We report on a new measurement of B0-B0 mixing at the CERN Spp̄S collider. Mixing is measured in the non-isolated high mass dimoun sample using data from the 1988-1989 collider runs. The measured value of the mixing parameter, χ, is 0.145±0.035(stat.) ± 0.014(syst.). The average of this measurement and that from our 1984-1985 data is ξ= 0.14 ± 0.029 (stat.) ± 0.017 (syst.) assuming fully correlated errors. Using the measurement of ξd from ARGUS and CLEO, we obtain χ = 0.50 ± 0.20, which gives a limit of χs > 0.17 (0.12) at 90% (95%) CL. Including the measurements of χ from the ALEPH and L3 experiments gives χs = 0.53 ± 0.15, and a limit of χs > 0.27 (0.23) at 90% (95%) CL.
Bibliographical noteFunding Information:
We are grateful to the management and staff of CERN and of all participating institutes for the vigorous support of this experiment. The following funding agencies have contributed to this programme: Fonds zur F6rderung der Wissenschaftlichen For-schung, Austria; Valtion luonnontieteellinen toimikunta, Suomen Akatemia, Finland; Institut National de Physique Nucl6aire et de Phy- sique des Particules, and Institut de Recherche Fondamentale (CEA), France; Bundesministerium fiir Forschung und Technolo-gie, FRG; Istituto Nazionale di Fisica Nucleare, Italy; Science and Engineering Research Council, UK; Stichting Voor Fundamenteel Onderzoek der Ma-terie, The Netherlands: Centro de Investigaciones Energetica, Medioam-bientales y Tecnologicas (CIEMAT), Spain; Department of Energy, USA. Thanks are due to the following people who have worked with the Collaboration in the preparation for and data collection on the runs described here: L. Baumard, F. Bernasconi, D. Brozzi, V. Cecconi, L. Dumps, G. Fetchenhauer, G. Gallay, S. Lazic, J.C. Michelon, S. Pavlon and L. Pollet.