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 measured differential cross sections for pion elastic scattering from H3 and He3 in the angular region near the minimum in the non-spin-flip amplitude. Data were acquired for incident pion energies of 180, 220, 256, and 295 MeV. Nuclear charge symmetry is investigated with the aid of several charge-symmetric ratios formed from combinations of measured cross sections. A particularly intriguing result is obtained from the superratio R, which is defined as R=dσ(π+3H)dσ(π−3H)/dσ(π+3He)dσ(π−3He). R is found to be greater than unity at 180 MeV and significantly smaller than unity at 256 MeV, with the transition occurring at around 210 MeV. The charge-symmetry prediction for this ratio (after allowance for the Coulomb force) is one, and is independent of energy and angle. © 1996 The American Physical Society.
Axis error includes +- 3/3 contribution.
Axis error includes +- 3/3 contribution.
Axis error includes +- 3/3 contribution.
We have measured differential cross sections for the elastic scattering of charged pions from H3 and He3 into the backward hemisphere. Near the peak of the delta resonance, at Tπ=180 MeV, an angular distribution covering 114° to 168° in the laboratory extends our earlier measurements. At Tπ=142, 180, 220, and 256 MeV, we have measured an excitation function at angles approaching 170°. The cross sections for the reactions He3(π+,π+)3He, H3(π−,π−)3H show a rise at back angles which is not seen for He3(π−,π−)3He and H3(π+,π+)3H. There is a dip in the cross sections near 130° for Tπ=180 MeV.
No description provided.
No description provided.
No description provided.
The g p -> K^0 Sigma^+ reaction has been measured from threshold to Eg=1.45 GeV (W_cm=1.9 GeV) using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. In the present experiment, this reaction was searched for in the 3pi^0 p final state, by assuming K^0_S -> pi^0 pi^0 and Sigma^+ -> pi^0 p. The experimental results include total and differential cross sections as well as the polarization of the recoil hyperon. The new data significantly improve empirical knowledge about the g p -> K^0 Sigma^+ reaction in the measured energy range. The results are compared to previous measurements and model predictions. It is demonstrated that adding the present g p -> K^0 Sigma^+ results to existing data allowed a better description of this reaction with various models.
The differential cross section for photon energies 1125, 1175 and 1225 MeV.
The differential cross section for photon energies 1275, 1325, 1375 and 1425 MeV.
The recoil polarization of the SIGMA+ for photon energy 1125, 1175 and 1225 MeV.
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.
Absolute differential cross sections for the photoproduction of pions of 33.8-MeV laboratory kinetic energy from protons were measured at eight angles between 29.5 and 146.1° in the center-of-mass system. The over-all absolute accuracy is 4%, while the relative accuracy within the angular distribution is 3%. Comparison is made to various theoretical calculations, with and without inclusion of the effect of a γ−π−ρ-meson coupling. Existing calculations based on dispersion theory give only fair agreement with the data.
No description provided.
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°.
No description provided.
No description provided.
No description provided.
Differential cross sections for π−p→γn have been determined from 427 to 625 MeV/c, mainly at 90° and 110° c.m. The data were obtained by combining measurements of the Panofsky ratio in flight with known charge-exchange cross sections. The results are compared with γn→π−p data derived from γd experiments; the difference is typically 30%. The radiative decay amplitudes of neutral πN resonances are therefore uncertain by at least 30%.
Charge exchange cross section from PWA.
PI- P --> GAMMA N cross section.
GAMMA N --> PI- P cross section calculated using detailed balance.
Differential cross sections have been measured for π+p and π−p elastic scattering at 378, 408, 427, 471, 509, 547, 586, 625, 657, and 687 MeV/c in the angular range -0.8<cosθc.m.<0.8. The scattered pion and recoil proton were detected in coincidence using scintillation-counter hodoscopes. A liquid-hydrogen target was used except for measurements at forward angles, in which a CH2 target was used. Statistical uncertainties in the data are typically less than 1%. Systematic uncertainties in acceptance and detection efficiency are estimated to be 1%. Absolute normalization uncertainties are 2–3 % for most of the data. The measurements are compared with previous data and with the results of recent partial-wave analyses. The data are fit with Legendre expansions from which total elastic cross sections are obtained.
Normalisation uncertainty = 3.1 pct.
Normalisation uncertainty = 4.1 pct.
Normalisation uncertainty = 2.1 pct.
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.
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