TY - JOUR

T1 - Search for anomalous production of photonic events with missing energy in e+e− collisions at √s=130–172 GeV

AU - Kartvelishvili, Vakhtang

AU - OPAL Collaboration

PY - 1998/5

Y1 - 1998/5

N2 - Photonic events with large missing energy have been observed in e+e−e+e− collisions at centre-of-mass energies of 130, 136, 161 and 172 GeV using the OPAL detector at LEP. Results are presented based on search topologies designed to select events with a single photon and missing transverse energy or events with a pair of acoplanar photons. In both search topologies, cross-section measurements are performed within the kinematic acceptance of the selection. These results are compared with the expectations from the Standard Model processes e+e−→νν¯¯¯γ(γ)e+e−→νν¯γ(γ) (single-photon) and e+e−→νν¯¯¯γγ(γ)e+e−→νν¯γγ(γ) (acoplanar-photons). No evidence is observed for new physics contributions to these final states. Upper limits on σ(e+e−→XY)⋅BR(X→Yγ)σ(e+e−→XY)⋅BR(X→Yγ) and σ(e+e−→XX)⋅BR2(X→Yγ)σ(e+e−→XX)⋅BR2(X→Yγ) are derived for the case of stable and invisible Y. These limits apply to single and pair production of excited neutrinos ( X=ν∗,Y=νX=ν∗,Y=ν ), to neutralino production ( X=χ~02,Y=χ~01X=χ~20,Y=χ~10 ), and to supersymmetric models in which X=χ~01X=χ~10 and Y=G~Y=G~ is a light gravitino. For the latter scenario, the results of the acoplanar-photons search are used to provide mode l-dependent lower limits on the mass of the lightest neutralino.

AB - Photonic events with large missing energy have been observed in e+e−e+e− collisions at centre-of-mass energies of 130, 136, 161 and 172 GeV using the OPAL detector at LEP. Results are presented based on search topologies designed to select events with a single photon and missing transverse energy or events with a pair of acoplanar photons. In both search topologies, cross-section measurements are performed within the kinematic acceptance of the selection. These results are compared with the expectations from the Standard Model processes e+e−→νν¯¯¯γ(γ)e+e−→νν¯γ(γ) (single-photon) and e+e−→νν¯¯¯γγ(γ)e+e−→νν¯γγ(γ) (acoplanar-photons). No evidence is observed for new physics contributions to these final states. Upper limits on σ(e+e−→XY)⋅BR(X→Yγ)σ(e+e−→XY)⋅BR(X→Yγ) and σ(e+e−→XX)⋅BR2(X→Yγ)σ(e+e−→XX)⋅BR2(X→Yγ) are derived for the case of stable and invisible Y. These limits apply to single and pair production of excited neutrinos ( X=ν∗,Y=νX=ν∗,Y=ν ), to neutralino production ( X=χ~02,Y=χ~01X=χ~20,Y=χ~10 ), and to supersymmetric models in which X=χ~01X=χ~10 and Y=G~Y=G~ is a light gravitino. For the latter scenario, the results of the acoplanar-photons search are used to provide mode l-dependent lower limits on the mass of the lightest neutralino.

U2 - 10.1007/s100529800865

DO - 10.1007/s100529800865

M3 - Journal article

VL - 2

SP - 607

EP - 625

JO - European Physical Journal C: Particles and Fields

JF - European Physical Journal C: Particles and Fields

SN - 1434-6044

IS - 4

ER -