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N IS FAST IN LABORATORY SYSTEM. CUT FOR 'FAST' SELECTION WAS:. PLAB(P=3) > PMIN(P=3), WHERE PMIN IS DETERMINED FROM ALL EVENTS.
N IS FAST IN LABORATORY SYSTEM. CUT FOR 'FAST' SELECTION WAS:. PLAB(P=3) > PMIN(P=4,5,6), WHERE PMIN IS DETERMINED FROM ALL EVENTS.
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Axis error includes +- 20/20 contribution.
Axis error includes +- 20/20 contribution.
Axis error includes +- 20/20 contribution.
K − p reactions have been studied at 13 different incident momenta between 1138 and 1434 MeV/ c . This interval corresponds to a mass of the K − p system varying from 1858 to 1993 MeV. About 300 000 photographs were taken in the 81 cm Saclay hydrogen bubble chamber exposed to a separated K − beam at the CERN proton-synchrotron. A total of about 44 000 events were analyzed, from which partial and differential cross sections were determined. Polarizations were obtained for the two-body reactions where the decay of the Λ or Σ hyperon allowed their measurement. Data for the two-body channels are presented here as well as for the main quasi-two-body reactions.
PARTIAL CROSS SECTIONS. DATA AT 1.305 TO 1.434 GEV/C FOR FINAL STATES K- P, K- P PI0 AND K- N PI+ COME FROM THE HAIFA GROUP, S. DADO ET AL.
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Results on the following π−p reactions involving a hyperon are studied at 4.5 and 6.0 GeV/c from a high-statistics bubble-chamber experiment. (1) π−p→(Λ, Σ0)K0: Differential cross sections and hyperon polarizations are presented. Comparison with the line-reversed reactions K¯N→(Λ, Σ0)π indicates the failure of the predictions of K*(890) and K*(1420) exchange degeneracy. Effective trajectories for these two reactions are compared. Shrinkage is observed in K¯N→Λπ and not in π−p→ΛK0. (2) π−p→(Λ, Σ0)K*(890)0: Differential cross sections, hyperon polarizations, and K*(890)0 density-matrix elements are determined. ΛK*(890)0 decay correlations are found to impose strong constraints on the scattering amplitudes. The data indicate that both natural- and unnatural-parity exchanges contribute large, but opposite, Λ polarizations. This behavior cannot be explained by a simple exchange model utilizing K and the exchange-degenerate K*(890) and K*(1420) only. Additional trajectories or absorption effects are required to obtain the observed Λ-polarization effects. Comparison of ΛK*(890)0 and Σ0K*(890)0 indicates the greater importance of unnatural-parity exchange in the former reaction. We observe no evidence for deviations from isospin predictions in ΛK*(890)0 production where K*(890)0→K+π− and KS0π0. (3) π−p→ΛK*(1420)0 and ΛK*(1300)0: K*(1420)0 density-matrix elements satisfying positivity constraints are determined allowing for s-wave interference effects. Evidence of the existence of a narrow K*(1300)0→Kππ with a dominant K+ρ− decay mode is observed in the 4.5- and 6-GeV/c data. (4) Σ(1385), Λ(1405), Λ(1520) production: Differential cross sections for the quasi-two-body reactions π−p→Y0K0, where Y0 is Λ(1405), Λ(1520), or Σ(1385)0, are presented and found to have a very similar flat slope in the forward direction. Data for forward K+ scattering in the reaction π−p→Σ(1385)−K+ are presented and discussed. It is argued that this forward peak cannot be explained by kinematic reflection or an s-channel effect and therefore must be due to either two-particle exchange or a single exotic exchange in the t channel.
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FIT FOR FORWARD CROSS SECTION AND SLOPE.
Experimental results are presented for the available channels in the 1.2 GeV/ c π + p interaction. An isobaric model with incoherent addition of the amplitudes is used to determine the π, Δ and N ∗ abundance rates in the π + π o p final state. The multipole parameters in the density matrix of the Δ ++ are determined as functions of its production angle.
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LEGENDRE POLYNOMIAL FIT USED TO CORRECT FOR ELASTIC EVENTS LOST FROM THE FORWARD BIN.
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We have used a magnetic spectrometer to study the production of charged pions in collisions of 600-MeV neutrons with nuclei of Be, C, Al, Cu, and Pb over a wide range of angles. For these nuclei we have obtained at five angles (16, 30, 60, 90, and 123°) the spectra of pions of both signs, on the basis of which we have found the cross sections, atomic-number dependences, and angular distributions of pion production. The influence of a number of effects on the characteristics of pion production in nuclei is discussed. The analysis performed permits us to obtain a qualitative picture of the basic regulari- ties of pion production.
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A more accurate value is obtained for the differential cross section for pp scattering at 8.35 BeV by measurement in photographic emulsions. It is found that the cross section is greater than cited in previous communications [ 3 - 5 ] in a large range of angles. The data are analyzed on the basis of the Regge pole technique and compared with those of other experiments. The total pp elastic scattering cross section is found to be 10.8 :1: 0.8 mb; the mean square interaction radius is (1.07 :1: 0.08) F.
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The rr- + p- n + rr0 charge-exchange scattering and the rr- + p- n + 1J ( 1J- 2y) reaction were investigated in 1.55-4.5 BeVIc region in a 17-liter propane-xenon bubble chamber. The total cross sections of both reactions were measured in this region. The angular distributions of the rr0 mesons in the charge-exchange reaction were obtained. The backward exchange-scattering cross sections du( rr- + p- n + rr 0 )ldQ were estimated.
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Data are presented for the reaction ep → ep π 0 at a nominal momentum transfer squared of 1.0 (GeV/ c ) 2 . The data were obtained using an extracted electron beam from NINA and two magnetic spectrometers for coincidence detection of the electron and proton. Differential cross sections have been measured for isobar masses in the range 1.19–1.73 GeV/ c 2 .
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Data are presented for the reaction ep → ep π 0 at a nominal four-momentum transfer squared of 0.5 (GeV/ c ) 2 . The data were obtained using an extracted electron beam from NINA and two magnetic spectrometers for coincidence detection of the electron and proton. Details are given of the experimental method and the results are given for isobar masses in the range 1.19 – 1.73 GeV/ c 2 .
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Results are presented from an experiment in which high-energy deuterons, produced by proton-proton interactions at 21.1 GeV/ c incident momentum, were detected over a range of angles from 12.5 mrad to 60 mrad in the laboratory system. From the momentum spectra of the deuterons, the final states D + π + and D + ϱ + have been identified. The angular distribution for these reactions are presented and compared with previous data at lower energies.
The statistical errors are presented.
The statistical errors are presented.
The statistical errors are presented. The data are from previous publications.
Double differential cross sections for photons above 20 MeV energy were measured for the p+d reaction at 200 MeV. A comparison is made with previous measurements at 140 and 197 MeV. Below 80 MeV photon energy the cross sections and the angular distribution are in reasonable agreement with a recent calculation of the free pnγ elementary process.
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'1'.
'1'.
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The results on the differential cross sections as well as the polarizations of $\Lambda$ and $\Sigma^0$ have been obtained for $\bar{K}^0 n$, $\pi^0 \Lambda$, and $\pi^0 \Sigma^0$ production in $K^- p$ interactions at eight $K^-$ momenta between 514 and 750 MeV/$c$. The study is conducted by measuring multiphoton final states with the Crystal Ball spectrometer, using a $K^-$ beam from the Alternating Gradient Synchrotron of BNL. The results improve substantially the existing data, allowing a detailed reexamination of the $\Lambda^*$ and $\Sigma^*$ states in our energy range.
Differential cross section for the K- P --> KBAR0 N reaction. Errors are statistical only.
Differential cross section for the K- P --> KBAR0 N reaction. Errors are statistical only.
Differential cross section for the K- P --> PI0 LAMBDA reaction. Errors are statistical only.
Cross sections have been measured for the reactions p¯p→π+π− and K+K− at 15 incident-beam momenta between 360 and 760 MeV/c with significantly better statistics than previous experiments in this momentum region. No significant structure has been found in either channel. The values of 90%-confidence-level upper limits for the possible resonance cross sections are given.
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The reactions e + e − → μ + μ − and τ + τ − were measured at s =52 GeV and 55 GeV by using the TOPAZ detector at TRISTAN. For the combined data, the observed charge asymmetry is −0.29±0.13 and the total cross section is 27.9±3.0 (stat.)±0.8 (syst.) pb for μ + μ − production, and those for τ + τ − production are −0.20±0.14 and 35.7±4.3 (stat.)±2.4 (syst.)pb, respectively. These values are consistent with predictions by the standard model of electroweak interactions.
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The gp-->etap reaction has been measured with the Crystal Ball and TAPS multiphoton spectrometers in the energy range from the production threshold of 707 MeV to 1.4 GeV (1.49 =< W >= 1.87 GeV). Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz Microtron MAMI-C and momentum analyzed by the Glasgow Tagging Spectrometer were used for the eta-meson production. Our accumulation of 3.8 x 10^6 gp-->etap-->3pi0p-->6gp events allows a detailed study of the reaction dynamics. The gp-->etap differential cross sections were determined for 120 energy bins and the full range of the production angles. Our data show a dip near W = 1680 MeV in the total cross section caused by a substantial dip in eta production at forward angles. The data are compared to predictions of previous SAID and MAID partial-wave analyses and to thelatest SAID and MAID fits that have included our data.
Total cross section for the reaction GAMMA P --> ETA P.
Differential cross section for the reaction GAMMA P --> ETA P at a photon energy of 710.4 MeV. The errors in the table are statistical only and there is an overall systematic uncertainty of 4.3 PCT.
Differential cross section for the reaction GAMMA P --> ETA P at a photon energy of 714.5 MeV. The errors in the table are statistical only and there is an overall systematic uncertainty of 4.3 PCT.
The reaction gamma p -> p pi0 gamma' has been measured with the Crystal Ball / TAPS detectors using the energy-tagged photon beam at the electron accelerator facility MAMI-B. Energy and angular differential cross sections for the emitted photon gamma' and angular differential cross sections for the pi0 have been determined with high statistics in the energy range of the Delta+(1232) resonance. Cross sections and the ratio of the cross section to the non-radiative process gamma p -> p pi0 are compared to theoretical reaction models, having the anomalous magnetic moment kappa_Delta+ as free parameter. As the shape of the experimental distributions is not reproduced in detail by the model calculations, currently no extraction of kappa_Delta+ is feasible.
Total cross section for the background reaction GAMMA P --> P PI0.
Total cross section for the background reaction GAMMA P --> P PI0 PI0.
Angular distribution of the PI0 in the reaction GAMMA P --> P PI0 at beam energy 400 MeV. Inclusive measurement where only the PI0 decay photons are detected.