Measurement of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>±</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>-He Scattering and Its Relation to the Pion Form Factor

Crowe, K. M.; Fainberg, A.; Miller, J.; Parsons, A.S.L.

doi:10.1103/physrev.180.1349

Cited by 88 publications

(21 citation statements)

References 18 publications

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“…Such more complete calculations, including also the principal value integrals in the Green functions (4), are in progress. We postpone the detailed comparison of the existing rr-4He experimental data [13,16] with the coupled channel calculations until completion of this work.…”

Section: Discussionmentioning

confidence: 97%

Coupled channel method for the ?-4He elastic and inelastic scattering

Gmitro

Mach

1979

Z Physik A

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Section: Discussionmentioning

confidence: 97%

Coupled channel method for the ?-4He elastic and inelastic scattering

Gmitro

Mach

1979

Z Physik A

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“…We further observe that at 70 MeV the measured cross section for this process is about equal to the free ir-a elastic-scattering cross section. 6 Also, the ratio of TT + to ir~ cross sections for the "a" removal is 0.58±0.08 for 27 A1 and 0.79±0.14 for 28 Si, similar to the free ir^a elastic scattering 6 (about 0.85).…”

mentioning

confidence: 86%

Interaction of Positive and Negative Pions withAl27andSi
Ashery
¹
,
Zaider
²
,
Shamai
³

et al. 1974
Phys. Rev. Lett.
32
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0
0
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The interaction of low-energy positive and negative pions with 27 A1 and 28 Si was studied by the detection of y radiation emitted from residual nuclei formed in the reaction. Large cross sections for the removal of "a" clusters were found for both nuclei and both pion charges. A large asymmetry is observed between the cross sections for the (ir" t ir"p) and (7r + ,7r + w) on 28 Si leading to mirror states in 27 A1 and 27 Si. The ratio of 7r + to IT' cross sections for proton knockout is about a third of the value predicted by a simple impulse approximation.Several studies in which the interaction of negative kaons and negative pions with nuclei was investigated have recently been reported. These studies were done for stopped 1 and for fast 2 ' 3 (220, 380 MeV) negative pions and for stopped negative kaons. 4 The method used in these studies was the detection of prompt y radiation emitted from residual nuclei formed in the reaction. No such experiments were reported to date in which positive pions were used. One of the most striking results of the IT" and K" studies was the relatively strong population of some low-lying states in nuclei formed by the removal of a particles or two protons and two neutrons from the target nucleus. The removal of two or more such "a" particles was also observed. The stopped-K" and -ir" experiments were interpreted in terms of the possible absorption of the incoming particle by a correlated substructure in the nucleus. 1 * 4 The fast-7r~ experiments were interpreted in terms of the knockout of such a correlated substructure or of the individual nucleons from which it could be composed, 2 ' 3 although contributions from pion absorption could not be ruled out.We report here experimental results for the interaction of both positive and negative pions with 27 Al and 28 Si. These are two neighboring nuclei and the self-conjugate nucleus 28 Si could be considered as composed of a substructures. The experiment was performed using the secondary pion beam from the electron linear accelerator at Saclay. Negative pions of 70 MeV and positive pions of 25, 70, and 100 MeV were used for the bombardment of natural aluminum (100% 27 A1) and silicon (92.2% 28 Si) targets. The target thickness was 3 g/cm 2 and the beam momentum spread was ±3%. A 45-cm 3 Ge(Li) detector was placed •below the target about 110° to the beam axis. The detector was shielded by lead and boron. Coincidence (2r^20 nsec) was required between the Ge(Li) detector and a coincidence pulse from two plastic scintillators placed about 50 cm in front of the target. An additional anticoincidence requirement between the Ge(Li) detector and a plastic scintillator placed on the Ge(Li) detector eliminated any background resulting from charged particles. The y spectrum (from 0.180 to 3.260 MeV) was recorded on a 4096-channel analyzer. The y-energy resolution obtained was about 3 keV at 511 keV. The coincidence between the two plastic scintillators was used to monitor the beam, The protons present in the beam were stopped with an absorber in ...

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“…The CEX cross section is found to be small, at the leval of 3-30 jub/sr, which is comparable to or just slightly smaller than the ir~ elastic-scattering cross section from 3 He at 7\ = 208 MeV at corresponding angles. 10 Elastic-scattering data on 3 He are not available for higher energies so we can only compare with the elastic-scattering cross section for 4 He, which decreases by a factor of 10 to 20 between 180 and 260 MeV. The CEX cross section, however, shows little or no energy dependence (Figo 2) for any of the angles studied.…”

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confidence: 92%

“…The absolute normalization of the cross sections was obtained by measuring ir m -p elastic scattering, using a CHg target, and comparing to the data of Bussey et ah 1 The target thickness was checked by measuring 160 77 + -4 He and 7r + -3 He elastic scattering and comparing with existing data. 10 The resulting differential cross sections, for incident pion energies of 200, 250, 275, and 290 MeV, are shown in Fig. 1.…”

mentioning

confidence: 99%

“…The predictions of current calculations have generally been put to a test by comparing with the extensive body of elastic-scattering data for these nuclei. 10 The amplitudes for pion elastic and CEX scattering from 3 He are simply related: The CEX amplitude is proportional to the difference between the 7i + and ir~ elastic-scattering amplitudes. Data on all of these cross sections are thus needed to help put the current scattering theories and their approximations to further test.…”

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confidence: 99%

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Large-Angle Charge-Exchange Scattering of Pions byHe3at 200, 250, 275, and 290 MeV

et al. 1979

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Differential cross sections for the reaction 8 He(7r" ,7r°) 3 H at energies of 200, 250, 275, and 290 MeV over the angular region 8O°^0 ColT]t>^ 150° are presented. Comparison is made with theoretical predictions based on Glauber theory and optical-potential calculations. Neither approach gives a satisfactory description of the data; in particular, the observed energy dependence is much smaller than the theoretical predictions.Pion charge-exchange (CEX) scattering from nuclei has been studied for some time by means of decay measurements of the residual nucleus, which have provided information on the angle-integrated cross section (see the recent review articles 1 ' 2 ). The energy dependence of this total cross section has attracted particular interest. It has generally been found to be very small, and roughly flat around the energy of the (3, 3) resonance of the ir-N interaction. Current scattering theories have had difficulty in reproducing this energy behavior. While there is an apparent need to include pion-nucleus distortion effects to reproduce the magnitude of the cross section, the strong pion absorption at resonant energies gives rise to a minimum in the predicted energy dependence; i 0 e 0 , the effect of the (3,3) resonance on absorption tends to dominate over the simple resonant behavior in the CEX transition amplitude,, Various remedies for this erroneous energy dependence have been tried, and the inclusion of second-order effects seems to yield some improvemento 2 ' 3 Until now, there has been no conclusive theoretical account of the CEX scattering in complex nuclei, and data on the three-body nuclear system 3 He (or 3 H) have been desirable» The distortion effects should be smaller for this system and the theoretical difficulties should be much reduced, making detailed multiple-scattering and optical-model calculations 4 " 9 manageable. The predictions of current calculations have generally been put to a test by comparing with the extensive body of elastic-scattering data for these nuclei. 10 The amplitudes for pion elastic and CEX scattering from 3 He are simply related: The CEX amplitude is proportional to the difference between the 7i + and ir~ elastic-scattering amplitudes. Data on all of these cross sections are thus needed to help put the current scattering theories and their approximations to further test. From an experimental point of view, the 3 He(7r",77°) 3 H process presents the opportunity to detect the recoil triton, circumventing the problem of ir° detection. We have exploited this technique in the present experiment, and in this Letter we report the first differential cross section of CEX scattering to a discrete final state.The angular distributions were measured using the EPICS pion channel at LAMPF (the Clinton P. Anderson Meson Physics Facility) in the course of measurements of the (IT" ,n) reaction on 3 He and 4 He. u Briefly, the beam used had a flux varying between 1 and 3X10 6 7r"/s« The target 12

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Measurement ofπ±-He Scattering and Its Relation to the Pion Form Factor

Cited by 88 publications

References 18 publications

Coupled channel method for the ?-4He elastic and inelastic scattering

Coupled channel method for the ?-4He elastic and inelastic scattering

Interaction of Positive and Negative Pions withAl27andSi
Ashery
¹
,
Zaider
²
,
Shamai
³

et al. 1974
Phys. Rev. Lett.
32
0
0
0
View full text Add to dashboard Cite

Large-Angle Charge-Exchange Scattering of Pions byHe3at 200, 250, 275, and 290 MeV

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Measurement ofπ±-He Scattering and Its Relation to the Pion Form Factor

Cited by 88 publications

References 18 publications

Coupled channel method for the ?-4He elastic and inelastic scattering

Coupled channel method for the ?-4He elastic and inelastic scattering

Interaction of Positive and Negative Pions withAl27andSiAshery1, Zaider2, Shamai3 et al. 1974Phys. Rev. Lett.32000View full textAdd to dashboardCite

Large-Angle Charge-Exchange Scattering of Pions byHe3at 200, 250, 275, and 290 MeV

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About

Interaction of Positive and Negative Pions withAl27andSi
Ashery
¹
,
Zaider
²
,
Shamai
³

et al. 1974
Phys. Rev. Lett.
32
0
0
0
View full text Add to dashboard Cite