Study of charge symmetry in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>by simultaneous<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:

Spahn, M.; Kihm, Th.; Knöpfle, K. T.; Friedrich, J.; Voegler, N.; Schmitt, C.; Walther, Valentin; Unkelbach, M.; Hofmann, H.

doi:10.1103/physrevlett.63.1574

Cited by 15 publications

(9 citation statements)

References 19 publications

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“…The value of bo for "He was determined from the relation [30] ( 'po nt) = (r h) -(r, ") (7) where (r,h)~= 1.676 fm [31] and (r2)i~2 = 0.80 fm are the rms charge radii of He and the proton, respectively, we find bo --1.39 fm.…”

Section: Introductionmentioning

confidence: 98%

“…Such a large deviation from unity would have fundamental implications for the hadronic interaction, since it implies the existence of a charge symmetry-breaking (CSB) component of the internucleon force which, under standard assumptions, cannot be accounted for with the Coulomb interaction alone [1 -3]. However, work involving separate measurements of the cr(p, p), o(p, p), and tr(p, n) reactions, as well as 4He(e, e'N) and pion inelastic scattering studies call these results seriously into question [4][5][6][7][8] Pion inelastic scattering data have provided valuable information on the isospin character of the 4He continuum and have also provided tests of microscopic approaches to the four-body nuclear structure problem [8].…”

Section: Introductionmentioning

confidence: 99%

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Inelastic scattering of polarized protons fromHe4at 500 and 800 MeV

et al. 1992

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Inclusive He(p, p') spectra were measured at incident energies T"=500 and 800 MeV over a range of forward scattering angles between 5' and 30'. The first excited 0+, T=O state at 20.1 MeV and the 2, T=O state at 22. 1 MeV appear as distinct structures in the spectra. Angular distributions of diR'erential cross sections o' and analyzing powers A"were extracted for these states and for regions of excitation in the continuum up to 40 MeV. Distorted-wave calculations for inelastic scattering using transition densities from the recoil corrected continuum shell model (RCCSM) were compared with the data. The RCCSM generally predicts too small cr and too large A". Assuming a pure giant monopole excitation for the 20.1-MeV, 0 state, we found greater giant monopole resonance strength than has been deduced from He(e, e') studies. PACS number(s): 25.40. Ep, 24.70.+s

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Inelastic scattering of polarized protons fromHe4at 500 and 800 MeV

et al. 1992

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“…, using wave functions that are derived from a Hamiltonian, and not fitted ones). On the contrary, He (e, e'x) experiments (x=p, n), performed at MAMI-A in Mainz [8], suggested rather high peak cross sections (of the order of 2 mb), but no need for chargesymmetry breaking was found.…”

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confidence: 90%

Direct measurement of theHe4(γ,p0<

Hoorebeke¹,

Vyver²,

Fiermans³

et al. 1993

Phys. Rev. C

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A direct measurement of the He(y, po) reaction was performed using 34 MeV end-point bremsstrahlung photons. Photoprotons were simultaneously detected at nine angles. The magnitude of the deduced cross section is at variance with the results from recent experiments but is in perfect agreement with the previously recommended values. Consequently, as yet no definite conclusion can be drawn about the validity of charge symmetry of the nuclear force.The question of the absolute magnitude of the "He(y, po) reaction continues to raise a lot of attention and debate. This reaction is of particular importance since a direct comparison of the (y,p ) and (y, n ) cross sections for the self-conjugate nucleus He yields valuable information [1] concerning the concept of charge symmetry of the nuclear force, which is considered to be one of its basic characteristics. If this property is valid, the ratio R of these two cross sections should be close to unity in the giant dipole resonance (GDR) region [2). Deviations from this value mainly arise from Coulomb e8'ects, but realistic calculations raise the value of R only to about 1.1 [2,3].However, as yet the experimental situation is not clear.In 1983, a balanced review by Calarco et al. [2,4] of all available experimental total cross section data for both the (y, p) and (y, n ) reactions yielded surprising results.In this evaluation much more credibility was given to the (p, y) capture data as compared to the direct (y, p) values, mainly because the latter ones were obtained with a bremsstrahlung beam (continuous spectrum) and only the proton was detected. Calarco et aI. concluded that the ratio R showed a maximum around 25 MeV, equaling a value of 1.7+0.2, its explanation requiring an extremely large amount of isospin mixing between the excited states of He and thus inconsistent with charge symmetry. Of particular interest here is the fact that Calarco recommends a (y,p ) cross section which reaches 1.85+0.12 mb at 26 MeV, gradually decreasing to about 1.3 mb at 34 MeV. The magnitude and behavior of such cross section could be reasonably well theoretically described by Wachter et al. [3]. However, these same authors concluded that, relying on a selected set of (y, n) data, the di8'erences between the cross sections for both mirror channels did not require any isospin violating nuclear force. Nevertheless, the (y, p ) cross section as recommended by Calarco was not confirmed by subsequent experiments. Bernabei et al. [5] reported a direct measurement of the absolute total "He(y, p) cross section in the 28.6 -58.1 MeV energy interval, using a quasimonoenergetic photon fiux and a nearly 4m. proton detector. These (y,p) cross section results had about the same magnitude as Calarco's suggested (y, n) cross section, leading to a mean value of R =1.01+0.06. A measurement [6] of the inverse H(p, y) He process in the energy region corresponding to photon energies between 21.3 and 31.1 MeV confirmed the latter data set. These new experimental (y,p) cross sections could be extremely well re...

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“…Dodge and Murphy [11]inferred R"above E"=30MeV from nearly simultaneous He(e, He)e'n and He(e, H)e'p measurements at a laboratory angle of 90 using a magnetic spectrometer. An extension of this work to lower energy by Spahn et al [12] used solid. -state telescopes at 60', 90'" and 120' to obtain simultaneous yields for the He(e, e' He)"and He(e, e' H)p reactions.…”

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confidence: 96%

Simultaneous measurement of the (γ,p)/(γ,n) cross-section ratio inHe4as a test of charge symmetry

et al. 1994

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We have measured (y, p) and (y, n) differential yields at 90' for the two-body photodisintegration of He using tagged photons of energy E"=25-60 MeV. Data for both channels were obtained simultaneously using windowless hE-E telescopes to detect the He and H recoils. The ratio of our angleintegrated yields, which is insensitive to systematic uncertainties due to the simultaneity of the measurements, agrees with calculations employing only charge-symmetric nuclear interactions. Thus, within the present errors, our data show no evidence of a significant charge-symmetry violation in He in this energy range. PACS numbers: 25.20.Dc, 25. 10.+s, 27. ]0.+h The question of charge symmetry in He has been a long-standing problem in nuclear physics. If charge symmetry is strictly valid, then the ratio of the two-body photodisintegration cross sections, R"=a(y-,p)/o(y, n), is expected to be unity (for pure E I radiation). EA'ects such as Coulomb interactions or non-E 1 multipoles can slightly modify this value, increasing the ratio to R~-1.1 in the photon energy range E"=25-35 MeV. The problem was summarized in 1983 by Calarco, Berman, and Donnelly [I] in a comprehensive review of all photonuclear (and capture) data up to that time, leading to the surprising conclusion that R"=1. 7-1.2 for E, =25-35 MeV, dilfering substantially from the simple charge-symmetry prediction. Theoretical attempts which include charge-symmetric nuclear interactions in a shell model [2,3] and a resonating group model [4,5] have failed to reproduce this large value of the ratio. It should be noted, however, that the recommended cross sections comprising the ratio in Ref. [I] were determined from in ditidual measurements of the (y,p) and (y, n) channels separately. Since this review, three new measurements of the proton channel have been reported [6-8]. The data from [6,7] are more consistent with the recommended photoneutron cross section, while [8] reports a cross section nearly twice as large, in agreement with the recommended proton cross section. The only new published neutron data are from a capture reaction [9] which finds a peak cross-section value that is consistent with the recommended neutron value.In addition to these new measurements of the individual two-body channels, a recent elastic photon scattering experiment [10] inferred the total photoabsorption cross section in a model-independent manner through the optical theorem and a dispersion relation. While their result can say nothing about the relative contributions of the (y,p) and (y, n) channels (and hence, the ratio), it does impose a significant constraint on the sum of the two cross sections. This new photon scattering result (a) agrees with the sum of the recommended cross sections in Ref. [I] (which give the large value of R"), (b) disagrees with the sum of the recent photoproton data [6,7] and the recommended photoneutron values (where R" is closer to unity), (c) agrees with the sum of Ref. [8] and the recommended neutron cross section, and (d) agrees with the sum of the latest...

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Study of charge symmetry inHe4by simultaneousHe

Abstract: We have measured the ( 3 H+p) and ( 3 He + «) breakup of 4 He by 4 He(e,e'c) coincidence experiments at low momentum transfer ( Show more

Cited by 15 publications

References 19 publications

Inelastic scattering of polarized protons fromHe4at 500 and 800 MeV

Inelastic scattering of polarized protons fromHe4at 500 and 800 MeV

Direct measurement of theHe4(γ,p0<

Simultaneous measurement of the (γ,p)/(γ,n) cross-section ratio inHe4as a test of charge symmetry

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