The production of single photons has been studied in the reaction e+e- -> gamma + invisible particles at centre-of-mass energies of 183 GeV and 189 GeV. A previously published analysis of events with multi-photon final states accompanied by missing energy has been updated with 189 GeV data. The data were collected with the DELPHI detector and correspond to integrated luminosities of about 51 pb^{-1} and 158 pb^{-1} at the two energies. The number of light neutrino families is measured to be 2.84 +/- 0.15(stat) +/- 0.14(syst). The absence of an excess of events beyond that expected from Standard Model processes is used to set limits on new physics as described by supersymmetric and composite models. A limit on the gravitational scale is also...
The production of single- and multi-photon events has been studied in the reaction e(+) e(-) --> gam...
The production of single- and multi-photon events has been studied in the reaction e+e- -> gamma (ga...
The production of single- and multi-photon events has been studied in the reaction e+e-→ γ(γ) + invi...
The production of single photons has been studiedin the reaction e+e- --> gamma+ invisible particles...
The production of single photons has been studied in the reaction e(+)e(-) --> gamma +invisible part...
The production of single photons has been studied in the reaction e+e- -> gamma + invisible particle...
The production of single photons has been studied in the reaction e+e- → γ+invisible particles at ce...
The production of single- and multi-photon events has been studied in the reaction e+e- -> gamma (ga...
DELPHIThe production of single- and multi-photon events has been studied in the reaction e+e- -> gam...
The production of single- and multi-photon events has been studied in the reaction e(+) e(-) --> gam...
The production of single- and multi-photon events has been studied in the reaction e+e- -> gamma (ga...
The production of single- and multi-photon events has been studied in the reaction e+e-→ γ(γ) + invi...
The production of single photons has been studiedin the reaction e+e- --> gamma+ invisible particles...
The production of single photons has been studied in the reaction e(+)e(-) --> gamma +invisible part...
The production of single photons has been studied in the reaction e+e- -> gamma + invisible particle...
The production of single photons has been studied in the reaction e+e- → γ+invisible particles at ce...
The production of single- and multi-photon events has been studied in the reaction e+e- -> gamma (ga...
DELPHIThe production of single- and multi-photon events has been studied in the reaction e+e- -> gam...
The production of single- and multi-photon events has been studied in the reaction e(+) e(-) --> gam...
The production of single- and multi-photon events has been studied in the reaction e+e- -> gamma (ga...
The production of single- and multi-photon events has been studied in the reaction e+e-→ γ(γ) + invi...