A new measurement of the differential cross section and of the analysing power A 0 n of the charge-exchange reaction p − p → n − n at 875 MeV/ c is presented. The A 0 n data cover the entire angular range and constitute a considerable improvement over previously published data, both in the forward and in the backward hemisphere. The cross-section data cover only the backward region, but are unique at this energy. A careful study of the long-term drifts of the apparatus has allowed to fully exploit the good statistics of the data.
Forward hemisphere measurement. Additional systematic error of 4 pct due to target polarization uncertainty.
Backward hemisphere measurement. Additional systematic error of 15 pct.
Differential cross section in the backward hemisphere. Additional systematic error of 15 pct.
The differential p p → n n charge-exchange cross section has been measured at the CERN Low Energy Antiproton Ring (LEAR), at two incident p momenta, 601 and 1202 MeV/c. features of the differential cross-section near the forward direction, i.e. a sharp peak at 0° scattering angle followed by an energy dependent dip-bump structure, are confirmed and measured with good precision and high statistical accuracy. The data show very clearly that the shape of the cross-section is a manifestation of the pion-exchange amplitude, and a simple extrapolation to the pion pole already indicates that the pion-nucleon coupling constant f c 2 can be determined with good precision.
No description provided.
Corrected with data from PL B405,389.
As part of a programme to study the spin structure of the p p→ n n channel, we have measured the analysing power A 0 n and the differential cross section at an incident antiproton beam momentum of 704 MeV/ c . The analysing power exhibits a remarkable angular dependence, which is poorly reproduced by the existing potential models.
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Results are presented on the charge exchange reaction\(\bar pp \to \bar nn\) and\(\bar np\) annihilations from bubble chamber exposures to antiproton beam of momenta 700 and 760 MeV/c. The differential cross section of\(\bar pp \to \bar nn\) shows a forward spike followed by a clear dip bump structure. Total annihilation cross section of\(\bar np\) for average\(\bar n\) momentum of 700 MeV/c has been evaluated to be 55.4±2.2 mb. The multiplicity, Feynmanx andpT2 distributions for inclusive charged pions in\(\bar pp\) and\(\bar np\) annihilations are found to be similar. The emission of charged pions from\(\bar np\) annihilations are found to be consistent with thermodynamic models with temperature ∼110 MeV.
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First measurements of the differential cross section are presented for p ̄ p → n ̄ n at LEAR in the momentum range between 180 and 600 MeV/ c . The differential cross sections show a forward peaking followed by a smooth drop-off. No indication of the “bump-dip” structure reported at higher momenta has been observed. The angle-integrated charge-exchange cross sections are determined down to E n ̄ n cm = 6.6 MeV .
No description provided.
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The differential cross sections of the reaction p―p→n―n were measured at 390, 490, 590, 690, and 780 MeV/c. The existence of the theoretically predicted forward dip is confirmed. The results are compared with the predictions of various N―N potential models.
NUMERICAL VALUES SUPPLIED BY F. SAI.
NUMERICAL VALUES SUPPLIED BY F. SAI.
NUMERICAL VALUES SUPPLIED BY F. SAI.
Reactions p p → p p and p p → n n were studied at the kinetic energy 230 MeV of incident p by using bubble chamber films. Total cross sections for both of the reactions were found to be 51.2 ± 1.6 mb and 9.1 ± 0.6 mb, respectively. Differential cross sections are well explained by the phenomenological theory given by Bryan and Phillips.
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The total and differential p¯p charge-exchange cross sections were obtained at seven momenta in the range 480 to 728 MeV/c. The total cross sections are roughly consistent with other data. The momentum dependences of the Legendre coefficients a1a0, a2a0, and a3a0 of the differential cross sections do not agree well with the predictions of the Bryan-Phillips model, unlike the case of elastic scattering.
TWO SETS OF DATA ARE GIVEN. THIS FIRST IS THAT PREFERRED USING THE CROSS SECTIONS OF BIZZARI ET AL.
SECOND SET USING BURROWS ET AL., CROSS SECTIONS.
DATA NORMALIZED TO THE CROSS SECTIONS OF HAMILTON ET AL., PRL 44, 1179 (1980).
The reaction p ̄ p → n ̄ n has been studied at an incident antiproton laboratory momentum of 1.13 GeV/ c . The antineutron was identified through a subsequent annihilation on a proton. In all, 2601 identified events were obtained. Total and differential cross sections are presented. Comparison is made with the predictions of the Bryan and Phillips model which, in this energy range, is succesful in describing the related reaction p ̄ p → p ̄ p . Here, the agreement is less good.
No description provided.
Based on a sample of about 3500 events, we have measured the total and differential cross sections of p p → n n in the 700–760 MeV/ c incident momentum region. It is found that σ CE = 10.7 ± 0.2 mb at the average momentum of 730 MeV/ c . The differential angular distribution is characterised by a sharp peak and a dip in the forward direction followed by a secondary maximum. The position of the dip corresponds to | t | ≈ m π 2 . These results are compared with the predictions of the model of Bryan-Phillips. On the other hand, this dip-bump structure can be well understood on a simple picture involving a π exchange and a constant background (for | t | ≲ 3 m π 2 ).
No description provided.
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