We have investigated the above processes at the CERN Intersecting Storage Rings (ISR). Results show a marked change of the slope parameter b ( t , s ) = (d/d t ) ln (d σ /d t ) around − t ≈ 0.10 GeV 2 . The s − and t − dependence of b ( t , s ) have been observed over the interval 460 GeV 2 < s < 2900 GeV 2 and 0.02 GeV 2 < t < 0.40 GeV 2 .
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We have investigated the pp elastic scattering at the CERN Intersecting Storage Rings (ISR). We report results for centre-of-mass scattering angles between 30 and 100 mrad and for centre-of-mass energies of 23.5,30.7, 44.9 and 53 GeV. The elastic differential cross-section shows a diffraction-like shape with a sharp minimum at about t = −1.4 GeV 2 .
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Differential cross sections for π − p and pp elastic scattering have been measured at incident momenta ranging from 30 to 345 GeV and in the t range 0.002 (GeV/ c ) 2 ⩽ | t | ⩽ 0.04 (GeV/ c ) 2 . From the analysis of the data, the ratio ϱ ( t = 0) of the real to the imaginary parts of the forward scattering amplitude was determined together with the logarithmic slope b of the diffraction cone.
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Final results of our measurements of elastic proton-proton scattering at the CERN Intersecting Storage Rings (ISR) for c.m. energies √ s from 23 to 63 GeV and momentum transfers | t | from 0.8 to 10 GeV 2 are presented. Absolute differential cross sections have been obtained using the split-field magnet detector facility (SFM) at the five standard energies for integrated luminosities ranging from 0.3 to 4.9 (pb) −1 . The rising total cross section is found to define a scale for diffractive phenomena near the forward peak, including the position of the diffraction minimum near t = −1.4 GeV 2 . The cross section at the minimum is strongly energy dependent, approximately as the ratio of the real to imaginary part of the scattering amplitude in the forward direction. The phase of the scattering amplitude is found to change sign near the minimum. The component of diffraction scattering beyond the second maximum has a much weaker t -dependence than expected in simple eikonal or constituent pictures connecting this region to the forward peak. A further break in slope is observed near t = −6 GeV 2 . There is no evidence for another minimum for t values up to 10 GeV 2 .
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New experimental results are presented on proton-proton elastic scattering at centre-of-mass energies s =23 GeV and s =62 GeV . The data are obtained using the Split Field Magnet detector at the CERN Intersecting Storage Rings. The absolute differential cross-sections show an energy-dependent behaviour. The position of the diffraction minimum changes from t =(−1.44±0.02)GeV 2 at 23 GeV to (−1.26±0.03)GeV 2 at 62 GeV. The cross-section at the second maximum is increasing with s . The connection of these observations with the hypothesis of “geometrical scaling” is discussed.
63 K EVENTS.
380 K EVENTS.
Proton-proton elastic scattering at 400 GeV/c has been measured in the region 5.4<−t<14.4 GeV2 with no sign of a second dip or "break." If the data are fitted by exp(At), the slope A decreases from 1.5±0.1 to 0.7±0.2 GeV−2 over the range. At fixed t the 400-GeV/c cross sections are about 0.6 times those at 200 GeV/c in this t range. At fixed θc.m.=15°, dσdt∝s−n where n=9.7±0.3.
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Proton-proton elastic scattering using 201- and 400-GeV/c extracted beams at Fermilab has been measured in the region 4.9<−t<14.4 GeV2. Contrary to predictions of diffraction models, there is no sign of a second dip or "break," and the slope A in the fit exp(At) is smaller than predicted. It drops from 1.5 to 0.8 GeV−2 over our t range. The shape of the t distribution can be fitted by the power law dσdt∝t−8.4 which is close to a quantum-chromodynamics (QCD) prediction of t−8. At fixed t the 201-GeV/c cross sections are about 2.3 times those at 400 GeV/c which is compatible with the QCD and constituent-interchange-model prediction that dσdt∝s−10 at fixed ts.
LOW T.
HIGH T.
LOW T.
We report results from a measurement of antiproton-proton and proton-proton small-angle elastic scattering at √ s = 24.3 GeV in the range 0.001 ⩽ | t | ⩽ 0.06 (GeV/ c ) 2 . The measurement was performed at the CERN p p Collider by using silicon detectors to observe protons recoiling from a hydrogen cluster-jet target intercepting the stored p and p beams. Fits to the measured differential cross sections yield the ratio of the real to the imaginary part of the forward nuclear scattering amplitude ρ and the nuclear slope parameter b for both p p and pp. We find that the difference Δρ = ρ ( p p ) − ρ( pp ) = 0.031 ± 0.010 agrees with conventional fits and disagrees with the “odderon” fit designed to accommodate the recent UA4 measurement of ρ( p p) at 546 GeV.
Data requested from authors.
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Nuclear slopes fixed to world average.
Measurements of proton-proton elastic scattering at angles around 6 mrad have been made at centre-of-mass energies of 23, 31, 45 and 53 GeV using the CERN Intersecting Storage Rings. The absolute scale of the cross-section was established by determination of the effective density of the colliding beans in their overlap region. Proton-proton total cross sections were deduced by extrapolation of the elastic differential cross-section to the forward direction and by application of the optical theorem. The results indicate that over the energy range studied the proton-proton total cross-section increases from about 39 to about 43 mb.
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NEW VALUES OF ELASTIC SLOPE USING APPARATUS DESCRIBED IN U. AMALDI ET AL., PL 43B, 231 (1973).
Proton-proton elastic scattering has been measured at the CERN Intersecting Storage Rings in the four-momentum transfer range 0.001 ⩽… t …⩽ 0.015 GeV 2 at centre-of-mass energies of 23 and 31 GeV. The detection of Coulomb scattering and of its interference with nuclear scattering leads to the determination of the real part of the nuclear amplitude and of the total proton-proton cross section by the optical theorem.
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