Lifetime Measurements of π+π− \pi ^+ \pi ^- and π+−K−+\pi^{+-} K^{-+} Atoms to Test Low-Energy QCD Predictions

%PS212 \\ \\ The proposed experiment aims to measure the lifetime of $\pi ^+ \pi ^-$ atoms in the ground state with 10\% precision, using the 24~GeV/c proton beam of the CERN Proton Synchrotron. As the value of the above lifetime of order 10 ^- ^{1} ^{5} s is dictated by a strong interaction at low energy, the precise measurement of this quantity enables to determine a combination of S-wave pion scattering lengths to 5\%. Pion scattering lengths have been calculated in the framework of chiral perturbation theory and values predicted at the same level of accuracy have, up to now, never been confronted with accurate experimental data. Such a measurement would submit the understanding of chiral symmetry breaking of QCD to a crucial test

Study of hadronic decays of the ZO boson

Hadronic decays of Z0 bosons are studied in the Delphi detector. Global event variables and single particle inclusive distributions are compared with QCD-based predictions. The mean charged multiplicity is found to be 20.6±1.0 (stat+syst). The mean values of the sphericity, aplanarity, thrust, minor value, pin T and pout T are compared with values found at lower energy e+e- colliders.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Search for low mass Higgs bosons produced in Z0 decays

A search for light Higgs bosons was performed using the data sample collected in 1990 by the DELPHI detector at LEP, at centre of mass energies between 88.2 and 94.2 GeV. Using the process e+e-→H0+Z0*, Z0*→ff, it is possible to exclude the existence of the standard model Higgs particle with a mass between 0 and 210 MeV/c2 at the 99% confidence level. Extending this analysis to the minimal supersymmetric standard model restricts the lightest neutral Higgs boson to masses above 28 GeV/c2 irrespective of the value of the mixing angle.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe