDF and AREVA NP, have launched a RetD program focused on the low leak rates detection of sodium on pipes. This program is focused on the development of innovating detectors, multilayer-type and Optic Fiber, involving tests in the FUTUNa sodium loop. This loop is designed to produce very accurate sodium leak rates within a range around 1cm/min, the tests being performed at different temperature (up to 550DC) on large-diameter pipe mock-ups (D 800 mm) at ambient atmosphere. This paper presents the first series of tests carried out with various materials of the first and second layer of the detector. The results are compared and discussed as well as the observations made after removing the mock-ups. The most interesting result of the overall tests is a detection time less than 2 hours for the two types of detectors
Solving integral equations in
A dispersive analysis of decays has been performed in the past
by many authors. The numerical analysis of the pertinent integral equations is
hampered by two technical difficulties: i) The angular averages of the
amplitudes need to be performed along a complicated path in the complex plane.
ii) The averaged amplitudes develop singularities along the path of integration
in the dispersive representation of the full amplitudes. It is a delicate
affair to handle these singularities properly, and independent checks of the
obtained solutions are demanding and time consuming. In the present article, we
propose a solution method that avoids these difficulties. It is based on a
simple deformation of the path of integration in the dispersive representation
(not in the angular average). Numerical solutions are then obtained rather
straightforwardly. We expect that the method also works for .Comment: 11 pages, 10 Figures. Version accepted for publication in EPJC. The
ancillary files contain an updated set of fundamental solutions. The
numerical differences to the former set are tiny, see the READMEv2 file for
detail
Dynamics in near-threshold photoproduction
The study of photoproduction at low energies has consequences for
the understanding of multiple aspects of nonperturbative QCD, ranging from
mechanical properties of the proton, to the binding inside nuclei, and the
existence of hidden-charm pentaquarks. Factorization of the photon-
and nucleon dynamics or Vector Meson Dominance are often invoked to justify
these studies. Alternatively, open charm intermediate states have been proposed
as the dominant mechanism underlying photoproduction. As the latter
violates this factorization, it is important to estimate the relevance of such
contributions. We analyse the latest differential and integrated
photoproduction cross sections from the GlueX and -007 experiments. We
show that the data can be adequately described by a small number of partial
waves, which we parameterize with generic models enforcing low-energy
unitarity. The results suggest a nonnegligible contribution from open charm
intermediate states. Furthermore, most of the models present an elastic
scattering length incompatible with previous extractions based on Vector Meson
Dominance, and thus call into question its applicability to heavy mesons. Our
results indicate a wide array of physics possibilities that are compatible with
present data and need to be disentangled.Comment: 15 pages, 7 figures, 2 table
Khuri-Treiman analysis of
We study the decay within the framework of
the Khuri-Treiman equations. We find that the BESIII experimental di-pion mass
distribution in the -region is well reproduced with a
once-subtracted -wave amplitude. Furthermore, we show that -wave
contributions to the amplitude improve the description of the data in the
mass region around 1.5 GeV. We also present predictions for the
transition form factor.Comment: 20 pages, 9 figure
Finite volume treatment of pi pi scattering and limits to phase shifts extraction from lattice QCD
We study theoretically the effects of finite volume for pipi scattering in
order to extract physical observables for infinite volume from lattice QCD. We
compare three different approaches for pipi scattering (lowest order
Bethe-Salpeter approach, N/D and inverse amplitude methods) with the aim to
study the effects of the finite size of the box in the potential of the
different theories, specially the left-hand cut contribution through loops in
the crossed t,u-channels. We quantify the error made by neglecting these
effects in usual extractions of physical observables from lattice QCD spectra.
We conclude that for pipi phase-shifts in the scalar-isoscalar channel up to
800 MeV this effect is negligible for box sizes bigger than 2.5m_pi^-1 and of
the order of 5% at around 1.5-2m_pi^-1. For isospin 2 the finite size effects
can reach up to 10% for that energy. We also quantify the error made when using
the standard Luscher method to extract physical observables from lattice QCD,
which is widely used in the literature but is an approximation of the one used
in the present work.Comment: 10 pages, 8 figure
Dynamical coupled-channel approaches on a momentum lattice
Dynamical coupled-channel approaches are a widely used tool in hadronic
physics that allow to analyze different reactions and partial waves in a
consistent way. In such approaches the basic interactions are derived within an
effective Lagrangian framework and the resulting pseudo-potentials are then
unitarized in a coupled-channel scattering equation. We propose a scheme that
allows for a solution of the arising integral equation in discretized momentum
space for periodic as well as twisted boundary conditions. This permits to
study finite size effects as they appear in lattice QCD simulations. The new
formalism, at this stage with a restriction to S-waves, is applied to
coupled-channel models for the sigma(600), f0(980), and a0(980) mesons, and
also for the Lambda(1405) baryon. Lattice spectra are predicted.Comment: 7 pages, 4 figure
Nucleon-Nucleon Interaction: A Typical/Concise Review
Nearly a recent century of work is divided to Nucleon-Nucleon (NN)
interaction issue. We review some overall perspectives of NN interaction with a
brief discussion about deuteron, general structure and symmetries of NN
Lagrangian as well as equations of motion and solutions. Meanwhile, the main NN
interaction models, as frameworks to build NN potentials, are reviewed
concisely. We try to include and study almost all well-known potentials in a
similar way, discuss more on various commonly used plain forms for two-nucleon
interaction with an emphasis on the phenomenological and meson-exchange
potentials as well as the constituent-quark potentials and new ones based on
chiral effective field theory and working in coordinate-space mostly. The
potentials are constructed in a way that fit NN scattering data, phase shifts,
and are also compared in this way usually. An extra goal of this study is to
start comparing various potentials forms in a unified manner. So, we also
comment on the advantages and disadvantages of the models and potentials partly
with reference to some relevant works and probable future studies.Comment: 85 pages, 5 figures, than the previous v3 edition, minor changes, and
typos fixe
Decay widths of the spin-2 partners of the X(3872)
We consider the X(3872) resonance as a JPC=1++ DDÂŻâ hadronic molecule. According to heavy quark spin symmetry, there will exist a partner with quantum numbers 2++, X2, which would be a DâDÂŻâ loosely bound state. The X2 is expected to decay dominantly into DDÂŻ, DDÂŻâ and DÂŻDâ in d-wave. In this work, we calculate the decay widths of the X2 resonance into the above channels, as well as those of its bottom partner, Xb2, the mass of which comes from assuming heavy flavor symmetry for the contact terms. We find partial widths of the X2 and Xb2 of the order of a few MeV. Finally, we also study the radiative X2âDDÂŻâÎł and Xb2âBÂŻBâÎł decays. These decay modes are more sensitive to the long-distance structure of the resonances and to the DDÂŻâ or BBÂŻâ final state interaction
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