Search for Single Top Production in $e^{+}e^{-}$ Collisions at $\sqrt{s}$ = 189 - 202 GeV

• Published in: Physics letters. B Vol. 494; pp. 33 - 45
• Main Authors: Barate, R., Decamp, D., Ghez, P., Goy, C., Jezequel, S., Lees, J P., Martin, F., Merle, E., Minard, M N., Pietrzyk, B., Alemany, R., Bravo, S., Casado, M P., Chmeissani, M., Crespo, J M., Fernandez, E., Fernandez-Bosman, M., Garrido, L., Grauges, E., Juste, A., Martinez, M., Merino, G., Miquel, R., Mir, L M., Morawitz, P., Pacheco, A., Riu, I., Ruiz, H., Colaleo, A., Creanza, D., de Palma, M., Iaselli, G., Maggi, G., Maggi, M., Nuzzo, S., Ranieri, A., Raso, G., Ruggieri, F., Selvaggi, G., Silvestris, L., Tempesta, P., Tricomi, A., Zito, G., Huang, X., Lin, Jiali, Ouyang, Q., Wang, T., Xie, Y., Xu, R., Xue, S., Zhang, J., Zhang, L., Zhao, W., Abbaneo, D., Boix, G., Buchmuller, O., Cattaneo, M., Cerutti, F., Ciulli, V., Davies, G., Dissertori, G., Drevermann, H., Forty, R W., Frank, M., Gianotti, F., Greening, T C., Halley, a W., Hansen, J B., Harvey, J., Janot, P., Jost, B., Kado, M., Leroy, O., Maley, P., Mato, P., Minten, A., Moutoussi, A., Ranjard, F., Rolandi, L., Schlatter, D., Schmitt, M., Schneider, O., Spagnolo, P., Tejessy, W., Teubert, F., Tournefier, E., Valassi, A., Wright, a E., Ajaltouni, Ziad Zj, Badaud, F., Chazelle, G., Deschamps, O., Dessagne, S., Falvard, Alain, Ferdi, C., Gay, Pascal, Guicheney, C., Henrard, Pierre, Jousset, J., Michel, B.
• Format: Journal Article
• Language: English
• Published: Elsevier 2000
• Subjects: High Energy Physics - Experiment; Physics
• ISSN: 0370-2693

The single top production via flavour changing neutral currents in the reactions ee -> t c/u is searched for in approximately 411 pb-1 of data collected by ALEPH at centre-of-mass energies in the range between 189 and 202 GeV. In total, 58 events are selected in the data to be compared with 50.3 expected from Standard Model backgrounds. No deviation from the Standard Model expectation is observed. A 95\%~CL upper limit of 0.72 pb on the single top production cross section at 202 GeV is derived assuming a top mass of 174 GeV/c^2 and a 100% branching ratio of the top decay into bW. A model dependent limit on the flavour-changing couplings kZ and kg is obtained by combining all centre-of-mass energies.