10122460
First order phase transition in quark matter
We investigate chiral phase transition of the first order in the quark matter. Using the Nambu-Jona-Lasinio model, an equation of state of the quark matter which is similar to the van der Waals's one is obtained. Moreover the specific heat and the compressibility are calculated. It is shown that they are enhanced in the symmetry broken phase, in particular, diverge near the tricritical point.
118969678
Tetraquark particle in the string model
We discuss the possibility of the existence of tetraquark states made of four quarks in the string (flux tube) model. The new particle is composed of a diquark and an antidiquark which are connected by a color flux. It is shown that the vibrational and rotational excited states of the string explain some non-qq mesons observed experimentally. Moreover we discuss the decay widths of such tetraquarks with the use of the Schwinger mechanism.
117897053
Shear viscosity and spectral function of the quark matter
We discuss the shear viscosity of the quark matter by using the Kubo-Mori formula. It is found that the shear viscosity is expressed in terms of the quark spectral function. If the spectral function is approximated by a modified Bright-Wigner type, the viscosity decreases as the width of the spectral function increases. We also discuss dependence of the shear viscosity on the temperature and the density.
119408373
Fluctuation modes in color-superconductors
We investigate fluctuation effects of a gap parameter in color-superconductors. The fluctuation modes in the super phase are described by two scalar fields of diquarks. One of them is a Nambu-Goldstone boson and the other is a diquark boson whose mass is about twice of the gap energy (an extended quasi-supersymmetry). In the normal phase the fluctuation becomes a precursory (soft) mode whose amplitude increases near the critical temperature.
120691222
Superconductivity of Quark Matter at Finite Temperature
123223657
A Vibrational Bag Model for Baryons
Surface monopole vibration of baryons is investigated on the basis of the soliton bag model. We derive a relativistic Lagrangian for the surface motion whose mass parameter is proportional to square of the bag radius. With the use of the WKB approximation, the energy spectra of Pl1 and F" resonances are reproduced by our model fairly well. The static properties of the nucleon are alsO studied in our vibrational bag model and compared with those of the static bag model. Our model predicts that the nucleon consists of the central high·density part and the surrounding low-density part. It is also shown that our model is capable to predict the experimental data as well as the static bag model.
122256238
Kaonic hydrogen X-ray experiment at KEK
Abstract For the further understanding of the K -N interaction in the low energy region, we are performing a measurement of K − p X rays at KEK which adopts a new technique to improve the signal-to-background ratio (S/N); specifying the final state of the K − p reaction and using a gaseous hydrogen target (4 atm at 100 K). With this technique three orders of magnitude better S/N and one order higher statistics are expected as compared to previous experiments.
123694791
A Search for $\phi $ Meson Nucleus Bound State Using Antiproton Annihilation on Nucleus
119456897
Spectroscopy of hypernuclei with stopped kaons — recent result of KEK experiment
Abstract Pion momentum spectra from K − absorption at rest on various nuclear targets were measured by means of a magnetic spectrometer with wide momentum range (100 ∼ 300 MeV/c). The ground state of Σ − hypernucleus, if well bound with a narrow width, is expected to be populated in 12 C(stopped K − , π + ) inclusive (untagged) spectrum, but such a peak was not observed. The spectrum is compared with the DWIA calculations by Morimatsu and Yazaki, indicating that the depth of the nuclear potential of Σ − is shallower than 12 MeV, and that its imaginary part is larger than 5 MeV if the potential depth is about 10 MeV. In the 12 C(stopped K − , π − ) spectrum, the ground state (( p 3 2 ) n −1 ( s 1 2 )Λ) and the excited states (( p3 2 ) n −1 ( p )Λ) of Λ 12 C were observed, and their formation probabilities were roughly in agreement with the results of DWIA calculations. In the π − spectra on 12 C, 9 Be, and 7 Li targets a distinct peak was observed at 132.1±0.7 MeV/c. It is ascribed to π − from the mesic decay of Λ 4 H; Λ 4 H → 4 He π − . The formation probability of Λ 4 H on C, Be, or Li target is much larger than those of the discrete states of Λ 12 C via the direct (stopped K − , π − ) reaction.
15085801
Search for a kaonic nuclear state via 4He(K−, N) reaction at rest
Very recently, we have performed a couple of experiments, KEK PS-E549/E570, for the detailed study of the strange tribaryon S 0(3115) obtained in KEK PS-E471. These experiments were performed to accumulate much higher statistics with improved experimental apparatus especially for the better proton spectroscopy of the 4He(stopped K −, N) reaction. In contrast to the previous proton spectrum, no narrow (∼ 20 MeV) peak structure was found either in the inclusive 4He(stopped K −, p) or in the semi-inclusive 4He(stopped K −, pX ±) reaction channel, which is equivalent to the previous E471 event trigger condition. Detailed analysis of the present data and simulation shows that the peak, corresponding to S 0(3115), has been an experimental artifact. Present analysis does not exclude the possible existence of a much wider structure. To be sensitive to such structure and for better understanding of the non-mesonic K − absorption reaction channel, detailed analysis of the data is in progress.
16314864
Electron identification using the TOPAZ detector at TRISTAN
Abstract We present an electron-identification method using the time-projection chamber and the lead-glass calorimeter in the TOPAZ detector system. Using this method we have achieved good electron identification against hadron backgrounds over a wide momentum range in the hadronic events produced by both single-photon exchange and two-photon processes. Pion-rejection factors and electron efficiencies were 163 and 68.4% for high- P T electrons and 137 and 42.7% for low- P T electrons in the single-photon-exchange process, and 8600 and 36.0% for the two-photon process, respectively.