Single-photon signal from neutralinos at LEP2 Original Research Article

The production of invisible pairs of lightest neutralinos accompanied by a large-angle hard photon in the reaction e+e− → χ10χ10γ is studied at LEP2 energies. The most general gaugino/higgsino composition of the χ10 within the Minimal Supersymmetric Standard Model is assumed. The spectrum of the observed photon is derived within the framework of the pt-dependent structure-function approach, whose accuracy is assessed to be within the foreseen experimental accuracy at LEP2. Higher-order QED corrections due to undetected initial-state radiation are also included. A comparison with the Standard Model main background from e+e− → ννγ is performed for optimized photon kinematical cuts. Quantitative conclusions on the signal/ background ratio are given for a wide range of values of the SUSY parameters.