1,050 research outputs found
The ccbar Pentaquarks by a Quark Model
Recent LHCb experiments have shown us that there are two resonances in the
channel in the decay, whose spin and parity are most
probably (3/2 5/2). In this work, we investigate the
, , and pentaquark
states by employing the quark cluster model. It is found that the color-octet
isospin-1/2 spin-3/2 configuration gives an attraction to such five-quark
systems. This configuration together with the color-octet pair
gives structures around the thresholds: one
bound state, two resonances, and one large cusp are found in the
negative parity channels. We argue that these resonances and cusp may
correspond to, or combine to form, the negative parity pentaquark peak observed
by LHCb.Comment: 4 pages, 4 figures, Proceedings of the 14th International Conference
on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2016
Effects of Instantons on the YN Interaction
We investigate the symmetric and anti-symmetric spin-orbit forces (SLS and
ALS) of the effective N interaction derived from a quark cluster model
with the instanton-induced interaction (\III), which can reproduce the observed
YN cross sections as well as the observed NN scattering data.
It is found that coupling to the N channel enhances N ALS,
and therefore that the cancellation between SLS and ALS in the N
channel becomes more complete. This may be one of the major reasons why the
single-particle spin-orbit force of in nuclei is weak.Comment: 3 pages, 2 figures, FewBody XV
On the origin of the narrow peak and the isospin symmetry breaking of the (3872)
The (3872) formation and decay processes in the -decay are investigated
by a -two-meson hybrid model. The two-meson state consists of the
, , , and channels.
The energy-dependent decay widths of the and mesons are
introduced. The - interaction is taken to be consistent with a
lack of the bound state. The coupling between the
and or the and channels is obtained
from a quark model. The - coupling is taken as a
parameter to fit the (3872) mass. The spectrum is calculated up to 4 GeV.
It is found that very narrow and peaks appear
around the threshold. The size of the peak we
calculated is 1.29-2.38 times as large as that of the . The
isospin symmetry breaking in the present model comes from the mass difference
of the charged and neutral and mesons, which gives a sufficiently
large isospin mixing to explain the experiments. It is also found that values
of the ratios of the transfer strengths can give the information on the
(3872) mass or the size of the - coupling.Comment: 33 pages, 12 figure
Contribution of Instanton Induced Interaction for Penta-quarks in MIT Bag Model
Roles of instanton induced interactions (III) in the masses of pentaquark
baryons, Theta^+ (J=1/2 and 3/2) and Xi^{--}, and a dibaryon, H, are discussed
using the MIT bag model. It is shown that the two-body terms in III give a
strong attraction mainly due to the increase of the number of pairs in
multi-quark systems. In contrast, the three-body -- interaction is
repulsive. It is found that III lowers the mass of negative-parity Theta^+ as
much as 100 MeV from the mass predicted by the bag model without III.Comment: 4 pages, 2 figures, Talk given at International Workshop PENTAQUARK04
at SPring-8, Japan, July 20-23, 200
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