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 ($n$), which participate in the exclusive reaction, is found by the scaling behavior of the cross section $d\sigma/dt \propto 1/s^{n-2}$ at large momentum transfer, where $s$ is the center-of-mass energy squared. As an example, we show that the internal structure of $\Lambda \, (1405)$ should be found, for example, by the reaction $\pi^- + p \to K^0 + \Lambda (1405)$. 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 $\gamma^* \gamma \to h\bar h$, for example $h=f_0$ or $a_0$, in electron-positron annihilation. Since the GDAs contain information on a time-like form factor, exotic nature should be found by studying the $h\bar h$ 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, $2M/R$, 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, $\rho-3p\ge0$, on the density, $\rho$, and pressure, $p$, 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, $^3$H, and $^3$He. It indicates that the cross section scales as $d\sigma /dt \sim 1/s^{n-2}$, where $s$ is the center-of-mass energy squared and $n$ is the total number of constituents. We apply this method for finding internal configurations of exotic hadron candidates, especially $\Lambda (1405)$. There is a possibility that $\Lambda (1405)$ could be five-quark state or a $\bar K N$ molecule, and scaling properties should be different between the ordinary three-quark state or five-quark one. We predict such a difference in $\pi^- + p \to K^0 + \Lambda (1405)$, and it could be experimentally tested, for example, at J-PARC. On the other hand, there are already measurements for $\gamma + p \to K^+ + \Lambda (1405)$ as well as the ground $\Lambda$ in photoproduction reactions. Analyzing such data, we found an interesting indication that $\Lambda (1405)$ 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 $f_0 (980)$ and $a_0 (980)$, 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

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, $\kappa_i = S_i^xS_{i+1}^y-S_i^yS_{i+1}^x$, 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