Measurement of αs from the structure of particle clusters produced in hadronic Z decays

• Published in: Physics letters. B Vol. 257; no. 3; pp. 479 - 491
• Main Authors: Deschizeaux, B., Gaitan, V., Miquel, R., Iaselli, G., Maggi, M., Quattromini, M., Zito, G., Gao, Y., Lou, J., Ruan, T., Bossi, F., Dydak, F., Forty, R.W., Hagelberg, R., Jost, B., Martinez, M., Menary, S., Miotto, A., Nash, J., Palazzi, P., Ranjard, F., Rothberg, J., Rotscheidt, H., Tejessy, W., Wachsmuth, H., Falvard, A., Harvey, J., Michel, B., Pallin, D., Hansen, J.R., Nilsson, B.S., Rosowsky, A., Candlin, D.J., Corden, M., Ikeda, M., Bologna, G., Capon, G., Chiarella, V., Laurelli, P., Murtas, F., Passalacqua, L., Boyle, O., Scarr, J.M., Smith, K., Thompson, A.S., Hepp, V., Kluge, E.E., Rensch, B., Rowlingson, B.S., Albanese, J.-P., Courvoisier, D., Etienne, F., Papalexiou, S., Qian, Z., Blum, W., Cowan, G., Dietl, H., Fernandez-Bosman, M., Schwarz, A.S., Stierlin, U., Thomas, J., Bertin, V., Boucrot, J., Kim, D.W., Veillet, J.-J., Videau, I., Zhang, Z., Bagliesi, G., Bottigli, U., Fidecaro, F., Foà, L., Focardi, E., Forti, F., Marrocchesi, P.S., Palla, F., Salmon, D.P., Thompson, J.C., Bloch-Devaux, B., Klopfenstein, C., Loucatos, S., Perez, P., Perrier, F., Rander, J., Schwindling, J., Booth, C.N., Carney, R., Martin, J., Thompson, L.F., Meinhard, H., Mirabito, L., Neugebauer, E., Seywerd, H., Giannini, G., Bellantoni, L., DeWeerd, A.J., Gao, Y.S., Hilgart, J., Pater, J.R., Wear, J.A., Zobernig, G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 28.03.1991; Elsevier
• Subjects: High Energy Physics - Experiment; Physics
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/0370-2693(91)91926-M

Using 106 000 hadronic events obtained with the ALEPH detector at LEP at energies close to the Z resonance peak, the strong coupling constant α s is measured by an analysis of energy-energy correlations (EEC) and the global event shape variables thrust, C-parameter and oblateness. It is shown that the theoretical uncertainties can be significantly reduced if the final state particles are first combined in clusters using a minimum scaled invariant mass cut, Y cut , before these variables are computed. The combined result from all shape variables of pre-clustered events is α s( M Z 2 = 0.117±0.005 for a renormalization scale μ= 1 2 M Z . For μ values between M Z and the b-quark mass, the result changes by −0.009 +0.006.