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Showing papers by "Heinrich Leutwyler published in 1996"


Journal ArticleDOI
TL;DR: In this article, the authors collected the various pieces of information concerning the relative size of mu, md and ms, which constrains the mass ratios to a rather narrow range: mu/md = 0.553 ± 0.043, ms/md=18.9 ± 0.8.

399 citations


Journal ArticleDOI
TL;DR: In this article, the decay η → 3π represents a sensitive probe for the breaking of chiral symmetry by the quark masses, and the transition amplitude is proportional to the mass ratio (m d 2 −m u 2 ) (m s 2 − m 2 ).

155 citations


Journal ArticleDOI
TL;DR: In this article, the corrections to the current algebra mass formulae for the pseudoscalar mesons are analyzed by means of a simultaneous exansion in powers of the light quark masses and powers of 1/N.
Abstract: The corrections to the current algebra mass formulae for the pseudoscalar mesons are analyzed by means of a simultaneous exansion in powers of the light quark masses and powers of 1/N A set of mass formulae is derived, including an inequality, which leads to bounds for ratios of quark masses

116 citations


Journal Article
TL;DR: In this article, the implications of the hidden, spontaneously broken symmetry for the properties of sound waves of a solid are analyzed, and it is shown that the equations of motion for a sound wave necessarily contain nonlinear terms, describing phonon-phonon scattering.
Abstract: The implications of the hidden, spontaneously broken symmetry for the properties of the sound waves of a solid are analyzed. Although the discussion does not go beyond standard wisdom, it presents some of the known results from a different perspective. In particular, I argue that, as a consequence of the hidden symmetry, the equations of motion for a sound wave necessarily contain nonlinear terms, describing phonon-phonon scattering and emphasize the analogy with the low energy theorems for pion-pion scattering.

107 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate that the decay eta -> 3 pi represents a sensitive probe for the breaking of chiral symmetry by the quark masses, and that the transition amplitude is proportional to the mass ratio (m_d^2 −m_u^2)/(m_s^2-m^2).
Abstract: We demonstrate that the decay eta -> 3 pi represents a sensitive probe for the breaking of chiral symmetry by the quark masses. The transition amplitude is proportional to the mass ratio (m_d^2-m_u^2)/(m_s^2-m^2). The factor of proportionality is calculated by means of dispersion relations, using chiral perturbation theory to determine the subtraction constants. The theoretical uncertainties in the result are shown to be remarkably small, so that eta-decay may be used to accurately measure this ratio of quark masses.

105 citations


Journal ArticleDOI
TL;DR: In this paper, the corrections to the current algebra mass formulae for the pseudoscalar mesons are analyzed by means of a simultaneous expansion in powers of the light quark masses and powers of 1 N c.

86 citations


Posted Content
TL;DR: In this article, the implications of the hidden, spontaneously broken symmetry for the properties of sound waves of a solid are analyzed, and it is shown that the equations of motion for a sound wave necessarily contain nonlinear terms, describing phonon-phonon scattering.
Abstract: The implications of the hidden, spontaneously broken symmetry for the properties of the sound waves of a solid are analyzed. Although the discussion does not go beyond standard wisdom, it presents some of the known results from a different perspective. In particular, I argue that, as a consequence of the hidden symmetry, the equations of motion for a sound wave necessarily contain nonlinear terms, describing phonon-phonon scattering and emphasize the analogy with the low energy theorems for pion-pion scattering.

68 citations


Journal ArticleDOI
TL;DR: In this paper, the same combination of effective coupling constants which determines the small deviations from the GellMann-Okubo formula also specifies the symmetry breaking effects in the decay amplitude and thus ensures that these are small.

51 citations


Journal ArticleDOI
TL;DR: In this article, the authors point out that the interference with the etaprime appears to strongly affect the amplitude of the transition eta-to-3 pi, and that this effect is fictitious and also occurs in the mass spectrum of the pseudoscalars.
Abstract: Taken by itself, the interference with the etaprime appears to strongly affect the amplitude of the transition eta->3 pi. I point out that this effect is fictitious and also occurs in the mass spectrum of the pseudoscalars. Chiral symmetry implies that the same combination of effective coupling constants which determines the small deviations from the Gell-Mann-Okubo formula also specifies the symmetry breaking effects in the decay amplitude and thus ensures that these are small.

36 citations


Journal ArticleDOI
TL;DR: In this paper, the relative size of m_u, m_d and m_s was collected and a coherent picture of the relative sizes of mǫ, d and s was presented.
Abstract: The paper collects the various pieces of information concerning the relative size of m_u, m_d and m_s. A coherent picture results, which constrains the mass ratios to a rather narrow range: m_u/m_d = 0.553 \pm 0.043, m_s/m_d = 18.9 \pm 0.8.

22 citations


01 Jan 1996
TL;DR: In this paper, a good theoretical understanding of the low energy properties of QCD is required for this purpose, and the recent developments at the interface between lattice and effective field theory methods provide an excellent basis for pion physics already now, while the extension required to explore the high energy properties in the strange quark sector yet calls for further work, also in view of a better determination of the light quark masses.
Abstract: Low energy precision experiments provide significant tests of the laws of nature that can reveal physics beyond the Standard Model A good theoretical understanding of the low energy properties of QCD is required for this purpose The recent developments at the interface between lattice and effective field theory methods provide an excellent basis for pion physics already now, while the extension required to explore the low energy properties in the strange quark sector yet calls for further work, also in view of a better determination of the light quark masses At the precision achieved in lattice determination of quark mass ratios, the em self-energies of the mesons play an important role I point out some unresolved issues occurring in this context and then summarize the present knowledge of the light quark masses

Posted Content
TL;DR: The application of effective field theory methods to the low energy structure of QCD is discussed in this paper, where the universal structure of the corresponding effective Lagrangian and the physics of the effective coupling constants are discussed.
Abstract: Lecture Notes, Summer School on Effective Theories and Fundamental Interactions, Erice, 1996. The application of effective field theory methods to the low energy structure of QCD is discussed. I emphasize the universal structure of the corresponding effective Lagrangian and then discuss the physics of the effective coupling constants. The implications of the effective theory for the masses of the light quarks are analyzed in some detail.

Posted Content
TL;DR: In this paper, the current status of knowledge concerning m_u, m_d and m_s is reviewed and the results of the chiral perturbation theory for the masses of the Goldstone bosons are discussed.
Abstract: Talk given at the Conference on Fundamental Interactions of Elementary Particles, ITEP, Moscow, Oct. 1995. The paper reviews the current status of knowledge concerning m_u, m_d and m_s. Qualitative aspects of the resulting picture for the breaking of isospin and eightfold way symmetries are discussed. At a more quantitative level, the review focuses on the chiral perturbation theory results for the masses of the Goldstone bosons. The corresponding bounds and estimates for the ratios m_u/m_d and m_s/m_d are described in some detail.

08 Feb 1996
TL;DR: In this paper, the current status of knowledge concerning the masses of the Goldstone bosons is reviewed and the results for the breaking of isospin and eightfold way symmetries are discussed.
Abstract: The talk reviews the current status of knowledge concerning mu,md and ms. Qualitative aspects of the resulting picture for the breaking of isospin and eightfold way symmetries are discussed. At a more quantitative level, the review focuses on the chiral perturbation theory results for the masses of the Goldstone bosons. The corresponding bounds and estimates for the ratios mu/md and ms/md are described in some detail.

01 Jan 1996
TL;DR: The application of effective field theory methods to the low energy structure of QCD is discussed in this paper, where the universal structure of the corresponding effective Lagrangian and the physics of the effective coupling constants are discussed.
Abstract: Lecture Notes, Summer School on Effective Theories and Fundamental Interactions, Erice, 1996. The application of effective field theory methods to the low energy structure of QCD is discussed. I emphasize the universal structure of the corresponding effective Lagrangian and then discuss the physics of the effective coupling constants. The implications of the effective theory for the masses of the light quarks are analyzed in some detail.