Leptonic and Semileptonic B Decays in Ba Bar
Leptonic and Semileptonic B Decays in Ba. Bar The Ba. Bar Collaboration represented by Robert V. Kowalewski University of Victoria March, 2002 R. V. Kowalewski
The Ba. Bar collaboration in 7 pt font The Ba. Bar Collaboration, B. Aubert, D. Boutigny, J. -M. Gaillard, A. Hicheur, Y. Karyotakis, J. P. Lees, P. Robbe, V. Tisserand, A. Zghiche inst{Laboratoire de Physique des Particules, F-74941 Annecy-le-Vieux, France } A. Palano, A. Pompili inst{Universit`a di Bari, Dipartimento di Fisica and INFN, I-70126 Bari, Italy } G. P. Chen, J. C. Chen, N. D. Qi, G. Rong, P. Wang, Y. S. Zhu inst{Institute of High Energy Physics, Beijing 100039, China } G. Eigen, I. Ofte, B. Stugu inst{University of Bergen, Inst. of Physics, N-5007 Bergen, Norway } G. S. Abrams, A. W. Borgland, A. B. Breon, D. N. Brown, J. Button-Shafer, R. N. Cahn, E. Charles, M. S. Gill, A. V. Gritsan, Y. Groysman, R. G. Jacobsen, R. W. Kadel, J. Kadyk, L. T. Kerth, Yu. G. Kolomensky, J. F. Kral, C. Le. Clerc, M. E. Levi, G. Lynch, L. M. Mir, P. J. Oddone, M. Pripstein, N. A. Roe, A. Romosan, M. T. Ronan, V. G. Shelkov, A. V. Telnov, W. A. Wenzel inst{Lawrence Berkeley National Laboratory and University of California, Berkeley, CA 94720, USA } T. J. Harrison, C. M. Hawkes, D. J. Knowles, S. W. O'Neale, R. C. Penny, A. T. Watson, N. K. Watson inst{University of Birmingham, B 15 2 TT, United Kingdom } T. Deppermann, K. Goetzen, H. Koch, B. Lewandowski, K. Peters, H. Schmuecker, M. Steinke inst{Ruhr Universit"at Bochum, Institut f"ur Experimentalphysik 1, D-44780 Bochum, Germany } N. R. Barlow, W. Bhimji, N. Chevalier, P. J. Clark, W. N. Cottingham, B. Foster, C. Mackay, F. F. Wilson inst{University of Bristol, Bristol BS 8 1 TL, United Kingdom } K. Abe, C. Hearty, T. S. Mattison, J. A. Mc. Kenna, D. Thiessen inst{University of British Columbia, Vancouver, BC, Canada V 6 T 1 Z 1 } S. Jolly, A. K. Mc. Kemey inst{Brunel University, Uxbridge, Middlesex UB 8 3 PH, United Kingdom } V. E. Blinov, A. D. Bukin, D. A. Bukin, A. R. Buzykaev, V. B. Golubev, V. N. Ivanchenko, A. A. Korol, E. A. Kravchenko, A. P. Onuchin, S. I. Serednyakov, Yu. I. Skovpen, A. N. Yushkov inst{Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia } D. Best, M. Chao, D. Kirkby, A. J. Lankford, M. Mandelkern, S. Mc. Mahon, D. P. Stoker inst{University of California at Irvine, CA 92697, USA } K. Arisaka, C. Buchanan, S. Chun inst{University of California at Los Angeles, CA 90024, USA } D. B. Mac. Farlane, S. Prell, Sh. Rahatlou, G. Raven, V. Sharma inst{University of California at San Diego, La Jolla, CA 92093, USA } C. Campagnari, B. Dahmes, P. A. Hart, N. Kuznetsova, S. L. Levy, O. Long, A. Lu, M. A. Mazur, J. D. Richman, W. Verkerke inst{University of California at Santa Barbara, CA 93106, USA } J. Beringer, A. M. Eisner, M. Grothe, C. A. Heusch, W. S. Lockman, T. Pulliam, T. Schalk, R. E. Schmitz, B. A. Schumm, A. Seiden, M. Turri, W. Walkowiak, D. C. Williams, M. G. Wilson inst{University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, CA 95064, USA } E. Chen, G. P. Dubois-Felsmann, A. Dvoretskii, D. G. Hitlin, S. Metzler, J. Oyang, F. C. Porter, A. Ryd, A. Samuel, S. Yang, R. Y. Zhu inst{California Institute of Technology, Pasadena, CA 91125, USA } S. Jayatilleke, G. Mancinelli, B. T. Meadows, M. D. Sokoloff inst{University of Cincinnati, OH 45221, USA } T. Barillari, P. Bloom, W. T. Ford, U. Nauenberg, A. Olivas, P. Rankin, J. Roy, J. G. Smith, W. C. van Hoek, L. Zhang inst{University of Colorado, Boulder, CO 80309, USA } J. Blouw, J. L. Harton, M. Krishnamurthy, A. Soffer, W. H. Toki, R. J. Wilson, J. Zhang inst{Colorado State University, Fort Collins, CO 80523, USA } T. Brandt, J. Brose, T. Colberg, M. Dickopp, R. S. Dubitzky, A. Hauke, E. Maly, R. M"uller-Pfefferkorn, S. Otto, K. R. Schubert, R. Schwierz, B. Spaan, L. Wilden inst{Technische Universit"at Dresden, Institut f"ur Kern- und Teilchenphysik, D-01062 Dresden, Germany } D. Bernard, G. R. Bonneaud, F. Brochard, J. Cohen-Tanugi, S. Ferrag, S. T'Jampens, Ch. Thiebaux, G. Vasileiadis, M. Verderi inst{Ecole Polytechnique, LLR, F-91128 Palaiseau, France } A. Anjomshoaa, R. Bernet, A. Khan, D. Lavin, F. Muheim, S. Playfer, J. E. Swain, J. Tinslay inst{University of Edinburgh, Edinburgh EH 9 3 JZ, United Kingdom } M. Falbo inst{Elon University, NC 27244 -2010, USA } C. Borean, C. Bozzi, L. Piemontese inst{Universit`a di Ferrara, Dipartimento di Fisica and INFN, I-44100 Ferrara, Italy } E. Treadwell inst{Florida A&M University, Tallahassee, FL 32307, USA } F. Anulli, footnote{ Also with Universit`a di Perugia, I-06100 Perugia, Italy } R. Baldini-Ferroli, A. Calcaterra, R. de Sangro, D. Falciai, G. Finocchiaro, P. Patteri, I. M. Peruzzi, footnote{ Also with Universit`a di Perugia, I-06100 Perugia, Italy } M. Piccolo, Y. Xie, A. Zallo inst{Laboratori Nazionali di Frascati dell'INFN, I-00044 Frascati, Italy } S. Bagnasco, A. Buzzo, R. Contri, G. Crosetti, M. Lo Vetere, M. Macri, M. R. Monge, S. Passaggio, F. C. Pastore, C. Patrignani, E. Robutti, A. Santroni, S. Tosi inst{Universit`a di Genova, Dipartimento di Fisica and INFN, I-16146 Genova, Italy } M. Morii inst{Harvard University, Cambridge, MA 02138, USA } R. Bartoldus, R. Hamilton, U. Mallik inst{University of Iowa, Iowa City, IA 52242, USA } J. Cochran, H. B. Crawley, J. Lamsa, W. T. Meyer, E. I. Rosenberg, J. Yi inst{Iowa State University, Ames, IA 50011 -3160, USA } G. Grosdidier, A. H"ocker, H. M. Lacker, S. Laplace, F. Le Diberder, V. Lepeltier, A. M. Lutz, S. Plaszczynski, M. H. Schune, S. Trincaz-Duvoid, G. Wormser inst{Laboratoire de l'Acc'el'erateur Lin'eaire, F-91898 Orsay, France } R. M. Bionta, V. Brigljevi'c , D. J. Lange, M. Mugge, K. van Bibber, D. M. Wright inst{Lawrence Livermore National Laboratory, Livermore, CA 94550, USA } A. J. Bevan, J. R. Fry, E. Gabathuler, R. Gamet, M. George, M. Kay, D. J. Payne, R. J. Sloane, C. Touramanis inst{University of Liverpool, Liverpool L 69 3 BX, United Kingdom } M. L. Aspinwall, D. A. Bowerman, P. D. Dauncey, U. Egede, I. Eschrich, G. W. Morton, J. A. Nash, P. Sanders, D. Smith inst{University of London, Imperial College, London, SW 7 2 BW, United Kingdom } J. J. Back, G. Bellodi, P. Dixon, P. F. Harrison, R. J. L. Potter, H. W. Shorthouse, P. Strother, P. B. Vidal inst{Queen Mary, University of London, E 1 4 NS, United Kingdom } G. Cowan, S. George, M. G. Green, A. Kurup, C. E. Marker, T. R. Mc. Mahon, S. Ricciardi, F. Salvatore, G. Vaitsas inst{University of London, Royal Holloway and Bedford New College, Egham, Surrey TW 20 0 EX, United Kingdom } D. Brown, C. L. Davis inst{University of Louisville, KY 40292, USA } J. Allison, R. J. Barlow, J. T. Boyd, A. C. Forti, F. Jackson, G. D. Lafferty, N. Savvas, J. H. Weatherall, J. C. Williams inst{University of Manchester, Manchester M 13 9 PL, United Kingdom } A. Farbin, A. Jawahery, V. Lillard, J. Olsen, D. A. Roberts, J. R. Schieck inst{University of Maryland, College Park, MD 20742, USA } G. Blaylock, C. Dallapiccola, K. T. Flood, S. S. Hertzbach, R. Kofler, V. B. Koptchev, T. B. Moore, H. Staengle, S. Willocq inst{University of Massachusetts, Amherst, MA 01003, USA } B. Brau, R. Cowan, G. Sciolla, F. Taylor, R. K. Yamamoto inst{Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, MA 02139, USA } M. Milek, P. M. Patel inst{Mc. Gill University, Montr'eal, QC, Canada H 3 A 2 T 8 } F. Palombo, C. Vite inst{Universit`a di Milano, Dipartimento di Fisica and INFN, I-20133 Milano, Italy } J. M. Bauer, L. Cremaldi, V. Eschenburg, R. Kroeger, J. Reidy, D. A. Sanders, D. J. Summers inst{University of Mississippi, University, MS 38677, USA } C. Hast, J. Y. Nief, P. Taras inst{Universit'e de Montr'eal, Laboratoire Ren'e J. A. L'evesque, Montr'eal, QC, Canada H 3 C 3 J 7 } H. Nicholson inst{Mount Holyoke College, South Hadley, MA 01075, USA } C. Cartaro, N. Cavallo, footnote{ Also with Universit`a della Basilicata, I-85100 Potenza, Italy } G. De Nardo, F. Fabozzi, C. Gatto, L. Lista, P. Paolucci, D. Piccolo, C. Sciacca inst{Universit`a di Napoli Federico II, Dipartimento di Scienze Fisiche and INFN, I 80126, Napoli, Italy } J. M. Lo. Secco inst{University of Notre Dame, IN 46556, USA } J. R. G. Alsmiller, T. A. Gabriel inst{Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA } J. Brau, R. Frey, E. Grauges , M. Iwasaki, C. T. Potter, N. B. Sinev, D. Strom inst{University of Oregon, Eugene, OR 97403, USA } F. Colecchia, F. Dal Corso, A. Dorigo, F. Galeazzi, M. Margoni, M. Morandin, M. Posocco, M. Rotondo, F. Simonetto, R. Stroili, E. Torassa, C. Voci inst{Universit`a di Padova, Dipartimento di Fisica and INFN, I-35131 Padova, Italy } M. Benayoun, H. Briand, J. Chauveau, P. David, Ch. de la Vaissi`ere, L. Del Buono, O. Hamon, Ph. Leruste, J. Ocariz, M. Pivk, L. Roos, J. Stark inst{Universit'es Paris VI et VII, Lab de Physique Nucl'eaire H. E. , F-75252 Paris, France } P. F. Manfredi, V. Re, V. Speziali inst{Universit`a di Pavia, Dipartimento di Elettronica and INFN, I-27100 Pavia, Italy } E. D. Frank, L. Gladney, Q. H. Guo, J. Panetta inst{University of Pennsylvania, Philadelphia, PA 19104, USA } C. Angelini, G. Batignani, S. Bettarini, M. Bondioli, F. Bucci, E. Campagna, M. Carpinelli, F. Forti, M. A. Giorgi, A. Lusiani, G. Marchiori, F. Martinez-Vidal, M. Morganti, N. Neri, E. Paoloni, M. Rama, G. Rizzo, F. Sandrelli, G. Simi, G. Triggiani, J. Walsh inst{Universit`a di Pisa, Scuola Normale Superiore and INFN, I-56010 Pisa, Italy } M. Haire, D. Judd, K. Paick, L. Turnbull, D. E. Wagoner inst{Prairie View A&M University, Prairie View, TX 77446, USA } J. Albert, P. Elmer, C. Lu, V. Miftakov, S. F. Schaffner, A. J. S. Smith, A. Tumanov, E. W. Varnes inst{Princeton University, Princeton, NJ 08544, USA } F. Bellini, G. Cavoto, D. del Re, R. Faccini, footnote{ Also with University of California at San Diego, La Jolla, CA 92093, USA } F. Ferrarotto, F. Ferroni, M. A. Mazzoni, S. Morganti, G. Piredda, M. Serra, C. Voena inst{Universit`a di Roma La Sapienza, Dipartimento di Fisica and INFN, I-00185 Roma, Italy } S. Christ, R. Waldi inst{Universit"at Rostock, D-18051 Rostock, Germany } T. Adye, N. De Groot, B. Franek, N. I. Geddes, G. P. Gopal, S. M. Xella inst{Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX 11 0 QX, United Kingdom } R. Aleksan, S. Emery, A. Gaidot, S. F. Ganzhur, P. -F. Giraud, G. Hamel de Monchenault, W. Kozanecki, M. Langer, G. W. London, B. Mayer, B. Serfass, G. Vasseur, Ch. Y`eche, M. Zito inst{DAPNIA, Commissariat `a l'Energie Atomique/Saclay, F-91191 Gif-sur. Yvette, France } M. V. Purohit, A. W. Weidemann, F. X. Yumiceva inst{University of South Carolina, Columbia, SC 29208, USA } I. Adam, D. Aston, N. Berger, A. M. Boyarski, G. Calderini, M. R. Convery, D. P. Coupal, D. Dong, J. Dorfan, W. Dunwoodie, R. C. Field, T. Glanzman, S. J. Gowdy, T. Haas, T. Hadig, V. Halyo, T. Himel, T. Hryn'ova, M. E. Huffer, W. R. Innes, C. P. Jessop, M. H. Kelsey, P. Kim, M. L. Kocian, U. Langenegger, D. W. G. S. Leith, S. Luitz, V. Luth, H. L. Lynch, H. Marsiske, S. Menke, R. Messner, D. R. Muller, C. P. O'Grady, V. E. Ozcan, A. Perazzo, M. Perl, S. Petrak, H. Quinn, B. N. Ratcliff, S. H. Robertson, A. Roodman, A. A. Salnikov, T. Schietinger, R. H. Schindler, J. Schwiening, A. Snyder, A. Soha, S. M. Spanier, J. Stelzer, D. Su, M. K. Sullivan, H. A. Tanaka, J. Va'vra, S. R. Wagner, M. Weaver, A. J. R. Weinstein, W. J. Wisniewski, D. H. Wright, C. C. Young inst{Stanford Linear Accelerator Center, Stanford, CA 94309, USA } P. R. Burchat, C. H. Cheng, T. I. Meyer, C. Roat inst{Stanford University, Stanford, CA 94305 -4060, USA } R. Henderson inst{TRIUMF, Vancouver, BC, Canada V 6 T 2 A 3 } W. Bugg, H. Cohn inst{University of Tennessee, Knoxville, TN 37996, USA } J. M. Izen, I. Kitayama, X. C. Lou inst{University of Texas at Dallas, Richardson, TX 75083, USA } F. Bianchi, M. Bona, D. Gamba inst{Universit`a di Torino, Dipartimento di Fisica Sperimentale and INFN, I-10125 Torino, Italy } L. Bosisio, G. Della Ricca, S. Dittongo, L. Lanceri, P. Poropat, L. Vitale, G. Vuagnin inst{Universit`a di Trieste, Dipartimento di Fisica and INFN, I-34127 Trieste, Italy } R. S. Panvini inst{Vanderbilt University, Nashville, TN 37235, USA } C. M. Brown, P. D. Jackson, R. Kowalewski, J. M. Roney inst{University of Victoria, BC, Canada V 8 W 3 P 6 } H. R. Band, S. Dasu, M. Datta, A. M. Eichenbaum, H. Hu, J. R. Johnson, R. Liu, F. Di Lodovico, Y. Pan, R. Prepost, I. J. Scott, S. J. Sekula, J. H. von Wimmersperg-Toeller, S. L. Wu, Z. Yu inst{University of Wisconsin, Madison, WI 53706, USA } T. M. B. Kordich, H. Neal inst{Yale University, New Haven, CT 06511, USA } March, 2002 R. V. Kowalewski
Topics and data sets Results on the following topics will be presented: Semileptonic B branching fraction and |Vcb| (5 fb-1) Separate semileptonic BF for B+ and B 0 (21 fb-1) NEW Determination of |Vub| using B→ρe+ν decays (21 fb-1) NEW Search for B 0→e+e- (54 fb-1) March, 2002 R. V. Kowalewski
Ba. Bar at PEP-II The PEP-II collider: good and getting better: as of March 4, 2002 • best day: 0. 30 fb-1 ; best month: 6. 35 fb-1 • peak: 4. 51 · 1033 cm-2 s-1 Ba. Bar has collected >74 fb-1 (>70 M BB pairs) 3. 1 Ge. V 9 Ge. V PEP-II collider March, 2002 R. V. Kowalewski
Semileptonic B decay Semileptonic decays are clean probes W of b quark decay (only one hadronic b current). Also clean experimentally: q e id efficiency ~ 90% π misid probability < 10 -3 • Electron identification based on shape of calorimeter cluster, Ecal / ptrack, d. E/dx and Cherenkov information • Dominant contribution is from b ce transitions; measuring (B Xe ) allows extraction of Vcb • (B+) and (B 0) known to ± 1. 5%; differ by ~4% measure BF(B+ X 0 e+ ) and BF(B 0 X-e+ ) → test (B+ Xe+ ) / (B 0 Xe+ ) March, 2002 R. V. Kowalewski e c, u q
Semileptonic B decay experimental backgrounds • Cascade decays: b→c→e+ e+ b c ν q s • Wrong-sign cascades: b→c→e. Ws eb c q s ν • J/ e+e- • Lepton misidentification • other electron sources: e+e-, 0 e+e. All backgrounds except J/ have a softer spectrum than B Xe+ March, 2002 R. V. Kowalewski
Inclusive B branching fraction. Method • Charge correlated dilepton technique used by ARGUS and CLEO allows separation of leptons from b and c decay Simulated semileptonic B decays (unlike-sign) • Require 1 high momentum lepton tag (p* > 1. 4 Ge. V) and measure b ce and c qe spectra using 2 nd lepton Simulated like-sign decays Plots show the 2 nd lepton J/y Cascade March, 2002 accepted region R. V. Kowalewski
Inclusive B branching fraction. Preliminary results • Given a measurement of (B Xe ), theoretical uncertainties[1] contribute an error of ~ 3 -4% to Vcb BF (B Xe ) = (10. 82 0. 21 stat 0. 38 sys)% Preliminary Systematic error mostly from wrong-sign cacade (b ccs e-) and electron efficiency Using B=1. 540 0. 024 ps (PDG 2001): Vcb = (40. 8 0. 4 0. 8 2. 0) · 10 -3 Preliminary (stat) (sys) (theory) Bigi, Shifman, Uraltsev, Ann. Rev. Nucl. Part. Science 47 (1997) 591. [1] March, 2002 R. V. Kowalewski Fully corrected B→Xe- ν spectrum
Tagging B flavor with fully reconstructed decays • Fully reconstruct one B in a hadronic decay mode, e. g. B D(*) , D(*)a 1, J/ K(*), (2 S)K(*) • charge correlation separates direct from cascade decays; must correct for the effect of B 0 mixing • Look for an electron from the other B Preliminary B reconstruction yields based on 20. 7 fb-1 collected on (4 S) resonance March, 2002 R. V. Kowalewski
Semileptonic branching fractions of B+ and B 0 • Direct lepton yields ~ 600 each for B+, B 0 • Systematic errors: - semileptonic decay model - B+ / B 0 cross-feed - hadron misidentification - electron ID efficiency -… Preliminary BF(B+ Xe ) (10. 3 0. 6 0. 5)% = = 0. 99 0. 10 0. 04 0 BF(B Xe ) (10. 4 0. 8 0. 5)% Averaging these, BF(B Xe ) = (10. 4 0. 5)% March, 2002 R. V. Kowalewski
Exclusive charmless semileptonic decays • Motivation: extract |Vub| from exclusive semileptonic decays and theoretical models Measure B→ρ-e+ν, B→ρ0 e+ν and consider cross-feed from B→ωe+ν, B→π-e+ν and B→π0 e+ν Use models to calculate form factors: • Quark models: ISGW 2, Beyer/Melikhov • Lattice: UKQCD • Sum rule: LCSR • relating D and B decays: Ligeti/Wise Analysis uses 20. 2 fb-1 on (4 S), 2. 6 fb-1 below resonance Method similar to published CLEO analysis of B→ρeν March, 2002 R. V. Kowalewski
Reconstructing B→ρeν decays • reduce non-BB contributions with event shape (Fox-Wolfram ratio R 2 < 0. 4) and multiplicity requirements • neutrino reconstructed from missing momentum • consider ΔE = Ehadron + Ee + |pmiss| - Ebeam • impose 0. 8 < cosΔθmin ≤ 1. 0 (~ pmiss · pν) • March, 2002 R. V. Kowalewski 5 modes considered: B→ρ-e+ν B→ρ0 e+ν B→ωe+ν B→π-e+ν B→π0 e+ν Unique choice of best candidate made per event
Determination of Branching fraction • Binned likelihood fit in ΔE, Mππ and Ee • Use Ee in region 2. 0 – 2. 35 Ge. V to normalize b→ceν background; separate background scale factor for each mode • Allow for other b→ueν modes • Perform fit using each of the 5 models • Signal sensitivity for Ee in 2. 35 – 2. 7 Ge. V • Cross-feed is substantial (50% or more); full efficiency matrix used in fit • Impose isospin constraints: Γ(B-→ρ0 eν) = Γ(B-→ωeν) = ½Γ(B 0→ρ+eν) Γ(B-→π0 eν) = ½Γ(B 0→ π+eν) March, 2002 R. V. Kowalewski Fit accounts for statistical fluctuations in off-resonance and MC samples; absorbed into statistical error.
Projections of the fitted result B→ρeν channel Mππ Ee Signal cross-feed other b→ueν ΔE b→ceν and other March, 2002 R. V. Kowalewski These plots show on -resonance minus off -resonance data for the region 2. 35 < Ee < 2. 7 Ge. V
Preliminary results for BF and |Vub| Preliminary March, 2002 stat sys spread R. V. Kowalewski stat sys spread/theory
Search for B 0→l+l • Motivation: highly suppressed (FCNC and helicity) • SM expectations: BF(B→e+e-) = 1. 9 ·10 -15 BF(B→μ+μ-) = 8. 0 ·10 -11 BF(B→e+μ-) = 0 • New physics can enhance the BFs Only the B→e+e- channel is being presented at this conference, using 54. 4 fb-1 of data March, 2002 R. V. Kowalewski
Search for B 0→e+e • Require two identified electrons (εe ≈ 91%) • Use multiplicity and missing momentum cuts to reduce radiative Bhabha and γγ events • Use thrust magnitude and angle to reduce background • Search for candidates with B mass and energy • Perform blind analysis: look at signal region in on-peak data only after extensive validation of sideband regions with offpeak data and MC March, 2002 R. V. Kowalewski
Limit on BF(B 0→e+e-) background dominated by e+e-→cc→ e+e-X bremsstrahlung tail Preliminary March, 2002 R. V. Kowalewski
Summary Semileptonic branching fractions: BF(B+ Xe ) (10. 3 0. 6 0. 5)% = = 0. 99 0. 10 0. 04 0 BF(B Xe ) (10. 4 0. 8 0. 5)% → improves with statistics From B→Xeν decays: Vcb = (40. 8 0. 4 0. 8 2. 0) · 10 -3 (stat) (sys) (theory) → method limited by theory From B→ρeν decays: → method limited by theory 90% c. l. limit on BF(B 0→e+e-): < 3. 3 · 10 -7 → most stringent limit to date All results are preliminary March, 2002 R. V. Kowalewski
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