Physics – High Energy Physics – High Energy Physics - Experiment
Scientific paper
2000-05-02
Eur.Phys.J.C18:253-272,2000
Physics
High Energy Physics
High Energy Physics - Experiment
41 pages, 15 figures, submitted to Eur. Phys. J. C CERN-EP number corrected
Scientific paper
10.1007/s100520000522
Photonic events with large missing energy have been observed in e+e- collisions at a centre-of-mass energy of 189GeV using the OPAL detector at LEP. Results are presented for event topologies consistent with a single photon or with an acoplanar photon pair. Cross-section measurements are performed within the kinematic acceptance of each selection, and the number of light neutrino species is measured. Cross-section results are compared with the expectations from the Standard Model process e+e- to nu nubar + photon(s). No evidence is observed for new physics contributions to these final states. Upper limits are derived on sigma(e+e- to XY).BR(X to Y gamma) and sigma(e+e- to XX).BR**2(X to Y gamma) for the case of stable and invisible Y. These limits apply to single and pair production of excited neutrinos (X=nu*, Y = nu), to neutralino production (X=neutralino_2, Y=neutralino_1) and to supersymmetric models in which X = neutralino_1 and Y = light gravitino. The case of macroscopic decay lengths of particle X is considered for e+e- to XX, X to Y gamma, when M_Y is of order zero. The single-photon results are also used to place upper limits on superlight gravitino pair production as well as graviton-photon production in the context of theories with additional space dimensions.
Abbiendi Giovanni
collaboration The OPAL
No associations
LandOfFree
Photonic events with missing energy in e+e- collisions at sqrt(s)=189 GeV does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Photonic events with missing energy in e+e- collisions at sqrt(s)=189 GeV, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photonic events with missing energy in e+e- collisions at sqrt(s)=189 GeV will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-98327