Testing chiral symmetry breaking at DAΦNE

Pennington, M.R.

doi:10.1016/s0375-9474(97)00438-7

Cited by 9 publications

(6 citation statements)

References 38 publications

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“…Indeed, the amplitude has a line of zeros, which in the physical regions generate dips in the corresponding differential cross-sections. The position of this zero contour depends crucially on the explicit breaking of chiral symmetry [27,30,31]. If the qq condensate is large, of the order of 250-270 MeV in scale, the zero in the π + π − → π 0 π 0 passes close to the symmetry point of the Mandelstam triangle, as required by Standard Chiral Perturbation Theory [27].…”

Section: Milc [22]mentioning

confidence: 99%

Translating Quark Dynamics Into Hadron Physics (And Back Again)

Pennington¹

2003

Meson 2002

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Why should we study mesons in 2002? Two approaches to relating quark and gluon dynamics to hadron physics, namely QCD sum rules and effective field theories, are briefly discussed. These are linked by progress in the study of strong QCD, both by lattice Monte Carlo methods and in the continuum. These provide the translation from quark dynamics to hadron physics and back again. Scope for more theoretical work and further experiments to elucidate the nature of the QCD vacuum and its precise relation to scalar mesons and their interactions is outlined. 13.65.+i, 14.40.Gx

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Section: Milc [22]mentioning

confidence: 99%

Translating Quark Dynamics Into Hadron Physics (And Back Again)

Pennington¹

2003

Meson 2002

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“…In the present case we have λ ≡ Λ t γγ ≡ 0, so that we can omit the index λ without loss of generality. The amplitudes F J I (t) have to be constructed such that they have the correct low-energy properties, reproduce the cross section of the photon fusion reaction γγ → ππ and incorporate the phases δ J I (t) [72][73][74][75][76]. For J = 0 the following form of Eq.…”

Section: The T-channel Part Of the Beft Sum Rulementioning

confidence: 99%

Dispersion theory of nucleon Compton scattering and polarizabilities

Schumacher

Scadron

2013

Fortschritte der Physik

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A status report on the topic Compton scattering and polarizabilities is presented with emphasis on the scalar t-channel as entering into dispersion theory. Precise values for the polarizabilities are obtained leading to $\alpha_p = 12.0\pm 0.6$ $(12.0)$, $\beta_p=1.9\mp 0.6$ $(1.9)$, $\alpha_n= 12.5\pm 1.7$ $(13.4)$, $\beta_n= 2.7 \mp 1.8$ $(1.8)$ in units of $10^{-4}$ fm$^3$ and $\gamma^{(p)}_\pi = -36.4 \pm 1.5$ $(-36.6)$, $\gamma^{(n)}_\pi = 58.6 \pm 4.0$ $(58.3)$, $(\gamma^{(p)}_0= -0.58\pm 0.20)$, $(\gamma^{(n)}_0 = +0.38\pm 0.22)$ in units of $10^{-4}$ fm$^4$, for the proton (p) and neutron (n), respectively. The data given with an error are {\it recommended} experimental values with updates compared to [1] where necessary, the data in parentheses are predicted values. These predicted values are not contained in [1], but are the result of a newly developed analysis which is the main topic of the present paper. The most important recent discovery is that the largest part of the electric polarizability and the total diamagnetic polarizability of the nucleon are properties of the $\sigma$ meson as part of the constituent-quark structure, as expected from the mechanism of chiral symmetry breaking. This view is supported by an experiment on Compton scattering by the proton carried out in the second resonance region, where a large contribution from the $\sigma$ meson enters into the scattering amplitudes. This experiment led to a determination of the mass of the $\sigma$ meson of $m_\sigma = 600 \pm 70$ MeV. From the experimental $\alpha_p$ and predicted differences $(\alpha_n - \alpha_p)$ neutron polarizabilities in the range $\alpha_n= 12.0 - 13.4$ are predicted, where the uncertainties are related to the $f_0(980)$ and $a_0(980)$ scalar mesons

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“…The amplitudes F J I (t) have to be constructed such that they have the correct low-energy properties, reproduce the cross section of the photon fusion reaction γγ → ππ and incorporate the phases δ J I (t) [78,[148][149][150][151]. For J = 0 the following form of Eq.…”

Section: The T-channel Part Of the Beft Sum Rulementioning

confidence: 99%

Polarizability of the nucleon and Compton scattering

Schumacher

2005

Progress in Particle and Nuclear Physics

112

196

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One of the central challenges of hadron physics in the regime of strong (non-perturbative) QCD is to identify the relevant degrees of freedom of the nucleon and to quantitatively explain experimental data in terms of these degrees of freedom. Among the processes studied so far Compton scattering plays a prominent role because of the well understood properties of the electromagnetic interaction. Different approaches to describe Compton scattering have been discussed up to now. It will be shown that the most appropriate ones are provided by nonsubtracted dispersion theories of the fixed-t and fixed-θ types, where the properties of these two versions are complementary so that advantage can be taken from both of them. In the frame of fixed-t dispersion theory it was possible to precisely reproduce experimental differential cross sections obtained for the proton in a wide angular range and for energies up to 1 GeV. At energies of the first resonance region and below, precise values for the electromagnetic polarizabilities and spin-polarizabilities have been determined for the proton and the neutron. As a summary we give the following recommended experimental values for the electromagnetic polarizabilities and backward spin-polarizabilities of the nucleon: α p = 12.0±0.6, β p = 1.9∓0.6, α n = 12.5±1.7, β n = 2.7∓1.8, in units of 10 −4 fm 3 and γ * Supported by Deutsche Forschungsgemeinschaft SPP(1034) and projects SCHU222 and 436RUS 113/510. Email address: mschuma3@gwdg.de (Martin Schumacher)

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Testing chiral symmetry breaking at DAΦNE

Cited by 9 publications

References 38 publications

Translating Quark Dynamics Into Hadron Physics (And Back Again)

Translating Quark Dynamics Into Hadron Physics (And Back Again)

Dispersion theory of nucleon Compton scattering and polarizabilities

Polarizability of the nucleon and Compton scattering

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