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Article type: Cover
2006 Volume 114 Issue 2 Pages
Cover1-
Published: November 20, 2006
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Article type: Appendix
2006 Volume 114 Issue 2 Pages
App1-
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Article type: Appendix
2006 Volume 114 Issue 2 Pages
B1-B5
Published: November 20, 2006
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Tetsuo Hatsuda
Article type: Article
2006 Volume 114 Issue 2 Pages
B6-
Published: November 20, 2006
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S. Yokkaichi, J. Chiba, H. En'yo, Y. Fukao, H. Funahashi, H. Hama ...
Article type: Article
2006 Volume 114 Issue 2 Pages
B7-B12
Published: November 20, 2006
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Invariant mass spectra of low-mass vector mesons in the e^+e^- channel are measured in 12 GeV p+C and p+Cu reactions (√<s>=5.1 GeV) at the KEK 12 GeV Proton Synchrotron. A significant excess is observed on the low-mass side of the ω meson peak over the known hadronic sources in the data of both C and Cu targets. Furthermore, an excess is found below the φ meson peak in the Cu target data in the slowest βγ region (βγ<1.25). They can be interpreted as signatures of the spectral modification of vector mesons in cold nuclear matter.
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D. Jido
Article type: Article
2006 Volume 114 Issue 2 Pages
B13-B15
Published: November 20, 2006
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In the first part of this talk, the partial restoration of chiral symmetry in nuclear medium was investigated in a model independent way at low density by exploiting the PCAC relation and the current algebra in QCD. In the second part of this talk, chiral symmetry for baryons is discussed.
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Tae-Sun Park
Article type: Article
2006 Volume 114 Issue 2 Pages
B16-B20
Published: November 20, 2006
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The pion decay constants in isospin symmetric nuclear matter have been calculated up to two-loop accuracy (or up to N^4LO) using chiral perturbation theory. The two-loop order contributions are found to be negligible and cannot cure the problematic one-loop prediction of having negative f^s_π for p≲0.8 p_0. Possible ways of overcoming this problem have also been discussed.
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Yoshimasa Hidaka, Osamu Morimatsu, Munehisa Ohtani
Article type: Article
2006 Volume 114 Issue 2 Pages
B21-B26
Published: November 20, 2006
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We study possible chiral symmetry restoration patterns in a generalized hidden local symmetry model, including pseudo-scalar, vector and axial-vector mesons. We find three types of the chiral restoration, which are classified as the standard, vector manifestation and intermediate scenarios, respectively. The rho and A_1 meson become massless in all the restoration patterns. These three scenarios are different in the violation of the vector meson dominance, which will be reflected on the pion background in the spectrum of dilepton decay from the vector meson.
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Su Houng Lee
Article type: Article
2006 Volume 114 Issue 2 Pages
B27-B31
Published: November 20, 2006
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We report on the quarkonium dissociation cross section in perturbative QCD at the NLO. While the NLO corrections are large in the vacuum, the corrections become mild at finite temperature due to the thermal mass of several hundred MeV acquired by the partons.
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Wei-min Sun, Hong-shi Zong, Fan Wang
Article type: Article
2006 Volume 114 Issue 2 Pages
B32-B38
Published: November 20, 2006
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By adopting the background field method, the response of the dressed quark propagator to the presence of finite chemical potential is analyzed up to second order. From this we obtain a model-independent formula for the chemical potential dependence (up to second order) of the in-medium two-quark condensate and show by both Lorentz covariance arguments and explicit calculations that the O(μ) contribution to the in-medium two-quark condensate vanishes identically.
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Setsuo Tamenaga, Hiroshi Toki, Akihiro Haga, Yoko Ogawa
Article type: Article
2006 Volume 114 Issue 2 Pages
B39-B44
Published: November 20, 2006
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We study the effect of one-loop corrections from nucleon together with those from boson in the massless chiral sigma model, where we perform the Coleman-Weinberg renormalization procedure[1, 2]. We find that the renormalization scale plays an important role for the breaking of the symmetry between fermion (nucleon) and boson, and eventually for the chiral symmetry at the same time. In addition, we find that the naturalness restores by means of the introduction of the vacuum fluctuation from both nucleon and boson. Finally we obtain a stable effective potential with the effect of Dirac sea in the chiral model for the first time.
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Shinji Ejiri
Article type: Article
2006 Volume 114 Issue 2 Pages
B45-B47
Published: November 20, 2006
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We will review the recent studies of the QCD phase structure by numerical simulations in the low density region. It is important to investigate the phase structure and the equation of state of QCD in the low density regime which is interesting for heavy-ion collision experiments. The studies of the phase structure and the equation of state can provide basic input for the analysis of the experimental signatures for QGP formation. In the last several years, remarkable progress in exploring the QCD phase structure in the temperature (T) and quark chemical potential (μ_q) plane have been made in numerical studies of lattice QCD. The phase transition line, separating hadron phase and quark-gluon plasma phase, was investigated from μq=0 to finite μ_q [1, 2, 3, 4, 5], and the equation of state was also analyzed quantitatively at low density [3, 6]. Moreover the study of the endpoint of first order phase transition line in the (T, μ_q) plane, whose existence is suggested by phenomenological studies [7, 8], is particularly interesting both from the experimental and theoretical points of view. To find this endpoint, event by event fluctuations have been measured in heavy ion collisions. In this report, we review recent progress of lattice QCD simulations, highlighting the study of the critical endpoint in the (T,μ_q) plane. The lattice QCD at nonzero baryon density is known to have a serious problem called "sign problem", however this problem is not very serious for the studies in the low density region, and interesting results have been gradually obtained using the following approaches.
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A. Tawfik
Article type: Article
2006 Volume 114 Issue 2 Pages
B48-B50
Published: November 20, 2006
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Screening masses of different hadronic states are studied in thermal and dense medium on lattice. It has been found that screening masses increase with the temperature. In deconfinement phase, chemical potential enhances the screening masses. We use the normalization with respect to lowest Matsubara frequency to characterize dissolving of hadronic bound states at high temperatures. It has been found that different hadronic states have different dissolving temperatures and their survivals are considerably improved at finite chemical potentials.
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Chang-Hwan Lee
Article type: Article
2006 Volume 114 Issue 2 Pages
B51-B55
Published: November 20, 2006
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Based on the renormalization group arguments of the vector manifestation of Harada-Yamawaki hidden local symmetry theory, we obtain a surprisingly simple description of kaon condensation by fluctuating around the "vector manifestation (VM)" fixed point identified to be the chiral restoration point. Our development establishes that the critical density for strangeness condensation is lower than the chiral symmetry restoration density. This result depends only on the renoramlization-group (RG) behavior of the vector interactions. Other effects involved in fluctuating about the bare vacuum are "irrelevant" in the RG about the fixed point. Our results have major effects on the collapse of neutron stars into black holes.
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A. Ohnishi, N. Kawamoto, K. Miura, T. Ohnuma, T. Tsubakihara
Article type: Article
2006 Volume 114 Issue 2 Pages
B56-B59
Published: November 20, 2006
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We study the properties of kigh density hadronic and quark matter in fundamental and phenomenological approaches. First we discuss the phase diagram of quark matter at finite temperature (T) and chemical potential (μ) in the strong coupling limit of lattice QCD for color SU(3) with baryon effects. In an analytically derived expression of the effective free energy as a function of T and μ, baryon effects are shown to extend the hadron phase to a larger chemical potential direction at low temperatures. Next we apply the idea from the strong coupling limit of lattice QCD to the chiral potential in RMF. By introducing logarithmic sigma potential, we can well describe both of the nuclear matter and finite nuclei in a chiral RMF model.
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Takumi Muto
Article type: Article
2006 Volume 114 Issue 2 Pages
B60-B65
Published: November 20, 2006
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Possible coexistence of kaon condensation and hyperons in high-density matter in neutron stars are reexamined, by the use of the effective chiral Lagrangian for the kaon-baryon interactions and the nonrelativistic baryon-baryon interaction model. It is shown that a critical density of K^- condensation, obtained based on the usual continuous phase transition, does not always give a correct ground state in the presence of the negatively charged hyperons (Σ^-). We also discuss the equation of state of the kaon-condensed phase in hyperonic matter. We suggest a possible existence of self-bound objects, the whole part of which is composed of high-density matter with kaon condensates.
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C. H. Hyun, C. Y. Ryu, S. W. Hong
Article type: Article
2006 Volume 114 Issue 2 Pages
B66-B71
Published: November 20, 2006
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In the framework of the modified quark-meson coupling model, we calculate the composition of the neutron star matter with octet baryons and negative charge kaon K^-. We focus on the magnitude of the kaon-nucleus optical potential, which is closely related to the strength of the interaction of the kaon with the nuclear matter of the neutron star. It is found that the onset of the kaon condensation is sensitive to the value of the kaon optical potential, and it can lead to quite a different state of matter at high densities.
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S. Yasui, A. Hosaka
Article type: Article
2006 Volume 114 Issue 2 Pages
B72-B76
Published: November 20, 2006
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We discuss chiral symmetry breaking and stability of strangelets. In order to consider the dynamical chiral symmetry breaking, we use the Nambu-Jona-Lasinio interaction for quarks confined in a chiral bag. As a vacuum polarization for massive quarks in the chiral bag, we discuss the baryon number conservation and chiral Casimir energy. We investigate the energy of the quark droplets with baryon numbers A≤5.
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T. Hyodo, Sourav Sarkar, A. Hosaka, E. Oset
Article type: Article
2006 Volume 114 Issue 2 Pages
B77-B82
Published: November 20, 2006
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We study the coupling of the Λ(1520)≡Λ* resonance to the K* vector meson and nucleon. This coupling is not directly measured from the resonance decay, but is expected to be important in hyperon production reactions. We compute the coupling in two different schemes, one in the chiral unitary model where the Λ* is dominated by the quasibound state of mesons and baryons, and the other in the quark model where the resonance is a p-wave excitation in the three valence quarks. It is found that there is a significant difference between the Λ*K*N couplings in the two models. In the chiral unitary model |gΛ*K*N|〜1.5, while in the quark model |gΛ*K*N|〜2.5. The difference of the results stems from the different structure of the Λ* in both models, and hence, an experimental determination of this coupling would shed light on the nature of the resonance.
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Masakiyo Kitazawa
Article type: Article
2006 Volume 114 Issue 2 Pages
B83-B86
Published: November 20, 2006
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Seung-il Nam, Hyun-Chul Kim
Article type: Article
2006 Volume 114 Issue 2 Pages
B87-B92
Published: November 20, 2006
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We investigate the effects of flavor SU(3)-symmetry breaking on the QCD condensates, based on the nonlocal effective chiral action from the instanton vacuum, focusing on the quark-gluon mixed one. We employ two different parameterizations for the dependence of the momentum-dependent dynamical quark mass on the strange current quark mass. We obtain the ratios of the mixed condensates: [numerical formula] It turns out that the dimensional parameter [numerical formula].
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Yu-xin Liu, Lei Chang, Bin Wang, Wei Yuan, Huan Chen
Article type: Article
2006 Volume 114 Issue 2 Pages
B93-B98
Published: November 20, 2006
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We discuss the chiral phase transition and the quark deconfinement phase transition in strong interaction matter in the Dyson-Schwinger equation approach of QCD in this report. It shows that, with a sophisticated effective gluon propagator, the Dyson-Schwinger Equation approach in the "rainbow" approximation can describe the density dependence of the QCD phase transitions well.
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Hideko Nagahiro
Article type: Article
2006 Volume 114 Issue 2 Pages
B99-B102
Published: November 20, 2006
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We calculate the formation spectra of mesic nuclei in order to investigate the meson properties at finite density. The properties of η-nucleus interaction reflect the behavior of the N*(1535) resonance in the nuclear medium. We study also η'(958)-mesic nuclei in order to study the U_A(1) anomaly effect in finite density. We find that we can deduce information on the QCD symmetries in finite density by investigating formation of mesic nuclei by (d,^3He) and (γ,p) reactions. This presentation is based on our studies in Refs. [1, 2].
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Shung-ichi Ando
Article type: Article
2006 Volume 114 Issue 2 Pages
B103-B108
Published: November 20, 2006
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In this talk, we review our resent work on pionless effective field theory with di-baryon fields for observables involving the deuteron[1]. We discuss our results on the deuteron electromagnetic form factors and ed→ed process.
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Toshimitsu Yamazaki, Yoshinori Akaishi
Article type: Article
2006 Volume 114 Issue 2 Pages
B109-B114
Published: November 20, 2006
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We examine the recent interpretations of stopped-K^- experimental data of KEK and FINUDA by Oset and Toki and by Magas, Oset, Ramos and Toki, by calculating the particle emission spectra and invariant-mass spectra realistically. We point out that their incorrect theoretical treatments result in disagreements with existing experimental data. We conclude that the FINUDA assignment of a 2250 MeV/c^2 peak in the invariant-mass spectrum of Λ-p to a predicted K^-pp bound state is plausible.
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E. Oset, V. K. Magas, A. Ramos, H. Toki
Article type: Article
2006 Volume 114 Issue 2 Pages
B115-B120
Published: November 20, 2006
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Junko Yamagata, Hideko Nagahiro, Satoru Hirenzaki
Article type: Article
2006 Volume 114 Issue 2 Pages
B121-B126
Published: November 20, 2006
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Article type: Appendix
2006 Volume 114 Issue 2 Pages
App2-
Published: November 20, 2006
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Article type: Appendix
2006 Volume 114 Issue 2 Pages
App3-
Published: November 20, 2006
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Article type: Cover
2006 Volume 114 Issue 2 Pages
Cover2-
Published: November 20, 2006
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Article type: Cover
2006 Volume 114 Issue 2 Pages
Cover3-
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