We have performed a high-statistics measurement of Bhabha scattering and of the production of hadrons in electron-positron annihilation at PETRA energies (12 GeV<~s<~36.7 GeV). Combining the results with measurements of μ+μ− and τ+τ− production enables us to compare our results with electroweak theory. We find sin2θw=0.27±0.08. This is in good agreement with the value obtained from neutrino experiments which were carried out in entirely different kinematic regions.
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ASYMMETRY WAS USED.
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).
The final states of charged hadrons produced in 280 GeV μp scattering are analysed with respect to their planarity and jet structure. Distributions of p ⊥ 2 in and p ⊥ out 2 are presented. A two jet structure in the forward hemisphere is observed for events with high p ⊥ tracks are predicted by QCD models.
PTIN**2 is the sum of the PTIN components squared.
PTOUT**2 is the sum of the PTOUT components squared.
We have measured the polarization for elastic scattering in the reaction π−p→π−p at 2.93 and 3.25 GeV/c using a polarized proton target and multiwire proportional chambers (MWPC's) with emphasis on large-angle scattering. Events were selected by fast scintillation-counter logic. Beam trajectories were measured with four MWPC's and the scattered-particle angles were measured with one or two MWPC's; elastic events were determined by coplanarity and angle-angle correlations. The polarization is in agreement with previous measurements below |t|=2.0 (GeV/c)2, and crosses from negative to positive near the secondary dip in the differential cross section dσdt. In the backward region, an energy dependence appears with the polarization being large and negative at 2.93 GeV/c and consistent with zero at 3.25 GeV/c.
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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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We have measured the reaction ee → μμ and ee → ττ at center of mass energies from 9.4 to 31.6 GeV. The production cross sections are in agreement with the predictions of quantum electrodynamics, resulting in cutoff parameter limits of 70–100 GeV at 95% c.l. The branching ratio for τ → μν ν has been determined as [1.78 ± 2.0 (statist.) ± 1.8(syst.)]% The existence of a new sequential heavy lepton with a mass <14.5 GeV is excluded at 95% c.l.
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The recoil proton polarization of proton Compton scattering (γp→γp) was measured in the photon energy range from 500 MeV to 1000 MeV atθ∗=100° and from 400MeV to 800 MeV atθ∗=130°. A recoil proton and a scattered photon were detected in coincidence with a magnetic spectrometer and a photon detector. The recoil proton polarization was measured with a carbon polarimeter. The results are compared with a phenomenological analysis based on an isobar model and a dynamical analysis based on the dispersion relation.
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Differential cross sections of p p forward elastic scattering were measured between 400 and 730 MeV/ c , and the real-to-imaginary ratio, ϱ, of the forward amplitude was deduced. We found that ρ increases from ∼ 0.1 to ∼ 0.4 in this momentum range. A dispersion-relation analysis shows the existence of a pole-like structure in the real part of the p p amplitude near threshold.
REAL/IMAG RATIO OF FORWARD AMPLITUDE DETERMINED FROM FIT TO COULOMB-NUCLEARINTERFERENCE.
Mesons decaying into π 0 or η and one charged meson were studied using a liquid-argon calorimeter in a non-magnetic double-arm spectrometer. Cross sections and energy dependences are presented. The ϱ ± production mechanisms are discussed in detail: ω and π exchange contribute the largest fractions, but also A 2 exchange is present. ϱ ± production by ω exchange is shown to follow the energy behaviour predicted by the Regge trajectory α ω ( t ) = 0.4 − | t |.
Axis error includes +- 0.0/0.0 contribution (13 TO 25////STATISTICAL ERRORS ARE SMALLER THAN THE SYSTEMATIC ERRORS).
No description provided.
The polarization of the recoil neutrons from the reaction γ p→ π + n was measured at a c.m. angle of 105° for incident photon energies between 675 and 1125 MeV. A scattered π + meson and a recoil neutron were detected in coincidence with a magnetic spectrometer and a neutron polarimeter system using liquid hydrogen. Results are compared with recent phenomenological analyses and the other existing data measured by the double polarization measurement technique.
ERRORS ARE STATISTICAL ONLY.
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