Photon Events with Missing Energy at sqrt(s) = 183 to 189 GeV

TL;DR

This study analyzes single photon production with missing energy at 183 and 189 GeV, measuring neutrino families and setting limits on new physics models using DELPHI detector data.

Contribution

It provides updated measurements of neutrino families and constraints on supersymmetric, composite, and gravitational models at high energies.

Findings

Number of light neutrino families measured as 2.84 +/- 0.15(stat) +/- 0.14(syst)

No excess events beyond Standard Model expectations observed

Limits set on new physics models including supersymmetry and gravity

Abstract

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 determined.