Search for the decay $B^0 \to a_1^{\pm} \rho^{\mp}$

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arXiv:hep-ex/0605024v1 9 May 2006

B B

Search for the decay B

0

→

a

±₁

ρ

∓

B. Aubert,1 _{R. Barate,}1 _{M. Bona,}1_{D. Boutigny,}1 _{F. Couderc,}1 _{Y. Karyotakis,}1 _{J. P. Lees,}1 _{V. Poireau,}1 V. Tisserand,1 _{A. Zghiche,}1 _{E. Grauges,}2_{A. Palano,}3_{M. Pappagallo,}3_{J. C. Chen,}4_{N. D. Qi,}4 _{G. Rong,}4 _{P. Wang,}4

Y. S. Zhu,4 _{G. Eigen,}5 _{I. Ofte,}5_{B. Stugu,}5 _{G. S. Abrams,}6 _{M. Battaglia,}6_{D. N. Brown,}6 _{J. Button-Shafer,}6 R. N. Cahn,6 _{E. Charles,}6_{C. T. Day,}6 _{M. S. Gill,}6 _{Y. Groysman,}6_{R. G. Jacobsen,}6 _{J. A. Kadyk,}6_{L. T. Kerth,}6

Yu. G. Kolomensky,6_{G. Kukartsev,}6 _{G. Lynch,}6 _{L. M. Mir,}6 _{P. J. Oddone,}6 _{T. J. Orimoto,}6_{M. Pripstein,}6 N. A. Roe,6 _{M. T. Ronan,}6_{W. A. Wenzel,}6_{M. Barrett,}7_{K. E. Ford,}7_{T. J. Harrison,}7_{A. J. Hart,}7 _{C. M. Hawkes,}7

S. E. Morgan,7 _{A. T. Watson,}7 _{K. Goetzen,}8 _{T. Held,}8 _{H. Koch,}8 _{B. Lewandowski,}8 _{M. Pelizaeus,}8 _{K. Peters,}8 T. Schroeder,8_{M. Steinke,}8_{J. T. Boyd,}9 _{J. P. Burke,}9_{W. N. Cottingham,}9_{D. Walker,}9_{T. Cuhadar-Donszelmann,}10

B. G. Fulsom,10 _{C. Hearty,}10 _{N. S. Knecht,}10 _{T. S. Mattison,}10 _{J. A. McKenna,}10 _{A. Khan,}11 _{P. Kyberd,}11 M. Saleem,11 _{L. Teodorescu,}11_{V. E. Blinov,}12 _{A. D. Bukin,}12 _{V. P. Druzhinin,}12 _{V. B. Golubev,}12 _{A. P. Onuchin,}12

S. I. Serednyakov,12 _{Yu. I. Skovpen,}12 _{E. P. Solodov,}12 _{K. Yu Todyshev,}12 _{D. S. Best,}13 _{M. Bondioli,}13 M. Bruinsma,13_{M. Chao,}13_{S. Curry,}13_{I. Eschrich,}13 _{D. Kirkby,}13_{A. J. Lankford,}13 _{P. Lund,}13 _{M. Mandelkern,}13

R. K. Mommsen,13 _{W. Roethel,}13 _{D. P. Stoker,}13 _{S. Abachi,}14 _{C. Buchanan,}14_{S. D. Foulkes,}15 _{J. W. Gary,}15 O. Long,15 _{B. C. Shen,}15_{K. Wang,}15 _{L. Zhang,}15 _{H. K. Hadavand,}16 _{E. J. Hill,}16 _{H. P. Paar,}16_{S. Rahatlou,}16 V. Sharma,16_{J. W. Berryhill,}17 _{C. Campagnari,}17 _{A. Cunha,}17 _{B. Dahmes,}17 _{T. M. Hong,}17_{D. Kovalskyi,}17 J. D. Richman,17_{T. W. Beck,}18 _{A. M. Eisner,}18_{C. J. Flacco,}18 _{C. A. Heusch,}18 _{J. Kroseberg,}18 _{W. S. Lockman,}18

G. Nesom,18 _{T. Schalk,}18 _{B. A. Schumm,}18 _{A. Seiden,}18 _{P. Spradlin,}18 _{D. C. Williams,}18 _{M. G. Wilson,}18 J. Albert,19 _{E. Chen,}19 _{A. Dvoretskii,}19 _{D. G. Hitlin,}19 _{I. Narsky,}19_{T. Piatenko,}19 _{F. C. Porter,}19 _{A. Ryd,}19 A. Samuel,19 _{R. Andreassen,}20 _{G. Mancinelli,}20 _{B. T. Meadows,}20_{M. D. Sokoloff,}20 _{F. Blanc,}21 _{P. C. Bloom,}21

S. Chen,21 _{W. T. Ford,}21 _{J. F. Hirschauer,}21_{A. Kreisel,}21_{U. Nauenberg,}21_{A. Olivas,}21_{W. O. Ruddick,}21 J. G. Smith,21_{K. A. Ulmer,}21 _{S. R. Wagner,}21_{J. Zhang,}21 _{A. Chen,}22 _{E. A. Eckhart,}22_{A. Soffer,}22_{W. H. Toki,}22 R. J. Wilson,22 _{F. Winklmeier,}22_{Q. Zeng,}22 _{D. D. Altenburg,}23_{E. Feltresi,}23 _{A. Hauke,}23_{H. Jasper,}23 _{B. Spaan,}23

T. Brandt,24 _{V. Klose,}24 _{H. M. Lacker,}24 _{W. F. Mader,}24 _{R. Nogowski,}24 _{A. Petzold,}24 _{J. Schubert,}24 K. R. Schubert,24 _{R. Schwierz,}24_{J. E. Sundermann,}24 _{A. Volk,}24_{D. Bernard,}25 _{G. R. Bonneaud,}25 _{P. Grenier,}25,∗

E. Latour,25_{Ch. Thiebaux,}25 _{M. Verderi,}25 _{D. J. Bard,}26 _{P. J. Clark,}26 _{W. Gradl,}26 _{F. Muheim,}26 _{S. Playfer,}26 A. I. Robertson,26 _{Y. Xie,}26 _{M. Andreotti,}27 _{D. Bettoni,}27_{C. Bozzi,}27 _{R. Calabrese,}27 _{G. Cibinetto,}27 _{E. Luppi,}27

M. Negrini,27 _{A. Petrella,}27 _{L. Piemontese,}27 _{E. Prencipe,}27 _{F. Anulli,}28 _{R. Baldini-Ferroli,}28 _{A. Calcaterra,}28 R. de Sangro,28_{G. Finocchiaro,}28 _{S. Pacetti,}28 _{P. Patteri,}28_{I. M. Peruzzi,}28,† _{M. Piccolo,}28 _{M. Rama,}28 A. Zallo,28_{A. Buzzo,}29_{R. Capra,}29_{R. Contri,}29_{M. Lo Vetere,}29 _{M. M. Macri,}29_{M. R. Monge,}29 _{S. Passaggio,}29 C. Patrignani,29 _{E. Robutti,}29 _{A. Santroni,}29_{S. Tosi,}29 _{G. Brandenburg,}30 _{K. S. Chaisanguanthum,}30 _{M. Morii,}30 J. Wu,30 _{R. S. Dubitzky,}31 _{J. Marks,}31 _{S. Schenk,}31_{U. Uwer,}31 _{W. Bhimji,}32_{D. A. Bowerman,}32_{P. D. Dauncey,}32

U. Egede,32 _{R. L. Flack,}32_{J. R. Gaillard,}32 _{J .A. Nash,}32 _{M. B. Nikolich,}32_{W. Panduro Vazquez,}32 _{X. Chai,}33 M. J. Charles,33_{U. Mallik,}33 _{N. T. Meyer,}33 _{V. Ziegler,}33_{J. Cochran,}34 _{H. B. Crawley,}34_{L. Dong,}34_{V. Eyges,}34

W. T. Meyer,34_{S. Prell,}34 _{E. I. Rosenberg,}34 _{A. E. Rubin,}34 _{A. V. Gritsan,}35 _{M. Fritsch,}36 _{G. Schott,}36 N. Arnaud,37 _{M. Davier,}37 _{G. Grosdidier,}37_{A. H¨}_ocker,37 _{F. Le Diberder,}37 _{V. Lepeltier,}37 _{A. M. Lutz,}37 A. Oyanguren,37_{S. Pruvot,}37_{S. Rodier,}37 _{P. Roudeau,}37 _{M. H. Schune,}37 _{A. Stocchi,}37 _{W. F. Wang,}37 G. Wormser,37 _{C. H. Cheng,}38 _{D. J. Lange,}38 _{D. M. Wright,}38 _{C. A. Chavez,}39 _{I. J. Forster,}39 _{J. R. Fry,}39

E. Gabathuler,39 _{R. Gamet,}39 _{K. A. George,}39 _{D. E. Hutchcroft,}39 _{D. J. Payne,}39 _{K. C. Schofield,}39 C. Touramanis,39 _{A. J. Bevan,}40 _{F. Di Lodovico,}40 _{W. Menges,}40 _{R. Sacco,}40 _{C. L. Brown,}41_{G. Cowan,}41 H. U. Flaecher,41 _{D. A. Hopkins,}41_{P. S. Jackson,}41_{T. R. McMahon,}41_{S. Ricciardi,}41_{F. Salvatore,}41_{D. N. Brown,}42

C. L. Davis,42 _{J. Allison,}43 _{N. R. Barlow,}43 _{R. J. Barlow,}43 _{Y. M. Chia,}43 _{C. L. Edgar,}43_{M. P. Kelly,}43 G. D. Lafferty,43 _{M. T. Naisbit,}43 _{J. C. Williams,}43 _{J. I. Yi,}43 _{C. Chen,}44 _{W. D. Hulsbergen,}44 _{A. Jawahery,}44 C. K. Lae,44_{D. A. Roberts,}44_{G. Simi,}44_{G. Blaylock,}45_{C. Dallapiccola,}45_{S. S. Hertzbach,}45_{X. Li,}45 _{T. B. Moore,}45 S. Saremi,45 _{H. Staengle,}45_{S. Y. Willocq,}45 _{R. Cowan,}46_{K. Koeneke,}46 _{G. Sciolla,}46_{S. J. Sekula,}46_{M. Spitznagel,}46

F. Taylor,46_{R. K. Yamamoto,}46 _{H. Kim,}47 _{P. M. Patel,}47 _{C. T. Potter,}47 _{S. H. Robertson,}47 _{A. Lazzaro,}48 V. Lombardo,48_{F. Palombo,}48_{J. M. Bauer,}49 _{L. Cremaldi,}49 _{V. Eschenburg,}49_{R. Godang,}49 _{R. Kroeger,}49 J. Reidy,49_{D. A. Sanders,}49_{D. J. Summers,}49 _{H. W. Zhao,}49 _{S. Brunet,}50_{D. Cˆot´e,}50 _{M. Simard,}50_{P. Taras,}50 F. B. Viaud,50_{H. Nicholson,}51 _{N. Cavallo,}52,‡ _{G. De Nardo,}52 _{D. del Re,}52 _{F. Fabozzi,}52,‡ _{C. Gatto,}52 _{L. Lista,}52

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D. Monorchio,52 _{P. Paolucci,}52_{D. Piccolo,}52 _{C. Sciacca,}52 _{M. Baak,}53 _{H. Bulten,}53 _{G. Raven,}53_{H. L. Snoek,}53 C. P. Jessop,54 _{J. M. LoSecco,}54 _{T. Allmendinger,}55_{G. Benelli,}55 _{K. K. Gan,}55 _{K. Honscheid,}55 _{D. Hufnagel,}55 P. D. Jackson,55 _{H. Kagan,}55 _{R. Kass,}55_{T. Pulliam,}55 _{A. M. Rahimi,}55 _{R. Ter-Antonyan,}55 _{Q. K. Wong,}55

N. L. Blount,56 _{J. Brau,}56 _{R. Frey,}56 _{O. Igonkina,}56_{M. Lu,}56 _{R. Rahmat,}56 _{N. B. Sinev,}56 _{D. Strom,}56 J. Strube,56 _{E. Torrence,}56_{F. Galeazzi,}57_{A. Gaz,}57_{M. Margoni,}57 _{M. Morandin,}57_{A. Pompili,}57 _{M. Posocco,}57 M. Rotondo,57 _{F. Simonetto,}57 _{R. Stroili,}57 _{C. Voci,}57_{M. Benayoun,}58_{J. Chauveau,}58_{P. David,}58_{L. Del Buono,}58

Ch. de la Vaissi`ere,58_{O. Hamon,}58 _{B. L. Hartfiel,}58_{M. J. J. John,}58 _{Ph. Leruste,}58 _{J. Malcl`es,}58 _{J. Ocariz,}58 L. Roos,58 _{G. Therin,}58 _{P. K. Behera,}59 _{L. Gladney,}59 _{J. Panetta,}59_{M. Biasini,}60 _{R. Covarelli,}60 _{M. Pioppi,}60 C. Angelini,61 _{G. Batignani,}61 _{S. Bettarini,}61 _{F. Bucci,}61_{G. Calderini,}61 _{M. Carpinelli,}61 _{R. Cenci,}61 _{F. Forti,}61 M. A. Giorgi,61_{A. Lusiani,}61_{G. Marchiori,}61_{M. A. Mazur,}61_{M. Morganti,}61_{N. Neri,}61 _{E. Paoloni,}61_{G. Rizzo,}61 J. Walsh,61 _{M. Haire,}62_{D. Judd,}62_{D. E. Wagoner,}62_{J. Biesiada,}63_{N. Danielson,}63_{P. Elmer,}63_{Y. P. Lau,}63_{C. Lu,}63

J. Olsen,63 _{A. J. S. Smith,}63 _{A. V. Telnov,}63_{F. Bellini,}64_{G. Cavoto,}64_{A. D’Orazio,}64_{E. Di Marco,}64 _{R. Faccini,}64 F. Ferrarotto,64 _{F. Ferroni,}64_{M. Gaspero,}64 _{L. Li Gioi,}64 _{M. A. Mazzoni,}64_{S. Morganti,}64_{G. Piredda,}64_{F. Polci,}64 F. Safai Tehrani,64_{C. Voena,}64 _{M. Ebert,}65 _{H. Schr¨oder,}65_{R. Waldi,}65 _{T. Adye,}66_{N. De Groot,}66 _{B. Franek,}66

E. O. Olaiya,66_{F. F. Wilson,}66 _{S. Emery,}67_{A. Gaidot,}67 _{S. F. Ganzhur,}67 _{G. Hamel de Monchenault,}67 W. Kozanecki,67 _{M. Legendre,}67 _{B. Mayer,}67_{G. Vasseur,}67 _{Ch. Y`eche,}67_{M. Zito,}67 _{W. Park,}68_{M. V. Purohit,}68

A. W. Weidemann,68 _{J. R. Wilson,}68 _{M. T. Allen,}69 _{D. Aston,}69 _{R. Bartoldus,}69 _{P. Bechtle,}69_{N. Berger,}69 A. M. Boyarski,69 _{R. Claus,}69_{J. P. Coleman,}69_{M. R. Convery,}69_{M. Cristinziani,}69 _{J. C. Dingfelder,}69 _{D. Dong,}69 J. Dorfan,69_{G. P. Dubois-Felsmann,}69_{D. Dujmic,}69_{W. Dunwoodie,}69_{R. C. Field,}69_{T. Glanzman,}69_{S. J. Gowdy,}69

M. T. Graham,69 _{V. Halyo,}69 _{C. Hast,}69 _{T. Hryn’ova,}69 _{W. R. Innes,}69 _{M. H. Kelsey,}69 _{P. Kim,}69 _{M. L. Kocian,}69 D. W. G. S. Leith,69 _{S. Li,}69 _{J. Libby,}69 _{S. Luitz,}69_{V. Luth,}69_{H. L. Lynch,}69_{D. B. MacFarlane,}69 _{H. Marsiske,}69

R. Messner,69 _{D. R. Muller,}69 _{C. P. O’Grady,}69 _{V. E. Ozcan,}69 _{A. Perazzo,}69 _{M. Perl,}69_{B. N. Ratcliff,}69 A. Roodman,69 _{A. A. Salnikov,}69 _{R. H. Schindler,}69 _{J. Schwiening,}69 _{A. Snyder,}69 _{J. Stelzer,}69 _{D. Su,}69 M. K. Sullivan,69 _{K. Suzuki,}69 _{S. K. Swain,}69 _{J. M. Thompson,}69_{J. Va’vra,}69_{N. van Bakel,}69_{M. Weaver,}69 A. J. R. Weinstein,69 _{W. J. Wisniewski,}69_{M. Wittgen,}69 _{D. H. Wright,}69 _{A. K. Yarritu,}69_{K. Yi,}69_{C. C. Young,}69

P. R. Burchat,70 _{A. J. Edwards,}70 _{S. A. Majewski,}70_{B. A. Petersen,}70_{C. Roat,}70_{L. Wilden,}70 _{S. Ahmed,}71 M. S. Alam,71 _{R. Bula,}71 _{J. A. Ernst,}71 _{V. Jain,}71_{B. Pan,}71 _{M. A. Saeed,}71 _{F. R. Wappler,}71 _{S. B. Zain,}71 W. Bugg,72_{M. Krishnamurthy,}72_{S. M. Spanier,}72 _{R. Eckmann,}73 _{J. L. Ritchie,}73 _{A. Satpathy,}73_{C. J. Schilling,}73

R. F. Schwitters,73 _{J. M. Izen,}74 _{I. Kitayama,}74 _{X. C. Lou,}74 _{S. Ye,}74 _{F. Bianchi,}75 _{F. Gallo,}75_{D. Gamba,}75 M. Bomben,76 _{L. Bosisio,}76 _{C. Cartaro,}76_{F. Cossutti,}76 _{G. Della Ricca,}76 _{S. Dittongo,}76 _{S. Grancagnolo,}76 L. Lanceri,76 _{L. Vitale,}76 _{V. Azzolini,}77 _{F. Martinez-Vidal,}77 _{Sw. Banerjee,}78 _{B. Bhuyan,}78 _{C. M. Brown,}78 D. Fortin,78 _{K. Hamano,}78 _{R. Kowalewski,}78 _{I. M. Nugent,}78 _{J. M. Roney,}78 _{R. J. Sobie,}78 _{J. J. Back,}79 P. F. Harrison,79_{T. E. Latham,}79 _{G. B. Mohanty,}79 _{H. R. Band,}80 _{X. Chen,}80 _{B. Cheng,}80 _{S. Dasu,}80 _{M. Datta,}80 A. M. Eichenbaum,80 _{K. T. Flood,}80 _{J. J. Hollar,}80_{J. R. Johnson,}80_{P. E. Kutter,}80 _{H. Li,}80_{R. Liu,}80 _{B. Mellado,}80 A. Mihalyi,80_{A. K. Mohapatra,}80_{Y. Pan,}80_{M. Pierini,}80_{R. Prepost,}80 _{P. Tan,}80_{S. L. Wu,}80_{Z. Yu,}80_{and H. Neal}81

(The BA_BAR _{Collaboration)}

1_{Laboratoire de Physique des Particules, F-74941 Annecy-le-Vieux, France} 2_{Universitat de Barcelona, Facultat de Fisica Dept. ECM, E-08028 Barcelona, Spain}

3_Universit`_{a di Bari, Dipartimento di Fisica and INFN, I-70126 Bari, Italy} 4_{Institute of High Energy Physics, Beijing 100039, China}

5_{University of Bergen, Institute of Physics, N-5007 Bergen, Norway}

6_{Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720, USA} 7_{University of Birmingham, Birmingham, B15 2TT, United Kingdom}

8_{Ruhr Universit¨}_{at Bochum, Institut f¨}_{ur Experimentalphysik 1, D-44780 Bochum, Germany} 9_{University of Bristol, Bristol BS8 1TL, United Kingdom}

10_{University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1} 11_{Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom}

12_{Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia} 13_{University of California at Irvine, Irvine, California 92697, USA} 14_{University of California at Los Angeles, Los Angeles, California 90024, USA}

15_{University of California at Riverside, Riverside, California 92521, USA} 16_{University of California at San Diego, La Jolla, California 92093, USA} 17_{University of California at Santa Barbara, Santa Barbara, California 93106, USA}

18_{University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064, USA} 19_{California Institute of Technology, Pasadena, California 91125, USA}

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20_{University of Cincinnati, Cincinnati, Ohio 45221, USA} 21_{University of Colorado, Boulder, Colorado 80309, USA} 22_{Colorado State University, Fort Collins, Colorado 80523, USA} 23_Universit¨_{at Dortmund, Institut f¨}_{ur Physik, D-44221 Dortmund, Germany}

24_{Technische Universit¨}_{at Dresden, Institut f¨}_{ur Kern- und Teilchenphysik, D-01062 Dresden, Germany} 25_{Ecole Polytechnique, LLR, F-91128 Palaiseau, France}

26_{University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom}

27_Universit`_{a di Ferrara, Dipartimento di Fisica and INFN, I-44100 Ferrara, Italy} 28_{Laboratori Nazionali di Frascati dell’INFN, I-00044 Frascati, Italy} 29_Universit`_{a di Genova, Dipartimento di Fisica and INFN, I-16146 Genova, Italy}

30_{Harvard University, Cambridge, Massachusetts 02138, USA}

31_Universit¨_{at Heidelberg, Physikalisches Institut, Philosophenweg 12, D-69120 Heidelberg, Germany} 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_Universit¨_{at Karlsruhe, Institut f¨}_{ur Experimentelle Kernphysik, D-76021 Karlsruhe, Germany} 37_{Laboratoire de l’Accélérateur Linéaire, IN2P3-CNRS et Université Paris-Sud 11,}

Centre Scientifique d’Orsay, B.P. 34, F-91898 ORSAY Cedex, France

38_{Lawrence Livermore National Laboratory, Livermore, California 94550, USA} 39_{University of Liverpool, Liverpool L69 7ZE, United Kingdom} 40_{Queen Mary, University of London, E1 4NS, United Kingdom}

41_{University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom} 42_{University of Louisville, Louisville, Kentucky 40292, USA}

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_Universit`_{a di Milano, Dipartimento di Fisica and INFN, I-20133 Milano, Italy} 49_{University of Mississippi, University, Mississippi 38677, USA}

50_{Université de Montréal, Physique des Particules, Montréal, Québec, Canada H3C 3J7} 51_{Mount Holyoke College, South Hadley, Massachusetts 01075, USA}

52_Universit`_{a di Napoli Federico II, Dipartimento di Scienze Fisiche and INFN, 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_Universit`_{a di Padova, Dipartimento di Fisica and INFN, I-35131 Padova, Italy}

58_{Universit´es Paris VI et VII, Laboratoire de Physique Nucl´eaire et de Hautes Energies, F-75252 Paris, France} 59_{University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA}

60_Universit`_{a di Perugia, Dipartimento di Fisica and INFN, I-06100 Perugia, Italy}

61_Universit`_{a di Pisa, Dipartimento di Fisica, Scuola Normale Superiore and INFN, I-56127 Pisa, Italy} 62_{Prairie View A&M University, Prairie View, Texas 77446, USA}

63_{Princeton University, Princeton, New Jersey 08544, USA}

64_Universit`_{a di Roma La Sapienza, Dipartimento di Fisica and INFN, I-00185 Roma, Italy} 65_Universit¨_{at Rostock, D-18051 Rostock, Germany}

66_{Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom} 67_{DSM/Dapnia, CEA/Saclay, F-91191 Gif-sur-Yvette, France}

68_{University of South Carolina, Columbia, South Carolina 29208, USA} 69_{Stanford Linear Accelerator Center, Stanford, California 94309, USA}

70_{Stanford University, Stanford, California 94305-4060, USA} 71_{State University of New York, Albany, New York 12222, USA}

72_{University of Tennessee, Knoxville, Tennessee 37996, USA} 73_{University of Texas at Austin, Austin, Texas 78712, USA} 74_{University of Texas at Dallas, Richardson, Texas 75083, USA}

75_Universit`_{a di Torino, Dipartimento di Fisica Sperimentale and INFN, I-10125 Torino, Italy} 76_Universit`_{a di Trieste, Dipartimento di Fisica and INFN, I-34127 Trieste, Italy}

77_{IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain} 78_{University of Victoria, Victoria, British Columbia, Canada V8W 3P6} 79_{Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom}

80_{University of Wisconsin, Madison, Wisconsin 53706, USA} 81_{Yale University, New Haven, Connecticut 06511, USA}

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We present a search for the rare B-meson decay B0

→ a±1ρ∓with a±1 → π

+_π−_π±_{. We use (110 ±}

1.2) × 106

Υ (4S) → BB decays collected with the BABAR_{detector at the PEP-II asymmetric-energy} B Factory at SLAC. We obtain an upper limit of 30×10−6_{(90% C.L.) for the branching fraction}

product B(B0

→ a±1ρ∓)B(a±1 → π

+_π−_π±_{), where we assume that the a}±

1 decays exclusively to

ρ0_π±_.

PACS numbers: 13.25.Hw, 12.15.Hh, 11.30.Er

In the Standard Model, CP -violating effects in the B-meson system arise from a single phase in the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix [1]. The decay B0

→ a±1ρ∓ proceeds via a b → uud tran-sition [2], and interference between direct decay and decay after B0_B0 _{mixing results in a time-dependent} decay-rate asymmetry that is sensitive to the angle α ≡ arg[−VtdVtb∗/VudVub∗] [3] in the unitarity triangle of the CKM matrix. An additional motivation for studying B0

→ a±1ρ∓ is that this is a significant background to B → ρρ decays, e.g. [4–8], which currently provide the most accurate measurement of α. The ARGUS exper-iment previously searched for the decay B0

→ a±1ρ∓, which resulted in an upper limit of B(B0

→ a±1ρ∓) < 3.4 × 10−3 _{(90% C.L.) [9]. This paper presents the result} of a search for B0

→ a±1ρ∓ with a±1 → π+π−π±, where we assume that the a±1 decays exclusively to ρ0π±. A theoretical prediction of the branching fraction B(B0 _→ a±

1ρ∓)B(a±1 → (3π)±) has been made by Bauer, Stech and Wirbel [10] within the framework of the factoriza-tion model. They predict a value of 43×10−6_{, assuming} |Vub/Vcb| = 0.08.

The data used in this analysis were collected with the BA_BAR_{detector at the PEP-II asymmetric-energy B}

Fac-tory at SLAC during the years 2003-2004. This repre-sents a total integrated luminosity of 100 fb−1 _{taken at} the Υ (4S) resonance (on-peak), corresponding to a sam-ple of 110 ± 1.2 million BB pairs. An additional 21.6 fb−1 _{of data, collected at approximately 40 MeV below} the Υ (4S) resonance (off-peak), were used to study back-ground from e+_e−_{→ qq (q = u, d, s, c) continuum events.} The BA_BAR _{detector is described in detail}

else-where [11]. Surrounding the interaction point is a sil-icon vertex tracker (SVT) with 5 double-sided layers which measures the impact parameters of charged par-ticle tracks in both the plane transverse to, and along the beam direction. A 40 layer drift chamber (DCH) sur-rounds the SVT and provides measurements of the trans-verse momenta for charged particles. Both the SVT and the DCH operate in the magnetic field of a 1.5 T solenoid. Charged hadron identification is achieved through mea-surements of particle energy-loss in the tracking system and the Cherenkov angle obtained from a detector of internally reflected Cherenkov light. A CsI(Tl) electro-magnetic calorimeter (EMC) provides photon detection, electron identification, and π0 _{reconstruction. Finally,} the instrumented flux return of the magnet allows dis-crimination of muons from pions.

We reconstruct B0

→ a+1ρ− candidates from combi-nations of a+1 → π+π−π+ and ρ− → π0π− candidates. The a1(1260) → 3π decay proceeds mainly through the intermediate states (ππ)ρπ and (ππ)σπ [12]. We do not distinguish between the dominant P-wave (ππ)ρ and S-wave (ππ)σin the channel π+π−. The Monte Carlo (MC) signal events are simulated as B0 _{decays to a}+

1(1260)ρ− with a+

1 → ρ0π+ using the GEANT4-based [13] BABAR MC simulation. Possible contributions from B0 _decays to a+

2(1320)ρ− and π

+_(1300)ρ− _{are investigated.} We only consider events that have a minimum of one π0_{and four charged tracks, where the charged tracks are} required to be inconsistent with lepton, proton and kaon hypotheses.

We form π0

→ γγ candidates from pairs of photon candidates that have been identified as localized energy deposits in the EMC that have the lateral energy distri-bution expected for a photon. Each photon is required to have an energy Eγ > 50 MeV, and the π0 is required to have an invariant mass of 0.10 < mγγ < 0.16 GeV/c2.

The ρ−_{mesons are formed from one track that is} con-sistent with a π− _{and the aforementioned π}0 _candidate. The candidate ρ− _{is required to have an invariant mass} of 0.5 < mρ−< 1.1 GeV/c2. We also constrain the cosine of the angle between the π0_{momentum and the direction} opposite to the B0 _{in the ρ}− _{rest frame (cos θ}

ρ−) to be between −0.9 and 0.98. This removes backgrounds which peak at the extremes of the distribution where the signal reconstruction efficiency also falls off.

We form the a+1 candidate from combinations of three charged pions. We first form a ρ0

→ π+_π− _candidate from two oppositely charged tracks. This combination is required to have an invariant mass of 0.4 < mρ0 < 1.1 GeV/c2_{. The a}+

1 candidate is then formed by adding another charged track to the ρ0_{, and requiring that the} mass of the a+

1 satisfies 0.6 < ma+

1 < 1.5 GeV/c

2_{. The} vertex of the B-candidate is constrained to originate from the beam spot. In order to reduce background from con-tinuum events we require that | cos(θT)| < 0.7, where θT is the angle between the B thrust axis and that of the rest of the event (ROE).

We use two kinematic variables, mESand ∆E, in order to isolate any signal. We define the beam-energy substi-tuted mass mES =p(√s/2)2− (p∗_B)2, where√s is the e+_e−_{center-of-mass (CM) energy. The second kinematic} variable, ∆E, is the difference between the B-candidate energy and the beam energy in the CM frame. We re-quire mES> 5.25 GeV/c2and −0.15 < ∆E < 0.1 GeV.

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Additional separation between signal and continuum is obtained by combining several kinematic and topolog-ical variables into a Fisher discriminant (F) [14]. The variables L0, L2, and | cos θT R|, and the output of a mul-tivariate tagging algorithm [15] are used as inputs to F. L0 and L2 are defined as

L0= X ROE |p∗ i|, L2= X ROE |p∗ i| cos(θi)2, (1) where the sum is over the ROE, p∗

i is the particle mo-mentum in the CM frame. θi is the angle of the particle direction relative to the thrust axis of the B-candidate, and cos θT R is the cosine of the angle between the B thrust axis and the beam axis. The multivariate tagging algorithm identifies the flavor of the other B in the event to be either a B0_{or B}0_{. The output of this algorithm is} ranked into categories of different signal purity.

We expect the polarization of the a+

1ρ−final state to be predominantly longitudinal, as was found in the similar decay B → ρρ [4–8]. We have used both longitudinal and transverse polarized signal MC simulated data in this analysis. After applying the selection cuts above, we have 2.8 (2.3) longitudinal (transverse) polarized signal MC simulated data candidates per event.

We define as self-cross-feed (SCF) the set of candi-dates that were incorrectly reconstructed from particles in events that contain a true signal candidate. We select one B candidate per event in which the mass of the re-constructed ρ0_{is closest to that of the true ρ}0_{mass [16].} Choosing the candidate using the ρ0 _{mass reduces the} SCF fraction by 18% relative to a random selection. To avoid potentially biasing our final result, we do not use information from the ρ0 _{meson in the remainder of the} analysis. After all selection cuts have been applied, the longitudinal and transverse signal SCF fractions are 0.58 and 0.42, respectively. The selection efficiency of longi-tudinal (transverse) signal is 9.44% (10.15%).

Besides the continuum background we also have back-ground from B decays. We divide the B-backback-ground into the following four categories according to B-meson charge and the charm content of the final states: (i) B0

→ charm, (ii) B0 _{→ charmless, (iii) B}± _{→ charm and (iv)} B± _{→ charmless. From large samples of inclusive MC} simulated data we expect 2394, 424, 3281 and 215 events of these background types, respectively. In addition, a number of exclusive B-background modes that have a similar final state to the signal were studied. This in-cludes those that have an intermediate a1 meson in the decay. None of these modes were seen to have a signifi-cant efficiency after the selection cuts had been applied. We perform an extended unbinned maximum likeli-hood fit to the data. The likelihood model has the following types: (i)-(iv) the four aforementioned in-clusive B-background categories, (v) true signal, (vi) SCF signal and the (vii) e+_e− _{→ qq (q = u, d, s, c)}

continuum background. The probability density func-tion (PDF) for each event i has the form Pi,c = Pi,c(mES, ∆E, F, m_a+

1, mρ−, cos θρ−). From these indi-vidual PDFs the total likelihood

L = e−n′ n Y i=1 X c NcPi,c, (2)

is constructed. The parameters n and n′_{are the numbers} of selected on-peak events, and the sum of the yields Nc, where c is one of the seven types in the likelihood model. Correlations between the mρ− and cos θ_ρ− variables are taken into account for the real (T) and fake combinato-rial (F) ρ− _{candidates. All other correlations between} fit variables are seen to be small. However, the effect of ignoring them results in a bias on the fitted signal yield which is discussed below.

Each of the signal distributions has a signal yield and a polarization fraction that are denoted by Nsig (Nsig′ ) and fL(fL′), for the true (SCF) signal, such that the sum of the true and SCF signal is described by

Nsig[fLPilong,true+ (1 − fL)Pitran,true] +

Nsig′ [fL′P long,SCF i + (1 − f ′ L)P tran, SCF i ]. (3)

The continuum yield, Nsig, Nsig′ , and the parameters of the continuum mESand ∆E PDFs are allowed to vary in the fit. Under the assumption that no significant signal is observed, the value of fLis fixed to 1.0 in the fit. The value of f′

L is also fixed to 1.0 in the fit since it is highly correlated with Nsig, Nsig′ and fL. Only the fitted value of Nsig is used to derive the final result. We also fix the B-background yields to the aforementioned values.

The PDFs used for each component are given in Ta-ble I. The signal and B-backgrounds are parameterized using MC. We use a non-parametric smoothing algo-rithm [17] when defining some of the background PDFs (as indicated by the abbreviation NP). We account for the difference between F and T ρ− _{→ π}−_π0 distribu-tions in the background using the product of 1D PDFs, denoted in Table I as ‘BG m-hel’, such that

Pi(mρ−, cos θρ−) = (1 − aT)PF,i(mρ−)PF,i(cos θρ−) + aTPT,i(mρ−)PT,i(cos θρ−), (4)

where aT is the fraction of T events. The continuum shape for cos θρ− (m_ρ−) is derived from off-peak (on-peak) data. The true ρ− _{resonance Breit Wigner shape} uses mρ− = 0.77 GeV/c2, and Γ = 0.150 GeV [16]. The parameterizations used for this PDF are summarized in Table II.

The results from the fit are Nsig= 90±38(stat), Nsig′ = 42 ±98 and a continuum yield of 25798±182 events. The bias on the fitted signal yield is evaluated by perform-ing ensembles of mock experiments usperform-ing signal MC em-bedded into MC samples of background generated from

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TABLE I: The types of PDFs used to model the different variables for each component in the likelihood fit, where the PDFs underlined have their parameters varying in the nominal fit. The abbreviations are: G = Gaussian, G2 = Double Gaussian, G3 = Triple Gaussian, CB = Crystal Ball (a Gaussian with a low side exponential tail) [18], ARGUS = ARGUS function x√1 − x2_exp_{−ξ(1 − x}2₎_{, with x ≡ 2m}

ES/√s and parameter ξ [19], which is allowed to vary in the fit, Pn = Polynomial

of order n, BW = Breit-Wigner, helicity = cos2_θ

ρ− or sin2θρ− depending on partial wave which is modified by a quadratic acceptance function, BG m-hel = Background cos θρ− and m−ρ PDF of Eq. 4, off-peak = PDF taken from off-peak data, and

1D = smoothed 1D histogram.

Component mES ∆E F m_a+

1

cos θρ− mρ−

signal (long/trans./true/SCF) CB CB+G G2 G3 helicity BW+P4

qq ARGUS P1 G2 (off-peak) 1D (off-peak) BG m-hel BG m-hel

B0 _(B±_{)→ charm (charmless)} _NP _NP _NP _NP _{BG m-hel BG m-hel}

TABLE II: The types of PDFs used to model the different background cos θρ−and mρ−PDF shapes. The abbreviations Pn and BW are defined in the caption of Table I.

Component T cos θρ− T mρ− F cos θρ− F mρ−

qq P2 BW + P1 P5 P4 B± → charmless P4 BW P5 P3 B0 → charmless P4 BW P5 P3 B±_{→ charm} _P2 _BW _P5 _P3 B0 → charm P2 BW P5 P3

the PDF. The bias is found to be +22 events (24%), re-sulting in a corrected signal yield of 68 ± 38(stat). In Fig. 1 we compare the true signal and continuum PDF shapes (solid curves) to the data (points) using the event-weighting technique described in Ref. [20]. The distribu-tions shown in Fig. 1 are not corrected for fit bias, and the uncertainty on each of the data points is statistical. No change in signal yield is seen when a+

2(1320)ρ− and π+_(1300)ρ− _{components are included in the fit.}

Table III summarises the systematic uncertainties on the signal yield. Each entry in the table indicates one sys-tematic effect, and the contributions are added in quadra-ture to give the total presented. The uncertainty due to PDF parameterisation is evaluated by variation of both the signal and the background PDF parameters within their uncertainties about their nominal values. The un-certainty from the continuum mESand ∆E PDFs which are allowed to vary in the fit, are only included in the quoted statistical uncertainty. We assign a systematic uncertainty due to fit bias, evaluated as half of the fit bias correction on the signal yield. To validate the expected B-background yields, and to assign a systematic uncer-tainty we perform a number of cross-checks in which we allow the background yields to vary in turn when fitting the data. We use a control sample of B → Dρ events to determine the systematic uncertainty in the fraction of

SCF signal events. The effect of exclusive B meson de-cays to final states including a1-mesons were evaluated using ensembles of mock experiments. In particular, the systematic uncertainty on the signal yield from neglect-ing B → a1a1 modes in the fit is 6 events. We assign a systematic uncertainty from using a relativistic Breit-Wigner with a Blatt-Weisskopf form factor with a range parameter of 3.0 GeV−1 _{for the a}+

1 meson line shape. In the fit we assume that the a+

1 meson width, Γa+1, is 400 MeV. We evaluate a systematic uncertainty due to this assumption by varying Γ_a+

1 over the experimentally allowed range: 250 - 600 MeV [16]. The difference in the distribution of F between data and MC is evaluated with a large sample of B → D⋆_{ρ decays. The systematic}

TABLE III: The systematic uncertainties on Nsig (events).

Source Uncertainty on Nsig

PDF parameterisation +27 −30 Fit bias _±11 B-background yields +29 −42 SCF fraction _±7

Neglecting B → a1a1 modes in fit ±6

a+1 line shape ±10

a+

1 width ±9

Fisher data/MC comparison ±6

Total +45

−56

uncertainties that contribute to the branching fraction only through the efficiency come from charged particle identification (6.0%), π0 _{meson reconstruction (3.0%),} tracking efficiency (3.2%), and the number of B meson pairs (1.1%). The systematic error contribution from MC statistics is negligible.

When the fit bias correction of −22 events is ap-plied to the signal yield, and one accounts for sys-tematic uncertainties, the significance of the result is

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) 2 (GeV / c ES m 5.25 5.26 5.27 5.28 5.29 2 Events / 2 MeV / c 0 50 E (GeV) ∆ -0.15 -0.1 -0.05 0 0.05 0.1 Events / 25 MeV 0 50 ) 2 (GeV / c + 1 a m 0.6 0.8 1 1.2 1.4 2 Events / 90 MeV / c -50 0 50 ) 2 (GeV / c ES m 5.25 5.26 5.27 5.28 5.29 2 Events / 2 MeV / c 0 1000 E (GeV) ∆ -0.15 -0.1 -0.05 0 0.05 0.1 Events / 25 MeV 0 2000 ) 2 (GeV / c + 1 a m 0.6 0.8 1 1.2 1.4 2 Events / 90 MeV / c ₀ 2000 4000

FIG. 1: The true signal (top) and continuum (bottom) distributions for (left to right) mES, ∆E, m_a+

1 using the weighting technique described in Ref. [20]. The points represent the weighted data, and solid curves represent the corresponding PDFs.

0.95 standard deviations. Figure 2 shows the distribu-tion of −ln(L/Lmax) for the fit, with and without these systematic errors. Lmax is the value of the likelihood corresponding to the nominal fit result. The branch-ing fraction value for the fit-bias-corrected signal yield of 68 ± 38(stat)+45−56(syst) is B(B0 → a + 1ρ−)B(a + 1 → π+_π−_π+

) = (15.7 ± 8.7(stat)+10.3−12.8(syst))×10−6. This as-sumes that fL = 1.0 and that the branching fraction of a+1 → π+π−π+ = 0.5. As the signal yield obtained is not significant, we calculate the upper limit xUL, by

Signal Yield 0 100 200 ) max -ln( L / L 0 2 4 6 8 10

FIG. 2: The −ln(L/Lmax) distribution from the fit to data

with fL=1.0 (fixed). This distribution has been corrected for

fit bias. The solid curve is for statistical errors only, and the dashed curve includes systematic errors.

integrating the likelihood function (including systematic uncertainties) from 0 to xUL, for different physically al-lowed values of fL, such that the C.L. of the upper limit is 90%. As the signal efficiency is a function of fL, we report the most conservative upper limit obtained, which corresponds to fL = 1.0. On doing this, an upper limit of 30×10−6_{(90% C.L.) is obtained.}

We have performed a search for the decay B0

→ a±1ρ∓ in a data sample of 100 fb−1_{. After correcting for fit bias} and accounting for systematic uncertainties, the signal yield is 68 ± 38(stat)+45−56(syst) events, with a significance of 0.95σ. As there is no significant evidence for a sig-nal, we place an upper limit of 30×10−6_{(90% C.L.) on} B(B0

→ a+1ρ−)B(a +

1 → π+π−π+), where we assume that the a+1 decays exclusively to ρ0π+. Assuming B(a

+ 1 → π+_π−_π+_{) is equal to B(a}+ 1 → π+π0π0), we obtain B(B0 _{→ a}+ 1ρ−)B(a + 1 → (3π)+) < 61×10−6(90% C.L.). This upper limit corresponds to a significant improve-ment over the previous bound and is compatible with theoretical expectations [10]. This result is a significant improvement in constraining an important B background contribution in B → ρρ decays.

ACKNOWLEDGMENTS

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 computing organizations that support BA_BAR_{. The collaborating}

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kind hospitality. This work is supported by DOE and NSF (USA), NSERC (Canada), IHEP (China), CEA and CNRS-IN2P3 (France), BMBF and DFG (Germany), INFN (Italy), FOM (The Netherlands), NFR (Norway), MIST (Russia), and PPARC (United Kingdom). Indi-viduals have received support from CONACyT (Mex-ico), Marie Curie EIF (European Union), the A. P. Sloan Foundation, the Research Corporation, and the Alexan-der von Humboldt Foundation.

∗ _Also _at _Laboratoire _de _Physique _{Corpusculaire,}

Clermont-Ferrand, France

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

Perugia, Italy

‡ _{Also with Universit`}_{a della Basilicata, Potenza, Italy}

[1] N. Cabibbo, Phys. Rev. Lett. 10, 531 (1963); M. Kobayashi and T. Maskawa, Prog. Theor. Phys. 49, 652 (1973).

[2] Charge-conjugate transitions are included implicitly un-less otherwise stated.

[3] A. Bevan, Mod. Phys. Lett. A 21, No. 4, 305 (2006). [4] The BABAR Collaboration, B. Aubert et al., Phys. Rev.

Lett. 95, 041805 (2005).

[5] The BABAR Collaboration, B. Aubert et al., Phys. Rev. Lett. 91, 171802 (2003).

[6] The BABARCollaboration, B. Aubert et al., Phys. Rev. Lett. 94, 131801 (2005).

[7] The Belle Collaboration, A. Somov et al., arXiv:hep-ex/0601024. Submitted to PRL.

[8] The Belle Collaboration, J. Zhang et al., Phys. Rev. Lett. 91, 221801 (2003).

[9] The ARGUS Collaboration, H. Albrecht et al., Phys. Lett. B 241, 278 (1990).

[10] M. Bauer, B. Stech and M. Wirbel, Z. Phys. C 34, 103 (1987).

[11] The BABAR_{Collaboration, B. Aubert et al., Nucl. Instr.} Methods Phys. Res., Sect. A 479, 1 (2002).

[12] The CLEO Collaboration, D. M. Asner et al., Phys. Rev. D 61, 012002 (1999).

[13] The GEANT4 Collaboration, S. Agostinelli et al., Nucl. Instr. Methods Phys. Res., Sect. A 506, 250 (2003). [14] R. A. Fisher, Annals of Eugenics 7, 179 (1936).

[15] The BABAR_{Collaboration, B. Aubert et al., Phys. Rev.} Lett. 89, 281802 (2002).

[16] S. Eidelman et al., Phys. Lett. B 592, 1 (2004).

[17] K. S. Cranmer, Comput. Phys. Commun. 136, 198 (2001).

[18] The Crystal Ball Collaboration, D. Antreasyan et al., Crystal Ball Note, 321 (1983).

[19] The ARGUS Collaboration, H. Albrecht et al., Phys. Lett. B 241, 278 (1990).

[20] M. Pivk and F. R. Le Diberder, Nucl. Instr. Methods Phys. Res., Sect. A 555, 356 (2005).