Measurement of the W mass in e +e − collisions at production threshold

• Published in: Physics letters. B 1997, Vol.401 (3), p.347-362
• Main Authors: Barate, R., Decamp, D., Goy, C., Nief, J.-Y., Pietrzyk, B., Casado, M.P., Fernandez, E., Juste, A., Sanchez, F., Creanza, D., Maggi, G., Marinelli, N., Zhang, J., Zhang, L., Bazarko, A.O., Becker, U., Forty, R.W., Harvey, J., Lehraus, I., Minten, A., Moneta, L., Pacheco, A., Rensing, P., Schmitt, M., Wagner, A., Barrès, A., Boyer, C., Gay, P., Monteil, S., Perret, P., Nilsson, B.S., Simopoulou, E., Blondel, A., Rougé, A., Jaffe, D.E., Capon, G., Chiarella, V., Curtis, L., Lynch, J.G., Thomson, E., Hansper, G., Tittel, K., Wunsch, M., Beuselinck, R., Binnie, D.M., Goodsir, S., Martin, E.B., Nash, J., Stacey, A.M., Colrain, P., Finch, A.J., Benchouk, C., Bujosa, G., Calvet, D., Carr, J., Coyle, P., Thulasidas, M., Berlich, R., Büscher, V., Moser, H.-G., Richter, R., Seywerd, H., Wiedenmann, W., Wolf, G., Chen, S., Cordier, A., Heusse, Ph, Jacquet, M., Nikolic, I., Tournefier, E., Zerwas, D., Azzurri, P., Batignani, G., Bozzi, C., Ferrante, I., Giassi, A., Ligabue, F., Marrocchesi, P.S., Sanguinetti, G., Sciabà, A., Tenchini, R., Botterill, D.R., Haywood, S., Colas, P., Lemaire, M.C., Locci, E., Renardy, J.-F., Dann, J.H., Reeve, J., Thompson, L.F., Böhrer, A., Apollonio, M., Rothberg, J., Williams, R.W., Armstrong, S.R., Charles, E., Elmer, P., Jin, S., Wu, X., Yamartino, J.M.
• Format: Article
• Language: English
• Subjects: High Energy Physics - Experiment; Physics
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/S0370-2693(97)00460-7

In June 1996, the LEP centre-of-mass energy was raised to 161 GeV. Pair production of W bosons in e +e − collisions was observed for the first time by the LEP experiments. An integrated luminosity of 11 pb −1 was recorded in the ALEPH detector, in which WW candidate events were observed. In 6 events both Ws decay leptonically. In 16 events, one W decays leptonically, the other into hadrons. In the channel where both Ws decay into hadrons, a signal was separated from the large background by means of several multi-variate analyses. The W pair cross-section is measured to be σ WW = 4.23 ± 0.73 (stat.) ± 0.19 (syst.) pb. From this cross-section, the W mass is derived within the framework of the Standard Model: m W = 80.14 ± 0.34 (stat.) ± 0.09 (syst.) ± 0.03 (LEP energy) GeV/ c 2