Radiation capture of π − on hydrogen has been measured in the momentum range from p π − = 210 MeV/ c to p π − = 385 MeV/ c and for c.m. angles between 30° and 120°, covering the Δ (1232) resonance. The unambiguous separation of the events from the charge exchange background is based on precise neutron time-of-flight measurements. Detector efficiencies were carefully determined in separate experiments. The experimental results are in good agreement with those of the inverse reaction and with most recent multipole analyses. An upper limit of ±2% can be set on the contribution of the isotensor term to the transition amplitude. A time reversal violating phase, when added to the resonant M 1+ 3 amplitude in the Donnachie-Shaw model, is found to be consistent with zero.
This results was extracted from the cross sections for the inverse reactionPI- P --> GAMMA N via detailed balance by applying relation: D(SIG(GAMMA))/D(OM EGA)=D(SIG(PI-))/D(OMEGA)*P(PI)**2/2/P(GAMMA)**2.
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Data are presented from a high statistics bubble chamber experiment to study K − p interactions in the c.m. energy range 1775 to 1957 MeV. For the reactions K − p → K − p, K − p → K 0 n , K − p → Λπ 0 and K − p → Σ ± π ∓ channel cross sections, differential cross sections and, where appropriate, polarisation distributions have been obtained. The channel cross sections for K − p → Σ 0 π 0 are presented. In general the results are in agreement with those previously published although a significant discrepancy has been found in the Σ ± π ∓ cross sections at the lower energies. New measurements of the Σ ± lifetimes have also been obtained ( τ Σ − = 1.49 ± 0.03 × 10 −10 sec, τ Σ + = 0.807 ± 0.013 × 10 −10 sec).
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THE FORWARD DIFFERENTIAL CROSS SECTION IS THE EXTRAPOLATED VALUE OF THE LEGENDRE POLYNOMIAL FIT.
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Differential cross-section measurements for π − p → γ n, consisting of three angular distributions at 618, 676 and 718 MeV/ c , and the energy dependence at θ γ = 90° for seven incident pion momenta between 502 and 888 MeV/ c , are presented. Our data qualitatively support recent multipole analyses. Agreement with the Scheffler et al. results for the inverse reaction, γ n → π − p, using a ( π − -recoil p) coincidence technique is good excluding a large violation of time reversal invariance. The agreement with γ n → π − p data obtained using the R ( π − / π + ) ratio technique or a deuterium bubble chamber is only qualitative.
Axis error includes +- 6.6/6.6 contribution.
Axis error includes +- 6.2/6.2 contribution.
Axis error includes +- 6.0/6.0 contribution.
Differential cross sections for π−p→π0n at five angles for 239, 264, 295, 323, and 375 MeV/c incident pions are presented. The measurements employ the neutron-photon coincidence method, using carefully calibrated neutron counters and an efficient, large-area photon detector. Good agreement is found with the results of the CERN phase-shift analysis.
Axis error includes +- 6.3/6.3 contribution.
Axis error includes +- 5.5/5.5 contribution.
Axis error includes +- 5.2/5.2 contribution.
Differential cross-section measurements are presented for π−p→γn at five energies around the p33(1232) resonance. A detailed comparison is made with γn→π−p deduced from γd experiments. In general, the results are in support of detailed balance. Using the Christ-Lee-Donnachie-Shaw model, our new data indicate that the T-violating phase in the isovector part of the M1+ multipole is less than 2°, which is a very sensitive test of time-reversal invariance. No evidence is found for a possible isotensor component of the electromagnetic current. Our data are compared to various multipole analyses. In general, the agreement is poor.
Axis error includes +- 6.3/6.3 contribution.
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Differential cross-sections for negative pion radiative capture on protons at c.m. angles of 60°, 90°, and 120° have been measured at nine incident laboratory energies between 110 and 270 MeV. Comparison with measured cross-sections for pion photoproduction and with conventional multipole analyses shows neither evidence for a violation of time reversal invariance nor for an isotensor component of the electromagnetic current of hardrons.
Axis error includes +- 0.0/0.0 contribution (QUOTED ERRORS INCLUDE THE 5 PCT AND 3 PCT UNCERTAINTIES IN THE NEUTRON AND PHOTON DETECTOR EFFICIENCIES).
Axis error includes +- 0.0/0.0 contribution (QUOTED ERRORS INCLUDE THE 5 PCT AND 3 PCT UNCERTAINTIES IN THE NEUTRON AND PHOTON DETECTOR EFFICIENCIES).
Axis error includes +- 0.0/0.0 contribution (QUOTED ERRORS INCLUDE THE 5 PCT AND 3 PCT UNCERTAINTIES IN THE NEUTRON AND PHOTON DETECTOR EFFICIENCIES).
The differential cross sections of π−p→γn at center-of-mass energy Ẽ=1363, 1337, and 1245 MeV are presented. The angular distributions are compared with recent γn→π−p experiments. Though the cross sections for π−p→γn are somewhat lower than those for the inverse reaction, when all uncertainties are considered, we find that our data are in acceptable agreement at all three energies with the inverse reaction determined from π−π+ ratio measurements, in support of time-reversal invariance. The agreement with bubble-chamber measurements at Ẽ=1363 and 1337 MeV is less satisfactory. The isotensor dip test applied to our data is inconclusive. Our measurements are compared with many multipole analyses, disagreeing with most, in particular with pure fixed- t dispersion relation calculations. We find no evidence, in the sense suggested by Donnachie, for the classification of the P11(1470) resonance in an SU(3) antidecuplet. The data are consistent with a small radiative decay of the P11(1470) resonance, as predicted by quark models.
Axis error includes +- 6/6 contribution.
Axis error includes +- 4.5/4.5 contribution.
Axis error includes +- 4.2/4.2 contribution.
We have used an optical spark-chamber spectrometer to perform a systematic study of the reaction π−p→ΛK0 at beam momenta between 930 and 1130 MeV/c. The cross section, angular distribution, and Λ polarization have been measured. We present our complete data from a sample of 11 400 events along with Legendre polynomial coefficients for the angular distributions. No striking cross-section enhancement at ΣK threshold is observed, but there is evidence for a small cusp effect. A simple model which takes account of the ΣK channel provides a good fit to our data.
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Seventeen differential cross sections of the pion-nucleon charge-exchange reaction have been measured at total center-of-mass energies of 1245, 1337, and 1363 MeV. Most measurements are based on the neutron-photon coincidence method, using carefully calibrated neutron counters and an efficient, large-area photon detector. The results are used to test the predictions of charge independence, with which they agree. The results also confirm the Ayed-Bareyre-Sonderegger phase-degeneracy hypothesis at θ̃π0=180°.
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