We have measured the cross section at 180° for K + p and K + n elastic scattering in the momentum range 1.0 to 1.5 GeV/ c . The K + n cross section was measured on deuterium and the K + p on hydrogen and deuterium. We were thus able to measure directly the difference between free nucleon (proton) scattering and bound nucleon (proton) scattering at large angles. This difference was found to be small and within our experimental accuracy the K + p(n) cross section should be equal to the K + p (free) cross section at 180°. We found no evidence for an s -channel resonance Z ∗ in either the K + p or K + n system. A comparison of our data and those of other groups with theoretical predictions is given.
HYDROGEN AND DEUTERIUM TARGET DATA ARE IN GOOD AGREEMENT. THESE CROSS SECTIONS ARE A WEIGHTED AVERAGE.
Differential cross sections for the elastic scattering of K + mesons on protons have been measured at 12 lab momenta between 130 and 755 MeV/ c using a hydrogen filled bubble chamber. The results are consistent with a repulsive S-wave nuclear force. A phase-shift analysis yielded the following values of the low-energy parameters: a S 1 2 =(0.309±0.002) fm , r S 1 2 =(0.032±0.02) fm a P 1 2 =(0.021±0.002) fm , a P 3 2 =(0.013±0.001) fm 3
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We have measured the polarization parameter and differential cross sections in K+p elastic scattering from a polarized target from small |t| and small |u| at five momentum points: 1.7, 2.1, 2.4, 2.7, and 3.0 GeV/c. The polarized-proton target was butanol cooled at 0.5° by a He3-He4 refrigerator; a combination of multiwire proportional chambers and scintillation counters detected the scattered particles. The results for small |u| are discussed in the context of pure Regge-pole models with exchange-degenerate Λ trajectories.
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We present data from a spark-chamber study of K+p elastic scattering between 432 and 939 MeV/c, over the range −0.6<cosθc.m.<+0.7. With measurements at 13 momenta, and between 2000 events at the lowest momentum and 5000 events at the highest momentum, there is a major improvement over previous data. The elastic cross sections deduced from the differential cross sections are almost independent of momentum through the range covered. The data are inconsistent with counter measurements of the total cross section which suggest a sharp shoulder in the cross section at about 700 MeV/c.
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The differential cross section for K+p elastic scattering has been measured at several momenta in the interval 200-600 MeV/c within a hydrogen bubble chamber. The data have been fitted with a partial-wave analysis. We obtain solutions which are dominated over the entire momentum range by s-wave scattering, with constructive interference between the nuclear and Coulomb scattering. The effective-range approximation with only s waves yields a K+p scattering length a=−0.314±0.007 F and an effective range r0=0.36±0.007 F. The measured total inelastic cross section at 588 MeV/c is 11−5+9 μb.
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The differential cross section for K + p elastic scattering has been measured at 864, 969 and 1207 MeV/ c . Our data show a smooth transition from low-energy s-wave scattering to high-energy diffraction, and are some-what in disagreement with a recent experiment on K + p backward scattering.
The data at COS(THETA) = -1 or 1 come from the Legendre fits (see text).
The data at COS(THETA) = -1 or 1 come from the Legendre fits (see text).
The data at COS(THETA) = -1 or 1 come from the Legendre fits (see text).
Polarization and differential cross-section data at 0.86, 0.97, 1.09, 1.37 and 1.45 GeV c are presented. An energy-independent phase-shift analysis from threshold up to 1.45 GeV c using random searches at 19 momenta and the shortest path method to link solutions at different momenta, yields three solutions. One of these is unlikely; the other two coincide up to 0.86 GeV c , and both show an anticlockwise half-circle in the P 3 -wave.
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A phase shift analysis of the K<sup loc="post">+</sup>p elastic scattering at 780 MeV/c has been performed. The experimental differential cross section is best explained by a solution with dominant s wave, negative s wave phase shift (−42.7 ± 1 deg.) and small contributions of p and d waves.
Corrected for PI+ P events and scanning efficiency.
Elastic and charge-exchange K + n differential cross sections have been measured from K + d interactions from 430 to 940 MeV/ c using spark chambers and scintillation counters. The data have been compared with existing results and in an accompanying paper have been included with other measurements in a phase-shift analysis.
NOTE COHERENT ELASTIC SCATTERING ON DEUTERIUM AT FORWARD ANGLES (-T < 0.13 GEV**2) REDUCES THE CROSS SECTION COMPARED WITH FREE NUCLEON ELASTIC SCATTERING.
SUM OF BREAK-UP AND COHERENT ELASTIC REACTIONS.
Measurements of complete angular distributions of elastic K + p scattering at closely spaced incident momenta from 1368 to 2259 MeV/ c are presented and discussed. A PDP-8 computer controlled system of scintillation counters and core-readout wire spark chambers was used for the detection of elastic events. Diffractive behaviour is already present at the lowest measured momentum and becomes more prominent as the incident momentum increases. An expansion of the angular distributions in terms of Legendre polynomials shows no marked structure of the expansion coefficients as functions of the incident momentum. Our measurements can be adequately described by a number of existing phase shift solutions within 5% of their published values. Also Regge pole extrapolations represent our data satisfactorily.
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Measurements of K + p elastic scattering have been carried out at 13 momenta between 432 MeV/ c and 939 MeV/ c using spark chambers. The data establish unambiguously the constructive interference of the Coulomb and nuclear amplitudes at 432 MeV/ c . The elastic cross section is found to be independent of momentum through the range covered. The phase shifts for S, P, D and F waves are obtained in an energy dependent analysis in which higher waves are held at theoretical values. The initial behaviour ofthe P, D and F amplitudes is quite close to that predicted by the calculation of the peripheral partial waves. Only the P3 and D5 amplitudes become strikingly different with increasing momentum.
COULOMB INTERFERENCE EFFECT SEEN AT SMALL ANGLES.
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Final results are presented of the analysis of the elastic channel in an exposure of 40 000 pictures at each of the four incident K + momenta 2.11, 2.31, 2.5 and 2.72 GeV/ c taken in the 1.5 m British National Hydrogen Bubble Chamber at the 8 GeV/ c proton synchrotron at the Rutherford High Energy Laboratory. Differential cross sections are presented and the results are compared with other published data. A Legendre polynomial analysis requires partial waves up to G wave at all momenta. For the backward peak, visible at each momentum, the slope and the intercept are calculated. A comparison of the forward peak is made with extrapolations from Regge models fitted at higher momenta.
RESULTS DIFFER SLIGHTLY FROM THOSE PREVIOUSLY REPORTED IN J. M. BRUNET ET AL., NP B36, 45 (1972).
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Polarization and differential cross-section data at 16 momenta between 0.86 and 2.74 GeV/ c are presented. (Preliminary data on some of the momenta have been published earlier.) In an energy-independent phase-shift analysis from threshold up to 2.5 GeV/ c , resonant-like as well as non-resonant solutions are found for the P 3 wave. An helicity flip-non-flip decomposition of the partial waves partly supports the indications found in the analyses of other reactions that the pomeron is built up mainly from s -channel helicity non-flip contributions.
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We report on an experiment to obtain differential cross sections for K+p elastic scattering in the vicinity of the possible exotic baryon, the Z1*(1900). The differential cross sections are based on typically 70 000 selected events in the angular region −0.9≤cosθc.m.≤0.9 at each of 22 momenta from 0.865 to 2.125 GeV/c. The data are intended for use in partial-wave analysis to search for the Z1*.
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Differential cross sections for elastic K + p scattering have been measured at nineteen momenta between 0.7 and 1.9 GeV/ c . The data represent between 10 thousand and 20 thousand elastic events at each momentum and cover a wide range of scattering angles ( −0.98 ≲ cos θ ∗ ≲ 0.95 ). A computer controlled system of scintillation counters and acoustic spark chambers was used to detect the elastic events. Various internal consistency checks indicate that the absolute normalization of the data is accurate to within 2–3%. The cross sections show a smooth transition from an isotropic angular distribution to a dominant forward peak over the range covered by the experiment. Phase-shift analyses including these results show little evidence for a direct-channel resonance, and fitting the results by t - and u -channel exchange processes alone gives a good fit.
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