Measurement of the Michel parameters and the nu(tau) helicity in tau lepton decays

Heister, A; Schael, S; Barate, R; De Bonis, I; Decamp, D; Goy, C; Lees, Jp; Merle, E; Minard, Mn; Pietrzyk, B; Bravo, S; Casado, Mp; Chmeissani, M; Crespo, Jm; Fernandez, E; Fernandez Bosman, M; Garrido, L; Grauges, E; Martinez, M; Merino, G; Miquel, R; Mir, Lm; Pacheco, A; 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, J; Ouyang, Q; Wang, T; Xie, Y; R, Xu; Xue, S; Zhang, J; Zhang, L; Zhao, W; Abbaneo, D; Azzurri, P; Boix, G; Buchmuller, O; Cattaneo, M; Cerutti, F; Clerbaux, B; Dissertori, G; Drevermann, H; Forty, Rw; Frank, M; Greening, Tc; Hansen, Jb; Harvey, J; Janot, P; Jost, B; Kado, M; Mato, P; Moutoussi, A; Ranjard, F; Rolandi, L; Schlatter, D; Schneider, O; Spagnolo, P; Tejessy, W; Teubert, F; Tournefier, E; Ward, J; Ajaltouni, Z; Badaud, F; Falvard, A; Gay, P; Henrard, P; Jousset, J; Michel, B; Monteil, S; Montret, Jc; Pallin, D; Perret, P; Podlyski, F; Hansen, Jd; Hansen, Jr; Hansen, Ph; Nilsson, Bs; Waananen, A; Kyriakis, A; Markou, C; Simopoulou, E; Vayaki, A; Zachariadou, K; Blondel, A; Bonneaud, G; Brient, Jc; Rouge, A; Rumpf, M; Swynghedauw, M; Verderi, M; Videau, H; Ciulli, V; Focardi, E; Parrini, G; Antonelli, A; Antonelli, M; Bencivenni, G; Bologna, G; Bossi, F; Campana, P; Capon, G; Chiarella, V; Laurelli, P; Mannocchi, G; Murtas, F; Murtas, Gp; Passalacqua, L; Pepe Altarelli, M; Halley, Aw; Lynch, Jg; Negus, P; O'Shea, V; Raine, C; Thompson, As; Wasserbaech, S; Cavanaugh, R; Dhamotharan, S; Geweniger, C; Hanke, P; Hansper, G; Hepp, V; Kluge, Ee; Putzer, A; Sommer, J; Tittel, K; Werner, S; Wunsch, M; Beuselinck, R; Binnie, Dm; Cameron, W; Dornan, Pj; Girone, M; Marinelli, N; Sedgbeer, Jk; Thompson, Jc; Ghete, Vm; Girtler, P; Kneringer, E; Kuhn, D; Rudolph, G; Bouhova Thacker, E; Bowdery, Ck; Finch, Aj; Foster, F; Hughes, G; Rwl, Jones; Pearson, Mr; Robertson, Na; Giehl, I; Jakobs, K; Kleinknecht, K; Quast, G; Renk, B; Rohne, E; Sander, Hg; Wachsmuth, H; Zeitnitz, C; Bonissent, A; Carr, J; Coyle, P; Leroy, O; Payre, P; Rousseau, D; Talby, M; Aleppo, M; Ragusa, F; David, A; Dietl, H; Ganis, G; Huttmann, K; Lutjens, G; Mannert, C; Manner, W; Moser, Hg; Settles, R; Stenzel, H; Wiedenmann, W; Wolf, G; Boucrot, J; Callot, O; Davier, M; Duflot, L; Grivaz, Jf; Heusse, P; Jacholkowska, A; Lefrancois, J; Veillet, Jj; Videau, I; Yuan, C; Bagliesi, G; Boccali, T; Calderini, G; Foa, L; Giassi, A; Ligabue, F; Messineo, ALBERTO MARIA; Palla, F; Sanguinetti, G; Sciaba, A; Sguazzoni, G; Tenchini, R; Venturi, A; Verdini, Pg; Blair, Ga; Cowan, G; Green, Mg; Medcalf, T; Misiejuk, A; Strong, Ja; Teixeira Dias, P; von Wimmersperg Toeller JH,; Clifft, Rw; Edgecock, Tr; Norton, Pr; Tomalin, Ir; Bloch Devaux, B; Colas, P; Emery, S; Kozanecki, W; Lancon, E; Lemaire, Mc; Locci, E; Perez, P; Rander, J; Renardy, Jf; Roussarie, A; Schuller, Jp; Schwindling, J; Trabelsi, A; Vallage, B; Konstantinidis, N; Litke, Am; Taylor, G; Booth, Cn; Cartwright, S; Combley, F; Lehto, M; Thompson, Lf; Affholderbach, K; Bohrer, A; Brandt, S; Grupen, C; Ngac, A; Prange, G; Sieler, U; Giannini, G; Rothberg, J; Armstrong, Sr; Cranmer, K; Elmer, P; Dps, Ferguson; Gao, Y; Gonzalez, S; Hayes, Oj; H, Hu; Jin, S; Kile, J; Mcnamara, Pa; Nielsen, J; Orejudos, W; Pan, Yb; Saadi, Y; Scott, Ij; Walsh, J; Sl, Wu; X, Wu; Zobernig, G.

doi:10.1007/s100520100813

A measurement of the Michel parameters and the average nu(tau) helicity in tau lepton decays is described. The data was collected with the ALEPH detector at LEP during the years 1991 to 1995. A total integrated luminosity of 155 pb(-1) is analysed. The Michel parameters rho(l), xi(l), (xidelta) l (l = e, mu), and eta(mu) are determined for the leptonic decays, and the chirality parameters xi(pi), xi(rho), and xi(a1) for the hadronic final states. Under the assumptions of e-mu universality and xi(pi) = xi(rho) = xi(a1), the values rho(i) = 0.742 +/- 0.016, eta(i) = 0.012 +/- 0.026, (xidelta)l = 0.776 +/- 0.051, xil = 0.986 +/- 0.074, and xi(h) = 0.992 +/- 0.011 are obtained. No significant deviation is observed from the Standard Model assumption of the V - A structure of the charged weak interaction.