1963 summer study report.

"AEC Contract AT(04-3)-476.""AEC Contract AT(04-3)-400.""SLAC Report No. 25.""Summer 1963."Cover title.Includes bibliographical references.Part 2. Authors include: L. Hand and R. WIson.Part 1. Authors include: K. Berkelman, G.R. Bishop, C. de Vries, G. Feldman, D.B. Isabelle, D.B. Lichtenberg, J. Mathews, J. Pine, R. Wilson.Mode of access: Internet

Radiative decays of the J/ψ\psi and evidence for a new heavy resonance

The three photon final state produced in e + e − collisions has been measured at the mass of the J ψ resonance using the nonmagnetic part of the double arm spectrometer DASP. The decays J ψ → ηγ, η'γ and π o γ were observed and their branching ratios are given. A four standard deviation signal was observed in the γγ mass spectrum at a mass of (2.83 ± 0.03) GeV. An upper limit is given for the direct decay J ψ → 3γ

The three photon final state produced in e+e−e^+ e^- collision at 3.6-GeV and at the ψ′\psi'

The three photon final state produced in e + e − collisions at 3.6 GeV and at the mass of the ψ′ resonance has been measured using the nonmagnetic part of the double arm spectrometer DASP. A total of 31 events is observed outside the resonance region compared to 35.1 events predicted from QED. At the mass of the ψ′ 49 events are observed compared to 37.2 events expected from QED. Limits on radiative decays via intermediate states are given

Improved search for B-S(0)-(B)over-bar(S)(0) oscillations

An improved search for Bs oscillations is performed in the ALEPH data sample collected during the first phase of LEP, and reprocessed in 1998. Three analyses based on complementary event selections are presented. First, decays of Bs mesons into hadronic flavour eigenstates are fully reconstructed. This selection yields a small sample of candidates with excellent decay length and momentum resolution and high average Bs purity. Semileptonic decays with a reconstructed Ds- meson provide a second sample with larger statistics, high average Bs purity, but a poorer momentum and decay length resolution due to the partial decay reconstruction. Finally, semileptonic b-hadron decays are inclusively selected and yield the data sample with the highest sensitivity to Bs oscillations, as the much higher statistics compensate for the low average Bs purity and poorer time resolution. A lower limit is set at 10.9 ps-1 at 95% CL, significantly lower than the expected limit of 15.7 ps-1

Study of hadronic final states from double tagged gammagammagammagamma events at LEP

The interaction of virtual photons is investigated using double tagged gammagamma events with hadronic final states recorded by the ALEPH experiment at e^+e^- centre-of-mass energies between 188 and 209 GeV. The measured cross section is compared to Monte Carlo models, and to next-to-leading-order QCD and BFKL calculations.The interaction of virtual photons is investigated using double tagged gammagamma events with hadronic final states recorded by the ALEPH experiment at e^+e^- centre-of-mass energies between 188 and 209 GeV. The measured cross section is compared to Monte Carlo models, and to next-to-leading-order QCD and BFKL calculations

Search for pentaquark states in Z decays

Exotic hadrons made of five quarks (pentaquarks) are searched for in hadronic Z decays collected by the ALEPH detector at LEP. No significant signal is observed. At 95% C.L., upper limits are set on the production rates N of such particles and their charge-conjugate state per Z deca

Search for the standard model Higgs boson at LEP

The four LEP Collaborations, ALEPH, DELPHI, L3 and OPAL, have collected a total of 2461 pb(-1) of e(+)e(-) collision data at centre-of-mass energies between 189 and 209 GeV. The data are used to search for the Standard Model Higgs boson. The search results of the four Collaborations are combined and examined in a likelihood test for their consistency with two hypotheses: the background hypothesis and the signal plus background hypothesis. The corresponding confidences have been computed as functions of the hypothetical Higgs boson mass. A lower bound of 114.4 GeV/c(2) is established, at the 95% confidence level, on the mass of the Standard Model Higgs boson. The LEP data are also used to set upper bounds on the HZZ coupling for various assumptions concerning the decay of the Higgs boson. (C) 2003 Elsevier B.V. All rights reserved