Single- and multi-photon final states with missing energy at e+e− colliders

• Published in: Nuclear physics. B Vol. 541; no. 1; pp. 31 - 49
• Main Authors: Montagna, G., Moretti, M., Nicrosini, O., Piccinini, F.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 22-02-1999
• Subjects: Electron-positron collisions; Irreducible background; Missing energy; New physics searches; Radiative corrections; Visible photons; Visible photons; Irreducible background; 13.10.+q; New physics searches; Missing energy; Radiative corrections; 13.85.Qk; 13.40.K; Electron-positron collisions
• ISSN: 0550-3213; 1873-1562
• DOI: 10.1016/S0550-3213(98)00795-0

The search for new physics in single- and multi-photon final states with large missing energy at LEP and future
e
+
e
− colliders requires precise predictions for the Standard Model irreducible background. While at LEP1 the theoretical situation is under control, going to LEP2 (and beyond) some improvements are necessary. To approach the aimed
O(1%) theoretical accuracy, the tree-level matrix elements for the processes
e
+e
− → ν
νnγ
, with
n = 1, 2, 3, are exactly computed in the Standard Model, including the possibility of anomalous couplings for single-photon production. Due to the presence of observed photons in the final state, particular attention is paid to the treatment of higher-order QED corrections. Comparisons with existing calculations are shown and commented on. An improved version of the event generator NUNUGPV is presented.