Future Colliders

Abstract:

We have determined the τ lifetime in e+e- annihilations at an average centre of mass energy of 42.5 GeV, using a pressurized drift chamber close to the interaction point. We find the lifetime to be (3.18-0.75+0.59 ± 0.56) × 10-13 s. The charged weak τ coupling constant relative to that of the μ is found to be Gτ/Gμ = 0.94-0.09+0.12 ± 0.09, in good agreement lepton universality. © 1984.

Abstract:

Samples of ∼1,900 identified protons and ∼500 Λ have been used to search for decuplet baryon production in e⁺e^- annihilation at a c.m. energy of 34.4 GeV. The p π⁺ and Λ π^± invariant mass spectra contain no Δ or Σ* signals. Upper limits, at 95% confidence level, are that less than 12% of all p and less than 26% of all Λ come from the decay of doubly charged Δ and singly charged Σ* states respectively. These limits correspond to production rates of <0.10 Δ⁺⁺ and <0.09 Σ*^± per event (inclusive of anti-particles). Production of the decuplet states Δ⁺⁺ and Σ*^± is suppressed by a factor ≳9 relative to octet baryons of the same strangeness. © 1984 Springer-Verlag.

Abstract:

We have studied at CM energies of 14, 22 and 30-36.7 GeV e⁺e^- annihilation events in which the hadronic final state contains both a proton and an antiproton in the momentum range 1.0 < p < GeV/c. We find that such pairs are produced predominantly in the same jet and conclude that baryon-antibaryon production is dominated by a mechanism involving local compensation of baryon number. © 1984.

Abstract:

e+e- annihilation into hadrons was studied at CM energies between 39.8 and 45.2 GeV and a search was made for new heavy quarks. No evidence was found for the existence of a narrow state excluding the possible existence of the lowest vector toponium state in this mass range. A search for continuum production of heavy quarks led to lower mass limits for new quarks of 22.0 GeV (eQ = 2 3) and 21.0 GeV (eQ = 1 3). Quarks are found to be pointlike, the corresponding mass parameter being larger than 288 GeV. A fit of the QCD and the electroweak contributions to R=σtot/σμμ yielded sin2θW = 0.30-0.07+0.23. © 1984.

Abstract:

Reconstruction of charged D*'s produced inclusively in e+e-. annihilation at CM energies near 34.4 GeV is accomplished in the decay modes D*+→D0π+→K -gp+π0π+ and D*+→D0π+→ K-gp+π-π+π+ and their charge conjugates. Using these and previously reported D*+→D0π+→K- gp+π+ and D*+→D0π+→ K-gp+π+ + missing π0 channels we present evidence for hard gluon bremsstrahlung from charm quarks and show that the ratio of the quark-gluon coupling constant of charm quarks to the coupling constant obtained in the average hadronic event, αsc αrms = 100 ± 0.20 ± 1.20. Our result provides evidence that the quark-gluon coupling constant is independent of flavor. © 1984.