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March, 2002R. V. Kowalewski1 The BaBar Collaboration represented by Robert V. Kowalewski University of Victoria Leptonic and Semileptonic B Decays in BaBar.

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Presentation on theme: "March, 2002R. V. Kowalewski1 The BaBar Collaboration represented by Robert V. Kowalewski University of Victoria Leptonic and Semileptonic B Decays in BaBar."— Presentation transcript:

1 March, 2002R. V. Kowalewski1 The BaBar Collaboration represented by Robert V. Kowalewski University of Victoria Leptonic and Semileptonic B Decays in BaBar

2 March, 2002R. V. Kowalewski2 The BaBar collaboration in 7pt font The BaBar 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 Annecy-le-Vieux, France } A. Palano, A. Pompili \inst{Universit\`a di Bari, Dipartimento di Fisica and INFN, I 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 , 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. LeClerc, 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, Birmingham, B15 2TT, 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 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 BS8 1TL, United Kingdom } K. Abe, C. Hearty, T. S. Mattison, J. A. McKenna, D. Thiessen \inst{University of British Columbia, Vancouver, BC, Canada V6T 1Z1 } S. Jolly, A. K. McKemey \inst{Brunel University, Uxbridge, Middlesex UB8 3PH, 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 , Russia } D. Best, M. Chao, D. Kirkby, A. J. Lankford, M. Mandelkern, S. McMahon, D. P. Stoker \inst{University of California at Irvine, Irvine, CA 92697, USA } K. Arisaka, C. Buchanan, S. Chun \inst{University of California at Los Angeles, Los Angeles, CA 90024, USA } D. B. MacFarlane, 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, 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, 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 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 Palaiseau, France } A. Anjomshoaa, R. Bernet, A. Khan, D. Lavin, F. Muheim, S. Playfer, J. E. Swain, J. Tinslay \inst{University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom } M. Falbo \inst{Elon University, Elon University, NC , USA } C. Borean, C. Bozzi, L. Piemontese \inst{Universit\`a di Ferrara, Dipartimento di Fisica and INFN, I Ferrara, Italy } E. Treadwell \inst{Florida A\&M University, Tallahassee, FL 32307, USA } F. Anulli,\footnote{ Also with Universit\`a di Perugia, I 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 Perugia, Italy } M. Piccolo, Y. Xie, A. Zallo \inst{Laboratori Nazionali di Frascati dell'INFN, I 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 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 , 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 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 L69 3BX, 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, SW7 2BW, 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, E1 4NS, United Kingdom } G. Cowan, S. George, M. G. Green, A. Kurup, C. E. Marker, T. R. McMahon, S. Ricciardi, F. Salvatore, G. Vaitsas \inst{University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom } D. Brown, C. L. Davis \inst{University of Louisville, 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 M13 9PL, 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{McGill University, Montr\'eal, QC, Canada H3A 2T8 } F. Palombo, C. Vite \inst{Universit\`a di Milano, Dipartimento di Fisica and INFN, I 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 H3C 3J7 } H. Nicholson \inst{Mount Holyoke College, South Hadley, MA 01075, USA } C. Cartaro, N. Cavallo,\footnote{ Also with Universit\`a della Basilicata, I 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 , Napoli, Italy } J. M. LoSecco \inst{University of Notre Dame, 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 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 Paris, France } P. F. Manfredi, V. Re, V. Speziali \inst{Universit\`a di Pavia, Dipartimento di Elettronica and INFN, I 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 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 Roma, Italy } S. Christ, R. Waldi \inst{Universit\"at Rostock, D 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, OX11 0QX, 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 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 , USA } R. Henderson \inst{TRIUMF, Vancouver, BC, Canada V6T 2A3 } 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 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 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, Victoria, BC, Canada V8W 3P6 } 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 }

3 March, 2002R. V. Kowalewski3 Topics and data sets Results on the following topics will be presented: Semileptonic B branching fraction and |V cb | (5 fb -1 ) Separate semileptonic BF for B + and B 0 (21 fb -1 ) Determination of |V ub | using B→ρe + ν decays (21 fb -1 ) Search for B 0 →e + e - (54 fb -1 ) NEW

4 March, 2002R. V. Kowalewski4 BaBar at PEP-II PEP-II collider 9 GeV 3.1 GeV 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 ·10 33 cm -2 s -1 BaBar has collected >74 fb -1 (>70M BB pairs)

5 March, 2002R. V. Kowalewski5 Semileptonic B decay Semileptonic decays are clean probes of b quark decay (only one hadronic current). Also clean experimentally: e id efficiency ~ 90% π misid probability < Electron identification based on shape of calorimeter cluster, E cal / p track, dE/dx and Cherenkov information Dominant contribution is from b  ce transitions; measuring  (B  Xe ) allows extraction of  V cb   (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 + ) e - b W q c, u q

6 March, 2002R. V. Kowalewski6 Wrong-sign cascades: b→c→e - Lepton misidentification Semileptonic B decay - experimental backgrounds Cascade decays: b→c→e + J/  e + e - other electron sources:  e + e -,  0  e + e - e + b c ν q s W - s e - b c q s ν All backgrounds except J/  have a softer spectrum than B  Xe +

7 March, 2002R. V. Kowalewski7 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) J/  Cascade accepted region Simulated like-sign decays Plots show the 2 nd lepton Require 1 high momentum lepton tag (p* > 1.4 GeV) and measure b  ce and c  qe spectra using 2 nd lepton

8 March, 2002R. V. Kowalewski8 Inclusive B branching fraction- Preliminary results Given a measurement of  (B  Xe ), theoretical uncertainties [1] contribute an error of ~ 3-4% to  V cb  BF (B  Xe ) = (10.82  0.21 stat  0.38 sys )% Systematic error mostly from wrong-sign cacade (b  ccs  e - ) and electron efficiency Using  B =1.540  ps (PDG 2001):  V cb  = (40.8  0.4  0.8  2.0) ·10 -3 (stat) (sys) (theory) Fully corrected B→Xe - ν spectrum [1] Bigi, Shifman, Uraltsev, Ann. Rev. Nucl. Part. Science 47 (1997) 591. Preliminary

9 March, 2002R. V. Kowalewski9 Tagging B flavor with fully reconstructed decays Fully reconstruct one B in a hadronic decay mode, e.g. B  D (*) , D (*) , D (*) a 1, J/  K (*),  (2S)K (*) Look for an electron from the other B B reconstruction yields based on 20.7 fb -1 collected on  (4S) resonance charge correlation separates direct from cascade decays; must correct for the effect of B 0 B 0 mixing Preliminary

10 March, 2002R. V. Kowalewski10 Semileptonic branching fractions of B + and B 0 BF(B +  Xe ) (10.3  0.6  0.5)% BF(B 0  Xe ) (10.4  0.8  0.5)% = = 0.99  0.10  0.04 Direct lepton yields ~ 600 each for B +, B 0 Systematic errors: - semileptonic decay model - B + / B 0 cross-feed - hadron misidentification - electron ID efficiency - … Averaging these, BF(B  Xe ) = (10.4  0.5  0.5)% Preliminary

11 March, 2002R. V. Kowalewski11 Exclusive charmless semileptonic decays Motivation: extract |V ub | from exclusive semileptonic decays and theoretical models Measure B→ρ - e + ν, B→ρ 0 e + ν and consider cross-feed from B→ωe + ν, B→π - e + ν and B→π 0 e + ν Use models to calculate form factors: Quark models: ISGW2, Beyer/Melikhov Lattice: UKQCD Sum rule: LCSR relating D and B decays: Ligeti/Wise Method similar to published CLEO analysis of B→ρeν Analysis uses 20.2 fb -1 on  (4S), 2.6 fb -1 below resonance

12 March, 2002R. V. Kowalewski12 Reconstructing B→ρeν decays 5 modes considered: B→ρ - e + ν B→ρ 0 e + ν B→ωe + ν B→π - e + ν B→π 0 e + ν Unique choice of best candidate made per event reduce non-BB contributions with event shape (Fox-Wolfram ratio R 2 < 0.4) and multiplicity requirements neutrino reconstructed from missing momentum consider ΔE = E hadron + E e + |p miss | - E beam impose 0.8 < cosΔθ min ≤ 1.0 (~ p miss · p ν )

13 March, 2002R. V. Kowalewski13 Determination of Branching fraction Binned likelihood fit in ΔE, M ππ and E e Use E e in region 2.0 – 2.35 GeV to normalize b→ceν background; separate background scale factor for each mode Signal sensitivity for E e in 2.35 – 2.7 GeV Cross-feed is substantial (50% or more); full efficiency matrix used in fit Impose isospin constraints: Γ(B - →ρ 0 eν) = Γ(B - →ωeν) = ½Γ(B 0 →ρ + eν) Γ(B - →π 0 eν) = ½Γ(B 0 → π + eν) Fit accounts for statistical fluctuations in off-resonance and MC samples; absorbed into statistical error. Allow for other b→ueν modes Perform fit using each of the 5 models

14 March, 2002R. V. Kowalewski14 Projections of the fitted result B→ρeν channel Signal cross-feed other b→ueν b→ceν and other M ππ ΔEΔE EeEe These plots show on-resonance minus off-resonance data for the region 2.35 < E e < 2.7 GeV

15 March, 2002R. V. Kowalewski15 Preliminary results for BF and |V ub | stat sys spreadstat sys spread/theory Preliminary

16 March, 2002R. V. Kowalewski16 Search for B 0 →l + l - Motivation: highly suppressed (FCNC and helicity) SM expectations: BF(B→e + e - ) = 1.9 · BF(B→μ + μ - ) = 8.0 · 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

17 March, 2002R. V. Kowalewski17 Search for B 0 →e + e - Require two identified electrons (ε e ≈ 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 off- peak data and MC

18 March, 2002R. V. Kowalewski18 Limit on BF(B 0 →e + e - ) background dominated by e + e - →cc→ e + e - X Preliminary bremsstrahlung tail

19 March, 2002R. V. Kowalewski19 Summary Semileptonic branching fractions: → improves with statistics From B→Xeν decays:  V cb  = (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 BF(B +  Xe ) (10.3  0.6  0.5)% BF(B 0  Xe ) (10.4  0.8  0.5)% = = 0.99  0.10  0.04 All results are preliminary


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