The elastic scattering of K ± mesons on protons has been studied at 5 GeV/c. A total of about 500 000 events have been measured in the c.m. angular range 17° < θ cm < 165° corresponding to 0.2 < − t < (GeV/ c ) 2 . We observed a K − p backward peak which we have parametrized as d σ /d u = (0.6 ± 0.2) exp [(3.3 ± 0.6) u ] μb /(GeV/c) 2 , while for the K + p backward peak we find d σ /d u = (17.5 ± 1) exp [(3.6 ± 0.2) u ] μb /(GeV/c) 2 . The K − p cross-section falls to about 0.03 μ b ( GeV /c) 2 around − t = 5 (GeV/ c ) 2 , while the K + p cross-section stays in the vicinity of 0.3 μ b ( GeV /c) 2 in the same t -region. The K + p and K − p differential cross-sections have cross-over points at − t = 0.2, 1.1 and about 3.5 (GeV/ c ) 2 .
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Differential cross sections in the t -range between 0.02 and 1.5 GeV 2 have been measured for the elastic scattering of particles and antiparticles on protons at 6.4, 10.4 and 14 GeV for K ± p and 10.4 GeV for π ± p and p ± p . Large statistics have been achieved and systematic uncertainties have been minimized. The relative systematic uncertainty between particle and antiparticle data is less than 0.5%. Accurate measurements of the position of the first crossover between particle and antiparticle differential cross sections have been performed. As the energy increases from 6.4 to 14 GeV the K ± p crossover moves to smaller values by 0.010 GeV 2 with a statistical error of 0.006 GeV 2 and a systematic uncertainty of 0.005 GeV 2 . The crossover positions at 10.4 GeV for π ± , K ± and p ± scale approximately with the interaction radii.
CROSSOVER POSITION IS -T = 0.209 +- 0.004 (DSYS = 0.003) GEV**2.
CROSSOVER POSITION IS -T = 0.209 +- 0.004 (DSYS = 0.003) GEV**2. SMALL ANGLE CROSS SECTIONS IN SMALLER T-BINS.
CROSSOVER POSITION IS -T = 0.211 +- 0.004 (DSYS = 0.0025) GEV**2.
Measurements of π±p, K±p, pp, and p¯p elastic scattering are presented for incident momenta of 3, 3.65, 5, and 6 GeVc and momentum transfers typically 0.03 to 1.8 GeV2. The angle and momentum of the scattered particle were measured with the Argonne Effective Mass Spectrometer for 300 000 events, yielding 930 cross-section values with an uncertainty in absolute normalization of ±4%. Only the K+ and proton data show any significant change in slope of the forward diffraction peak with incident momentum. The particle-antiparticle crossover positions are consistent with no energy dependence, average values being 0.14 ± 0.03, 0.190 ± 0.006, and 0.162 ± 0.004 GeV2 for π' s, K' s, and protons, respectively; these errors reflect both statistics and the ±1.5% uncertainty in particle-antiparticle relative normalization. Differences between particle and antiparticle cross sections isolate interference terms between amplitudes of opposite C parity in the t channel; these differences indicate that the imaginary part of the odd-C nonflip-helicity amplitude has a J0(r(−t)12) structure for −t<0.8 GeV2, as predicted by strong absorption models. The cross-section differences for K± and proton-antiproton are in qualitative agreement with the predictions of ω universality, the agreement improving with increasing energy. The corresponding quark-model predictions relating the π± and K± differences failed by more than a factor of 2. We have combined our π± cross sections with other data to better determine the πN amplitudes in a model-independent way; results of this analysis are presented.
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Cross sections or upper limits are reported for 12 meson-baryon and two baryon-baryon reactions for an incident momentum of 9.9 GeV/c, near 90° c.m.: π±p→pπ±,pp±,π+°±,K+Σ±, (Λ0/Σ0)K0; K±p→pK±; p±p→pp. By studying the flavor dependence of the different reactions, we have been able to isolate the quark-interchange mechanism as dominant over gluon exchange and quark-antiquark annihilation.
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We present results of measurements of K ± p and p p elastic scattering and of the annihilation reactions p p →π + π − and p p → K + K − at an incident laboratory momentum of 5 GeV/ c . Nearly complete angular distributions were obtained. Results are also presented for π -meson proton elastic scattering in the momentum transfer ranges 2 < − t < 8 (GeV/ c ) 2 (for π + ) and 0.16 < − t < 7 (GeV/ c ) 2 (for π − ). All measurements were done in one experimental geometry. The measured differential cross sections range from 10 to 10 −5 mb/(GeV/ c ) 2 .
-U = T + 8.486 GEV**2.
THE DATA FOR -T = 7.31 TO 8.45 GEV**2 WERE NORMALIZED TO OTHER EXPERIMENTS.
-U = T + 8.304 GEV**2.
The differential cross sections for elastic π − p, K − p , p p and π + p, pp scattering at 39 and 44.5 GeV/ c , respectively, have been measured in the interval of momentum transfer squared 0.15 ≤ ovbt | ≤ 2 (GeV/ c ) 2 .
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The differential cross section of K − p and K + p elastic scattering has been measured at 4.2, 7 and 10 GeV/ c in the very forward region of scattering angles. The measurements have been made at the CERN PS by means of multiwire proportional chambers and counters. The region of momentum transfers t is 0.001 ⩽ | t | ⩽ 0.10 GeV 2 at the highest momentum and 0.001 ⩽ | t | ⩽ 0.03 GeV 2 at the lowest. Over these regions the Coulomb and the nuclear amplitudes reach their maximum interference. We have used a parametrisation of the above amplitudes to determine the value of the real part of the nuclear forward scattering amplitude. A dispersion relation fit has then been performed using these and earlier measurements; the asymptotic behaviour of the K ± p real parts has been examined in the light of this fit.
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Results are presented from experiment WA7 at the CERN SPS, which has measured the elastic differential cross sections of π ± p, K ± p, p p and pp at incident momen ta of 20, 30 and 50 GeV/ c . The measurements cover the momentum transfer range 0.5 < | t | < 8 (GeV/ c ) 2 , corresponding to c.m. scattering angles between 10° and 50°. The experimental set-up, trigger logic and data analysis are described. The experimental results are compared with existing meson-proton and nucleon-proton data at lower and higher energies covering the medium- and large-| t | region. Some prominent models and their predictions for elastic scattering at WA7 energies and beyond are reviewed, with emphasis on geometrical scaling, factorizing eikonal models, lowest-order QCD and other dynamical exchange-type models. Results for p p two-body annihilation into π − π + and K − K + at 30 and 50 GeV/ c , obtained in parallel with the elastic p p data, are also presented.
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We present results of measurements of the differential cross sections for the following elastic-scattering reactions: (i) π + p at 5.2 and 7.0 GeV/ c in the range −1 < u < 0.02 (GeV/ c ) 2 , (ii) π − p at 7.0 GeV/ c in the range −0.7 < u < 0.05 (GeV/ c ) 2 , (iii) K + p at 5.2 and 7.0 GeV/ c in the ranges −1 < t < −0.01 (GeV/ c ) 2 and −1 < u < 0 (GeV/ c ) 2 , and K − p at 7.0 GeV/ c in the range −1 < u < 0 (GeV/ c ) 2 .
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SIDE GEOMETRY.
A description is given of an experiment to study elastic scattering of π ± , K ± and p on protons at c.m. scattering angles from 45° to 100° at incident laboratory momenta 20 GeV/ c and 30 GeV/ c . The corresponding t range is from −6.2 (GeV/ c ) 2 to −28 (GeV/ c ) 2 . There are no previous observations for these reactions in this t range. High intensity and large geometrical acceptance were required in order to measure the low cross sections. The experiment used a double-arm spectrometer. MWPCs were used for reconstruction, and threshold and differential Čerenkov counters for identification. Scintillation counters, Čerenkov counters and a hadron calorimeter were used in the trigger. The trigger logic utilized specially designed matrices and a hard wired microprocessor. The π − p elastic scattering cross sections follow approximately the dimensional counting rule from 3.5 GeV/ c .and up to 30 GeV/ c . The cross sections decrease by seven orders of magnitude in this energy range. The data is compared to quark models. None of these models give a comprehensive description of the results. However, some modifications to these models improve their consistency with the data.
EARLIER RESULTS GIVEN IN 'A'.
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