Electroproduction of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">π</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>on the proton near threshold

Welch, T. P.; Karen, P.; Mitchell, J.; Norum, B.; Blok, H. P.; Brink, H. B. van den; Jager, C. W. de; Jans, E.; Lapikás, L.; Vries, H. de; Wesseling, J.; Bergstrom, J.C.; Deady, M.

doi:10.1103/physrevlett.69.2761

Cited by 43 publications

(66 citation statements)

References 18 publications

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“…The leading nonzero contributions therefore comes from tree graphs with one insertion from L (2) πN . The two non-vanishing diagrams are shown in fig.2.…”

Section: Iv1 the Transverse Threshold Amplitudesmentioning

confidence: 99%

See 1 more Smart Citation

Threshold two-pion photo- and electroproduction: More neutrals than expected

Bernard¹,

Kaiser

Meiβner³

et al. 1994

Nuclear Physics A

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“…The leading nonzero contributions therefore comes from tree graphs with one insertion from L (2) πN . The two non-vanishing diagrams are shown in fig.2.…”

Section: Iv1 the Transverse Threshold Amplitudesmentioning

confidence: 99%

“…In particular, new accurate data for the processes γp → π 0 p and γ ⋆ p → π 0 p close to production threshold have become available [1,2]. * These have led to many theoretical investigations.…”

Section: Introductionmentioning

confidence: 99%

Threshold two-pion photo- and electroproduction: More neutrals than expected

Bernard¹,

Kaiser

Meiβner³

et al. 1994

Nuclear Physics A

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“…This indicates that a calculation beyond the isosymmetric one-loop approximation should be performed. Very recently, new accurate data very close to threshold have become available for the electroproduction process γ ⋆ p → π 0 p [172]. In particular, the S-wave cross section a 0 , which is a particular combination of E 0+ and L 0+ , was analyzed (for the first time in this kinematical regime).…”

Section: Photo-nucleon Processesmentioning

confidence: 99%

Recent developments in chiral perturbation theory

1993

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I review recent developments in chiral perturbation theory (CHPT) which is the effective field theory of the standard model below the chiral symmetry breaking scale. The effective chiral Lagrangian formulated in terms of the pseudoscalar Goldstone bosons (π, K, η) is briefly discussed. It is shown how one can gain insight into the ratios of the light quark masses and to what extent these statements are modelindependent. A few selected topics concerning the dynamics and interactions of the Goldstone bosons are considered. These are ππ and πK scattering, some non-leptonic kaon decays and the problem of strong pionic final state interactions. CHPT also allows to make precise statements about the temperature dependence of QCD Green functions and the finite size effects related to the propagation of the (almost) massless pseudoscalar mesons. A central topic is the inclusion of matter fields, baryon CHPT. The relativistic and the heavy fermion formulation of coupling the baryons to the Goldstone fields are discussed. As applications, photo-nucleon processes, the πN Σ-term and non-leptonic hyperon decays are presented. Implications of the spontaneously broken chiral symmetry on the nuclear forces and meson exchange currents are also described. Finally, the use of effective field theory methods in the strongly coupled Higgs sector and in the calculation of oblique electroweak corrections is touched upon.

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“…The corresponding Lagrangians are one order higher since the photon polarization vector counts as order q. For the P-waves, we thus have to consider tree graphs with insertions from L (1,2,3) πN and one loop graphs with insertions solely from L (1) πN . For the S-wave multipoles, we have in addition to consider one loop diagrams with exactly one insertion from L (2) πN and tree graphs from L (4) πN .…”

Section: Formal Aspectsmentioning

confidence: 99%

Threshold neutral pion electroproduction in heavy baryon chiral perturbation theory

1996

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We investigate neutral pion electroproduction off protons in the framework of heavy baryon chiral perturbation theory. The chiral expansion of the S-wave multipoles E 0+ and L 0+ is carried out to three orders. There appear several undetermined lowenergy constants. Three are taken from a recent study of the new TAPS threshold π 0 photoproduction data, one is fixed from the proton Dirac form factor and the novel S-wave constants appearing at orders q 4 and q 5 are determined from a best fit (constrained by resonance exchange) to the recent NIKHEF and MAMI data at photon momentum transfer squared k 2 = −0.1 GeV 2 . The inclusion of a particular set of dimension five operators is forced upon the fit by a soft-pion theorem which severely constrains the momentum dependence of the longitudinal S-wave multipole L 0+ at order q 4 . We give predictions for lower photon virtualities for the various multipoles and differential cross sections. Further improvements are briefly touched upon.1

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Electroproduction ofπ0on the proton near threshold

Cited by 43 publications

References 18 publications

Threshold two-pion photo- and electroproduction: More neutrals than expected

Threshold two-pion photo- and electroproduction: More neutrals than expected

Recent developments in chiral perturbation theory

Threshold neutral pion electroproduction in heavy baryon chiral perturbation theory

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