A study of the hadronic resonance structure in the decay $\tau \rightarrow 3 \pi \nu_{\tau}

• Published in: Physics letters. B Vol. 426; pp. 411 - 427
• Main Authors: Abreu, P., Adam, W., Adye, T., Adzic, P., Alekseev, G D., Alemany, R., Allport, P P., Almehed, S., Amaldi, U., Amato, S., Andersson, P., Andreazza, A., Antilogus, P., Apel, W D., Arnoud, Y., Asman, B., Augustin, J.-E., Augustinus, A., Baillon, P., Bambade, P., Barao, F., Barbiellini, Guido, Barbier, R., Bardin, D Y., Barker, G., Baroncelli, A., Barring, O., Bates, M J., Battaglia, M., Baubillier, M., Becks, K H., Begalli, M., Beilliere, P., Belokopytov, Yu, Belous, K., Benvenuti, a C., Berat, C., Berggren, M., Bertini, D., Bertrand, D., Besancon, M., Bianchi, F., Bigi, M., Bilenky, M S., Bizouard, M A., Bloch, D., Bonesini, M., Bonivento, W., Boonekamp, M., Booth, P S L., Borgland, a W., Borisov, G., Bosio, C., Botner, O., Boudinov, E., Bouquet, B., Bourdarios, C., Bowcock, T J V., Boyko, I., Bozovic, I., Bozzo, M., Branchini, P., Brand, K D., Brenke, T., Brenner, R A., Brown, R., Bruckman, P., Brunet, J M., Bugge, L., Buran, T., Burgsmueller, T., Buschmann, P., Cabrera, S., Caccia, M., Calvi, M., Camacho Rozas, a J., Camporesi, T., Canale, V., Canepa, M., Carena, F., Carroll, L., Caso, C., Castillo Gimenez, M V., Cattai, A., Cavallo, F R., Cerruti, C., Chabaud, V., Chapkin, M., Charpentier, P., Chaussard, L., Checchia, P., Chelkov, G A., Chen, M., Chierici, R., Chliapnikov, P V., Chochula, P., Chorowicz, V., Chudoba, J., Cieslik, K., Collins, P.
• Format: Journal Article
• Language: English
• Published: Elsevier 1998
• Subjects: High Energy Physics - Experiment; Physics
• ISSN: 0370-2693
• DOI: 10.1016/S0370-2693(98)00347-5

The hadronic structure of the decay of the $\tau$ lepton to three charged particles, $\tau\rightarrow 3\pi\nu_\tau$, is studied using data collected by the DELPHI detector at LEP between 1992 and 1995. The invariant mass of the $3\pi$ system, $m_{3\pi}$, is fitted using the models of KÏhn and Santamaria, Isgur Morningstar and Reader, and Feindt. The $3\pi$ mass spectrum and the Dalitz projections are compared with each model. Below \mbox{$m_{3\pi}^2 = 2.3~ {\GeV}^2$}, all are in good qualitative agreement. Above \mbox{$m_{3\pi}^2 = 2.3~ {\GeV}^2$}, anomalous behaviour is observed, consistent with the existence of a hitherto unseen decay mode of the $\tau$ through a radial excitation of the $a_1$ meson.