3,791 research outputs found
Pentaquarks
Since LEPS collaboration reported the first evidence of pentaquark
in early 2003, eleven other experimental groups have confirmed this exotic
state while many other groups didn't see any signal. If this state is further
established by future high statistical experiments, its discovery shall be one
of the most important events in hadron physics for the past three decades. This
exotic baryon with such a low mass and so narrow a width imposes a big
challenge to hadron theorists. Up to now, there have appeared more than two
hundred theoretical papers trying to interpret this charming state. I will
review some important theoretical developments on pentaquarks based on my
biased personal views.Comment: Review Commissioned by International Journal of Modern Physics
Pentaquark baryons in SU(3) quark model
We study the SU(3) group structure of pentaquark baryons which are made of
four quarks and one antiquark. The pentaquark baryons form {1}, {8}, {10},
{10}-bar, {27}, and {35} multiplets in SU(3) quark model. First, the flavor
wave functions of all the pentaquark baryons are constructed in SU(3) quark
model and then the flavor SU(3) symmetry relations for the interactions of the
pentaquarks with three-quark baryons and pentaquark baryons are obtained.Comment: REVTeX, 36 pages, 8 figures, references added, section for mass sum
rules is added, to appear in Phys. Rev.
A pentaquark model of the negative parity Lambda(1405)
We test a pentaquark model of the negative parity hyperon Lambda(1405). We
use the model where valence four quarks and one antiquark move in a potential
relativisticaly and interact with themselves and each other through gluon and
NG boson. We calculate mass shift of the system and find that there are two
Lambda(1405) with almost degenerate mass: one flavor singlet and one flavor
octet. We calclate also sigma-term and scalar form factor of the hyperon and
show their usefulness to deduce the number of valence quark in the hypeon.Comment: 4 pages, 1 figure, to appear in the proceedings of the Yukawa
International Seminar (YKIS) 2006, "New frontiers in QCD", Kyoto, Japa
Some (further) Comments on the Theta(1540) Pentaquark
Additional broader I=0 states in the KN channel near (1540) are
expected in many models, making the absence of any signature in the
K-deuteron scattering data even more puzzling.
In an ideal "three-body" picture the is viewed as two compact
ud(1)ud(2) color diquarks and an quark. A "QCD-type"
inequality involving , the mass of the L=1 excitation and that of a new I=0 tetraquark vector meson then follows.
The inequality suggests a very light new vector meson, and is violated.
We note that "associated production" of the pentaquark with another
quadriquark or anti-pentaquark may be favored. This along with some estimates
of the actual production cross sections suggest that the can be found
in BaBar or Belle e-e colliders.Comment: 6 page
Exotic hadrons from dynamical clustering of quarks in ultrarelativistic heavy ion collisions
Results from a model study on the formation of exotic quark clusters at the
hadronization stage of a heavy ion collision are presented. The dynamical quark
molecular dynamics (qMD) model which is used is sketched, and results for
exotica made of up to six (anti-)quarks are shown. The second part focuses on
pentaquarks. The rapidity distribution are shown, and the distribution of
strangeness is found to yield an indicator of thermalization and homogenisation
of the deconfined quark system. Relative Theta^+ yields are found to be lower
than thermal model estimates.Comment: 4 pages, 5 figures, to appear in the proceedings of Strangeness in
Quark Matter 2004 (SQM2004), Cape Town, South Africa, 15-20 September 200
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