We present a measurement of the cross section for the reaction e + e − → e + e − π + π − π + π − at SPEAR. This channel is found to be large and dominated by the process γγ → ϱ 0 ϱ 0 → π + π − π + π − . The cross section, which is small just above the four-pion threshold, exhibits a large enhancement near the ϱ 0 ϱ 0 threshold.
Axis error includes +- 0.0/0.0 contribution (THE QUOTED ERRORS INCLUDE VARIOUS SYSTEMATIC ERRORS ADDED QUADRATICALLY).
Results are reported of an experiment to measure the cross section for production of the D*+ (D*−) in 200-GeV/c π−N interactions. We observe 78 ± 26 events corresponding to a D*-production cross section dσdy=1.6±0.5 μb at y=0.
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We present results on inclusive study of particle production ratios in 405-GeV/c pp interactions from a Fermilab experiment using the 30-in. hydrogen bubble chamber. Single- and double-pion ratios π+π−, π+π−π−π−, and π+π−π+π+ as a function of the Feynman variable x are presented. From these analyses, it is shown that the quark-recombination picture seems to work well for particle production in the fragmentation region. The data on π+π− ratios in association with a leading π± or Λ are compared with each other and also with the π+π−π−π− ratio. These results further support a prediction of the quark-recombination model.
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Inclusive production of ϱ0,f, andg0 mesons and ofKs0,K*0 (892), ϕ andK*0(1430)mesons has been measured at
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Inclusive charged pion production is studied in an exposure of BEBC, filled with hydrogen, to an incidentK+ beam of 70 GeV/c. Total cross sections for pion production and inclusive longitudinal and transverse momentum distributions of π−'s and of positive particles are presented and compared with data at lower energies. Earlier evidence for scaling in the fragmentation regions is confirmed. The central region π− cross section increases proportionally topLAB−1/4; positive particles show almost no energy dependence atx=0. Particle ratios π+/π− are studied as a function ofx andy* and a comparison with 70 GeV/cK−p data is made. Analysis of structure functions for (ππ) pairs and of particle production associated with π± triggers at large |x| in the context of quark/parton models, provides qualitative evidence for the diquark-quark structure of the proton.
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Data are presented on the reaction pp → pX in the range of four-momentum transfer squared 0.04< − t <0.80 GeV 2 and of c.m. energy squared 550 < s < 3880 GeV 2 . Invariant cross sections are given as a function of M 2 / s , where M is the mass of the missing system X, and of t . The cross sections are shown to scale in the variable M 2 / s , for M 2 / s > 0.01. The total diffractive cross section integrated over t and M 2 / s up to M 2 / s =0.05 rises by approximately 15% from σ dif =6.5±0.2 mb at 550 GeV 2 to σ dif =7.5±0.3 mb at 3880 GeV 2 .
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The inclusive reactions h+p→ φ +X, (h= π ±, ,K ± ,p ± ), are studied for 0⪅ x F ⪅0.3 and p ⊥ ⩽ 1 GeV at 93 and and 63 GeV incident momentum. Differential cross sections d σ /d p ⊥ 2 and dσ /d x F are presented and are compared with predictions of the naive parton model.
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The reaction π − p→ π 0 ηn ↳2y ↳2y has been analyzed using data of an experimental performed at the 70 GeV accelerator, with the NICE 648 channel hodoscope spectrometer for γ ray detection. Events with 4 γ seen are used for the analysis. A method is applied, which allows the determination of the number of π 0 η events for each mass, cos θ GJ and t bin. Mass spectra, t distributions and decay angular distributions for the π 0 η system are presented. The cross section for the production of A 2 0 is found to be 2.7 ± 1.1 μ b at 40 GeV/ c beam momentum. No indication of a resonant 1 − state in the π 0 η system is observed, in spite of the fact that this state is allowed for the π 0 η system on the same footing as the observed 0 + and 2 + resonances.
ERROR INCLUDES UNCERTAINTIES IN SEVERAL CORRECTIONS AND IN BACKGROUND SUBTRACTION.
The Track Sensitive Target technique has been used to isolate 5000 events from the reaction π + p→ π + p π 0 π 0 at 4 GeV/ c . Channel cross sections are measured. The data agree with predictions from phase-shift analyses of π + π − data: the effect of the S ∗ is clearly seen. There is strong evidence against any narrow ϵ below 1 GeV/ c 2 .
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We present results for the hypercharge exchange reaction K − p→f' λ from a high statistics experiment at 8.25 GeV/ c using the CERN 2m HBC. The total and differential cross sections have been measured; the polarisation of the Λ hyperon and the f' density matrix elements have been calculated as functions of momentum transfer. We also present detailed information on the relative strength of the natural and unnatural parity exchange contributions to the production mechanism.
D-WAVE RELATIVISTIC BREIT-WIGNER RESONANCE PLUS POLYNOMIAL BACKGROUND FIT.
FITTED FOR INDIVIDUAL TP BINS.
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