37 research outputs found
Amplitude analysis and the nature of the Zc(3900)
The microscopic nature of the XYZ states remains an unsettled topic. We show
how a thorough amplitude analysis of the data can help constraining models of
these states. Specifically, we consider the case of the Zc(3900) peak and
discuss possible scenarios of a QCD state, virtual state, or a kinematical
enhancement. We conclude that current data are not precise enough to
distinguish between these hypotheses, however, the method we propose, when
applied to the forthcoming high-statistics measurements should shed light on
the nature of these exotic enhancements.Comment: 14 pages, 10 figures, 3 tables. Version accepted for publication on
Phys.Lett.
Structure of Pion Photoproduction Amplitudes
We derive and apply the finite energy sum rules to pion photoproduction. We
evaluate the low energy part of the sum rules using several state-of-the-art
models. We show how the differences in the low energy side of the sum rules
might originate from different quantum number assignments of baryon resonances.
We interpret the observed features in the low energy side of the sum rules with
the expectation from Regge theory. Finally, we present a model, in terms of a
Regge-pole expansion, that matches the sum rules and the high-energy
observables.Comment: 19 pages, 15 figures and 4 table
On the and Photoproduction Beam Asymmetry at High Energies
We show that, in the Regge limit, beam asymmetries in and
photoproduction are sensitive to hidden strangeness components. Under
reasonable assumptions about the couplings we estimate the contribution of the
Regge pole, which is expected to be the dominant hidden strangeness
contribution. The ratio of the asymmetries in and production is
estimated to be close to unity in the forward region at the photon energy ~GeV, relevant for the upcoming
measurements at Jefferson Lab.Comment: 9 pages, 4 figure
Finite-Energy Sum Rules in Eta Photoproduction off the Nucleon
The reaction is studied in the high-energy regime
(with photon lab energies GeV) using
information from the resonance region through the use of finite-energy sum
rules (FESR). We illustrate how analyticity allows one to map the t-dependence
of the unknown Regge residue functions. We provide predictions for the energy
dependence of the beam asymmetry at high energies.Comment: Joint Physics Analysis Cente
Analyticity constraints for hadron amplitudes : going high to heal low energy issues
Analyticity constitutes a rigid constraint on hadron scattering amplitudes. This property is used to relate models in different energy regimes. Using meson photoproduction as a benchmark, we show how to test contemporary low-energy models directly against high-energy data. This method pinpoints deficiencies of the models and treads a path to further improvement. The implementation of this technique enables one to produce more stable and reliable partial waves for future use in hadron spectroscopy and new physics searches
Determination of the pole position of the lightest hybrid meson candidate
Mapping states with explicit gluonic degrees of freedom in the light sector
is a challenge, and has led to controversies in the past. In particular, the
experiments have reported two different hybrid candidates with spin-exotic
signature, pi1(1400) and pi1(1600), which couple separately to eta pi and eta'
pi. This picture is not compatible with recent Lattice QCD estimates for hybrid
states, nor with most phenomenological models. We consider the recent partial
wave analysis of the eta(') pi system by the COMPASS collaboration. We fit the
extracted intensities and phases with a coupled-channel amplitude that enforces
the unitarity and analyticity of the S-matrix. We provide a robust extraction
of a single exotic pi1 resonant pole, with mass and width 1564 +- 24 +- 86 MeV
and 492 +- 54 +- 102 MeV, which couples to both eta(') pi channels. We find no
evidence for a second exotic state. We also provide the resonance parameters of
the a2(1320) and a2'(1700).Comment: 6 pages + 3 pages of supplemental material. Version to appear on
Phys.Rev.Let
Global analysis of charge exchange meson production at high energies
Many experiments that are conducted to study the hadron spectrum rely on
peripheral resonance production. Hereby, the rapidity gap allows the process to
be viewed as an independent fragmen- tation of the beam and the target, with
the beam fragmentation dominated by production and decays of meson resonances.
We test this separation by determining the kinematic regimes that are dominated
by factorizable contributions, indicating the most favorable regions to perform
this kind of experiments. In doing so, we use a Regge model to analyze the
available world data of charge exchange meson production with beam momentum
above 5 GeV in the laboratory frame, that are not dominated by either pion or
Pomeron exchanges. We determine the Regge residues and point out the kinematic
regimes which are dominated by factorizable contributions
Issues and Opportunities in Exotic Hadrons
The last few years have been witness to a proliferation of new results
concerning heavy exotic hadrons. Experimentally, many new signals have been
discovered that could be pointing towards the existence of tetraquarks,
pentaquarks, and other exotic configurations of quarks and gluons.
Theoretically, advances in lattice field theory techniques place us at the cusp
of understanding complex coupled-channel phenomena, modelling grows more
sophisticated, and effective field theories are being applied to an ever
greater range of situations. It is thus an opportune time to evaluate the
status of the field. In the following, a series of high priority experimental
and theoretical issues concerning heavy exotic hadrons is presented.Comment: White paper from INT workshop, "Modern Exotic Hadrons". References
added. Version to appear in Chinese Physics
Image Processing Based Detection of Fungal Diseases in Plants
AbstractThis paper presents a study on the image processing techniques used to identify and classify fungal disease symptoms affected on different agriculture/horticulture crops. Computers have been used to mechanization, automation, and to develop decision support system for taking strategic decision on the agricultural production and protection research. The plant disease diagnosis is limited by the human visual capabilities because most of the first symptoms are microscopic. As plant health monitoring is still carried out by humans due to the visual nature of the plant monitoring task, computer vision techniques seem to be well adapted. One of the areas considered here is the processing of images of disease affected agriculture/horticulture crops. The quantity and quality of plant products gets reduced by plant diseases. The goal is to detect, to identify, and to accurately quantify the first symptoms of diseases. Plant diseases are caused by bacteria, fungi, virus, nematodes, etc., of which fungi is the main disease causing organism. Focus has been done on the early detection of fungal disease based on the symptoms