Evidence is presented for production of Ξ* resonances, decaying into Ξπ, Ξ(1530)π, ΛK¯, and ΣK¯, in K−p interactions at 2.87 Gev/c. The data represent final combined results from a 30-events/μb hydrogen exposure and an 18-events/μb exposure in deuterium designed to study Ξ* production in the mass interval 1.46-2.07 GeV/c2. In addition to Ξ(1820) and Ξ(1940), signals have been observed at masses of 1630 MeV/c2 and 1860 MeV/c2 decaying into Ξ−π+ and YK¯, respectively. Reaction cross sections have been measured for all final states containing two visible signs of strangeness, and for the final states ΛK−K+ and Σ0K−K+.
CROSS SECTIONS ARISING FROM VARIOUS TOPOLOGIES.
K- P CROSS SECTIONS FROM DEUTERIUM TARGET EXPERIMENT. RESULTS ARE IN GOOD AGREEMENT WITH THE HYDROGEN DATA.
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Inclusive single-particle spectra for π± production are presented for data from π±p interactions at 100 GeV/c. The spectra for the four reactions π±p→π±+anything are compared as a function of laboratory longitudinal momentum, Feynman x, center-of-mass (c.m.) rapidity, and transverse momentum squared. Comparisons are also made between these data and analogous data from 16 and 18.5 GeV/c π±p interactions and the energy dependence is discussed. Average values of the transverse momentum are given as a function of the longitudinal momentum and charged-particle multiplicity. A comparison of the charge distributions is presented as a function of rapidity and c.m. energy.
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For the first time, the line reversed reactions π + p→K + Σ + and K − p→ π − Σ + have been studied in the same apparatus. We present the differential cross sections and polarizations over a large t range and at two momenta, 7.0 and 10.1 GeV/ c . The differential cross sections as a function of t are shown for the first time to cross over. Going from the lower to the higher momentum, the differences in cross section between the two reactions diminish at low | t | by about a factor 2. We find large polarizations of opposite sign for the two reactions. The momentum dependence, presented in the form of α eff ( t ) for the t range 0 to −2 (GeV/ c ) 2 , is compared with the expectations from the K ∗ −K ∗∗ trajectory.
-TMIN = 0.0100 GEV**2.
-TMIN = -0.0087 GEV**2.
-TMIN = 0.0067 GEV**2.
The reaction p p → π − π + has been studied at 10.1 GeV/ c in the − t interval from 0.15 to 1.5 (GeV/ c ) 2 . A line-reversal comparison with backward elastic scattering π + p → p π + shows good agreement for − t > 0.3 (GeV/ c ) 2 .
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The differential cross sections for K − p and p p elastic scattering have been measured over the range of four-momentum transfer squared 0.18<− t <3.3 (GeV/ c ) 2 . The K − p data decrease smoothly as a function of − t , whereas, the p p data shows a break at − t = 0.6 (GeV/ c ) 2 followed by a fast drop to − t ≅ 1.6 (GeV/ c ) 2 where the differential cross section levels off and stays constant out to − t = 3 (GeV/ c ) 2 .
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A charge hyperon beam has been brought into operation at the CERN SPS. Particles are identified by a DISC Čerenkov counter, and decay products are analysed by a magnetic spectrometer. Cross sections for the inclusive production of π + , K + , p , Σ + , Σ − , ζ − , d, and π − , K − , p , Σ + , Σ − , ζ − , ω − , d in the forward direction have been measured at laboratory momenta between 70 and 130 GeV/ c . This range of momenta corresponds to 0.35 ⩽ x ⩽ 0.66 for an incident proton momentum of 200 GeV/ c . Antihyperon ( Σ − , ζ − , Σ + ) and Σ + and ω − fluxes have been measured for the first time in a hyperon beam.
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The differential cross sections for γp→γp and γp→π0p have been measured for incident photon energies in the range of 2 to 6 GeV and for |t| ranging from 0.7 to 4.3 GeV2. This corresponds to a center-of-mass angle range of 45° to 128°. The energy dependence of the data is compared to that predicted by several parton models.
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A description is given of an experimental study of exchange degeneracy (EXD) in hypercharge-exchange reactions using the line-reversed partners π + p→K + Σ + (K − p→ π − Σ + ) and π + p→ K + Σ + (1385) (K − p→ π − Σ + (1385)) at incident momenta of 7.0 and 10.1 GeV/ c . Both pairs of reaction were measured in the same apparatus, with particular care being taken to minimize relative normalization errors. For the Σ production reactions we present high statistics measurements of the differential cross sections and polarizations from t ′=0 to large t . The general trends of the data agree with naive expectations from weak EXD. The cross-section difference in the extreme forward direction at the higher momentum is consistent with zero and there is a general reduction in the cross-section differences going from the lower to the higher momentum. The polarizations are approximately equal in magnitude and of opposite sign between the two reactions. On the other hand, the data do not agree with the detailed predictions of EXD. The slope for the positive reaction is systematically steeper in the forward region than for the negative reaction and there is a complex s and t dependence for the cross-section differences including a cross-over at t ⋍ −0.8( GeV /c) 2 . For the Σ(1385) production reactions, we present differential cross-section measurements in the forward region (| t |<0.3(GeV/ c ) 2 ). The cross-section differences are substantial and essentially constant over the s and t ranges studied.
THESE RESULTS WERE BRIEFLY REPORTED IN A. BERGLUND ET AL., PL 73B, 369 (1978), THE RECORD OF WHICH INCLUDES THE TABULATED DATA.
THE RESULTS AT 10.1 GEV WERE FIRST PUBLISHED IN A. BERGLUND ET AL., PL 60B, 117 (1975), THE RECORD OF WHICH INCLUDES THE TABULATED DATA.
Measurements of the production inp-BeO collisions of charged baryons and antibaryons with strangeness between −3 and +3 at\(\sqrt s= 21.2GeV\)x=0.48, andpT=600MeV/c are reported. The experimental results can be interpreted within the framework of a simple proton fragmentation-recombination model.
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The polarization and Q2 dependence of muoproduced ψ→μ+μ− have been analyzed in a magnetized-steel calorimeter at Fermilab. The reaction γVN→ψN is found to be helicity conserving. Even after allowance for possible Q2 dependence of the decay angular distribution, the ψ muoproduction cross section falls more steeply in Q2 than predicted by ψ dominance.
EFFECTIVE CROSS SECTION IN ARBITRARY UNITS.
EFFECTIVE CROSS SECTION IN ARBITRARY UNITS.
EFFECTIVE CROSS SECTION IN ARBITRARY UNITS.
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