The general features of p p interactions at 32 GeV/ c are analysed in a bubble chamber experiment with a statistics of 5.2 μb/event. The inclusive production of neutral strange particles and pions is analysed and compared to results obtained at other energies and in pp interactions. Total cross sections are determined for various 4C reactions and the relative contributions of diffractive dissociation and Δ Δ production to the reaction p p → p p π + π − are estimated.
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TOTAL CROSS SECTIONS FOR 4C REACTIONS.
New experimental results are presented on proton-proton elastic scattering in the range of momentum transfer 4 GeV 2 < − t < 10 GeV 2 at the centre-of-mass energy of √ s = 53 GeV. The data have been obtained using the Split-Field Magnet detector at the CERN Intersecting Storage Rings. We observe another change of slope of the differential cross section near − t =6.5 GeV 2 .
NUMERICAL VALUES SUPPLIED BY K. WINTER.
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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The polarization parameter has been measured in K − p elastic scattering at eight incident beam momenta between 650 MeV/ c and 1071 MeV/ c throughout a center of mass angular range of −0.75 < cos θ ∗ < 0.85 . Experimental results and coefficients of Legendre polynomial fits to the data are presented and compared with other measurements and partial wave analysis.
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The polarization parameter in proton-proton elastic scattering has been measured at an incident momentum of 7.9 GeV/ c and four-momentum transfers in the range 0.9 < | t | < 6.5 (GeV/ c ) 2 using a high intensity unpolarized proton beam incident on a polarized proton target. The angle and momentum of the forward scattered protons were measured with a magnet spectrometer and scintillation counter hodoscopes and the angle of the recoil proton was measured using similar hodoscopes. A clean separation between the elastic scattering from free hydrogen and that coming from inelastic interactions and from interactions with complex nuclei in the target was obtained. The polarization shows substantial structure rising from zero at | t | = 1.0 (GeV/ c ) 2 to a maximum at | t | = 1.7 (GeV/ c ) 2 and then falling to zero at | t | = 2.0 (GeV/ c ) 2 . There is evidence of a further peak at | t | = 2.8 (GeV/ c ) 2 . Above | t | = 3.25 (GeV/ c ) 2 the polarization is small and consistent with zero. A comparison of these data with data obtained at other beam momenta shows that the polarization parameter has a strong momentum dependence.
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A measurement of the polarization parameter P 0 in pp elastic scattering has been made at 24 GeV/ c over the range | t | = 0.1 to 0.9 (GeV/ c ) 2 , positive, falling to zero around | t | = 0.8 (GeV/ c ) 2 . For the range 0.1 ⪕ |t| ⪕ 0.4 GeV /c) 2 , P 0 is constant at about 0.03.
Axis error includes +- 5/5 contribution (SYS-ERR DUE MAINLY TO UNCERTAINTY IN KNOWLEDGE OF ABSOLUTE VALUE OF TARGET POLARIZATION).
We report the results of a pion-electron scattering experiment to measure the charge radius of the pion. The experiment was performed in a 50 GeV/ c negative, unseparated beam at the IHEP accelerator, Serpukhov, and has been briefly reported in an earlier publication [1]. A magnetic spectrometer instrumented with wire spark chambers was used to record the incident pion trajectory and the angles and momenta of the scattered particles. Events are reconstructed by detailed trackfinding programs, and a set of kinematic and geometric cuts define the elastic sample. Electrons are identified both by kinematic criteria and pulse height information from total absorption lead glass Čerenkov counters. The final elastic sample consisted of 40 000 πe events in the region of four-momentum transfer squared 0.013 (GeV/ c ) 2 ⩽ q 2 ⩽ 0.036 (GeV/ c ) 2 . A full error matrix fit to the form factors of the pion gave the r.m.s. charge radius of the pion: 〈r π 2 〉 1 2 = (0.78 −0.10 +0.09 ) fm .
Axis error includes +- 0.7/0.7 contribution (DUE TO ACCIDENTAL ANTI-COINCIDENCES).
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The differential elastic p−p scattering cross section was measured at 6 GeV/c at the Argonne Zero Gradient Synchrotron in the range p⊥2 = 0.6−1.0 (GeV/c)2 using a 65%-polarized target and a 75%-polarized extracted beam of intensity 3 × 109 protons/pulse. We simultaneously measured the polarization of the recoil proton with a well-calibrated carbon-target polarimeter. All three polarizations were measured perpendicular to the horizontal scattering plane. Our results indicate that P and T invariance are both obeyed to good precision even at large p⊥2. Parity invariance implies that the eight single-flip transversity cross sections are zero, so our data give the relative magnitudes of the eight remaining pure spin cross sections where all spins are measured. We find that the double-flip transversity cross sections are nonzero.
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A study of 205-GeV/c π−p interactions has been made with a 48 800-picture exposure in the bare Fermilab 30-inch hydrogen bubble chamber. The average number of charged particles produced per inelastic interaction is 7.99±0.06. The elastic cross section is 3.18±0.13 mb and the total cross section is 24.19±0.44 mb. The inclusive cross sections for neutral-particle production are: σ(γ)=171.3±15.3 mb, σ(KS0)=3.64±0.61 mb (x<0.3), σ(Λ)=1.71±0.34 mb (x<0.3), and σ(Λ¯)=0.59±0.23 mb (x<0.1). The average number of π0's produced per inelastic collision is consistent with a linear rise with the number of charged particles, and about equal to the number of produced π− or π+. The average number of K0's, Λ's, and Λ¯'s is consistent with very little dependence on the number of charged particles. General characteristics of neutral-particle production are presented and compared with other experiments. For each topology the produced neutral energy is ∼13 of the incident energy.
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The differential cross sections for the elastic scattering of π+, π−, K+, K−, p, and p¯ on protons have been measured in the t interval -0.04 to -0.75 GeV2 at five momenta: 50, 70, 100, 140, and 175 GeV/c. The t distributions have been parametrized by the quadratic exponential form dσdt=Aexp(B|t|+C|t|2) and the energy dependence has been described in terms of a single-pole Regge model. The pp and K+p diffraction peaks are found to shrink with α′∼0.20 and ∼0.15 GeV−2, respectively. The p¯p diffraction peak is antishrinking while π±p and K−p are relatively energy-independent. Total elastic cross sections are calculated by integrating the differential cross sections. The rapid decline in σel observed at low energies has stopped and all six reactions approach relatively constant values of σel. The ratio of σelσtot approaches a constant value for all six reactions by 100 GeV, consistent with the predictions of the geometric-scaling hypothesis. This ratio is ∼0.18 for pp and p¯p, and ∼0.12-0.14 for π±p and K±p. A crossover is observed between K+p and K−p scattering at |t|∼0.19 GeV2, and between pp and p¯p at |t|∼0.11 GeV2. Inversion of the cross sections into impact-parameter space shows that protons are quite transparent to mesons even in head-on collisions. The probability for a meson to pass through a proton head-on without interaction inelastically is ∼20% while it is only ∼6% for an incident proton or antiproton. Finally, the results are compared with various quark-model predictions.
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