π<i>NN</i>coupling constants from<i>NN</i>elastic data between 210 and 800 MeV

Bugg, D.V.; Machleidt, R.

doi:10.1103/physrevc.52.1203

Cited by 33 publications

(31 citation statements)

References 43 publications

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“…These deviations are larger than the differences expected from the neutron energy changes among the various experiments. As the backangle rise is particularly influential in pole extrapolations used [8,12] to extract the pion-nucleon-nucleon coupling constant, the present data strongly favor the value (f 2 c = 0.0748 ± 0.0003) given by the Nijmegen [6] and other [5] partial-wave analyses.…”

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confidence: 66%

“…The neutron-proton elastic scattering database at intermediate energies is plagued by experimental inconsistencies and cross section normalization difficulties [1,2,3]. These problems have led the most sophisticated partial wave analyses (PWA) of the data [4,5,6] to ignore the majority (including the most recent) of measured cross sections, while the literature is filled with heated debates over experimental and theoretical methods [7,8], including proposed radical "doctoring" (angledependent renormalization) to "salvage" allegedly flawed data [9]. Meanwhile, an empirical evaluation of a fundamental parameter of meson-exchange theories of the nuclear force -the charged πNN coupling constant, f 2 c -hangs in the balance [8].…”

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Measurement of the AbsolutenpScattering Differential Cross Section at 194 MeV

et al. 2005

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We describe a double-scattering experiment with a novel tagged neutron beam to measure differential cross sections for np back-scattering to better than ±2% absolute precision. The measurement focuses on angles and energies where the cross section magnitude and angle-dependence constrain the charged pion-nucleon coupling constant, but existing data show serious discrepancies among themselves and with energy-dependent partial wave analyses (PWA). The present results are in good accord with the PWA, but deviate systematically from other recent measurements.PACS numbers: 25.40. Dn, 25.10.+s, 28.20.Cz The neutron-proton elastic scattering database at intermediate energies is plagued by experimental inconsistencies and cross section normalization difficulties [1,2,3]. These problems have led the most sophisticated partial wave analyses (PWA) of the data [4,5,6] to ignore the majority (including the most recent) of measured cross sections, while the literature is filled with heated debates over experimental and theoretical methods [7,8], including proposed radical "doctoring" (angledependent renormalization) to "salvage" allegedly flawed data [9]. Meanwhile, an empirical evaluation of a fundamental parameter of meson-exchange theories of the nuclear force -the charged πNN coupling constant, f 2 c -hangs in the balance [8]. We report here the results of a new experiment, carried out utilizing quite different techniques from earlier measurements in an attempt to resolve the most worrisome experimental discrepancies.The present experiment involves a kinematically complete double-scattering measurement to produce and utilize a "tagged" intermediate-energy neutron beam [10], thus greatly reducing the usual systematic uncertainties associated with the determination of neutron flux. Products from the second scattering were detected over the full angle range of interest simultaneously in a largeacceptance detector array, to eliminate the need for crossnormalization of different regions of the angular distribution. The use of carefully matched solid CH 2 and C targets permitted frequent measurement and accurate subtraction of quasifree scattering background, thereby minimizing reliance on kinematic cuts to isolate the free np-scattering sample. These methods, combined with multiple internal crosschecks built into the data analysis procedures, have allowed us to achieve systematic error levels in the absolute cross section below 2%. In addition to addressing the previous discrepancies, the results provide a useful absolute cross section calibration for intermediate-energy neutron-induced reactions.

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Measurement of the AbsolutenpScattering Differential Cross Section at 194 MeV

et al. 2005

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“…The influence of these observables on the determination of g 2 p has also been established empirically [13] through an extensive study of local (single-energy) phase shift analyses. Yet the current NN database [14] contains few data for D NN 0 in this energy and angle range, and none for D LL 0 between 150 and 400 MeV.…”

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Spin Transfer inppElastic Scattering at 198 MeV: Implications for theπNNCoupling Constant

et al. 1999

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A precision measurement of spin transfer in pp elastic scattering at 197.8 MeV has been completed recently at the Indiana University Cyclotron Facility. The new data span a kinematic regime chosen specifically to maximize sensitivity to the neutral pNN coupling constant. Our results provide strong support for modern potential models of the NN interaction in which a relatively weak pion coupling (g 2 0 ഠ 13.6, f 2 0 ഠ 0.075) is employed, but disagree significantly with predictions of older models in which g 2 0 ഠ 14.4. Calculations in a one-boson-exchange framework indicate that most of these latter differences can be removed by reducing g 2 0 from 14.4 to 13.6 in these models. PACS numbers: 13.75.Cs, 21.30.Cb, 25.10. + sWhile quantum chromodynamics (QCD) is widely regarded as the underlying theory of the strong interaction, our best quantitative descriptions of most low and intermediate energy nuclear phenomena are still provided by effective theories of the interaction, in which baryons and mesons serve as efficient, collective degrees of freedom. Thus, there is great interest in determining precisely the values of the constants that appear, for example, in mesonbased models of the NN interaction. In these models, the one-pion-exchange process plays a fundamental role, dominating the long-range hadronic force, especially the tensor terms, with a strength determined primarily by the size of g 2 p , the pNN coupling constant [1]. Accurate knowledge of this coupling strength is therefore crucial for predictions of NN and pN scattering behavior and deuteron ground-state properties, or in descriptions of the NN interaction that serve as input to microscopic nuclear reaction or structure models. The strength of g 2 p also plays a critical role in testing low-energy theorems of charged pion photo-or leptoproduction, and allows one to gauge the extent to which chiral-symmetry breaking is present in the pN interaction via the Goldberger-Treiman discrepancy [2].Thus, it was quite a surprise a few years ago when new determinations of both the neutral [3] and charged [4] pion coupling constants, g 2 0 and g 2 c , based largely on global analyses of pp and pN scattering data, respectively, yielded values in striking disagreement with previous determinations and favoring much weaker couplings. The new couplings also appeared to be incompatible with the strengths required in meson-exchange models to produce the correct deuteron quadrupole moment and asymptotic D͞S state ratio [5], and with values for g 2 c recently extracted from back-angle np cross section data [6,7]. These concerns have been described at length in the literature (see, for example, [8,9]), and will not be discussed further here. It is clear, though, that many of the most contentious issues hinge on the reliability, reproducibility, or indeed the availability of data for particular sets of observables in the most critical regions of momentum transfer.Such thinking led us to investigate the sensitivity of g 2 p to various subsets of the NN database. We have sho...

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“…Based upon precise π ± p data in the 100-310 MeV range and applying fixed-t dispersion relations, they obtained the value g 2 π ± /4π = 13.96 ± 0.25 (equivalent to f 2 π ± = 0.0771 ± 0.0014) [15]. From the analysis of N N elastic data between 210 and 800 MeV, Bugg and Machleidt [16] have deduced g 2 π ± /4π = 13.69 ± 0.39 and g 2 π 0 /4π = 13.94 ± 0.24. Thus, it may appear that recent determinations show a consistent trend towards a lower value for g π with no indication for substantial charge dependence.…”

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Charge Dependence of the πNN Coupling Constant and Charge Dependence of the Nucleon-Nucleon Interaction

Machleidt

Banerjee

2000

Few-Body Systems

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Abstract. The recent determination of the charged πN N coupling constant, g π ± , by the Uppsala Neutron Research Group implies that there may be considerable charge-splitting of the pion coupling constant. We investigate the consequences of this for the charge-independence breaking (CIB) of the 1 S 0 scattering length, ∆a CIB . We find that ∆a CIB depends sensitively on the difference between g π ± and the neutral πN N coupling constant, g π 0 . Moreover, if g 2 π ± is only about 3% larger than g 2 π 0 , then the established theoretical explanation of ∆a CIB (in terms of pion mass splitting) is completely wiped out.

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πNNcoupling constants fromNNelastic data between 210 and 800 MeV

Cited by 33 publications

References 43 publications

Measurement of the AbsolutenpScattering Differential Cross Section at 194 MeV

Measurement of the AbsolutenpScattering Differential Cross Section at 194 MeV

Spin Transfer inppElastic Scattering at 198 MeV: Implications for theπNNCoupling Constant

Charge Dependence of the πNN Coupling Constant and Charge Dependence of the Nucleon-Nucleon Interaction

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