CLEO 98-1 The hadronic transitions Υ ( 2 S ) → Υ ( 1 S )

Using a 73.6 pb−1 data sample of Υ(2S) events collected with the CLEO II detector at the Cornell Electron Storage Ring, we have investigated the hadronic transitions between the Υ(2S) and the Υ(1S). The dipion transition Υ(2S) → Υ(1S)π+π− was studied using two different analysis techniques. Selecting events in which Υ(1S) → e+e−, μ+μ− (“exclusive” analysis), and using the Υ(1S) leptonic branching ratios world averages from the PDG review, we found B(Υ(2S) → Υ(1S)π+π−) = 0.189 ± 0.004 ± 0.010, while using a method allowing Υ(1S) → anything (“inclusive” analysis) we found B(Υ(2S) → Υ(1S)π+π−) = 0.196 ± 0.002 ± 0.010. The appropriate average of the two measurements gives B(Υ(2S) → Υ(1S)π+π−) = 0.192 ± 0.002 ± 0.010. Combining the exclusive and inclusive results we derive the Υ(1S) leptonic branching ratios Bee = 0.0229 ± 0.0008 ± 0.0011 and Bμμ = 0.0249 ± 0.0008 ± 0.0013. We also studied Υ(2S) → Υ(1S)π0π0 and obtained B(Υ(2S) → Υ(1S)π0π0) = 0.092 ± 0.006 ± 0.008. Parameters of the ππ system (dipion invariant mass spectra, angular distributions) were analyzed and found to be consistent with current theoretical models. Lastly, we searched for the η and single π0 transitions and obtained the upper limits B(Υ(2S) → Υ(1S)η) < 0.0028 and B(Υ(2S) → Υ(1S)π0) < 0.0011. Typeset using REVTEX 1 J. P. Alexander, R. Baker, C. Bebek, B. E. Berger, K. Berkelman, K. Bloom, V. Boisvert, D. G. Cassel, D. S. Crowcroft, M. Dickson, S. von Dombrowski, P. S. Drell, K. M. Ecklund, R. Ehrlich, A. D. Foland, P. Gaidarev, R. S. Galik, L. Gibbons, B. Gittelman, S. W. Gray, D. L. Hartill, B. K. Heltsley, P. I. Hopman, J. Kandaswamy, P. C. Kim, D. L. Kreinick, T. Lee, Y. Liu, N. B. Mistry, C. R. Ng, E. Nordberg, M. Ogg, J. R. Patterson, D. Peterson, D. Riley, A. Soffer, B. Valant-Spaight, C. Ward, M. Athanas, P. Avery, C. D. Jones, M. Lohner, S. Patton, C. Prescott, J. Yelton, J. Zheng, G. Brandenburg, R. A. Briere, A. Ershov, Y. S. Gao, D. Y.-J. Kim, R. Wilson, H. Yamamoto, T. E. Browder, Y. Li, J. L. Rodriguez, T. Bergfeld, B. I. Eisenstein, J. Ernst, G. E. Gladding, G. D. Gollin, R. M. Hans, E. Johnson, I. Karliner, M. A. Marsh, M. Palmer, M. Selen, J. J. Thaler, K. W. Edwards, A. Bellerive, R. Janicek, D. B. MacFarlane, P. M. Patel, A. J. Sadoff, R. Ammar, P. Baringer, A. Bean, D. Besson, D. Coppage, C. Darling, R. Davis, S. Kotov, I. Kravchenko, N. Kwak, L. Zhou, S. Anderson, Y. Kubota, S. J. Lee, J. J. O’Neill, R. Poling, T. Riehle, A. Smith, M. S. Alam, S. B. Athar, Z. Ling, A. H. Mahmood, S. Timm, F. Wappler, A. Anastassov, J. E. Duboscq, D. Fujino, K. K. Gan, T. Hart, K. Honscheid, H. Kagan, R. Kass, J. Lee, M. B. Spencer, M. Sung, A. Undrus, R. Wanke, A. Wolf, M. M. Zoeller, B. Nemati, S. J. Richichi, W. R. Ross, H. Severini, P. Skubic, M. Bishai, J. Fast, J. W. Hinson, N. Menon, D. H. Miller, E. I. Shibata, I. P. J. Shipsey, M. Yurko, S. Glenn, S. D. Johnson, Y. Kwon, S. Roberts, E. H. Thorndike, C. P. Jessop, K. Lingel, H. Marsiske, M. L. Perl, V. Savinov, D. Ugolini, R. Wang, X. Zhou, T. E. Coan, V. Fadeyev, I. Korolkov, Y. Maravin, I. Narsky, V. Shelkov, J. Staeck, R. Stroynowski, I. Volobouev, J. Ye, M. Artuso, F. Azfar, A. Efimov, M. Goldberg, D. He, S. Kopp, G. C. Moneti, R. Mountain, S. Schuh, T. Skwarnicki, S. Stone, G. Viehhauser, X. Xing, J. Bartelt, S. E. Csorna, V. Jain, K. W. McLean, S. Marka, R. Godang, K. Kinoshita, I. C. Lai, P. Pomianowski, S. Schrenk, G. Bonvicini, D. Cinabro, R. Greene, L. P. Perera, G. J. Zhou, M. Chadha, S. Chan, G. Eigen, J. S. Miller, C. O’Grady, M. Schmidtler, J. Urheim, A. J. Weinstein, F. Würthwein, D. W. Bliss, G. Masek, H. P. Paar, S. Prell, V. Sharma, D. M. Asner, J. Gronberg, T. S. Hill, D. J. Lange, R. J. Morrison, H. N. Nelson, T. K. Nelson, D. Roberts, A. Ryd, R. Balest, B. H. Behrens, W. T. Ford, A. Gritsan, H. Park, J. Roy, and J. G. Smith Permanent address: University of Texas, Austin TX 78712. Permanent address: Lawrence Livermore National Laboratory, Livermore, CA 94551. Permanent address: BINP, RU-630090 Novosibirsk, Russia. Permanent address: Yonsei University, Seoul 120-749, Korea. Permanent address: Brookhaven National Laboratory, Upton, NY 11973.