Measurements of branching fractions and CP-violating asymmetries in B-0 ->rho(+/-)h(-/+) decays

Measurements of Branching Fractions and

CP

-Violating Asymmetries in

B

_!

_h

_Decays

B. Aubert,1R. Barate,1D. Boutigny,1J.-M. Gaillard,1A. Hicheur,1Y. Karyotakis,1J. P. Lees,1P. Robbe,1V. Tisserand,1 A. Zghiche,1A. Palano,2A. Pompili,2J. C. Chen,3N. D. Qi,3G. Rong,3P. Wang,3Y. S. Zhu,3G. Eigen,4I. Ofte,4 B. Stugu,4G. S. Abrams,5A.W. Borgland,5A. B. Breon,5D. N. Brown,5J. Button-Shafer,5R. N. Cahn,5E. Charles,5

C. T. Day,5M. S. Gill,5A.V. Gritsan,5Y. Groysman,5R. G. Jacobsen,5R.W. Kadel,5J. Kadyk,5L. T. Kerth,5 Yu. G. Kolomensky,5J. F. Kral,5G. Kukartsev,5C. LeClerc,5M. E. Levi,5G. Lynch,5L. M. Mir,5P. J. Oddone,5 T. J. Orimoto,5M. Pripstein,5N. A. Roe,5A. Romosan,5M. T. Ronan,5V. G. Shelkov,5A.V. Telnov,5W. A. Wenzel,5

K. Ford,6T. J. Harrison,6C. M. Hawkes,6D. J. Knowles,6S. E. Morgan,6R. C. Penny,6A. T. Watson,6N. K. Watson,6 T. Deppermann,7K. Goetzen,7H. Koch,7B. Lewandowski,7M. Pelizaeus,7K. Peters,7H. Schmuecker,7M. Steinke,7

N. R. Barlow,8J. T. Boyd,8N. Chevalier,8W. N. Cottingham,8M. P. Kelly,8T. E. Latham,8C. Mackay,8F. F. Wilson,8 K. Abe,9T. Cuhadar-Donszelmann,9C. Hearty,9T. S. Mattison,9J. A. McKenna,9D. Thiessen,9P. Kyberd,10

A. K. McKemey,10V. E. Blinov,11A. D. Bukin,11V. B. Golubev,11V. N. Ivanchenko,11E. A. Kravchenko,11 A. P. Onuchin,11S. I. Serednyakov,11Yu. I. Skovpen,11E. P. Solodov,11A. N. Yushkov,11D. Best,12M. Chao,12D. Kirkby,12

A. J. Lankford,12M. Mandelkern,12S. McMahon,12R. K. Mommsen,12W. Roethel,12D. P. Stoker,12C. Buchanan,13 D. del Re,14H. K. Hadavand,14E. J. Hill,14D. B. MacFarlane,14H. P. Paar,14Sh. Rahatlou,14U. Schwanke,14V. Sharma,14 J.W. Berryhill,15C. Campagnari,15B. Dahmes,15N. Kuznetsova,15S. L. Levy,15O. Long,15A. Lu,15M. A. Mazur,15 J. D. Richman,15W.Verkerke,15T.W. Beck,16J. Beringer,16A. M. Eisner,16C. A. Heusch,16W. S. Lockman,16T. Schalk,16 R. E. Schmitz,16B. A. Schumm,16A. Seiden,16M. Turri,16W. Walkowiak,16D. C. Williams,16M. G. Wilson,16J. Albert,17 E. Chen,17G. P. Dubois-Felsmann,17A. Dvoretskii,17 D. G. Hitlin,17I. Narsky,17 F. C. Porter,17A. Ryd,17A. Samuel,17

S. Yang,17S. Jayatilleke,18G. Mancinelli,18B. T. Meadows,18M. D. Sokoloff,18T. Abe,19T. Barillari,19F. Blanc,19 P. Bloom,19P. J. Clark,19W. T. Ford,19U. Nauenberg,19A. Olivas,19P. Rankin,19J. Roy,19J. G. Smith,19W. C. van Hoek,19

L. Zhang,19J. L. Harton,20T. Hu,20A. Soffer,20W. H. Toki,20R. J. Wilson,20J. Zhang,20D. Altenburg,21T. Brandt,21 J. Brose,21T. Colberg,21M. Dickopp,21R. S. Dubitzky,21A. Hauke,21H. M. Lacker,21E. Maly,21

R. Mu¨ller-Pfefferkorn,21R. Nogowski,21S. Otto,21K. R. Schubert,21R. Schwierz,21B. Spaan,21L. Wilden,21 D. Bernard,22G. R. Bonneaud,22F. Brochard,22J. Cohen-Tanugi,22Ch. Thiebaux,22G. Vasileiadis,22M. Verderi,22 A. Khan,23D. Lavin,23F. Muheim,23S. Playfer,23J. E. Swain,23J. Tinslay,23M. Andreotti,24D. Bettoni,24C. Bozzi,24

R. Calabrese,24G. Cibinetto,24 E. Luppi,24M. Negrini,24 L. Piemontese,24A. Sarti,24 E. Treadwell,25F. Anulli,1,* R. Baldini-Ferroli,26A. Calcaterra,26R. de Sangro,26D. Falciai,26G. Finocchiaro,26P. Patteri,26I. M. Peruzzi,26,*

M. Piccolo,26A. Zallo,26A. Buzzo,27R. Contri,27G. Crosetti,27M. Lo Vetere,27M. Macri,27M. R. Monge,27 S. Passaggio,27F. C. Pastore,27C. Patrignani,27E. Robutti,27A. Santroni,27S. Tosi,27S. Bailey,28M. Morii,28 M. L. Aspinwall,29W. Bhimji,29D. A. Bowerman,29P. D. Dauncey,29U. Egede,29I. Eschrich,29G.W. Morton,29

J. A. Nash,29P. Sanders,29G. P. Taylor,29G. J. Grenier,30S.-J. Lee,30U. Mallik,30J. Cochran,31H. B. Crawley,31 J. Lamsa,31W. T. Meyer,31S. Prell,31E. I. Rosenberg,31J. Yi,31M. Davier,32G. Grosdidier,32A. Ho¨cker,32S. Laplace,32

F. Le Diberder,32V. Lepeltier,32A. M. Lutz,32T. C. Petersen,32S. Plaszczynski,32M. H. Schune,32L. Tantot,32 G. Wormser,32V. Brigljevic´,33C. H. Cheng,33D. J. Lange,33D. M. Wright,33A. J. Bevan,34J. P. Coleman,34J. R. Fry,34

E. Gabathuler,34R. Gamet,34M. Kay,34R. J. Parry,34D. J. Payne,34R. J. Sloane,34C. Touramanis,34J. J. Back,35 P. F. Harrison,35H.W. Shorthouse,35P. Strother,35P. B. Vidal,35C. L. Brown,36G. Cowan,36R. L. Flack,36 H. U. Flaecher,36S. George,36M. G. Green,36A. Kurup,36C. E. Marker,36T. R. McMahon,36S. Ricciardi,36 F. Salvatore,36G. Vaitsas,36M. A. Winter,36D. Brown,37C. L. Davis,37J. Allison,38R. J. Barlow,38A. C. Forti,38 P. A. Hart,38F. Jackson,38G. D. Lafferty,38A. J. Lyon,38J. H. Weatherall,38J. C. Williams,38A. Farbin,39A. Jawahery,39

D. Kovalskyi,39C. K. Lae,39V. Lillard,39D. A. Roberts,39G. Blaylock,40C. Dallapiccola,40K. T. Flood,40 S. S. Hertzbach,40R. Kofler,40V. B. Koptchev,40T. B. Moore,40S. Saremi,40H. Staengle,40S. Willocq,40R. Cowan,41 G. Sciolla,41F. Taylor,41R. K. Yamamoto,41D. J. J. Mangeol,42M. Milek,42P. M. Patel,42A. Lazzaro,43F. Palombo,43 J. M. Bauer,44L. Cremaldi,44V. Eschenburg,44R. Godang,44R. Kroeger,44J. Reidy,44D. A. Sanders,44D. J. Summers,44

H.W. Zhao,44C. Hast,45P. Taras,45H. Nicholson,46C. Cartaro,47N. Cavallo,47,†G. De Nardo,47F. Fabozzi,47,† C. Gatto,47L. Lista,47P. Paolucci,47D. Piccolo,47C. Sciacca,47M. A. Baak,48G. Raven,48J. M. LoSecco,49 T. A. Gabriel,50B. Brau,51T. Pulliam,51J. Brau,52R. Frey,52C. T. Potter,52N. B. Sinev,52D. Strom,52E. Torrence,52 F. Colecchia,53A. Dorigo,53F. Galeazzi,53M. Margoni,53M. Morandin,53M. Posocco,53M. Rotondo,53F. Simonetto,53

L. Del Buono,54O. Hamon,54M. J. J. John,54Ph. Leruste,54J. Ocariz,54M. Pivk,54L. Roos,54J. Stark,54S. T’Jampens,54 P. F. Manfredi,55V. Re,55L. Gladney,56Q. H. Guo,56J. Panetta,56C. Angelini,57G. Batignani,57S. Bettarini,57 M. Bondioli,57F. Bucci,57G. Calderini,57M. Carpinelli,57F. Forti,57M. A. Giorgi,57A. Lusiani,57G. Marchiori,57

F. Martinez-Vidal,57,‡M. Morganti,57N. Neri,57E. Paoloni,57M. Rama,57G. Rizzo,57F. Sandrelli,57J. Walsh,57 M. Haire,58D. Judd,58K. Paick,58D. E. Wagoner,58N. Danielson,59P. Elmer,59C. Lu,59V. Miftakov,59J. Olsen,59 A. J. S. Smith,59E.W. Varnes,59F. Bellini,60G. Cavoto,59,60R. Faccini,14,60F. Ferrarotto,60F. Ferroni,60M. Gaspero,60

M. A. Mazzoni,60S. Morganti,60M. Pierini,60G. Piredda,60F. Safai Tehrani,60C. Voena,60S. Christ,61G. Wagner,61 R. Waldi,61T. Adye,62N. De Groot,62B. Franek,62N. I. Geddes,62G. P. Gopal,62E. O. Olaiya,62S. M. Xella,62 R. Aleksan,63S. Emery,63A. Gaidot,63S. F. Ganzhur,63P.-F. Giraud,63G. Hamel de Monchenault,63W. Kozanecki,63

M. Langer,63G.W. London,63B. Mayer,63G. Schott,63G. Vasseur,63Ch. Yeche,63M. Zito,63M.V. Purohit,64 A.W. Weidemann,64F. X. Yumiceva,64D. Aston,65R. Bartoldus,65N. Berger,65A. M. Boyarski,65O. L. Buchmueller,65 M. R. Convery,65D. P. Coupal,65D. Dong,65J. Dorfan,65D. Dujmic,65W. Dunwoodie,65R. C. Field,65T. Glanzman,65 S. J. Gowdy,65E. Grauges-Pous,65T. Hadig,65V. Halyo,65T. Hryn’ova,65W. R. Innes,65C. P. Jessop,65M. H. Kelsey,65 P. Kim,65M. L. Kocian,65U. Langenegger,65D.W. G. S. Leith,65S. Luitz,65V. Luth,65H. L. Lynch,65H. Marsiske,65

S. Menke,65R. Messner,65D. R. Muller,65C. P. O’Grady,65V. E. Ozcan,65A. Perazzo,65M. Perl,65S. Petrak,65 B. N. Ratcliff,65S. H. Robertson,65A. Roodman,65A. A. Salnikov,65R. H. Schindler,65J. Schwiening,65G. Simi,65 A. Snyder,65A. Soha,65J. Stelzer,65D. Su,65M. K. Sullivan,65H. A. Tanaka,65J. Va’vra,65S. R. Wagner,65M. Weaver,65

A. J. R. Weinstein,65W. J. Wisniewski,65D. H. Wright,65C. C. Young,65P. R. Burchat,66A. J. Edwards,66T. I. Meyer,66 C. Roat,66S. Ahmed,67M. S. Alam,67J. A. Ernst,67M. Saleem,67F. R. Wappler,67W. Bugg,68M. Krishnamurthy,68 S. M. Spanier,68R. Eckmann,69H. Kim,69J. L. Ritchie,69R. F. Schwitters,69J. M. Izen,70I. Kitayama,70X. C. Lou,70 S. Ye,70F. Bianchi,71M. Bona,71F. Gallo,71D. Gamba,71C. Borean,72L. Bosisio,72G. Della Ricca,72S. Dittongo,72 S. Grancagnolo,72L. Lanceri,72P. Poropat,72,xL. Vitale,72G. Vuagnin,72R. S. Panvini,73Sw. Banerjee,74C. M. Brown,74 D. Fortin,74P. D. Jackson,74R. Kowalewski,74J. M. Roney,74H. R. Band,75S. Dasu,75M. Datta,75A. M. Eichenbaum,75 H. Hu,75J. R. Johnson,75P. E. Kutter,75H. Li,75R. Liu,75F. Di Lodovico,75A. Mihalyi,75A. K. Mohapatra,75Y. Pan,75

R. Prepost,75S. J. Sekula,75J. H. von Wimmersperg-Toeller,75J. Wu,75S. L. Wu,75and Z. Yu75H. Neal76

(BABARCollaboration)

1_{Laboratoire de Physique des Particules, F-74941 Annecy-le-Vieux, France} 2_{Universita` di Bari, Dipartimento di Fisica and INFN, I-70126 Bari, Italy}

3_{Institute of High Energy Physics, Beijing 100039, China} 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 Universita¨t Bochum, Institut fu¨r 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 San Diego, La Jolla, California 92093, USA} 15_{University of California at Santa Barbara, Santa Barbara, California 93106, USA}

16_{University of California at Santa Cruz, Institute for Particle Physics, Santa Cruz, California 95064, USA} 17_{California Institute of Technology, Pasadena, California 91125, USA}

18_{University of Cincinnati, Cincinnati, Ohio 45221, USA} 19_{University of Colorado, Boulder, Colorado 80309, USA} 20_{Colorado State University, Fort Collins, Colorado 80523, USA}

21_{Technische Universita¨t Dresden, Institut fu¨r Kern- und Teilchenphysik, D-01062 Dresden, Germany} 22_{Ecole Polytechnique, LLR, F-91128 Palaiseau, France}

23_{University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom}

24_{Universita` di Ferrara, Dipartimento di Fisica and INFN, I-44100 Ferrara, Italy} 25_{Florida A&M University, Tallahassee, Florida 32307, USA}

26_{Laboratori Nazionali di Frascati dell’INFN, I-00044 Frascati, Italy} 27_{Universita` di Genova, Dipartimento di Fisica and INFN, I-16146 Genova, Italy}

29_{Imperial College London, London, SW7 2BW, United Kingdom} 30_{University of Iowa, Iowa City, Iowa 52242, USA} 31_{Iowa State University, Ames, Iowa 50011-3160, USA} 32_{Laboratoire de l’Acce´le´rateur Line´aire, F-91898 Orsay, France} 33_{Lawrence Livermore National Laboratory, Livermore, California 94550, USA}

34_{University of Liverpool, Liverpool L69 3BX, United Kingdom} 35_{Queen Mary, University of London, E1 4NS, United Kingdom}

36_{University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom} 37_{University of Louisville, Louisville, Kentucky 40292, USA}

38_{University of Manchester, Manchester M13 9PL, United Kingdom} 39_{University of Maryland, College Park, Maryland 20742, USA} 40_{University of Massachusetts, Amherst, Massachusetts 01003, USA}

41_{Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA} 42_{McGill University, Montre´al, Quebec, Canada H3A 2T8}

43_{Universita` di Milano, Dipartimento di Fisica and INFN, I-20133 Milano, Italy} 44_{University of Mississippi, University, Mississippi 38677, USA}

45_{Universite´ de Montre´al, Laboratoire Rene´ J. A. Le´vesque, Montre´al, Quebec, Canada H3C 3J7} 46_{Mount Holyoke College, South Hadley, Massachusetts 01075, USA}

47_{Universita` di Napoli Federico II, Dipartimento di Scienze Fisiche and INFN, I-80126, Napoli, Italy}

48_{NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DB Amsterdam, The Netherlands} 49_{University of Notre Dame, Notre Dame, Indiana 46556, USA}

50_{Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA} 51_{Ohio State University, Columbus, Ohio 43210, USA} 52_{University of Oregon, Eugene, Oregon 97403, USA}

53_{Universita` di Padova, Dipartimento di Fisica and INFN, I-35131 Padova, Italy} 54_{Universite´s Paris VI et VII, Lab de Physique Nucle´aire H. E., F-75252 Paris, France}

55_{Universita` di Pavia, Dipartimento di Elettronica and INFN, I-27100 Pavia, Italy} 56_{University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA}

57_{Universita` di Pisa, Dipartimento di Fisica, Scuola Normale Superiore and INFN, I-56127 Pisa, Italy} 58_{Prairie View A&M University, Prairie View, Texas 77446, USA}

59_{Princeton University, Princeton, New Jersey 08544, USA}

60_{Universita` di Roma La Sapienza, Dipartimento di Fisica and INFN, I-00185 Roma, Italy} 61_{Universita¨t Rostock, D-18051 Rostock, Germany}

62_{Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom} 63_{DSM/Dapnia, CEA/Saclay, F-91191 Gif-sur-Yvette, France}

64_{University of South Carolina, Columbia, South Carolina 29208, USA} 65_{Stanford Linear Accelerator Center, Stanford, California 94309, USA}

66_{Stanford University, Stanford, California 94305-4060, USA} 67_{State University of New York, Albany, New York 12222, USA} 68_{University of Tennessee, Knoxville, Tennessee 37996, USA}

69_{University of Texas at Austin, Austin, Texas 78712, USA} 70_{University of Texas at Dallas, Richardson, Texas 75083, USA}

71_{Universita` di Torino, Dipartimento di Fisica Sperimentale and INFN, I-10125 Torino, Italy</sub> 72<sub>Universita` di Trieste, Dipartimento di Fisica and INFN, I-34127 Trieste, Italy}

73_{Vanderbilt University, Nashville, Tennessee 37235, USA} 74_{University of Victoria, Victoria, British Columbia, Canada V8W 3P6}

75_{University of Wisconsin, Madison, Wisconsin 53706, USA} 76_{Yale University, New Haven, Connecticut 06511, USA}

(Received 13 June 2003; published 13 November 2003)

We present measurements of branching fractions andCP-violating asymmetries inB0_!and

B0_{!K decays. The results are obtained from a data sample of88:910}6 _{4S !BBdecays}

collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B Factory. From a

time-dependent maximum likelihood fit we measure the branching fractions BB0 _!

22:61:8stat 2:2syst 106 _{and BB}0 _{!K 7:3}1:3

1:21:3 10

6_{, and the}

CP-violating charge asymmetries ACP 0:180:080:03 and A

K

CP 0:280:170:08, the

direct CP violation parameter C0:360:180:04 and the mixing-induced CP violation

parameter S0:190:240:03, and the dilution parameters C0:2800::18190:04 and

S0:150:250:03.

One of the central issues in particle physics is whether the single complex phase of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix [1] is sufficient to explain the observed pattern of CP violation. We present here a simultaneous measurement of branching fractions and CP-violating asymmetries in the decays B0_!

and B0_{!K (and their charge conjugates). The} BABAR and Belle experiments have performed searches forCP-violating asymmetries inBdecays to[2,3], where the mixing-induced CP asymmetry is related to the angleargVtdVtb=VudVub of the unitarity

tri-angle as it is for. However, unlike,is not aCPeigenstate, and four flavor-charge configurations

B0_B0 _{!must be considered [4]. Although this}

leads to a more complicated analysis, it benefits from a branching fraction that is nearly 5 times larger [5,6]. The extraction of from is complicated by the inter-ference of decay amplitudes with different strong and weak phases. One strategy for overcoming this problem is to perform an isospin analysis including all final states [7]. Another approach exploits the dynamical in-formation of the full Dalitz plot to extract and the strong amplitudes simultaneously [8].

Following a quasi-two-body approach [9], we restrict the analysis to the two regions of the0_{hDalitz plot}

(h or K) that are dominated by either h or h. With tthttag defined as the proper time

interval between the decay of the reconstructedB0_hand that of the other meson B0

tag, the time-dependent decay

rates are given by

f_Qh

tag t 1A

h CP

ejt_j= 4

1QtagShSh sinmdt

Q_tagC_hC_h cosm_dt ; (1)

whereQ_tag 11 when the tagging mesonB0

tag is aB0

B0 _{, is the mean B}0 _{lifetime, and m}

d is the B0B0

oscillation frequency. The time- and flavor-integrated charge asymmetries A_CP and AK_CP measure direct CP violation. For the mode, the quantities S and C parametrize mixing-induced CP violation related

to the angle , and flavor-dependent direct CP vio-lation, respectively. The parametersCandSare

insensitive to CP violation. C describes the

asymmetry between the rates B0_! B0 ! and B0! B0! , while S is related to the strong phase difference

between the amplitudes contributing toB0 !decays. More precisely, one finds the relations SS

1 CC

q

2 _sin2

eff , where 2

eff

argq=p A=A , argA=A, argq=p is

theB0_B0 _{mixing phase, andA}

A andAA are

the transition amplitudes of the processes B0_B0 _!

and B0_B0 _{!, respectively. The angles}

_eff are equal toin the absence of contributions from penguin amplitudes. For the self-tagging K mode, the values of the four time-dependent parameters are CK0,CK 1,SK0, andSK0.

The data used in this analysis were accumulated with the BABAR detector [10], at the SLAC PEP-II asymmetric-energy ee storage ring. The sample con-sists of88:91:0 106_{BBpairs collected at the4S}

resonance (‘‘on-resonance’’), and an integrated luminos-ity of 9:6 fb collected about 40 MeV below the 4S (‘‘off-resonance’’). In Ref. [10] we describe the silicon vertex tracker and drift chamber used for track and vertex reconstruction, the Cherenkov detector (DIRC), the elec-tromagnetic calorimeter (EMC), and their use in particle identification (PID).

We reconstruct B0

h candidates from combinations of

two tracks and a0_{candidate. We require that the PID of}

both tracks be inconsistent with the electron hypothesis, and the PID of the track used to form thebe inconsistent with the kaon hypothesis. The 0 _{candidate mass must}

satisfy 0:11< m <0:16 GeV=c2_{, where each}

pho-ton is required to have an energy greater than 50 MeV

in the laboratory frame and to exhibit an EMC cluster profile consistent with an electromagnetic shower. The mass of the candidate must satisfy 0:4< m0 _<

1:3 GeV=c2_{. To avoid most of the interference region, the}

Bcandidate is rejected if both the0_and0_pairs

satisfy this requirement. Taking advantage of the helicity structure of B!hdecays (his denotedbachelor track hereafter), we require jcosj>00:25, where is the

angle between the 0 _{momentum and the negative B}

momentum in the rest frame. The bachelor track from the h decay must have a ee center-of-mass (c.m.) momentum above2:4 GeV=c.

For 86% of the B0 _{!h decays that pass the event}

selection, the pion from thehas momentum below this value, and thus the charge of the is determined unam-biguously. For the remaining events, the charge of theis taken to be that of the selected0_{combination. With}

this procedure,5%of the selected simulated signal events are assigned an incorrect charge.

To reject background from two-body B decays, the invariant masses of the h and h0 combinations must each be less than5:14 GeV=c2. Two kinematic vari-ables are used to discriminate between signal-B de-cays and combinatorial background. One variable is the difference, E, between the c.m. energy of the B can-didate and ps=2, wherepsis the total c.m. energy. The other variable is the beam-energy-substituted mass

m_ES s=2p_ip_B 2_=E2

i p2B

q

, where theB momen-tumpBand the four-momentum of the initial state (Ei,pi)

pion mass is always assigned to the bachelor track. We require 5:23< m_ES<5:29 GeV=c2 _{and 0:12<E <}

0:15 GeV, where the asymmetricEwindow suppresses higher-multiplicityBbackground, which leads to mostly negativeEvalues. Discrimination betweenandK events is provided by the Cherenkov angle C and, to a

lesser extent, byE.

The dominant continuum background from ee !

qqq(qu; d; s; c) events is suppressed through the use of a neural network (NN) combining four discriminating variables: the reconstructedmass,cos, and the two

event-shape variables that are used in the Fisher discrim-inant of Ref. [2]. The NN is trained in the signal region with off-resonance data and simulated signal events. The final sample of signal candidates is selected with a cut on the NN output that retains 65% (5%) of the signal (continuum).

Approximately 23% 20% of simulated (K) events have more than one h candidate passing the selection criteria. In these cases, we choose the candidate with the reconstructed0_{mass closest to the nominal}0

mass. A total of 20 497 events pass all selection criteria. The signal efficiency determined from Monte Carlo (MC) simulation is 20:7% (18:5%) for (K) events; 31%

(30%) of the selected events are misreconstructed, mostly due to combinatorial-0 background.

We use MC-simulated events to study the cross feed from other Bdecays. The charmless modes are grouped into 11 classes with similar kinematic and topo-logical properties. Two additional classes account for the neutral and charged b!c decays. For each of the background classes, a component is introduced into the likelihood, with a fixed number of events. Backgrounds from two-, three-, and four-body decays to are dominated byB!0_{,B !}0_{, and}

longitudi-nally polarizedB0 _{! decays. The dominant}

two-body background for the K sample is B!K0_,

while for three- and four-body sources it is B!K and higher kaon resonances, estimated from inclusive B!Kmeasurements.

The time differencetis obtained from the measured distance between thezpositions (along the beam direc-tion) of the B0_h and B0tag decay vertices, and the boost

$0:56 of theee system [2,11]. To determine the flavor of theB0

tagwe use the tagging algorithm of Ref. [11].

This produces four mutually exclusive tagging categories. We also retain untagged events in a fifth category to improve the efficiency of the signal selection and the sensitivity to charge asymmetries. Correlations between theB flavor tag and the charge of the reconstructedh candidate are observed in variousB-background channels and evaluated with MC simulation.

We use an unbinned extended maximum likelihood fit to extract theandKevent yields, theCPparameters, and the other parameters defined in Eq. (1). The like-lihood for theNk candidatesitagged in categorykis

Lk eN

0

k

YNk

i1

X

;K

h

( Nh_'

kP h i;k N

qqq;h

k P qqq;h

i;k

XNB

j1

LB;hij;k

) ;

(2)

whereN_k0is the sum of the signal and continuum yields (to be determined by the fit) and the fixed B-background yields,Nh _{is the number of signal events of typehin}

the entire sample, 'k is the fraction of signal events

tagged in category k, andNq_kqq;h is the number of contin-uum background events with bachelor track of typehthat are tagged in category k. The total likelihood L is the product of likelihoods for each tagging category.

The probability density functions (PDFs) Phk , P qqq;h

k

and the likelihood termsLB;hj;k are the product of the PDFs

of five discriminating variables. The signal PDF is thus given by Ph_k Ph_m

ES PhE PhNN

Ph

C P h

k t, whereP h

k t contains the measured

physics quantities defined in Eq. (1), diluted by the effects of mistagging and the t resolution. The PDF of the continuum contribution with bachelor trackhis denoted

Pqkqq;h . The likelihood termL B;h j;k N

B;h j;kP

B;h

ij;kcorresponds

to theB-background contributionjof theNBclasses with

an expected event yieldNB;h_j;k.

The signal PDFs are decomposed into three parts with distinct distributions: signal events that are correctly re-constructed, misreconstructed signal events with right-sign charge, and misreconstructed signal events with wrong-sign charge. Their individual fractions are esti-mated by MC simulation. ThemES,E, and NN output

PDFs for signal and B background are taken from the simulation except for the means of the signal Gaussian PDFs for m_ES and E, which are free to vary in the fit. The continuum PDFs are described by six free parame-ters. The _C PDF is modeled as in Ref. [2]. The

t-resolution function for signal and B-background events is a sum of three Gaussian distributions, with parameters determined from a fit to fully reconstructed B0_{decays [11]. The continuumtdistribution is}

parame-trized as the sum of three Gaussian distributions with common mean, two relative fractions, and three distinct widths that scale thetevent-by-event error, yielding six free parameters. For continuum, two charge asymmetries and the ten parameters N_kqqq;h are free. A total of 34 parameters, including signal yields and the parameters from Eq. (1), are varied in the fit.

The contributions to the systematic error on the signal parameters are summarized in Table I. The uncertainties associated with m_d and are estimated by varying these parameters within the uncertainty on the world average [12]. The uncertainties due to the signal model (PDF shapes, fraction of misreconstructed events) are obtained from a control sample of fully reconstructed B0_{!Ddecays. We perform fits on large MC samples}

continuum andBbackgrounds. Biases observed in these tests are due to imperfections in the PDF model; e.g., unaccounted correlations between discriminating vari-ables. The biases are added in quadrature and assigned as a systematic uncertainty of the fit procedure. The sys-tematic errors due to interference between the doubly-Cabibbo-suppressed (DCS)bb!uuc dd amplitude with the Cabibbo-favoredb!cuud amplitude for tagsideBdecays have been estimated from simulation by varying freely all relevant strong phases [13].

The main source of systematic uncertainty is the B-background model. The expected event yields from the background modes are varied according to the uncer-tainties in the measured or estimated branching fractions. Systematic errors due to possible nonresonant B0 _!

0 decays are derived from experimental limits [5]. Repeating the fit without using the-candidate mass and helicity angle gives results that are compatible with those reported here. SinceB-background modes may ex-hibit CP violation, the corresponding parameters are varied within their physical ranges.

The maximum likelihood fit results in the event yields N₄₂₈34

33 and NK120

21

20, where the errors are

statistical. Correcting the yields by a small fit bias deter-mined using the MC simulation (3% forand 0%for

K), we find for the branching fractions

BB0_{! 22:61:82:2 10}6_;

BB0 !K 7:311::321:3 10

6_; (3)

where the first errors are statistical and the second system-atic. The systematic errors include an uncertainty of7:7%

for efficiency corrections, dominated by the uncertainty in the 0 reconstruction efficiency. Figure 1 shows dis-tributions ofmESandE, enhanced in signal content by

cuts on the signal-to-continuum likelihood ratios of the other discriminating variables. Distributions of discrimi-nating variables show satisfactory agreement with the fit. For theCP-violating parameters, we obtain

A_CP 0:180:080:03; AK_CP0:280:170:08;

C0:360:180:04; S0:190:240:03:

(4)

For the other parameters in the description of the B0_B0 _{!decay-time dependence, we find}

C0:2800::18190:04;

S0:150:250:03:

We find the linear correlation coefficients cC;C 0:18 and cS;S0:23, while all other correlations are

smaller. As a validation of our treatment of the time dependence we allow and md to vary in the fit. We

find 1:640:13 psandm_d 0:520:12 ps1_;

the remaining free parameters are consistent with the nominal fit. The raw time-dependent asymmetry A_B0_=B0 N_B0N

B0 =N_B0N

B0 in the tagging

cate-gories dominated by kaons and leptons is represented in Fig. 2.

In summary, we have presented measurements of branching fractions and CP-violating asymmetries in B0_{! and K decays. We do not find evidence}

m_ES GeV/c2

Events / 2 MeV/c

2

(a)

0 20 40 60 80 100

5.24 5.25 5.26 5.27 5.28

m_ES GeV/c2

Events / 2 MeV/c

2

(b)

0 10 20 30 40 50

5.24 5.25 5.26 5.27 5.28

∆E GeV

Events / 18 MeV

(c)

0 20 40 60 80

-0.1 -0.05 0 0.05 0.1 0.15

∆E GeV

Events / 18 MeV

(d)

0 10 20 30 40

-0.1 -0.05 0 0.05 0.1 0.15

FIG. 1. Distributions ofmESandEfor samples enhanced in

signal (a),(c) and K signal (b),(d). The solid curve

represents a projection of the maximum likelihood fit result. The dashed curve represents the contribution from continuum events, and the dotted line indicates the combined

contribu-tions from continuum events andB-related backgrounds.

TABLE I. Summary of the systematic uncertainties.

NK _{N A}K

CP A

CP C C S S

Error source (Events) (in units of102₎

md and 0.1 0.1 0.0 0.0 0.4 0.4 0.2 0.1

tPDF 1.2 1.9 0.4 0.2 1.4 0.8 1.5 1.2

Signal model 4.0 13.1 1.2 0.8 0.7 0.8 1.4 1.0

Particle ID 0.6 0.7 0.5 0.2 0.1 0.1 0.1 0.1

Fit procedure 8.0 15.7 0.4 0.2 0.4 0.4 0.4 0.3

DCS decays 0.0 0.3 0.0 0.1 2.2 2.2 0.8 0.7

Bbackground 16.0 14.2 7.9 2.8 3.0 3.5 2.1 1.8

for either mixing-induced CP violation in the time-dependent asymmetry of B0_{! decays, or direct}

CPviolation inB0 _{!K. Our measurement of direct}

CP violation in B0! is consistent with zero within2:0standard deviations, when both statistical and systematic errors are taken into account.

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 supportBABAR. The collaborating in-stitutions wish to thank SLAC for its support and 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). Individuals have received support from the A. P. Sloan Foundation, Research Corporation, and Alexander von Humboldt Foundation.

*Also with Universita` di Perugia, Perugia, Italy.

†_{Also with Universita` della Basilicata, Potenza, Italy.}

‡_{Also with IFIC, Instituto de Fı´sica Corpuscular,}

CSIC-Universidad de Valencia, Valencia, Spain.

x

Deceased.

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FIG. 2. Time distributions for events selected to enhance the

signal tagged as (a) B0

tag and (b) B0tag, and (c)

time-dependent asymmetry betweenB0

tag and B0tag. The solid curve

is a likelihood projection of the fit result. The dashed line is the