Search for the highly suppressed decays B > K+π π and B > K K π+

University of Warwick institutional repository: http://go.warwick.ac.uk/wrap

This paper is made available online in accordance with

publisher policies. Please scroll down to view the document

itself. Please refer to the repository record for this item and our

policy information available from the repository home page for

further information.

To see the final version of this paper please visit the publisher’s website.

Access to the published version may require a subscription.

Author(s): The BABAR Collaboration: B. Aubert, et al

Article Title: Search for the highly suppressed decays B- -> K+ pi- pi-

and B- -> K- K- pi+

Year of publication: 2008

Link to published article:

arXiv:0808.0900v2 [hep-ex] 14 Nov 2008

SLAC-PUB-13356

BA_BAR-PUB-08/033

Search for the highly suppressed decays

B

→

K

π

π

_and

B

→

K

K

π

B. Aubert,1 _{M. Bona,}1 _{Y. Karyotakis,}1_{J. P. Lees,}1 _{V. Poireau,}1 _{E. Prencipe,}1 _{X. Prudent,}1 _{V. Tisserand,}1

J. Garra Tico,2 _{E. Grauges,}2 _{L. Lopez}ab_,3 _{A. Palano}ab_,3 _{M. Pappagallo}ab_,3 _{G. Eigen,}4 _{B. Stugu,}4 _{L. Sun,}4

G. S. Abrams,5 _{M. Battaglia,}5_{D. N. Brown,}5 _{R. N. Cahn,}5_{R. G. Jacobsen,}5 _{L. T. Kerth,}5 _{Yu. G. Kolomensky,}5

G. Lynch,5_{I. L. Osipenkov,}5_{M. T. Ronan,}5,∗_{K. Tackmann,}5 _{T. Tanabe,}5_{C. M. Hawkes,}6_{N. Soni,}6 _{A. T. Watson,}6

H. Koch,7 _{T. Schroeder,}7 _{D. Walker,}8 _{D. J. Asgeirsson,}9 _{B. G. Fulsom,}9 _{C. Hearty,}9 _{T. S. Mattison,}9

J. A. McKenna,9_{M. Barrett,}10_{A. Khan,}10_{V. E. Blinov,}11_{A. D. Bukin,}11 _{A. R. Buzykaev,}11 _{V. P. Druzhinin,}11

V. B. Golubev,11 _{A. P. Onuchin,}11 _{S. I. Serednyakov,}11 _{Yu. I. Skovpen,}11_{E. P. Solodov,}11_{K. Yu. Todyshev,}11

M. Bondioli,12 _{S. Curry,}12 _{I. Eschrich,}12 _{D. Kirkby,}12 _{A. J. Lankford,}12 _{P. Lund,}12 _{M. Mandelkern,}12

E. C. Martin,12_{D. P. Stoker,}12 _{S. Abachi,}13 _{C. Buchanan,}13 _{J. W. Gary,}14_{F. Liu,}14 _{O. Long,}14_{B. C. Shen,}14,∗ G. M. Vitug,14 _{Z. Yasin,}14 _{L. Zhang,}14 _{V. Sharma,}15 _{C. Campagnari,}16 _{T. M. Hong,}16 _{D. Kovalskyi,}16

M. A. Mazur,16 _{J. D. Richman,}16_{T. W. Beck,}17_{A. M. Eisner,}17 _{C. J. Flacco,}17 _{C. A. Heusch,}17 _{J. Kroseberg,}17

W. S. Lockman,17 _{A. J. Martinez,}17_{T. Schalk,}17 _{B. A. Schumm,}17 _{A. Seiden,}17_{M. G. Wilson,}17_{L. O. Winstrom,}17

C. H. Cheng,18 _{D. A. Doll,}18 _{B. Echenard,}18 _{F. Fang,}18 _{D. G. Hitlin,}18 _{I. Narsky,}18_{T. Piatenko,}18 _{F. C. Porter,}18

R. Andreassen,19 _{G. Mancinelli,}19 _{B. T. Meadows,}19 _{K. Mishra,}19 _{M. D. Sokoloff,}19 _{P. C. Bloom,}20

W. T. Ford,20 _{A. Gaz,}20 _{J. F. Hirschauer,}20_{M. Nagel,}20 _{U. Nauenberg,}20 _{J. G. Smith,}20 _{K. A. Ulmer,}20

S. R. Wagner,20 _{R. Ayad,}21,† _{A. Soffer,}21,‡ _{W. H. Toki,}21 _{R. J. Wilson,}21 _{D. D. Altenburg,}22 _{E. Feltresi,}22

A. Hauke,22 _{H. Jasper,}22 _{M. Karbach,}22 _{J. Merkel,}22_{A. Petzold,}22 _{B. Spaan,}22 _{K. Wacker,}22 _{M. J. Kobel,}23

W. F. Mader,23 _{R. Nogowski,}23_{K. R. Schubert,}23_{R. Schwierz,}23_{A. Volk,}23_{D. Bernard,}24_{G. R. Bonneaud,}24

E. Latour,24 _{M. Verderi,}24 _{P. J. Clark,}25 _{S. Playfer,}25_{J. E. Watson,}25_{M. Andreotti}ab_,26 _{D. Bettoni}a_,26_{C. Bozzi}a_,26

R. Calabreseab_,26 _{A. Cecchi}ab_,26 _{G. Cibinetto}ab_,26_{P. Franchini}ab_,26_{E. Luppi}ab_,26 _{M. Negrini}ab_,26 _{A. Petrella}ab_,26

L. Piemontesea_,26 _{V. Santoro}ab_,26 _{R. Baldini-Ferroli,}27 _{A. Calcaterra,}27_{R. de Sangro,}27 _{G. Finocchiaro,}27

S. Pacetti,27_{P. Patteri,}27_{I. M. Peruzzi,}27,§ _{M. Piccolo,}27_{M. Rama,}27 _{A. Zallo,}27 _{A. Buzzo}a_,28 _{R. Contri}ab_,28

M. Lo Vetereab_,28 _{M. M. Macri}a_,28 _{M. R. Monge}ab_,28 _{S. Passaggio}a_,28 _{C. Patrignani}ab_,28 _{E. Robutti}a_,28

A. Santroniab_,28 _{S. Tosi}ab_,28 _{K. S. Chaisanguanthum,}29_{M. Morii,}29 _{A. Adametz,}30 _{J. Marks,}30 _{S. Schenk,}30

U. Uwer,30_{V. Klose,}31 _{H. M. Lacker,}31_{D. J. Bard,}32_{P. D. Dauncey,}32_{J. A. Nash,}32 _{M. Tibbetts,}32_{P. K. Behera,}33

X. Chai,33_{M. J. Charles,}33 _{U. Mallik,}33 _{J. Cochran,}34 _{H. B. Crawley,}34 _{L. Dong,}34 _{W. T. Meyer,}34 _{S. Prell,}34

E. I. Rosenberg,34 A. E. Rubin,34 Y. Y. Gao,35 A. V. Gritsan,35 Z. J. Guo,35 C. K. Lae,35 N. Arnaud,36 J. B´equilleux,36_{A. D’Orazio,}36_{M. Davier,}36_{J. Firmino da Costa,}36 _{G. Grosdidier,}36 _{A. H¨ocker,}36_{V. Lepeltier,}36

F. Le Diberder,36 _{A. M. Lutz,}36 _{S. Pruvot,}36 _{P. Roudeau,}36 _{M. H. Schune,}36 _{J. Serrano,}36 _{V. Sordini,}36,¶ A. Stocchi,36 _{G. Wormser,}36 _{D. J. Lange,}37_{D. M. Wright,}37 _{I. Bingham,}38 _{J. P. Burke,}38 _{C. A. Chavez,}38

J. R. Fry,38_{E. Gabathuler,}38 _{R. Gamet,}38 _{D. E. Hutchcroft,}38_{D. J. Payne,}38 _{C. Touramanis,}38 _{A. J. Bevan,}39

C. K. Clarke,39 _{K. A. George,}39_{F. Di Lodovico,}39 _{R. Sacco,}39 _{M. Sigamani,}39 _{G. Cowan,}40 _{H. U. Flaecher,}40

D. A. Hopkins,40 _{S. Paramesvaran,}40_{F. Salvatore,}40_{A. C. Wren,}40 _{D. N. Brown,}41_{C. L. Davis,}41 _{A. G. Denig,}42

M. Fritsch,42 _{W. Gradl,}42 _{G. Schott,}42_{K. E. Alwyn,}43 _{D. Bailey,}43_{R. J. Barlow,}43_{Y. M. Chia,}43_{C. L. Edgar,}43

G. Jackson,43_{G. D. Lafferty,}43 _{T. J. West,}43 _{J. I. Yi,}43_{J. Anderson,}44_{C. Chen,}44 _{A. Jawahery,}44_{D. A. Roberts,}44

G. Simi,44 _{J. M. Tuggle,}44 _{C. Dallapiccola,}45 _{X. Li,}45 _{E. Salvati,}45 _{S. Saremi,}45 _{R. Cowan,}46 _{D. Dujmic,}46

P. H. Fisher,46 _{G. Sciolla,}46 _{M. Spitznagel,}46 _{F. Taylor,}46 _{R. K. Yamamoto,}46 _{M. Zhao,}46 _{P. M. Patel,}47

S. H. Robertson,47 _{A. Lazzaro}ab_,48 _{V. Lombardo}a_,48 _{F. Palombo}ab_,48 _{J. M. Bauer,}49 _{L. Cremaldi,}49

R. Godang,49,∗∗ _{R. Kroeger,}49 _{D. A. Sanders,}49_{D. J. Summers,}49_{H. W. Zhao,}49_{M. Simard,}50 _{P. Taras,}50

F. B. Viaud,50 H. Nicholson,51G. De Nardoab_,52 _{L. Lista}a_,52 _{D. Monorchio}ab_,52 _{G. Onorato}ab_,52 _{C. Sciacca}ab_,52

G. Raven,53 _{H. L. Snoek,}53 _{C. P. Jessop,}54 _{K. J. Knoepfel,}54 _{J. M. LoSecco,}54 _{W. F. Wang,}54 _{G. Benelli,}55

L. A. Corwin,55_{K. Honscheid,}55 _{H. Kagan,}55 _{R. Kass,}55 _{J. P. Morris,}55 _{A. M. Rahimi,}55 _{J. J. Regensburger,}55

S. J. Sekula,55 _{Q. K. Wong,}55 _{N. L. Blount,}56 _{J. Brau,}56_{R. Frey,}56 _{O. Igonkina,}56 _{J. A. Kolb,}56 _{M. Lu,}56

R. Rahmat,56 _{N. B. Sinev,}56 _{D. Strom,}56 _{J. Strube,}56 _{E. Torrence,}56 _{G. Castelli}ab_,57 _{N. Gagliardi}ab_,57

M. Margoniab_,57 _{M. Morandin}a_,57 _{M. Posocco}a_,57 _{M. Rotondo}a_,57 _{F. Simonetto}ab_,57 _{R. Stroili}ab_,57 _{C. Voci}ab_,57

P. del Amo Sanchez,58 _{E. Ben-Haim,}58_{H. Briand,}58_{G. Calderini,}58 _{J. Chauveau,}58 _{P. David,}58 _{L. Del Buono,}58

2

R. Covarelliab_,60 _{E. Manoni}ab_,60 _{C. Angelini}ab_,61 _{G. Batignani}ab_,61 _{S. Bettarini}ab_,61 _{M. Carpinelli}ab_,61,†† A. Cervelliab_,61 _{F. Forti}ab_,61_{M. A. Giorgi}ab_,61_{A. Lusiani}ac_,61 _{G. Marchiori}ab_,61 _{M. Morganti}ab_,61 _{N. Neri}ab_,61

E. Paoloniab_,61 _{G. Rizzo}ab_,61 _{J. J. Walsh}a_,61 _{D. Lopes Pegna,}62 _{C. Lu,}62 _{J. Olsen,}62 _{A. J. S. Smith,}62

A. V. Telnov,62_{F. Anulli}a_,63_{E. Baracchini}ab_,63 _{G. Cavoto}a_,63 _{D. del Re}ab_,63 _{E. Di Marco}ab_,63 _{R. Faccini}ab_,63

F. Ferrarottoa_,63_{F. Ferroni}ab_,63 _{M. Gaspero}ab_,63_{P. D. Jackson}a_,63_{L. Li Gioi}a_,63_{M. A. Mazzoni}a_,63_{S. Morganti}a_,63

G. Pireddaa_,63 _{F. Polci}ab_,63 _{F. Renga}ab_,63 _{C. Voena}a_,63 _{M. Ebert,}64 _{T. Hartmann,}64 _{H. Schr¨oder,}64 _{R. Waldi,}64

T. Adye,65_{B. Franek,}65 _{E. O. Olaiya,}65_{F. F. Wilson,}65_{S. Emery,}66 _{M. Escalier,}66 _{L. Esteve,}66 _{S. F. Ganzhur,}66

G. Hamel de Monchenault,66 W. Kozanecki,66 G. Vasseur,66 Ch. Y`eche,66 M. Zito,66 X. R. Chen,67 H. Liu,67 W. Park,67 _{M. V. Purohit,}67 _{R. M. White,}67 _{J. R. Wilson,}67 _{M. T. Allen,}68 _{D. Aston,}68 _{R. Bartoldus,}68

P. Bechtle,68 _{J. F. Benitez,}68 _{R. Cenci,}68 _{J. P. Coleman,}68 _{M. R. Convery,}68_{J. C. Dingfelder,}68 _{J. Dorfan,}68

G. P. Dubois-Felsmann,68 _{W. Dunwoodie,}68_{R. C. Field,}68 _{A. M. Gabareen,}68 _{S. J. Gowdy,}68 _{M. T. Graham,}68

P. Grenier,68 _{C. Hast,}68 _{W. R. Innes,}68 _{J. Kaminski,}68 _{M. H. Kelsey,}68 _{H. Kim,}68_{P. Kim,}68 _{M. L. Kocian,}68

D. W. G. S. Leith,68 _{S. Li,}68 _{B. Lindquist,}68 _{S. Luitz,}68 _{V. Luth,}68 _{H. L. Lynch,}68 _{D. B. MacFarlane,}68

H. Marsiske,68_{R. Messner,}68 _{D. R. Muller,}68_{H. Neal,}68_{S. Nelson,}68 _{C. P. O’Grady,}68 _{I. Ofte,}68_{A. Perazzo,}68

M. Perl,68_{B. N. Ratcliff,}68 _{A. Roodman,}68 _{A. A. Salnikov,}68 _{R. H. Schindler,}68 _{J. Schwiening,}68 _{A. Snyder,}68

D. Su,68 _{M. K. Sullivan,}68 _{K. Suzuki,}68 _{S. K. Swain,}68 _{J. M. Thompson,}68 _{J. Va’vra,}68 _{A. P. Wagner,}68

M. Weaver,68 _{C. A. West,}68 _{W. J. Wisniewski,}68 _{M. Wittgen,}68_{D. H. Wright,}68 _{H. W. Wulsin,}68_{A. K. Yarritu,}68

K. Yi,68 _{C. C. Young,}68 _{V. Ziegler,}68_{P. R. Burchat,}69_{A. J. Edwards,}69 _{S. A. Majewski,}69 _{T. S. Miyashita,}69

B. A. Petersen,69 _{L. Wilden,}69 _{S. Ahmed,}70 _{M. S. Alam,}70_{J. A. Ernst,}70 _{B. Pan,}70 _{M. A. Saeed,}70 _{S. B. Zain,}70

S. M. Spanier,71 _{B. J. Wogsland,}71 _{R. Eckmann,}72 _{J. L. Ritchie,}72 _{A. M. Ruland,}72 _{C. J. Schilling,}72

R. F. Schwitters,72B. W. Drummond,73J. M. Izen,73 X. C. Lou,73F. Bianchiab_,74 _{D. Gamba}ab_,74_{M. Pelliccioni}ab_,74

M. Bombenab_,75_{L. Bosisio}ab_,75 _{C. Cartaro}ab_,75_{G. Della Ricca}ab_,75 _{L. Lanceri}ab_,75_{L. Vitale}ab_,75 _{V. Azzolini,}76

N. Lopez-March,76 _{F. Martinez-Vidal,}76 _{D. A. Milanes,}76 _{A. Oyanguren,}76 _{J. Albert,}77 _{Sw. Banerjee,}77

B. Bhuyan,77 H. H. F. Choi,77K. Hamano,77 R. Kowalewski,77 M. J. Lewczuk,77I. M. Nugent,77 J. M. Roney,77 R. J. Sobie,77 _{T. J. Gershon,}78 _{P. F. Harrison,}78 _{J. Ilic,}78 _{T. E. Latham,}78 _{G. B. Mohanty,}78 _{H. R. Band,}79

X. Chen,79 _{S. Dasu,}79 _{K. T. Flood,}79 _{Y. Pan,}79_{M. Pierini,}79 _{R. Prepost,}79 _{C. O. Vuosalo,}79 _{and S. L. Wu}79

(The BA_BAR Collaboration)

1_{Laboratoire de Physique des Particules, IN2P3/CNRS et Universit´e de Savoie, F-74941 Annecy-Le-Vieux, France} 2_{Universitat de Barcelona, Facultat de Fisica, Departament ECM, E-08028 Barcelona, Spain}

3_{INFN Sezione di Bari}a

; Dipartmento di Fisica, Universit`a di Barib

, I-70126 Bari, Italy 4_{University of Bergen, Institute of Physics, N-5007 Bergen, Norway}

5_{Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720, USA} 6_{University of Birmingham, Birmingham, B15 2TT, United Kingdom}

7_{Ruhr Universit¨at Bochum, Institut f¨ur Experimentalphysik 1, D-44780 Bochum, Germany} 8_{University of Bristol, Bristol BS8 1TL, United Kingdom}

9_{University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1} 10_{Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom}

11_{Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia} 12_{University of California at Irvine, Irvine, California 92697, USA} 13_{University of California at Los Angeles, Los Angeles, California 90024, USA}

14_{University of California at Riverside, Riverside, California 92521, USA} 15_{University of California at San Diego, La Jolla, California 92093, USA} 16_{University of California at Santa Barbara, Santa Barbara, California 93106, USA}

17_{University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064, USA} 18_{California Institute of Technology, Pasadena, California 91125, USA}

19_{University of Cincinnati, Cincinnati, Ohio 45221, USA} 20_{University of Colorado, Boulder, Colorado 80309, USA} 21_{Colorado State University, Fort Collins, Colorado 80523, USA}

22_{Technische Universit¨at Dortmund, Fakult¨at Physik, D-44221 Dortmund, Germany}

23_{Technische Universit¨at Dresden, Institut f¨ur Kern- und Teilchenphysik, D-01062 Dresden, Germany} 24_{Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, F-91128 Palaiseau, France}

25_{University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom} 26_{INFN Sezione di Ferrara}a

; Dipartimento di Fisica, Universit`a di Ferrarab

, I-44100 Ferrara, Italy 27_{INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy}

28_{INFN Sezione di Genova}a

; Dipartimento di Fisica, Universit`a di Genovab

, I-16146 Genova, Italy 29_{Harvard University, Cambridge, Massachusetts 02138, USA}

32_{Imperial College London, London, SW7 2AZ, United Kingdom} 33_{University of Iowa, Iowa City, Iowa 52242, USA} 34_{Iowa State University, Ames, Iowa 50011-3160, USA} 35_{Johns Hopkins University, Baltimore, Maryland 21218, USA}

36_{Laboratoire de l’Acc´el´erateur Lin´eaire, IN2P3/CNRS et Universit´e Paris-Sud 11,} Centre Scientifique d’Orsay, B. P. 34, F-91898 Orsay Cedex, France 37_{Lawrence Livermore National Laboratory, Livermore, California 94550, USA}

38_{University of Liverpool, Liverpool L69 7ZE, United Kingdom} 39_{Queen Mary, University of London, London, E1 4NS, United Kingdom}

40_{University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom} 41_{University of Louisville, Louisville, Kentucky 40292, USA}

42_{Johannes Gutenberg-Universit¨at Mainz, Institut f¨ur Kernphysik, D-55099 Mainz, Germany} 43_{University of Manchester, Manchester M13 9PL, United Kingdom}

44_{University of Maryland, College Park, Maryland 20742, USA} 45_{University of Massachusetts, Amherst, Massachusetts 01003, USA}

46_{Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA} 47_{McGill University, Montr´eal, Qu´ebec, Canada H3A 2T8}

48_{INFN Sezione di Milano}a

; Dipartimento di Fisica, Universit`a di Milanob

, I-20133 Milano, Italy 49_{University of Mississippi, University, Mississippi 38677, USA}

50_{Universit´e de Montr´eal, Physique des Particules, Montr´eal, Qu´ebec, Canada H3C 3J7} 51_{Mount Holyoke College, South Hadley, Massachusetts 01075, USA}

52_{INFN Sezione di Napoli}a

; Dipartimento di Scienze Fisiche, Universit`a di Napoli Federico IIb

, I-80126 Napoli, Italy

53_{NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, The Netherlands} 54_{University of Notre Dame, Notre Dame, Indiana 46556, USA}

55_{Ohio State University, Columbus, Ohio 43210, USA} 56_{University of Oregon, Eugene, Oregon 97403, USA} 57_{INFN Sezione di Padova}a

; Dipartimento di Fisica, Universit`a di Padovab

, I-35131 Padova, Italy 58_{Laboratoire de Physique Nucl´eaire et de Hautes Energies,}

IN2P3/CNRS, Universit´e Pierre et Marie Curie-Paris6, Universit´e Denis Diderot-Paris7, F-75252 Paris, France 59_{University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA} 60_{INFN Sezione di Perugia}a

; Dipartimento di Fisica, Universit`a di Perugiab

, I-06100 Perugia, Italy 61_{INFN Sezione di Pisa}a

; Dipartimento di Fisica, Universit`a di Pisab

; Scuola Normale Superiore di Pisac

, I-56127 Pisa, Italy 62_{Princeton University, Princeton, New Jersey 08544, USA}

63_{INFN Sezione di Roma}a

; Dipartimento di Fisica, Universit`a di Roma La Sapienzab

, I-00185 Roma, Italy 64_{Universit¨at Rostock, D-18051 Rostock, Germany}

65_{Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom} 66_{CEA, Irfu, SPP, Centre de Saclay, F-91191 Gif-sur-Yvette, France}

67_{University of South Carolina, Columbia, South Carolina 29208, USA} 68_{Stanford Linear Accelerator Center, Stanford, California 94309, USA}

69_{Stanford University, Stanford, California 94305-4060, USA} 70_{State University of New York, Albany, New York 12222, USA}

71_{University of Tennessee, Knoxville, Tennessee 37996, USA} 72_{University of Texas at Austin, Austin, Texas 78712, USA} 73_{University of Texas at Dallas, Richardson, Texas 75083, USA} 74_{INFN Sezione di Torino}a

; Dipartimento di Fisica Sperimentale, Universit`a di Torinob

, I-10125 Torino, Italy 75_{INFN Sezione di Trieste}a

; Dipartimento di Fisica, Universit`a di Triesteb

, I-34127 Trieste, Italy 76_{IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain}

77_{University of Victoria, Victoria, British Columbia, Canada V8W 3P6} 78_{Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom}

79_{University of Wisconsin, Madison, Wisconsin 53706, USA}

(Dated: November 14, 2008)

We report a search for the decaysB−_→K+_π−_π−_andB−_→K−_K−_π+_{, which are highly}

sup-pressed in the standard model. Using a sample of (467±5)×106 _{BB pairs collected with the}

BA_BAR detector, we do not see any evidence of these decays and determine 90% confidence level upper limits of B₍B−→K+π−π−) < 9.5×₁₀−7 _{and B(B}−_→K−_K−_π+_{) < 1.6×10}−7 _{on the}

corresponding branching fractions, including systematic uncertainties.

4

The decays B−_→K+_π−_π− _{and B}−_→K−_K−_π+

proceed via b→dds and b→ssdquark transitions, re-spectively. These are highly suppressed in the standard model (SM). Compared with the penguin (loop) transi-tions b → qqd, and b → qqs they are additionally sup-pressed by the small Cabibbo-Kobayashi-Maskawa ma-trix [1, 2] element factor |VtdVts∗| ≃ 3×10−4, leading

to predicted branching fractions of only O(10−14_{) and}

O(10−11_{), respectively [3, 4]. Example SM decay}

dia-grams can be seen in Fig. 1.

− B b u − π d u + K u s − π d u W W u,c,t t , c , u d − B b u − K s u + π u d − K s u W W u,c,t t , c , u s

FIG. 1: Example standard model decay diagrams for the decaysB−→K+π−π−andB−→K−K−π+, respectively.

These branching fractions can be significantly en-hanced in SM extensions such as the minimal supersym-metric standard model (MSSM) with or without con-servedRparity, or in models containing extraU(1) gauge bosons. For example, the branching fraction for the

b→dds transitionB− _→π−_K∗0_{can be enhanced from}

about 10−16 _{in the SM to about 10}−6_{in the presence of}

an extra Z′ _{boson [4]. The branching fraction for the}

∗_Deceased

†_{Now at Temple University, Philadelphia, Pennsylvania 19122,}

USA

‡_{Now at Tel Aviv University, Tel Aviv, 69978, Israel}

§_{Also with Universit`a di Perugia, Dipartimento di Fisica, Perugia,}

Italy

¶_{Also with Universit`a di Roma La Sapienza, I-00185 Roma, Italy} ∗∗_{Now at University of South Alabama, Mobile, Alabama 36688,}

USA

††_{Also with Universit`a di Sassari, Sassari, Italy}

b → ssd decay B− _{→ K}−_K∗0 _{can be enhanced from}

about 7×10−14 _{in the SM to about 6×10}−9 _{in the}

MSSM [5].

Observations of the decays B− _→K+_π−_π− _and

B−_→K−_K−_π+_{would be clear experimental signals for}

theb→dds andb→ssdquark transitions [6, 7]. These decay modes have been previously searched for [8, 9, 10, 11], and the most restrictive 90% confidence level exper-imental upper limits B(B− _→K+_π−_π−_{) < 1.8×10}−6

andB(B−_→K−_K−_π+_)<1.3×10−6_{[10] were obtained}

from an analysis of 81.8 fb−1_of

BA_BARdata. Upper

lim-its onb → ssd transitions have also been set using the decays B− _{→ K}∗−_K−_π+ _{[12], B}0 _{→ K}∗0_K−_π+ _[13],

andB0_→K∗0_K∗0 _[14].

We report the results of a search for the decays

B−_→K+_π−_π− _{and B}−_→K−_K−_π+_{. Inclusion of the}

charge conjugate modes is implied throughout this paper. The data used in this analysis, collected at the PEP-II asymmetric energye+_e− _{collider [15], consist of an} inte-grated luminosity of 426 fb−1_{recorded at theΥ(4S)}

reso-nance. In addition, 44 fb−1of data were collected 40 MeV below the resonance and are used for background charac-terization. These samples are referred to as on-resonance and off-resonance data, respectively. The on-resonance data sample contains (467±5)×106 _{BB pairs. Beyond}

the larger sample size, we utilize improved analysis tech-niques for background rejection and signal identification compared with our previous study [10].

The BA_BAR _{detector is described in detail}

else-where [16]. Charged particles are detected and their mo-menta measured with a five-layer silicon vertex tracker and a 40-layer drift chamber (DCH) inside a 1.5 T solenoidal magnet. Surrounding the DCH is a detec-tor of internally reflected Cherenkov radiation. Energy deposited by electrons and photons is measured by a CsI(Tl) crystal electromagnetic calorimeter.

We select B−_→K+_π−_π− _{candidates by combining} a charged kaon candidate with two charged pion candi-dates, each of which has charge opposite to the kaon. Similarly, B− _→K−_K−_π+ _{candidates are selected by}

of the shower energy and track momentum.

To avoid a potentially large source of background aris-ing fromB decays mediated by the favoredb→c tran-sition, we vetoB candidates for which pairs of daughter tracks have invariant mass combinations in the ranges

1.76< mKπ <1.94 GeV/c2, 2.85< mKπ<3.25 GeV/c2,

and 3.65 < mKπ < 3.75 GeV/c2. These remove events

containing the decays D0_→K−_π+_{, J/ψ →ℓ}+_ℓ−_{, and}

ψ(2S)→ℓ+_ℓ−_{, respectively, where the leptons in theJ/ψ} andψ(2S) decays are misidentified as pions or kaons.

Continuum e+_e− _{→ qq (q = u, d, s,)¸ events are the} dominant background. To discriminate this type of event from signal, we use a neural network that combines five variables. The first of these is the ratio ofL2toL0, with

Lj = Pip⋆i|cosθ⋆i|

j

, where p⋆

i is the particle

momen-tum,θ⋆

i is the angle between the particle and the thrust

axis determined from the B candidate decay products, the sum is over all tracks and neutral clusters not asso-ciated with the B candidate, and all quantities are cal-culated in the e+_e− _{center-of-mass (CM) frame. The} other four variables are the absolute value of the co-sine of the angle between theB direction and the beam axis; the magnitude of the cosine of the angle between the B thrust axis and the beam axis; the product of theB candidate’s charge and the output of a multivari-ate algorithm that identifies the flavor of the recoiling

B meson [17]; and the proper time difference between the decays of the two B mesons divided by its uncer-tainty. The angles with respect to the beam axis are calculated in the CM frame. The neural network out-put NNout is distributed such that it peaks around 0 for

continuum background and around 1 for signal. We re-quire NNout > 0.5 (NNout > 0.4) for B− →K+π−π−

(B−_→K−_K−_π+_{) candidates. These requirements}

re-tain approximately 90% of the signal, while rejecting ap-proximately 80% of the continuum background.

In addition to the neural network output, we distin-guish signal from background events using two kinematic variables: the difference ∆E between the CM energy of theBcandidate and√s/2, and the beam-energy substi-tuted mass mES =

p

s/4−p⋆_B2, where √s is the total CM energy and p⋆_B is the momentum of the candidate

B meson in the CM frame. The ∆E distribution peaks near zero with a resolution of around 19 MeV, while the

mESdistribution for signal events peaks near theBmass

with a resolution of around 2.4 MeV/c2_{. We select signal}

candidates that satisfy 5.260< mES<5.286 GeV/c2 and

|∆E| < 0.100 GeV. This region includes a sufficiently large range of mES below the signal peak to determine

properties of the continuum distribution.

The efficiency for signal events to pass the se-lection criteria is 21.6% (17.8%) for B− _→K+_π−_π− (B−_→K−_K−_π+_{), determined with a Monte Carlo}

(MC) simulation in which the decays are generated uniformly in three-body phase space. The BA_BAR

detector Monte Carlo simulation is based on GEANT 4 [18] and EvtGen _{[19]. We find that 8.2% (5.1%) of}

B−_→K+_π−_π− _(B−_→K−_K−_π+_{) selected events}

con-tain more than one candidate, in which case we choose the one with the highest probability that the three tracks originate from a common vertex.

We study possible residual backgrounds from BB

events using MC event samples. Backgrounds arise from decays with topologies similar to the signal but with some misreconstruction. Such effects include kaon/pion misidentification, the loss of a soft neutral particle, and the association of a particle from the decay of the otherB

in the event with the signal candidate or vice versa. We find that the backgrounds can be conveniently divided into five categories for both theK+_π−_π−_andK−_K−_π+

channels, each of which is dominated by one or two par-ticular decays but also includes other decay modes that result in similarmES and ∆E shapes. Table I provides

details of the composition of the background categories. In order to obtain the B− _→K+_π−_π− _and

B−_→K−_K−_π+ _{signal yields, we perform unbinned}

extended maximum likelihood fits to the candidate events using three variables: mES, ∆E, and NNout. For

each event hypothesisj (signal, continuum background, or one of the fiveBB background categories), we define a probability density function (PDF)

Pi

j ≡ Pj(mESi,∆Ei)· Pj(NNiout), (1)

where i denotes the event index. For the signal, con-tinuum background, and theBB background categories with small correlations betweenmESand ∆E, the PDF

is further factorized

Pj(mESi,∆Ei) =Pj(mESi)· Pj(∆Ei). (2)

The extended likelihood function is

L= exp −X

k

nk

! Y

i 

 X

j

njPji



, (3)

wherenj(nk) is the yield belonging to the event

hypoth-esisj (k).

The signal mES and ∆E shapes are parametrized

with the sum of a Gaussian and a Crystal Ball func-tion [20, 21, 22] and the sum of two Gaussian funcfunc-tions, respectively. We determine the shape parameters by tak-ing the values obtained from signal MC and correcttak-ing for differences between data and MC seen in a control sample of B−_→D0_π− _withD0_→K−_π+ _{decays. The}

contin-uum backgroundmESshape is described by the function

x√1−x2_exp

−ξ(1−x2₎

, with x≡2mES/√s and ξ a

free parameter [23], while the continuum ∆E shape is modeled with a linear function. We describe the mES

6

TABLE I: Summary of the B background categories, giving the dominant decay mode, numbers of expected and observed events and the character of the mES and ∆E distributions. “Peaking” indicates that the shape is similar to that of the

signal. “Broad peak,” “left peak,” and “right peak” differ from the signal in being wider or shifted to lower or higher values, respectively. The number of expected and observed events are also given for the continuum background.

B−_→K+_π−_π−

Category 1 2 3 4 5 Continuum

Dominant mode(s) B−→D0π−; B−→π−π+π− B−→K−π+π−& B0→K+π− GenericBB · · ·

D0_→K−_K+ _B0_→K+_π−_π0

Number of expected events 80±_{3 57}±_{4 472}±_{24 43}±_{1 917}±_{19 25552}±₄₉₅

Number of observed events 61±₇₀ −₁₅₃±_{94 1116}±₃₄₇ −₂₆±_{152 197}±_{273 25261}±₁₉₈

mESStructure Peaking Peaking Broad peak Broad peak Continuum-like · · ·

∆EStructure Left peak Right peak Broad peak Right peak Continuum-like · · ·

B−→K−K−π+

Category 1 2 3 4 5 Continuum

Dominant mode(s) B−_→K−_K+_K− _B−_→K−_π+_π− _B−_→D0_π−_{; GenericB}+_B− _GenericB0_B0 _{· · ·}

D0→K−π+π0

Number of expected events 190±_{9 198}±_{9 61}±_{4 312}±_{11 173}±_{8 6088}±₂₄₁

Number of observed events 213±_{41 240}±₃₇ −₃₄±_{55 380}±_{117 95}±_{107 6953}±₁₀₀

mESStructure Peaking Peaking Broad peak Broad peak Continuum-like · · ·

∆EStructure Left peak Right peak Left peak Continuum-like Continuum-like · · ·

are modeled using 2D histograms. We use 1D histograms to describe all NNout distributions. These histograms

are obtained from MC samples for the signal and BB

background categories, and from a combination of on-resonance data, in a continuum-dominated sideband of

mES and ∆E, and off-resonance data for the continuum

background.

The nine free parameters in our fits are the yields of the signal, continuum and all fiveBBbackground categories, the ξ parameter of the continuum mES shape, and the

slope of the continuum ∆E shape.

We test the fitting procedure by applying it to ensem-bles of simulated experiments where events are generated from the PDF shapes described above for all seven cat-egories of events. We repeat the exercise with qqevents generated from the PDF while signal events are randomly extracted from the MC samples. The BB background events are either generated from PDF shapes or drawn from MC samples. In all cases, these tests confirm that our fit performs as expected, with very small biases on the fitted signal yields, for which we correct the measured yields and include systematic uncertainties.

We apply the fit described above to the 26 478

B−_→K+_π−_π− _{and 7 822 B}− _→K−_K−_π+ _candidate

events selected from the data recorded at theΥ(4S) res-onance. We find 22±43 and −26±19 signal events, respectively, (statistical uncertainties only). The yields of continuum and allBB background categories (shown in Table I) are generally consistent with expectations. The yields of BB background categories 3 and 5 from the fit to B−_→K+_π−_π− _{candidates do not show} per-fect agreement; however, the sum of their yields is consis-tent with the expectation and, owing to the strong neg-ative correlation between the yields of these categories, the discrepancy with the expectation is not significant.

Such behavior was seen in the fit validations and has been shown not to effect the signal yield. The results of the fits are shown in Fig. 2.

We determine the branching fractions for

B−_→K+_π−_π− _{and B}− _→K−_K−_π+ _{by applying}

corrections for the small biases evaluated in the MC studies (3.6±2.4 and 0.5±1.0 events, respectively) and then dividing by the selection efficiencies and the total number of BB pairs in the data sample. We assume equal decay rates of Υ(4S) → B+_B− _and

B0_B0_{. Systematic uncertainties on the fitted yields}

arise from uncertainties in the PDF shapes (10.0 and 3.5 events, respectively) including possible data/MC differences in the signal PDF shapes studied using the B−_→D0_π− _{control samples discussed above. We} estimate the uncertainty on the fit bias (3.1 and 1.0 events, respectively) to be half the value of the correc-tion combined in quadrature with the precision with which the bias is known. Uncertainties on the efficiency arise from possible data/MC differences for tracking (1.2%) and particle identification (4.2%). We consider two sources of uncertainty related to the Dalitz plot distributions of the signal decays. The first is related to the variation of the efficiency over the parts of the Dalitz plots that are included in the analysis: from MC studies, the uncertainties are found to be 13.0% for B− _→K+_π−_π− _{and 13.5% for B}−_→K−_K−_π+_.

The second is due to the correction for the vetoed parts of the Dalitz plots, which we estimate for various signal decay distributions. In addition to the nominal phase-space distribution, we consider decays dominated by the intermediate states K∗0_{(892) or K}∗0

0 (1430)

(modeled using the LASS [24] shape, as implemented in our Dalitz plot analysis of B+_→K+_π−_π+ _[25]).

)

2

(GeV/c

ES

m

5.26 5.27 5.28

)

2

Events / (2.6 MeV/c 0 50 100 150

E (GeV)

∆

-0.1 -0.05 0 0.05 0.1

Events / (0.02 GeV) ₀ 50 100 150

out

NN

0.6 0.8 1

Events / (0.065 Units) 0 100 200 300

)

2

(GeV/c

ES

m

5.26 5.27 5.28

)

2

Events / (2.6 MeV/c 0 20 40 60

E (GeV)

∆

-0.1 -0.05 0 0.05 0.1

Events / (0.02 GeV) ₀ 20 40 60

out

NN

0.4 0.6 0.8 1

Events / (0.075 Units) 0 50

FIG. 2: Projections of the selected events with the fit results overlaid. The top (bottom) set of plots are forB−→K+π−π− (B−→K−K−π+). From left to right the plots show the projections ontomES, ∆E, and the output of the neural network.

The black points are the data, the solid blue curve is the total fit, the dotted red curve is the continuum background, the dashed green curve is the total background, and the dash-dotted black curve at the bottom is the signal. The continuum component has been suppressed in these plots by applying an additional requirement on the ratio of the signal likelihood to the sum of the signal and continuum likelihoods, calculated without use of the plotted variable. The value of the requirement for each plot is chosen to reject about 95% of the continuum background while retaining about 55% of the signal.

K−_K− _{invariant mass by employing an ad hoc doubly} charged scalar resonance with mass 1500 MeV/c2

and width 300 MeV/c2_{. The efficiency of the veto}

requirement is larger than that for the phase-space MC in all alternative models, so we assign asymmetric systematic errors of+0%_−18% forB−_→K+_π−_π− _and+25%

−0%

forB−_→K−_K−_π+_{. The uncertainty on the number of}

BB pairs is 1.1%. Including all systematic uncertainties, we obtain the following results for the branching frac-tions: B(B− _→K+_π−_π−_{) = (1.8±4.3±0.9)×10}−7_and

B(B−_→K−_K−_π+_{) = (−3.2±2.3}+1.0

−0.6)×10−7, where

the first uncertainties are statistical and the second are systematic.

We have also calculated the branching fractions using event-by-event efficiencies applied to signal weights ob-tained from the fit result [26, 27]. We obtain results con-sistent with our main results within the efficiency varia-tion systematic uncertainty. We have also checked that removing each of the discriminating variables from the fit, in turn, gives consistent results.

To obtain 90% confidence level upper limits on the branching fractions, we use the frequentist approach of Feldman and Cousins [28]. We determine 90% confi-dence region bands that relate the true values of the branching fractions to the measured numbers of sig-nal events. These bands are constructed using the re-sults of MC studies that account for relevant biases in the fit procedure and include systematic

uncertain-ties. The construction of the confidence region bands is shown in Fig. 3. The 90% confidence level upper limits are found to be B(B−_→K+_π−_π−_{) < 9.5×10}−7 _and

B(B−_→K−_K−_π+_{) < 1.6×10}−7_{. To aid comparison}

with other experiments, we also extract the sensitivities B0 defined as the 90% confidence level upper limits that

would be obtained in the case of zero fitted signal yield. The sensitivities areB0(B−→K+π−π−) < 7.4×10−7

andB0(B−→K−K−π+)<4.2×10−7.

In conclusion, we present searches for the standard model suppressedB meson decaysB−_→K+_π−_π− _and

B−_→K−_K−_π+_{. We do not see any evidence of these}

decays and obtain improved 90% confidence level upper limits on the branching fractions. These results super-sede those of our previous publication [10] and can be used to constrain models of new physics.

We are grateful for the excellent luminosity and ma-chine conditions provided by our PEP-II colleagues, and for the substantial dedicated effort from the comput-ing organizations that supportBA_BAR_{. The}

8

fit N

-50 0 50 100 150 200 250

)

-π

-π

+

K

→

-BF(B

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

-6 10 ×

fit N

-50 0 50 100 150 200 250

)

+

π

-K

K

→

-BF(B

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

-6 10 ×

FIG. 3: Construction of the confidence region bands. The left (right) plot is forB−→K+π−π−(B−→K−K−π+). In each figure the blue dotted line shows the expected central value ofNfitas a function of the true branching fraction, the green solid

(red dashed) lines show the 90% confidence level upper and lower limits including statistical and systematic errors (statistical errors only), the black dashed horizontal line marks the position of the previous upper limit [10], and the black dash-dotted lines indicate the results of this study.

[1] N. Cabibbo, Phys. Rev. Lett.10_{, 531 (1963).}

[2] M. Kobayashi and T. Maskawa, Prog. Theor. Phys.49, 652 (1973).

[3] K. Huitu, D. X. Zhang, C. D. Lu, and P. Singer, Phys. Rev. Lett.81, 4313 (1998).

[4] S. Fajfer, J. F. Kamenik, and N. Kosnik, Phys. Rev.D74, 034027 (2006).

[5] S. Fajfer and P. Singer, Phys. Rev.D62, 117702 (2000). [6] E. J. Chun and J. S. Lee (2003), hep-ph/0307108. [7] T. E. Browder, T. Gershon, D. Pirjol, A. Soni, and J.

Zu-pan (2008), arXiv:0802.3201 [hep-ph].

[8] T. Bergfeld et al. (CLEO Collaboration), Phys. Rev. Lett.77, 4503 (1996).

[9] G. Abbiendi et al. (OPAL Collaboration), Phys. Lett. B476, 233 (2000).

[10] B. Aubert et al. (BA_BARCollaboration), Phys. Rev. Lett. 91_{, 051801 (2003).}

[11] A. Garmash et al. (Belle Collaboration), Phys. Rev.D69, 012001 (2004).

[12] B. Aubert et al. (BA_BAR_{Collaboration), Phys. Rev.}D74_, 051104 (2006).

[13] B. Aubert et al. (BA_BARCollaboration), Phys. Rev.D76, 071104 (2007).

[14] B. Aubert et al. (BA_BAR_{Collaboration), Phys. Rev. Lett.}

100, 081801 (2008).

[15] W. Kozanecki, Nucl. Instrum. Methods Phys. Res., Sect.

A446_{, 59 (2000).}

[16] B. Aubert et al. (BA_BARCollaboration), Nucl. Instrum. Methods Phys. Res., Sect. A479, 1 (2002).

[17] B. Aubert et al. (BA_BAR_{Collaboration), Phys. Rev. Lett.}

94, 161803 (2005).

[18] S. Agostinelli et al. (GEANT4 Collaboration), Nucl. In-strum. Methods Phys. Res., Sect. A506_{, 250 (2003).} [19] D. J. Lange, Nucl. Instrum. Methods Phys. Res., Sect. A

462, 152 (2001).

[20] M. Oreglia (1980), PhD Thesis, SLAC-0236, Appendix D.

[21] J. Gaiser (1982), PhD Thesis, SLAC-0255, Appendix F. [22] T. Skwarnicki (1986), PhD Thesis, DESY-F31-86-02,

Ap-pendix E.

[23] H. Albrecht et al. (ARGUS Collaboration), Z. Phys.C48, 543 (1990).

[24] D. Aston et al., Nucl. Phys.B296_{, 493 (1988).}

[25] B. Aubert et al. (BA_BARCollaboration), Phys. Rev.D78, 012004 (2008).

[26] M. Pivk and F. R. Le Diberder, Nucl. Instrum. Methods Phys. Res., Sect. A555_{, 356 (2005).}

[27] B. Aubert et al. (BA_BARCollaboration), Phys. Rev. Lett. 99, 221801 (2007).