Earlier measurements at LEP of isolated hard photons in hadronic Z decays, attributed to radiation from primary quark pairs, have been extended in the ALEPH experiment to include hard photon productioninside hadron jets. Events are selected where all particles combine democratically to form hadron jets, one of which contains a photon with a fractional energyz≥0.7. After statistical subtraction of non-prompt photons, the quark-to-photon fragmentation function,D(z), is extracted directly from the measured 2-jet rate. By taking into account the perturbative contributions toD(z) obtained from anO(ααs) QCD calculation, the unknown non-perturbative component ofD(z) is then determined at highz. Provided due account is taken of hadronization effects nearz=1, a good description of the other event topologies is then found.
2-jet events. Variable Z has been defined as E(gamma)/(E(gamma)+E(had)), where E(gamma) is the energy of the hard photon in 'photon-jet', E(had) is the energy of the rest hadrons in jet. Ycut is jet resolution parameter (see paper).
2-jet events. Variable Z has been defined as E(gamma)/(E(gamma)+E(had)), where E(gamma) is the energy of the hard photon in 'photon-jet', E(had) is the energy of the rest hadrons in jet. Ycut is jet resolution parameter (see paper).
2-jet events. Variable Z has been defined as E(gamma)/(E(gamma)+E(had)), where E(gamma) is the energy of the hard photon in 'photon-jet', E(had) is the energy of the rest hadrons in jet. Ycut is jet resolution parameter (see paper).
The ϒ′ state has been observed as a narrow resonance at M ( ϒ ′) = 10.02 ± 0.02 GeV in e + e − annihilations, using a NaI and lead-glass detector in the DORIS storage ring at DESY. The ratio Г ee Г had /Г tot of electronic, hadronic, and total widths has been measured to be 0.32 ± 0.13 keV. The parameters of the Г particle have also been determined to be/ M (Г)
The data renormalized to the expected level of continuum based on the ratioof R=sigma(hadrons)/sigma(mu+mu-) = 4.7 at sqrt(s) = 5 GeV.
The data renormalized to the expected level of continuum based on the ratioof R=sigma(hadrons)/sigma(mu+mu-) = 4.7 at sqrt(s) = 5 GeV.