11,582 research outputs found
Studies of exotic hadrons by high-energy exclusive reactions
We investigate the possibility of clarifying internal structure of exotic
hadrons by high-energy exclusive reactions. In particular, the
constituent-counting rule could be used for determining the internal
configuration in large-angle exclusive scattering. As an example, we show the
cross section pi^- + p -> K^0 + Lambda(1405) in comparison with the one for the
ground-state Lambda production pi^- + p -> K^0 + Lambda. The counting rule
indicates that the cross section scales as s^8 dsigma /dt=constant if
Lambda(1405) is an ordinary three-quark baryon, whereas it is s^{10} dsigma
/dt=constant if Lambda(1405) is a five-quark baryon. Here, s and t are
Mandelstam variables. Such experiments could be possible at J-PARC, LEP, JLab,
CERN-COMPASS, and other high-energy facilities.Comment: 4 pages, 7 figures, 12th Asia Pacific Physics Conference (APPC12),
JPS Conference Proceedings in pres
Internal structure of exotic hadrons by high-energy exclusive reactions
We propose to use high-energy exclusive reactions for probing internal
structure of exotic hadron candidates. First, the constituent counting rule of
perturbative QCD can be used for finding internal configurations of an exotic
hadron candidate. It is because the number of constituents (), which
participate in the exclusive reaction, is found by the scaling behavior of the
cross section at large momentum transfer, where
is the center-of-mass energy squared. As an example, we show that the
internal structure of should be found, for example, by the
reaction . Second, the internal structure
of exotic hadron candidates should be investigated by hadron tomography with
generalized parton distributions (GPDs) and generalized distribution amplitudes
(GDAs) in exclusive reactions. Exotic nature should be reflected in the GPDs
which contain two factors, longitudinal parton distributions as indicated by
the constituent counting rule and transverse form factors as suggested by the
hadron size. The GDAs should be investigated by the two-photon process
, for example or , in
electron-positron annihilation. Since the GDAs contain information on a
time-like form factor, exotic nature should be found by studying the
invariant mass dependence of the cross section. The internal structure of
exotic hadron candidates should be clarified by the exclusive reactions at
facilities such as J-PARC and KEKB.Comment: 6 pages, LaTeX, 9 eps files, JPS Conference Proceedings of the 2nd
International Symposium on Science at J-PARC (J-PARC 2014), Tsukuba, Japan,
July 12-15, 201
Ground-State Phase Diagram of Frustrated Anisotropic Quantum Spin Chains
Recent studies on the frustrated quantum spin chains with easy-plane
anisotropy are reviewed. We are particularly interested in novel "chiral"
phases characterized by the spontaneous breaking of the parity symmetry. The
ground-state phase diagrams of the chains are discussed.Comment: 6 pages (ptptex.sty), 3 figures, to appear in Prog. Theor. Phys.
Suppl. (Proc. of the 16th Nishinomiya-Yukawa Symposium and YITP International
Workshop, Nov. 2001
A Maximum Mass-to-Size Ratio in Scalar-Tensor Theories of Gravity
We derive a modified Buchdahl inequality for scalar-tensor theories of
gravity. In general relativity, Buchdahl has shown that the maximum value of
the mass-to-size ratio, , is 8/9 for static and spherically symmetric
stars under some physically reasonable assumptions. We formally apply
Buchdahl's method to scalar-tensor theories and obtain theory-independent
inequalities. After discussing the mass definition in scalar-tensor theories,
these inequalities are related to a theory-dependent maximum mass-to-size
ratio. We show that its value can exceed not only Buchdahl's limit, 8/9, but
also unity, which we call {\it the black hole limit}, in contrast to general
relativity. Next, we numerically examine the validity of the assumptions made
in deriving the inequalities and the applicability of our analytic results. We
find that the assumptions are mostly satisfied and that the mass-to-size ratio
exceeds both Buchdahl's limit and the black hole limit. However, we also find
that this ratio never exceeds Buchdahl's limit when we impose the further
condition, , on the density, , and pressure, , of the
matter.Comment: 23 pages, 13 figures and 1 tabl
Exotic-Hadron Signature by Constituent-Counting Rule in Perturbative QCD
We explain a method to find internal quark configurations of exotic hadron
candidates by using the constituent counting rule. The counting rule was
theoretically predicted in perturbative QCD for hard exclusive hadron
reactions, and it has been tested in experiments for stable hadrons including
compound systems of hadrons such as the deuteron, H, and He. It
indicates that the cross section scales as , where
is the center-of-mass energy squared and is the total number of
constituents. We apply this method for finding internal configurations of
exotic hadron candidates, especially . There is a possibility
that could be five-quark state or a molecule, and
scaling properties should be different between the ordinary three-quark state
or five-quark one. We predict such a difference in , and it could be experimentally tested, for example, at J-PARC. On the
other hand, there are already measurements for as well as the ground in photoproduction reactions. Analyzing
such data, we found an interesting indication that looks like
a five-quark state at medium energies and a three-quark one at high energies.
However, accurate higher-energy measurements are necessary for drawing a solid
conclusion, and it should be done at JLab by using the updated 12 GeV electron
beam. Furthermore, we discuss studies of exotic hadron candidates, such as and , in electron-positron annihilation by using generalized
distribution amplitudes and the counting rule. These studies should be possible
as a KEKB experiment.Comment: 6 pages, LaTeX, 10 eps files, to be published in JPS Conf. Proc.,
Proceedings of the 14th International Conference on Meson-Nucleon Physics and
the Structure of the Nucleon (MENU2016), July 25-30, 2016, Kyoto, Japa
Recommended from our members
Re-Analysis of HFT Data Using the Apollo Lunar Surface Gravimeter Data
Introduction: The Apollo Passive Seismic Experiment (PSE) was carried out on Apollo 12, 14, 15 and 16. Network observations of four seismic stations were performed for five years from 1972 to 1977. The PSE was a successful mission that informed us of the lunar crustal thickness and seismic velocity structure of the Moon from direct observations of the lunar interior (e.g. [1]). However, the paucity of seismic stations and the limited number of usable seismic events have been a major problem of lunar seismology. An additional observation point enables us to expand the network and the observable area will expand accordingly. Using a data set called the Work Tape, Kawamura et al. (2008) [2] showed that the Lunar Surface Gravimeter (LSG) on Apollo 17 functioned as a seismograph.
With this additional seismic station, we tried the first seismic analysis using the LSG data
Spin and chiral orderings of frustrated quantum spin chains
Ordering of frustrated S=1/2 and 1 XY and Heisenberg spin chains with the
competing nearest- and next-nearest-neighbor antiferromagnetic couplings is
studied by exact diagonalization and density-matrix renormalization-group
methods. It is found that the S=1 XY chain exhibits both gapless and gapped
`chiral' phases characterized by the spontaneous breaking of parity, in which
the long-range order parameter is a chirality, , whereas the spin correlation decays either
algebraically or exponentially. Such chiral phases are not realized in the
S=1/2 XY chain nor in the Heisenberg chains.Comment: 4 pages, 5 EPS-figures, LaTeX(RevTeX),to appear in J.Phys.Soc.Japa
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