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Article type: Cover
2001 Volume 102 Issue 5 Pages
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Published: February 20, 2001
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
App1-
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
E1-E4
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
E5-
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Teiji KUNIHIRO
Article type: Article
2001 Volume 102 Issue 5 Pages
E6-E13
Published: February 20, 2001
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We first review the recent accumulating evidences of the existence of a scalar-isoscalar meson with the mass 500 to 800 MeV which may be identified with the sigma meson as the quantum fluctuation of the amplitude of the chiral order parameter <q^^-q>. We indicate that phase shift analyses which respect chiral symmetry (ChS ), analyticity and crossing symmetry of the scattering amplitude show the sigma meson pole in the s-channel as well as the ρ meson pole in the t-channel in the π-π scattering in the I = J = 0 channel. We emphasize that the existence of the σ resonance does not contradict with the success of the chiral perturbation theory; phenomenological difficulties with the renormalizable linear sigma model do not necessarily deny the validity of the linear representation of ChS of QCD as given by the NJL-like models which not only admit the σ resonance but also reproduce the coupling constants L_i and H_i appearing the nonlinear chiral lagrangian. We give some examples of the hadronic phenomena which are naturally accounted for with the σ meson. We show that the the σ meson as the amplitude fluctuation of the chiral order parameter may be more clearly identified than in free space in hot and/or dense matter, even in finite nuclei where partial restoration of ChS may be realized.
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Shoji SAWADA
Article type: Article
2001 Volume 102 Issue 5 Pages
E14-E19
Published: February 20, 2001
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In the early sixties, from analyses of nuclear force by the one-boson-exchange model which is a model of strong reaction based on the composite theory of hadrons, a scalar meson with I = 0 had been required. This talk reviews the motivation of the one-boson-exchange models, analyses of nuclear force in terms of one-boson-exchange models, mass and coupling constant of scalar meson, and finally presents a viewpoint for the scalar meson based on the QCD.
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Ryozo TAMAGAKI
Article type: Article
2001 Volume 102 Issue 5 Pages
E20-E25
Published: February 20, 2001
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Remarks are given as to a long-standing problem in nuclear physics, whether the sigma-meson is a real meson resonance or a substitute for the two-pion exchange effects with I = 0, J^P = 0^+ via the excitation from the octet to the decuplet baryons. Relevance of the ΛΛ ^1S_0 interaction to this problem is noted in connection with the binding of the double hypernuclei.
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Shin ISHIDA, Muneyuki ISHIDA
Article type: Article
2001 Volume 102 Issue 5 Pages
E26-E31
Published: February 20, 2001
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It is stated that the requirement of unitarity and of analyticity should be made on the S-matrix elements with right bases, and the "universality argument" made with the bases, which do not regard quark physical picture, is not right. Accordingly the result of the conventional analyses of the ππ production amplitudes following to this argument, leading to non-existence of the light σ-meson, is proved to lose its theoretical bases.
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
E32-
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Jose Antonio OLLER
Article type: Article
2001 Volume 102 Issue 5 Pages
E33-E40
Published: February 20, 2001
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It is the purpose of the present manuscript to emphasize those aspects that make the scalar sector with vacuum quantum numbers rather unique. Chiral symmetry is the basic tool for our study together with a resummation of Chiral Perturbation Theory (CHPT) that stresses the role of unitarity but also allows one to include explicit resonance fields and to match with the CHPT expansion at low energies.
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Robert KAMINSKI
Article type: Article
2001 Volume 102 Issue 5 Pages
E41-E45
Published: February 20, 2001
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The ππ interaction amplitudes have been calculated using a three coupled channel model both with and without constraints imposed by chiral models. Roy's equations have been used to compare the amplitudes and to study the role played by chiral constraints in the ππ interaction.
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Masayasu HARADA, J. Schechter, F. Sannino
Article type: Article
2001 Volume 102 Issue 5 Pages
E46-E51
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In this talk I summarize recently proposed mechanisms to understand ππ scattering to 1 GeV in an effective chiral Lagrangian. The Lagrangian includes higher resonances in addition to pions consistently with the chiral symmetry. Iso-spin zero S-wave partial wave amplitude is reproduced up till about 1.2 GeV by including a pion self-interaction and resonant pole exchanges of ρ, f_0(980) and σ derived from the effective chiral Lagrangian. The best fit shows that σ has a mass of around 560 MeV and a width of about 370 MeV.
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Kunio TAKAMATSU, M.Y. Ishida, S. Ishida, T. Ishida, T. Komada, A.M. Ma ...
Article type: Article
2001 Volume 102 Issue 5 Pages
E52-E57
Published: February 20, 2001
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The evidences for σ(600) and κ(900) observed in our analyses on the ππ and K_π scattering phase shift data are described, briefly. The analysis have been performed by the interfering amplitude method, which satisfies the unitarity requirement, using physically meaningful parameters. The introduction of the negative phase shifts (repulsive force) are essential in the analysis. New data for the π^0π^0 scattering amplitudes and the I=0 S wave phase shifts are presented. The data have been obtained in the π^-p charge exchange reaction, π^-p → π^0π^0n at 9 GeV by the E135 experiment at the KEK PS. The amplitude analysis are performed. The behavior of the I=0 S wave phase shifts below KK^^- threshold are consistent with those of the π^+π^-, so called, standard data and those of the down-flat solution of the CEBN-Cracow-Munich polarization data. The analysis of the π^0π^0 phase shift data observes σ(600) with the B-W parameters, M_σ= 588 ± 12 MeV and Γ_σ= 281 ± 25 MeV, which are in good agreement with those in our analysis on the π^+π^- data.
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Muneyuki ISHIDA
Article type: Article
2001 Volume 102 Issue 5 Pages
E58-E62
Published: February 20, 2001
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The phenomenologically observed property of σ(600) in our recent analyses of various ππ-scattering and -production processes is reviewed and compared with the prediction of SU(2) linear σ model. Furthermore, a possibility of the scalar σ-nonet (σ(600), κ(900), f_0(980) and a_0(980)) forming with the pseudoscalar π-nonet a linear representation of SU(3) chiral symmetry is investigated. The origin of repulsive background phase shift δ_<BG>, which is essential to lead us to the σ-existence in our phase shift analysis, is shown to come from the repulsive λφ^4 interaction.
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Evgeny SHABALIN
Article type: Article
2001 Volume 102 Issue 5 Pages
E63-E66
Published: February 20, 2001
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Using the principle of the most conformity of the QCD and real world objects we argue that σ-meson and other q^^-q scalar mesons are the natural elements of the Chiral Theory. An existance of the light isoscalar σ-meson allows to understand many interesting features of K-decays. In ππ scattering, σ exchange gives the main contribution into phase shifts at energy near threshold and together with intermediate spin 1 and spin 2 resonances allows to obtain a good description of the phase shifts δ^0_0(s), δ^2_0(s), δ^1_1(s), δ^0_2(s) andδ^2_2(s) for √<s> ≦ 1 GeV.
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Tetsuo SAWADA
Article type: Article
2001 Volume 102 Issue 5 Pages
E67-E72
Published: February 20, 2001
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In order to examine the existence of the strong Van der Waals interaction acting between hadrons in addition to the ordinary forces arising from the exchanges of the mesons, the phase shift data of the pion-pion scattering are analysed. Large deviation of the P-wave amplitude from the predictions of Roy's equations indicates the extra long range force between pions. The parameters of such a long range force are determined from the P-wave data. It is also shown that the consistency of the curvatures of the S-wave amplitude of I=0 state in Roy's equations is recovered if we add the extra long range force with the strength fixed by the analysis of the P-wave.
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Mitsuaki OBU
Article type: Article
2001 Volume 102 Issue 5 Pages
E73-E78
Published: February 20, 2001
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A simple hamiltonian model for ππ scattering and production is presented which incorporates resonant and background interactions. Analysis of isoscalar S wave ππ phase shift indicates that the background interaction plays only a minor role and the σ may be a dynamical resonance which is not originated from a corresponding bare state.
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Keiji IGI, Ken-ichi HIKASA
Article type: Article
2001 Volume 102 Issue 5 Pages
E79-E84
Published: February 20, 2001
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
E85-
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Tsuneaki TSURU, M.Y. Ishida, S. Ishida, T. Ishida, T. Komada, A.M. Ma, ...
Article type: Article
2001 Volume 102 Issue 5 Pages
E86-E91
Published: February 20, 2001
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A brief review is given on the ππ system below 1 GeV reported in production processes of pp central production, J/Ψ decay and D decay. It can be said that an isoscalar scalar state exists in the mass range between 400 and 700 Mev.
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Masaaki KOBAYASHI, T. TSURU, K. TAKAMATSU, S. ISHIDA, T. KOMADA, A. WA ...
Article type: Article
2001 Volume 102 Issue 5 Pages
E92-E97
Published: February 20, 2001
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The data on the π^-p → M^0n, with M^0 = π^0π^0π^0 orπ^0π^0η obtained in the GAMS experiment may be useful to study the σ(400 〜 700) and a^χ_1(〜1000), which can be taken as chiral partners of π and ρ, respectively. A preliminary analysis for 3π^0 invariant mass spectra gives a support for the assumed a^χ_1 with a mass of 〜 930MeV and Γ 〜 170MeV.
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Toshihiko KOMADA, Shin ISHIDA, Muneyuki ISHIDA
Article type: Article
2001 Volume 102 Issue 5 Pages
E98-E102
Published: February 20, 2001
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We analyze the ππ production amplitudes in the excited Υ decay processes, Υ(2S) →Υ(1S)π^+π-,Υ(3S) →Υ(1S)π^+π^- andΥ(3S) →Υ(2S)π^+π^-, and the ππ and KK^^- production amplitudes in the charmoniurn decay processes, Ψ(2S) → J/Ψπ^+π^- and J/Ψ→ φπ^+π^-, φK^+K^-. The amplitudes are parametrized by the sum of Breit-Wigner amplitudes for the σ, and the other relevant particles and of the direct 2π-production amplitude, following the VMW method. All the ππ (and KK^^-) invariant mass spectra are reproduced well with the σ Breit-Wigner amplitude by using the common parameters, m_σ = 526^<+48>_<-37>MeV and Γ_σ = 301^<+145>_<-100>MeV, which is almost consistent with the values obtained in our previous 100 phase shift analyses. This strongly suggests the existence of light σ-meson.
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Muneyuki ISHIDA, Shin ISHIDA, Toshihiko KOMADA
Article type: Article
2001 Volume 102 Issue 5 Pages
E103-E107
Published: February 20, 2001
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The results of analyses obtained in Part I are examined from the viewpoint of chiral symmetry. The mass spectra of ππ system are widely believed to be suppressed generally near the threshold, because of the derivative coupling property of Nambu-Goldstone π meson. However, this suppression does not hold in the processes with large energy release, and the steep increase from the ππ threshold observed in the transition Υ(3S → 1S) is shown to be consistent with general constraints from chiral symmetry.
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
E108-
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Robert KAMINSKI, Leonard LESNIAK, Benoit LOISEAU
Article type: Article
2001 Volume 102 Issue 5 Pages
E109-E114
Published: February 20, 2001
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Interactions in three coupled channels: ππ, KK^^- and σσ have been investigated in a wide two-pion effective mass region from the ππ threshold up to 1600 MeV. Analytical structure of amplitudes in all channels has been studied. It was shown that its knowledge is necessary to understand spectrum of scalar mesons and their nature.
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Deirdre BLACK, Amir H. FARIBORZ, Joseph SCHECHTER
Article type: Article
2001 Volume 102 Issue 5 Pages
E115-E122
Published: February 20, 2001
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We first review the work of the Syracuse group, which uses an effective chiral Lagrangian approach, on meson-meson scattering. An illustration providing evidence for the existence of a strange scalar resonance of mass around 900 MeV is given. An attempt to fit this κ(900) together with a similarly obtained σ(560) and the well known a_0(980) and f_0(980) into a nonet pattern. suggests that the underlying structure is closer to a dual quark-dual antiquark than to a quark-antiquark. A possible mechanism to explain a next higher-in mass scalar meson nonet is also discussed. This involves mixing between qq^^- and qqq^^-q^^- states.
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Stephan NARISON
Article type: Article
2001 Volume 102 Issue 5 Pages
E123-E132
Published: February 20, 2001
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Within the increasing experimental evidence of the existence of the I = 0 scalar low mass and wide σ meson, we review the first analysis of its quark and gluon substructure from QCD spectral sum rules and some low-energy theorems. The present data favour equal components of u^^-u + d^^-d and of gg in its wave function, which make the wide σ and the narrow f_0(980) as η'-like particles. A coherent picture of the other I = 0 scalar mesons spectra within this mixing scheme is shortly discussed. We also expect the a_0(980) to be the lowest isovector u^^-d state, and the K^*_0 (1430) its d^^-s partner.
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Nils A. TORNQVIST
Article type: Article
2001 Volume 102 Issue 5 Pages
E133-E138
Published: February 20, 2001
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Based on previous papers I discuss how I understand the lightest scalars using a general coupled channel model. This model includes all light two-pseudoscalar thresholds, constraints from Adler zeroes, flavour symmetric couplings, unitarity and physically acceptable analyticity. One finds that with a large coupling there can appear two physical resonance poles on the second sheet although only one bare quark-antiquark state is put in. The f_0(≈ 980) and f_0(≈ 1370) resonance poles are thus in this model two manifestations of the same strange-antistrange quark state. On the other hand, the isoscalax state containing u and d quarks becomes (when unitarized and strongly distorted by hadronic mass shifts) a very broad resonance, with its pole at 470-i250 MeV. This is the sigma meson required by models for spontaneous breaking of chiral symmetry.
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Shin ISHIDA, Muneyuki ISHIDA, Tomohito MAEDA
Article type: Article
2001 Volume 102 Issue 5 Pages
E139-E144
Published: February 20, 2001
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Starting from the bi-local Klein-Gordon Equation with spin-independent squared-mass operator, we give a covariant quark representation of general composite meson systems with definite Lorentz transformation properties. For benefit of this representation we are able to deduce automatically the transformation rules of composite mesons for general symmetry operations from those of constituent (exciton) quarks. Applying this we investigate especially physical implication of chiral symmetry for the meson systems, and present a covariant level-classification scheme, leading to a possible existence of new meson multiplets of "chiralons."
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
E145-
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Michael D. SCADRON
Article type: Article
2001 Volume 102 Issue 5 Pages
E146-E153
Published: February 20, 2001
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First, the LσM is nonperturbatively solved via loop-order gap equations. Then the Nambu-Goldstone theorem (NGT) is expressed in LσM language. Next, the Lee null tadpole sum for this SU(2) LσM theory is shown to require N_c = 3. Then LσM s-wave chiral cancellations are studied in tree-and in loop-order. Also, vector meson dominance (VMD) is shown to follow from this LσM. Next, the scalar nonet is studied in the infinite momentum frame (IMF). Finally, the LσM is suggested as the infrared limit of nonperturbative QCD.
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Kunihiko TERASAKI
Article type: Article
2001 Volume 102 Issue 5 Pages
E154-E159
Published: February 20, 2001
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The hypothesis of σ meson pole dominance in the |ΔI| = 1/2 K → ππ amplitudes is tested qualitatively by using the K_L-K_S mass difference.
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A. I. SANDA
Article type: Article
2001 Volume 102 Issue 5 Pages
E160-E164
Published: February 20, 2001
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We point out that σ meson is responsible for explaining the ΔI = 1/2 rule.
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Yuichiro KIYO
Article type: Article
2001 Volume 102 Issue 5 Pages
E165-E168
Published: February 20, 2001
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We discuss the hadronic matrix elements of the QCD and electroweak penguin operators in kaon decay, K → ππ, using nonlinear sigma model with scalar resonances. The scalar mesons are introduced as a nonet representation of flavor SU(3) transformation. The propagators of these scalar resonances have effect of resumming a certain class of chiral corrections to the matrix elements to all order in chiral perturbation theory. Using this model impact on the physical observable in kaon decay, ΔI=1/2 rule and ε'/ε, are discussed. We show the effects of σ, meson axe of great importance in kaon decay when mass of the σ meson is near to the kaon mass due to propagator enhancement. However results show that we are still missing some large amount of contributions to explain both of ΔI=1/2 rule and ε'/ε consistently.
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Makoto TAKIZAWA
Article type: Article
2001 Volume 102 Issue 5 Pages
E169-E171
Published: February 20, 2001
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We discuss (i)K → 2π decays using the U_L(3)×U_R(3) version of the Nambu-Jona-Lasinio model with the effective ΔS = 1 nonleptonic weak interaction and (ii)the effects of the U_A(1) breaking 6-quark interaction on the nonet scalar mesons in the context of the Nambu-Jona-Lasinio model. The ΔI = 3/2 amplitude of the K → 2π decay is in reasonable agreement with the experimental date. On the other hand, the calculated ΔI = 1/2 amplitudes of the K → 2π decay strongly depend on the mass of the low-lying scalar-isoscalar σ meson, and the observed values are reproduced with m_σ 〜 570 [MeV]. The low-lying scalar-isoscalar σ meson plays a central role in the enhancement of the ΔI = 1/2 amplitudes of the K → 2π decay. As for the effects of U_A(1) breaking 6-quark interaction on the nonet scalar mesons, it may explain the spectrum of the nonet scalar mesons obtained by the recent analyses of the experimental data.
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
E172-
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Tetsuo HATSUDA, Teiji KUNIHIRO
Article type: Article
2001 Volume 102 Issue 5 Pages
E173-E178
Published: February 20, 2001
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The σ-meson, which is at best a broad resonance in the vacuum, may suffer a substantial red-shift and appear as a soft and narrow collective mode at finite temperature and baryon densities. The physics behind this softening phenomena and its relation to the partial restoration of chiral symmetry are discussed. Possible experiments in laboratory to test the idea are also summarized.
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Hajime SHIMIZU, Toru MATSUMURA, Tetsuhiko YORITA
Article type: Article
2001 Volume 102 Issue 5 Pages
E179-E184
Published: February 20, 2001
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An experiment for 2π^0 photoproduction in nuclei is proposed by utilizing a multi-GeV Laser-Electron Photon beam at SPring-8. A backward γ-detector consisting of lead/scintillating fiber blocks is employed to detect 4γs at backward angles. The -γ-detector covers the polar angle from 30° to 100° with full azimuthal angles. The acceptance of the detector is estimated to be more than 0.3 for the σ meson with a mass of 500 MeV, produced in a high momentum transfer region of |t| > 1.5 GeV^2 at E_γ = 2.4 GeV. The γ-detector is capable of detecting some medium effects, especially of finding an enhancement in the π^0π^0 invariant mass distribution near the 2π threshold region. On the other hand, a new method is proposed for the test of the existence of the σ meson through the inverse process of σ → 2γat a very small momentum-transfer region.
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Satoru HIRENZAKI, Hideko NAGAHIRO, Tetsuo HATSUDA, Teiji KUNIHIRO
Article type: Article
2001 Volume 102 Issue 5 Pages
E185-E190
Published: February 20, 2001
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We investigate the possibility to observe the properties of the σ channel in nuclei by (d,t) reactions to obtain new information on the partial restoration of chiral symmetry in nuclear medium. The sensitivity of the (d,t) spectra on the chiral symmetry restoration is examined theoretically.
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Kyoichiro OZAWA, J. Chiba, H. En'yo, H. Funahashi, H. Hamagaki, M ...
Article type: Article
2001 Volume 102 Issue 5 Pages
E191-E194
Published: February 20, 2001
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We have measured Invariant mass spectra of electron-positron and K^+K^- pair produced in 12GeV p+A reactions. We have observed a significantthe line shapes of ρ and ω mesons p+C and p+Cu interactions, which is attributed to the in media mass modification of the ρ and ω meson.
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Masahiko IWASAKI, Kenta ITAHASHI
Article type: Article
2001 Volume 102 Issue 5 Pages
E195-E200
Published: February 20, 2001
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In this manuscript, we try to give an overview of the recent experiments to study meson bound states in nuclei. "In-medium hadron property" is not well known and it is an essential key to understand the low energy QCD, existence of chiral symmetry and the reason of its breaking. Particular attention was focussed on the experiment to search for the deeply bound kaonic state in ^3He nuclei.
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
E201-
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Chong-Sa LIM
Article type: Article
2001 Volume 102 Issue 5 Pages
E202-E207
Published: February 20, 2001
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After a brief introduction to the sigma model in QCD, we discuss how the sigma model can be relevant in the Standard Model. It is shown to be useful in the analysis of weak processes, such as the study of ΔI = 1/2 rule, and in the analysis of the Higgs sector as well. The sigma model description is also shown to be quite useful in searching for the effects of New Physics via gauge boson self-interactions.
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Takayuki MATSUKI, Masashi SHIOTANI
Article type: Article
2001 Volume 102 Issue 5 Pages
E208-E212
Published: February 20, 2001
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Recently we found a rather general method for calculating an effective action for massless gauge theory without scalar fields, in which only fermions acquire their masses while gauge bosons do not. Upon performing the calculation, we used the functional integration and the Fierz-transformation and also introduced the gaussian quadratic bilocal auxiliary fields. Here we applied this technique to an example of gauge symmetry breakdown from SU(5) to SU(4). Though this breaking pattern was intuitively discussed by Raby, Dimpoulos and Susskind long ago, they did not derive various physical quantites. We developed their idea and calculated them as well as the generated gauge boson masses.
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Seiya NISHIYAMA, Joao da PROVIDENCIA, Osamu OHNO
Article type: Article
2001 Volume 102 Issue 5 Pages
E213-E218
Published: February 20, 2001
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Using the Nambu-Jona-Lasinio (NJL) model, dynamical chiral-symmetry breaking, light-mesons spectra and properties of the mesons have been investigated on the basis of conventional Hartree-Fock approach. In order to show the advantage of the resonating mean-field theory for a fermion system with large-quantum fluctuations over the usual mean-field theory, we have applied it successfully to the NJL model to describe precisely phenomena associated with pionic excitation. We apply it further to describe more accurately phenomena which associate simaltaneously with pionic and sigma mesonic excitations.
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Takayuki MATSUKI, Masashi SHIOTANI
Article type: Article
2001 Volume 102 Issue 5 Pages
E219-E223
Published: February 20, 2001
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Applying our recently developed method, we study a possibility that a sigma particle may be a composite of a fermion-anti-fermion pair starting from pure QCD Lagrangian and derive a mass formula for a sigma particle.
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Nils A. TORNQVIST
Article type: Article
2001 Volume 102 Issue 5 Pages
E224-E231
Published: February 20, 2001
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This report summarizes the most important results presented at the recent conference held at the Yukawa Institute of Theoretical Physics in Kyoto, devoted to the recently confirmed light σ, resonance. Remarkably, all speakers at this meeting took the light σ for granted and many mass and width estimations near 500 MeV were presented. We emphasize that if the light and broad σ is accepted as a true resonance it explains many basic problems of low energy hadronic physics in a simple way, especially if the linear sigma model (LσM) is used as an approximate effective low energy theory.
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
E232-
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
45-
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Article type: Appendix
2001 Volume 102 Issue 5 Pages
App2-
Published: February 20, 2001
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