100 research outputs found
Effect of three-pion unitarity on resonance poles from heavy meson decays
We study the final state interaction in 3-pion decay of meson resonances at
the Excited Baryon Analysis Center (EBAC) of JLab. We apply the dynamical
coupled-channels formulation which has been extensively used by EBAC to extract
N* information. The formulation satisfies the 3-pion unitarity condition which
has been missed in the existing works with the isobar models. We report the
effect of the 3-pion unitarity on the meson resonance pole positions and Dalitz
plot.Comment: 4 pages, 4 figures, Contribution to the proceedings of International
conference on the structure of baryons (BARYONS'10), Osaka, Japan, Dec. 7-11,
201
Theoretical analysis of Lambda(1405) photoproduction
We develop a model that describes the gamma p -> K^+ pi Sigma reaction in the
Lambda(1405) region. The model consists of gauge invariant photo-production
mechanisms, and the chiral unitary model that gives the rescattering amplitudes
where Lambda(1405) is contained. The model also contains phenomenological
parameters, associated with short-range dynamics, to be used in fitting data.
We successfully fit recent CLAS data for the pi-Sigma invariant mass
distributions (line-shape) in the gamma p -> K^+ pi Sigma reaction for all the
charge states. We find that the higher mass pole for Lambda(1405) of the chiral
unitary model plays an important role in the reaction. We also find the
non-resonant background contribution is not negligible, and its sizable effect
shifts the Lambda(1405) peak position by several MeV. This work sets a starting
point for a fuller analysis in which line-shape as well as K^+ angular
distribution data are simultaneously analyzed for extracting Lambda(1405)
pole(s).Comment: 5 pages, 6 figures, Contribution to the proceedings of XV
International Conference on Hadron Spectroscopy (Hadron 2013), November 4-8
2013, Nara, Japa
Renormalization group analysis of nuclear current operators
A Wilsonian renormalization group (WRG) equation for nuclear current
operators in two-nucleon systems is derived. Nuclear current operators relevant
to low-energy Gamow-Teller transitions are analyzed using the WRG equation. We
employ the axial two-body current operators from phenomenological models and
heavy-baryon chiral perturbation theory, which are quite different from one
another in describing small scale physics. After reducing the model space of
the operators using the WRG equation, we find that there still remains a
significant model dependence at \Lambda = 200 MeV, where \Lambda is the sharp
cutoff specifying the size of the model space. A model independent effective
current operator is found at a rather small cutoff value, \Lambda = 70 MeV. By
simulating the effective current operator at \Lambda=70 MeV, we obtain a
current operator based on a pionless theory, thereby arguing an equivalence
relation between nuclear current operators of phenomenological models and those
of effective field theories.Comment: 26 pages, 11 figure
, , , and as triangle singularities
discovered in , found
in , and and observed in
are candidates of charged charmonium-like
states. All surviving theoretical models interpreted these candidates as
four-quark states, until we recently identified a compelling alternative. We
discuss that kinematical singularities in triangle loop diagrams induce a
resonance-like behavior that can consistently explain the properties (such as
spin-parity, mass, width, and Argand plot) of , ,
and from experiments. In terms of the triangle
singularities, we can also naturally understand interesting experimental
findings such as the appearance (absence) of ()-like
contribution in , and the highly asymmetric shape
of the spectrum bump for ; the other theoretical models have not
successfully addressed these points. Although Pakhlov et al. proposed another
triangle diagram to generate a -like bump, we argue that this
scenario is very unlikely.Comment: 7 pages, 5 figures, Contribution to the Proceedings for 15th
International Conference on Meson-Nucleon Physics and the Structure of the
Nucleon (MENU-2019), June 2-7 2019, Pittsburgh, US
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