Search for New Particles ine+e−Annihilation from 39.79 to 45.52 GeV

B. Adeva, D. P. Barber, U. Becker, J. Berdugo, A. Boehm, J. G. Branson, J. D. Burger, M. Capell, M. Cerrada, H. S. Chen, M. Chen, M. L. Chen (+52 others)
1984 Physical Review Letters  
We have searched for resonances in the reaction e+ e hadrons, yy, p, p, , and ee, in the energy range 39.79( js (45.52 GeV, using the Mark J detector at PETRA. We obtain stringent upper limits on the production of toponium and particles postulated to explain Z lepton pair+y events observed at the CERN Pp collider. We also set limits on the mass and coupling constant of excited electrons. PACS numbers: 13.65.+i, 14.40.6x, 14.80.Pb High-energy e+e collisions are well suited for searching for new
more » ... searching for new particles, and at ps=45 GeV PETRA provides a unique opportunity for particle searches. The reaction e+ e hadrons (I) has been used to search for new quark-antiquark states. ' Excited electrons, e', modify the angular distribution of the reaction e+ e yy. (2) Muons at large transverse momentum can be used in searches for sequential heavy leptons. New particles may be seen in lepton-pair final states e e~p, p, (3) e+e e+e (4) as well as in reactions (I) and (2). We have measured cross sections for reactions (I) through (4) in a continuous energy scan from 39.79 to 45.52 GeV with the Mark J detector and with an integrated luminosity of 13.0 pb ' to search for toponium' and other resonances. In particular, we look for resonances postulated to explain the abnormally large rate of Z decays which contain lepton pairs 134 1984 The Americ accompanied by a hard photon. The recent observation of the neutral intermediate boson Z in the dilepton channel with an invariant mass around 93 GeV was predicted by the standard electroweak unification model. However, in three out of seventeen events, the Z decays into a lepton pair and an energetic gamma. The standard model fails to explain the rate and the energy spectrum of the particles from this decay mode. It has been suggested that a new particle Xis produced4 5 in the reaction Z-X+y, X-l+t-. The mass of the Xparticle, as computed from the two eey events observed at the CERN collider, lies between 40 and 50 GeV. This X particle can have either spin 1 or spin 0. The decay channels for a spin-1 particle are expected to be lepton or quark pairs, and for a spin-0 particle, 5 lepton pairs, quark pairs, or two photons. If the reaction (5) were to explain the apparent abundance of hard photon plus dilepton events, the partial widths of Z X+y and X e+e would both have to be unusually large. The X particle could then be observed in e+ e annihilation into an Physical Society
doi:10.1103/physrevlett.53.134 fatcat:i4fkw5u5qzgs5kktl6iahtergm