Search for anomalous Z → γγγ events at LEP

• Published in: Physics letters. B Vol. 345; no. 4; pp. 609 - 616
• Main Authors: Aloisio, A., Ambrosi, G., An, Q., Alkhazov, G., Baba, P.V.K.S., Bakken, J.A., Ball, R.C., Banerjee, S., Barillère, R., Bencze, Gy.L., Bertucci, B., Bilei, G.M., Bizzarri, R., Böhm, A., Bouwens, B., Cai, X.D., Casaus, J., Castello, R., Chaturvedi, U.K., Chen, H.F., Chen, H.S., Cifarelli, L., Clare, I., Coignet, G., Commichau, V., Costantini, S., D'Alessandro, R., DeNotaristefani, F., DiBitonto, D., Dionisi, C., Duhem, F., El Mamouni, H., Engler, A., Eppling, F.J., Fesefeldt, H., Field, J.H., Forconi, G., Gailloud, M., Gheordanescu, N., Goldfarb, S., Goldstein, J., Guanziroli, M., He, J.T., Ilyas, M.M., Innocente, V., Jin, B.N., Jones, L.W., Kapustinsky, J.S., Karyotakis, Y., Kim Do, J.K., Krsch, S., Kornadt, O., Landi, G., Lecomte, P., Lin, W.T., Liu, Y., Lohmann, W., Lu, Y.S., Lubbers, J.M., Liibelsmeyer, K., MacDermott, M., Maity, M., Malinin, A., Maña, C., Merkah, M., Mount, R., Nagy, E., Nippe, A., Paoletti, S., Pauss, F., Pinto, J.C., Pistolesi, E., Ren, Z., Reucroft, S., Röhner, S., Rosier-Lees, S., Rosmalen, R., Rosselet, Ph, Santocchia, A., Sarakinos, M.E., Sassowsky, M., Schulte, R., Servoli, L., Shevchenko, S., Sticozzi, F., Stone, H., Syed, A.A., Toker, O., Uwer, U., Valente, E., Vetlitsky, I., Wu, S.X., Yang, C.G., Yang, G., Zaccardelli, C., Zhang, D.H., Zhou, B., Zhou, G.J., Zhu, R.Y., Zichichi, A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 23.02.1995
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/0370-2693(95)01612-T

We have searched for anomalous Z → γγγ events with the L3 detector at LEP. No significant deviations from the expected QED e +e − → γγγ events are observed. The branching ratio upper limit for a compoite Z decaying directly into three photons is found to be 1.0 × 10 −5 at 95% C.L. The branching ratio upper limits for the process Z → γX, X → γγ are in the range of 0.4 to 1.3 × 10 −5, depending on the mass and width of the scalar particle X. In the context of a model with magnetic monopoles coupling to the Z, we find BR(Z → γγγ) < 0.8 × 10 −5 at 95% C.L.; this results in a lower mass limit of 510 GeV for a magnetic monopole.