Sensitivity to the Pion-Nucleon Coupling Constant in Partial-Wave Analyses of pN?pN, NN?NN, and ?N?pN

“…Via the Goldberger-Treiman relation, g πNN = g A M N / f π , our value for g A together with f π = 92.4 MeV and M N = 938.918 MeV implies g 2 πNN /4π = 13.67 which is consistent with the empirical values obtained from πN and NN data analysis [38,39].…”

Section: Leading Order (Lo)supporting

confidence: 88%

Chiral Symmetry and the Nucleon-Nucleon Interaction

Machleidt¹

2016

Symmetry

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Abstract:We review how nuclear forces emerge from low-energy quantum chromodynamics (QCD) via chiral effective field theory (EFT). During the past two decades, this approach has evolved into a powerful tool to derive nuclear two-and many-body forces in a systematic and model-independent way. We then focus on the nucleon-nucleon (NN) interaction and show in detail how, governed by chiral symmetry, the long-and intermediate-range of the NN potential builds up order by order. We proceed up to sixth order in small momenta, where convergence is achieved. The final result allows for a full assessment of the validity of the chiral EFT approach to the NN interaction.Keywords: low-energy quantum chromodynamics (QCD); effective field theory; chiral perturbation theory; nucleon-nucleon scattering; nucleon-nucleon potentials PACS classifications: 13.75.Cs; 12.39.Fe; 21.30.-x; 21.45.Ff Historical PerspectiveAfter the discovery of the neutron by Chadwick in 1932 [1], it was clear that the atomic nucleus is made up from protons and neutrons. In such a system, electromagnetic forces cannot be the reason why the constituents of the nucleus are sticking together. Therefore, the concept of a new strong nuclear interaction was introduced. In 1935, the first theory for this new force was developed by the Japanese physicist Yukawa [2], who suggested that the nucleons would exchange particles between each other and this mechanism would create the force. Yukawa constructed his theory in analogy to the theory of the electromagnetic interaction where the exchange of a (massless) photon is the cause of the force. However, in the case of the nuclear force, Yukawa assumed that the "force-makers" carry a mass that was in-between the masses of the electron and the proton (which is why these particles were eventually called "mesons"). The mass of the mesons limits the effect of the force to a finite range, since the uncertainty principal allows massive virtual particles to travel only a finite distance. The meson predicted by Yukawa was finally found in 1947 in cosmic ray and in 1948 in the laboratory and called the pion. Yukawa was awarded the Nobel Prize in 1949. In the 1950s and 60s more mesons were found in accelerator experiments and the meson theory of nuclear forces was extended to include many mesons. These models became known as one-boson-exchange models, which is a reference to the fact that the different mesons are exchanged singly in this model. The one-boson-exchange model is very successful in explaining essentially all properties of the nucleon-nucleon interaction at low energies [3][4][5][6][7][8][9]. In the 1970s and 80s, also meson models were developed that went beyond the simple single-particle exchange mechanism. These models included, in particular, the explicit exchange of two pions with all its complications. Well-known representatives of the latter kind are the Paris [10] and the Bonn potentials [11].Since these meson models were quantitatively very successful, it appeared that they were the solution of the nuclear for...

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“…The amplitudes of the photoproduction data were also presented with a binning close to 18 MeV [17]. Many other papers were published from year to year by the same group [18], testing the sensitivity of different reactions to the pion-nucleon coupling constant [19], or studying the parameter of the multipole analysis in the region of the first ∆ resonance [20] or in the range of the N(1535) and N(1650) resonances [21].…”

Section: Iva1(a) Cross Sections Versus M Psxmentioning

confidence: 99%