249 research outputs found
Exotic mesons with hidden charm and bottom near thresholds
We study heavy hadron spectroscopy near heavy meson thresholds. We employ
heavy pseudoscalar meson P and heavy vector meson P* as effective degrees of
freedom and consider meson exchange potentials between them. All possible
composite states which can be constructed from the P and P* mesons are studied
up to the total angular momentum J <= 2. We consider, as exotic states,
isosinglet states with exotic J^{PC} quantum numbers and isotriplet states. We
solve numerically the Schr\"odinger equation with channel-couplings for each
state. We found B(*)barB(*) molecule states for I^G(J^{PC}) = 1^+(1^{+-})
correspond to the masses of twin resonances Zb(10610) and Zb(10650). We predict
several possible B(*)barB(*) bound and/or resonant states in other channels. On
the other hand, there are no B(*)barB(*) bound and/or resonant states whose
quantum numbers are exotic.Comment: 10 pages, 1 figure, to appear in the proceedings of The 5th
International Workshop on Charm Physics (Charm 2012
Exotic mesons with double charm and bottom flavor
We study exotic mesons with double charm and bottom flavor, whose quark
configuration is \bar{Q}\bar{Q}qq. This quark configuration has no annihilation
process of quark and antiquark, and hence is a genuinely exotic states. We take
a hadronic picture by considering the molecular states composed of a pair of
heavy mesons, such as DD, DD* and D*D* for charm flavor, and BB, BB* and B*B*
for bottom flavor. The interactions between heavy mesons are derived from the
heavy quark effective theory. All molecular states are classified by I(J^P)
quantum numbers, and are systematically studied up to the total angular
momentum J \leq 2. By solving the coupled channel Schrodinger equations, due to
the strong tensor force of one pion exchanging, we find bound and/or resonant
states of various quantum numbers.Comment: 24 pages, 3 figure
and mesons in nuclear medium
We discuss the mass modifications of and
( and ) mesons in
nuclear medium. The heavy quark symmetry for and
( and ) mesons is
adopted, and the interaction between a or
( or ) meson and a
nucleon is supplied from the pion exchange. We find the negative mass shifts
for meson and meson, and hence that the
and mesons are bound in the nuclear medium. As
applications, we consider the atomic nuclei with a meson,
and
, and investigate the energy levels of
the meson in each nucleus. We also discuss the mass shifts
in the isospin asymmetric nuclear medium, and present the possible phenomenon
about distribution of isospin density around a or
meson in nuclear medium. We find that the mass shifts of
and mesons have large imaginary
parts, which would prevent precise study of the energy levels of
and mesons in nuclei.Comment: 21 pages, 9 figure
Polarized Parton Distribution in Neutrino Induced Heavy Flavor Production
In order to examine polarized strange quark distribution, semi-inclusive
D/\Dbar production in neutrino deep inelastic scattering is studied including
corrections. Cross section and spin asymmetry are
calculated by using various parametrizations of polarized parton distribution
functions. It is found that \Dbar production is promising to directly extract
the polarized strange sea.Comment: 3 pages, 2 figures. Talk given at the NuFact02 workshop, London, UK,
July 1-6, 200
Spin degeneracy in multi-hadron systems with a heavy quark
We study multi-hadron systems with a single heavy quark (charm or bottom) in
the limit of heavy quark mass. The spin degeneracy of the states with quantum
numbers and for , known in a normal
hadron, can be generalized to multi-hadron systems. The spin degeneracy is the
universal phenomena for any multi-hadron systems with a single heavy quark,
irrespective of their internal structures, including compact multi-quarks,
hadronic molecules and exotic nuclei. We demonstrate the spin degeneracy in the
hadronic systems formed by a heavy hadron effective theory;
states with a , meson and a nucleon
, and a meson in nuclear matter.Comment: 9 pages, 1 figur
Effect of polarized gluon distribution on spin asymmetries for neutral and charged pion production
A longitudinal double spin asymmetry for \pi^0 production has been measured
by the PHENIX collaboration. The asymmetry is sensitive to the polarized gluon
distribution and is indicated to be positive by theoretical predictions. We
study a correlation between behavior of the asymmetry and polarized gluon
distribution in neutral and charged pion production at RHIC.Comment: 7 pages, 5 eps figures, section added, typos corrected. to be
published in PR
Homologous and heterologous desensitization of guanylyl cyclase-B signaling in GH3 somatolactotropes
The guanylyl cyclases, GC-A and GC-B, are selective receptors for atrial and C-type natriuretic peptides (ANP and CNP, respectively). In the anterior pituitary, CNP and GC-B are major regulators of cGMP production in gonadotropes and yet mouse models of disrupted CNP and GC-B indicate a potential role in growth hormone secretion. In the current study, we investigate the molecular and pharmacological properties of the CNP/GC-B system in somatotrope lineage cells. Primary rat pituitary and GH3 somatolactotropes expressed functional GC-A and GC-B receptors that had similar EC50 properties in terms of cGMP production. Interestingly, GC-B signaling underwent rapid homologous desensitization in a protein phosphatase 2A (PP2A)-dependent manner. Chronic exposure to either CNP or ANP caused a significant down-regulation of both GC-A- and GC-B-dependent cGMP accumulation in a ligand-specific manner. However, this down-regulation was not accompanied by alterations in the sub-cellular localization of these receptors. Heterologous desensitization of GC-B signaling occurred in GH3 cells following exposure to either sphingosine-1-phosphate or thyrotrophin-releasing hormone (TRH). This heterologous desensitization was protein kinase C (PKC)-dependent, as pre-treatment with GF109203X prevented the effect of TRH on CNP/GC-B signaling. Collectively, these data indicate common and distinct properties of particulate guanylyl cyclase receptors in somatotropes and reveal that independent mechanisms of homologous and heterologous desensitization occur involving either PP2A or PKC. Guanylyl cyclase receptors thus represent potential novel therapeutic targets for treating growth-hormone-associated disorders
Two-Spin Asymmetry for Photoproduction with Color-Octet Mechanism
We studied the photoproduction of in the forward regions in
polarized collisions at relevant HERA energies. We found that this
reaction is very effective to test the color-octet mechanism which is based on
the NRQCD factorization formalism. Furthermore we found that the value of the
NRQCD matrix elements can be severely constrained by measuring the two-spin
asymmetry, though the process depends on the polarized gluon distribution
.Comment: 8 pages including 4 eps-figures, use epsfig.tex, Late
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