VOLUME 70, NUMBER 18 PH YSICAL REVIEW LETTERS 3 MA+ 1993 Search for Exclusive b = u Semileptonic Decays of 8 Mesons A. Bean, ' J. Gronberg, ' R. Kutschke, ' S. Menary, ' R. J. Morrison, ' H. N. Nelson, ' J. D. Richman, ' H. Tajima, ' D. Schmidt, ' D. Sperka, ' M. S. Witherell, ' M. Procario, S. Yang, R. Ballest, M. Daoudi, W. T. Ford, D. R. 3ohnson, K. Lingel, M. Lohner, P. Rankin, 3. G. Smith, J. P. Alexander, C. Bebek, K. Berkelman, D. Besson, T. E. Browder, D. G. Cassel, H. A. Cho, D. M. Coffman, P. S. Drell, R. Ehrlich, R. S. Galik, M. Garcia-Sciveres, B. Geiser, B. Gittelman, S. W. Gray, " D. L. Hartill, B. K. Heltsley, " K. Honscheid, C. D. Jones, J. Kandaswamy, N. Katayama, P. C. Kim, " D. L. Kreinick, G. S. Ludwig, J. Masui, J. Mevissen, N. B. Mistry, C. R. Ng, " E. Nordberg, M. Ogg, ' " C. O' Grady, J. R. Patterson, D. Peterson, D. Riley, M. Sapper, M. Selen, H. Worden, M. Worris, F. Wiirthwein, ~ P. Avery, A. Freyberger, J. Rodriguez, R. Stephens, J. Yelton, D. Cinabro, S. Henderson, K. Kinoshita, T. Liu, M. Saulnier, R. Wilson, H. Yamamoto, A. J. Sadoff, R. Ammar, S. Ball, P. Baringer, D. Coppage, N. Copty, " R. Davis, N. Hancock, M. Kelly N. Kwak H. Lam Y. Kubota, M. Lattery, 3. K. Nelson, S. Patton, D. Perticone, R. Poling, V. Savinov, S. Schrenk, R. Wang, M. S. Alam, ' I. J. Kim, ' B. Nemati, ' J. J. O' Neill, ' V. Romero ' H. Severini, '0 C. R Sun '0 M. M. Zoeller ' G Crawford, ~' ' R. Fulton, ' ' K. K. Gan, ' ' H. Kagan, ' ' ~ R Kass, '' J. Lee, '' R. Malchow, ~' ' F Morrow, '' Y. Skovpen, '' ' M. Sung '' C White, ' ' J. Whitmore, ' ' P. Wilson, ' F. Butler, ' X Fu, ' G. Kalbfleisch ~' M. Lambrecht, ' W. R. Ross, ' P. Skubic, ' 3. Snow, ' P L. Wang M. Wood ' ~ D. Bortoletto, ' D. N. Brown, ' ~ 3. Dominick ' R. L. McIlwain, ' T Miao ' D H Miller, ' M. Modesitt, ' S. F. Schaffner, ' E. I. Shibata, ' I. P. 3. Shipsey, ' P. N. Wang ' M Battle, ' J. Ernst ' H. Kroha, ' S. Roberts, ' K Sparks ' E. H. Thorndike, ' C H. Wang ' S. Sanghera, ' T. Skwarnicki, ' R. Stroynowski, ' M. Artuso, ' M. Goldberg, ' N. Horwitz, ' R. Kennett, ' G. C. Moneti, ' F. Muheim ' S. Playfer, ' Y. Rozen ' P Rub&n ' S. Stone, ' M Thulasidas ' G. Zhu, ' A. V. Barnes, ' J. Bartelt, ' S. E. Csorna, ' Z Egyed, ' V. Jain, ' P. Sheldon, ' D S Akerib, ' B. Barish ' M. Chadha ' S Chan, ' D. F Cowen ' G. Eigen ' 3 S. Miller, ' J. Urheim ' A. 3. Weinstein ' D. Acosta, ' M. Athanas, ' G. Masek, ' B. Ong H. Paar, ' and M. Sivertz ' (CLEO Collaboration) ' Uni versity of California, Santa Barbara, California 93l06 Carnegie-Mellon Unic ersi ty, Pittsburgh, Pennsylc ania 15213 Unit ersity of Colorado, Boulder, Colorado 80309-0390 Cornell Unicersity, Ithaca, Rem York 14853 Unit ersity of Florida, GainesvilleFlorida 3, 26l l Hare ard Unic ersity, Cambridge, Massachusetts 02138 Ithaca College, Ithaca, 1Vew York 14850 University of Kansas, LawrenceKansas 6, 6045 University of Minnesota, Minneapolis, Minnesota 55455 State Unit ersity of New York at Albany, Albany, New York l2222 '' Ohio State Unic ersity, Columbus, Ohio 43210 University of Oklahoma, Norman, Oklahoma 730I9 Purdue University, West Lafayette, indiana 47907 University of Rochester, Rochester, New York, l4627 Southern Methodist Unic ersity, Dallas, Texas 75275 Syracuse Unic ersity, Syracuse, A'e~ York, 13244 Vanderbilt University, nashville, Tennessee 37235 California Institute of TechnologyPasadena, Cali, fornia 9I l25 University of California at San DiegoLa Jolla, Ca, lifornia 92093 (Received 21 December 1992) Using a sample of 935000 88 pairs collected with the CLEO-lf detector at the Cornell Storage Ring, we have obtained upper limits on the branching ratios for the b ul v processes 8 col 8 p I v, and 8 @+I v. The combined result Using the relationships among the widths for these three modes is B(B p l v) & (1. 6-2. 7) x 10 at 90% C. L. , where the range of values is due to model dependence of the detection e%ciencies. These measurements yield the limits ~ V„b/V, t, ~ & 0.08-0. 13. PACS numbers: 13. 20.Jf, 12. 15.Ff, 14. 40. Jz 1993 The American Physical Society