Search for T, CP and CPT Violation in $B^0 \bar{B}^0$ Mixing with Inclusive Dilepton Events

arXiv:hep-ex/0603053v1 28 Mar 2006

SLAC-PUB-11787

Search for T , CP and CP T Violation in B

-B

Mixing with Inclusive Dilepton Events

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 D. Monorchio,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,</sub>58 O. Hamon,58 <sub>B. L. Hartfiel,</sub>58 <sub>M. J. J. John,</sub>58<sub>Ph. Leruste,</sub>58 <sub>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 Fac. Fisica. Dept. ECM Avda Diagonal 647, 6a planta 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}

19_{California Institute of Technology, Pasadena, California 91125, USA} 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</sub> 28<sub>Laboratori Nazionali di Frascati dell’INFN, I-00044 Frascati, Italy</sub> 29<sub>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 Univ. Dept of Physics & Astronomy 3400 N. Charles Street Baltimore, Maryland 21218} 36_{Universit¨at Karlsruhe, Institut f¨ur Experimentelle Kernphysik, D-76021 Karlsruhe, Germany}

37_{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 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_{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_{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</sub> 76<sub>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}

(Dated: October 29, 2018)

We report the results of a search for T , CP and CP T violation in B0_-B0 _{mixing using an inclusive} dilepton sample collected by the BABAR_{experiment at the PEP-II B Factory. Using a sample of 232}

million BB pairs, with a simultaneous likelihood fit of the same-sign and opposite-sign dileptons, we measure the T and CP violation parameter |q/p| − 1 = (−0.8 ± 2.7(stat.) ± 1.9(syst.)) × 10−3_, and the CP T and CP parameters Im z = (−13.9 ± 7.3(stat.) ± 3.2(syst.)) × 10−3 and ∆Γ × Re z = (−7.1 ± 3.9(stat.) ± 2.0(syst.)) × 10−3ps−1. The statistical correlation between the measurements of Im z and ∆Γ × Re z is 76 %.

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

Since the first observation of CP violation in 1964 [1], the neutral kaon system has provided many results prob-ing the CP T and T discrete symmetries [2] in K0_-K0 mixing. Similarly, the BA_BAR_{experiment can investigate}

T , CP , and CP T violation in B0_-B0 _mixing.

The physical states (solutions of the complex effective Hamiltonian for the B0_-B0_{system) [3] can be written as}

|BLi = p √ 1 − z|B0 i + q√1 + z|B0 i, |BHi = p √ 1 + z|B0 i − q√1 − z|B0 i.

where H and L stand for Heavy and Light. In the case of CP T invariance, the complex parameter z is equal to 0. Similarly, T invariance leads to |q/p| = 1. Finally, CP invariance requires both |q/p| = 1 and z = 0.

Inclusive dilepton events, where both B mesons decay semileptonically b → Xℓν (l = e or µ), represent 4% of all Υ (4S) → BB decays and provide a very large sample to study T , CP T and CP violation in mixing. In the direct b → ℓ decay process, the flavor B0_(B0_{) is tagged} by the charge of the lepton ℓ+_(ℓ−_).

At the Υ (4S) resonance, neutral B mesons are produced in a coherent p-wave state. At the instant that the first B meson decays, the second B meson has the opposite flavor. Then, the second B meson will continue to evolve in time. Defining the time difference as ∆t = t+_{− t}− _{where t}+_(t−_{) is the decay time of the} neutral B tagged by ℓ+_(ℓ−_{), and neglecting second order} terms in z, the decay rates for the three configurations (ℓ+_ℓ+_{, ℓ}−_ℓ− _{and ℓ}+_ℓ−_{) are given by}

N++ ∝ e −Γ|∆t| 2 | p q| 2n cosh(∆Γ∆t 2 ) − cos(∆m∆t) o , N−− ∝ e −Γ|∆t| 2 | q p| 2n cosh(∆Γ∆t 2 ) − cos(∆m∆t) o , N+− _∝ e−Γ|∆t| 2 n cosh(∆Γ∆t 2 ) − 2 Re z sinh( ∆Γ∆t 2 ) + cos(∆m∆t) + 2 Im z sin(∆m∆t)o, (1)

where ∆m is the B0_-B0 _{oscillation frequency, Γ is the} average neutral B decay rate and ∆Γ is the decay rate difference between the two physical states.

The same-sign dilepton asymmetry AT /CP, between the two oscillation probabilities P (B0 _{→ B}0_{) and}

P (B0 _{→ B}0_{) probes both T and CP symmetries and} can be expressed in terms of |q/p|:

AT /CP = P (B0_{→ B}0_{) − P (B}0_{→ B}0₎ P (B0_{→ B}0_{) + P (B}0_{→ B}0₎ = N ++_{− N}−− N++_{+ N}−− = 1 − |q/p|4 1 + |q/p|4. (2) Standard Model calculations [4] predict the size of this asymmetry to be at or below 10−3_{. A large measured} value would be an indication of new physics.

Similarly, the opposite-sign dilepton asymmetry, ACP T /CP, between events with ∆t > 0 and ∆t < 0 com-pares the B0 _{→ B}0 _{and B}0 _{→ B}0 _{probabilities and is} sensitive to CP T and CP violation. This asymmetry is given by ACP T /CP(|∆t|) = P (B0_{→ B}0_{) − P (B}0_{→ B}0₎ P (B0_{→ B}0_{) + P (B}0_{→ B}0₎ = N +−_{(∆t > 0) − N}+−_{(∆t < 0)} N+−_{(∆t > 0) + N}+−_{(∆t < 0)} ≃ 2Im z sin(∆m∆t)−Re z sinh( ∆Γ∆t 2 ) cosh(∆Γ∆t 2 ) + cos(∆m∆t) .(3) As |∆Γ|/Γ ≪ 1 [3], we have Re z sinh(∆Γ∆t/2) ≃ ∆Γ × Re z × (∆t/2) and this asymmetry is not sensitive to the CP T -violating term Re z alone, but to the product ∆Γ × Re z.

In this Letter, we present measurements of |q/p|, Im z and ∆Γ × Re z with a simultaneous likelihood fit of the same-sign and opposite-sign dilepton ∆t distributions. In the cosh(∆Γ∆t/2) term, we fix |∆Γ| to 0.005 ps−1_{, the} value reported in [3] with a 90% confidence-level limit of 0.055 ps−1_.

This study is performed with events collected by the BA_BAR_{detector [5] at the PEP-II asymmetric-energy B}

Factory between October 1999 and July 2004. The in-tegrated luminosity of this sample is about 211 fb−1 recorded at the Υ (4S) resonance (“on-resonance”) (232 million BB pairs) and about 16 fb−1 recorded about 40

MeV below the Υ (4S) resonance (“off-resonance”). The event selection is identical to that described in [6]. Non-BB events are suppressed by applying requirements on the ratio of second to zeroth order Fox-Wolfram mo-ments [7], the squared invariant mass, the aplanarity and the number of charged tracks of the event.

Lepton candidate tracks must have at least 12 hits in the drift chamber, at least one z-coordinate hit in the sili-con vertex tracker (SVT), and a momentum in the Υ (4S) center-of-mass system between 0.8 and 2.3 GeV/c. Elec-trons are selected by requirements on the ratio of the energy deposited in the electromagnetic calorimeter and the momentum measured in the drift chamber. Muons are identified through the energy released in the calorime-ter, as well as the strip multiplicity, track continuity, and penetration depth in the instrumented flux return. Lep-ton candidates are rejected if their signal in the detector of internally reflected Cherenkov light is consistent with that of a kaon or a proton. The electron and muon se-lection efficiencies are about 85% and 55%, with pion misidentification probabilities around 0.2% and 3%, re-spectively.

Electrons from photon conversions are identified and rejected with a negligible loss of efficiency for signal events. Leptons from J/ψ and ψ(2S) decays are identi-fied by pairing them with other oppositely-charged can-didates of the same lepton species, selected with looser criteria.

The separation between direct leptons (b → ℓ) and background from the b → c → ℓ decay chain (cascade decays) is achieved with a neural network that combines five discriminating variables: the momenta and opening angles of the two lepton candidates, and the total visible energy and missing momentum of the event, all computed in the Υ (4S) rest frame.

Of the original sample of 232 million BB pairs, 1.4 million pass this dilepton selection.

Since the asymmetry AT /CP is expected to be small, we have determined the possible charge asymmetries in-duced by the detection and reconstruction of electrons and muons. The charge asymmetries are defined by a ≡ (ε+_−ε−_)/(ε+_+ε−_{) where ε}+_(ε−_{) is the efficiency for} positive and negative particles. As the lepton efficiencies and purities depend on their allowed phase space, we con-sider separately the asymmetry for the higher and lower momentum lepton, respectively, a1and a2.

The charge asymmetry of track reconstruction is mea-sured in the data by comparing tracks reconstructed us-ing only the SVT with those passus-ing the dilepton track selection, obtaining atrk= (0.8 ± 0.2) × 10−3.

The lepton identification efficiencies are measured as a function of total momentum and polar and azimuthal an-gles, with a control sample of radiative Bhabha events for electrons, and with a ee → µµγ control sample for muons. The misidentification probabilities are determined with control samples of kaons produced in D∗+ _{→ π}+_D0 _→ π+_K−_π+_{(and charge conjugate) decays, pions produced} in KS → π+π− decays, one-prong and three-prong τ de-cays, and protons produced in Λ decays.

The control samples show that the muon track re-construction efficiency has a charge asymmetry reaching ∼ 5 × 10−3 _{and that the positive kaons are more likely}

than negative kaons to be misidentified as muons at the 20-30% level. As a consequence, in the likelihood fit (de-scribed below), we float the charge asymmetries adir

µ and acasc

µ for direct and cascade muons.

For electrons, the charge asymmetry averaged over the signal phase space is ae= (0.4 ± 0.2) × 10−3 and we find that antiprotons with momentum ∼ 1 GeV/c are signifi-cantly more likely than protons to be misidentified, due to annihilation with nucleons in the calorimeter material. Based on the charge asymmetry in tracking and in identi-fication, we fix the charge asymmetry for the direct elec-trons with the higher momentum to adir

e1 = 1.2 × 10

−3_. For the lower momentum direct electrons and the cas-cade electrons, for which antiprotons contamination is more important, we correct the initial charge asymmetry by the fraction of antiprotons estimated with generic BB Monte Carlo samples and the proton control sample, this gives the following charge asymmetries: adir

e2 = 0.8×10 −3_, acasc e1 = 0.5 × 10 −3_{, and a}casc e2 = 0.2 × 10 −3_.

In the inclusive approach used here, the z coordinate of the B decay point is approximated by the z position of the point of closest approach between the lepton candi-date and an estimate of the Υ (4S) decay point in the transverse plane. The Υ (4S) decay point is obtained by fitting the two lepton tracks to a common vertex in the transverse plane that is constrained to be consistent with the beam-spot position. The proper time difference ∆t between the two B meson decays is determined from ∆z = z+_{− z}−_{, the difference in z between the leptons} ℓ+ _{and ℓ}−_{, by ∆t = ∆z/hβγic with a nominal Lorentz} boost hβγi = 0.55. In case of same-sign dileptons, the sign of ∆t is chosen randomly.

We model the contributions to our sample from BB de-cays using five categories of events, i, each represented by a probability density function (PDF) in ∆t, Pin,c. Their shapes are determined using the B0_B0_{(n) and B}+_B−_(c) Monte Carlo simulation separately, with the approach de-scribed in [8].

The five categories are the following. First, the pure signal events with two direct leptons (sig) represent 81% of the BB events and give information on the T , CP T and CP parameters. Then, we consider two categories of cascade decays: those with a direct lepton and cascade lepton from the opposite B decays (obc), and those with direct lepton and cascade lepton from the same B decay (sbc). According to generic BB Monte Carlo simulation, their contributions are around 9% and 4% respectively. In addition, 3% of the dilepton events originate from the decay chain b → τ−_{→ ℓ}−_{(1d1τ ) which tags the B flavor} correctly. Finally, the remaining events (other) consist mainly of one direct lepton and one lepton from charmo-nium resonances in the B decays.

The sig event PDF, Psign,c, is obtained by the convolu-tion of an oscillatory term containing the T , CP T and CP parameters (Eq. 1) for neutral B decays or an expo-nential function for charged B decays, with a resolution

function which is the sum of three Gaussians. The widths of the core and tail Gaussians and the fractions of core and outlier Gaussians are free parameters in the fit. The width of the outlier Gaussian is fixed to 8 ps. The means of the Gaussians are fixed to zero [9].

The obc event PDF, Pobcn,c, is modeled by the convo-lution of ∆t-dependent terms of a form similar to those of the signal with a resolution function which takes into account the effect of the charmed meson lifetimes. Since both short-lived D0 _{and D}

S, and long-lived D+ mesons are involved in cascade decays, the resolution function for the long-lived and short-lived components is a sum of three Gaussians, which are convoluted with double-sided exponentials. To correct the effect of possible outliers not observed with the Monte Carlo simulation, the fraction of the third Gaussian is free in the fit. Similarly, we take the effect of the charmed mesons into account in the sbc event PDF, Psbcn,c.

The PDF for 1d1τ events, P1d1τn,c is similar to that of the sig events. The resolution function used takes into account the τ lifetime effect and is chosen to be two Gaus-sians convoluted with two double-sided exponentials. Fi-nally, the PDF for the remaining events, Pothern,c , is the convolution of an exponential function with an effective lifetime and two Gaussians.

The fractions (f_sbcn,c,f_1d1τn,c and f_othern,c ) of sbc, 1d1τ and other events, are determined directly with the B0_B0 _and B+_B− _{Monte Carlo simulation. The fractions f}n,c

obc of obc events are fitted to the data, constraining the ra-tio fn

obc/fobcc to the estimate obtained with Monte Carlo samples. The fraction f+−of B+B−events is determined from the data themselves.

The last component of the dilepton sample originates from non-BB events, mainly continuum events, and has been estimated using off-resonance events to represent a fraction fcont= (3.1±0.1)% of the data set. To model its PDF we use off-resonance events with looser cuts and on-resonance events that fail the continuum-rejection cut on the Fox-Wolfram moment ratio. The charge asymmetries acont

e,µ obtained with the two samples are consistent with zero at the 1% level and thus are fixed to zero in the likelihood.

The T /CP and CP T /CP violation parameters are ex-tracted from a binned maximum likelihood fit of the events that pass the dilepton selection. The likelihood L combines the charge asymmetries in detection and the time-dependent PDFs described previously. As the charge asymmetries are significantly different for elec-trons and muons, we split the sample into four lepton combinations: ee, eµ, µe and µµ, in which the first lep-ton has the higher momentum.

The likelihood is given by

L(∆t) = (1 + q1acontf1 )(1 + q2a

cont

f2 )fcontPcont

+(1 − fcont){f+−PB+_B−+ (1 − f+−)P

B0_B0}

P_B0_B0 = (1 − f_sign )(1 + q1acascf1 )(1 + q2a

casc f2 )P

n casc +fsig(1 + q1n adirf1 )(1 + q2a

dir f2 )P n sig PB+_B− = (1 − f_sigc )(1 + q1acasc_f 1 )(1 + q2a casc f2 )P c casc +fsig(1 + q1c adirf1 )(1 + q2a

dir f2 )P c sig Pcascn,c = fothern,c P n,c other+ f n,c 1d1τP n,c 1d1τ + f n,c sbcP n,c sbc + f n,c obcP n,c obc,

where q1, q2, f1 and f2 are the charges and the flavors (e, µ) of the two leptons.

The likelihood fit gives |q/p| − 1 = (−0.8 ± 2.7) × 10−3_, Im z = (−13.9 ± 7.3) × 10−3_{, and ∆Γ × Re z = (−7.1 ±} 3.9) × 10−3_ps−1_{. The correlation between the} measure-ments of Im z and ∆Γ × Re z is 76 %. If we fix ∆Γ = 0, we obtain Im z = (−3.7 ± 4.6) × 10−3_{. Figure 1 shows the} AT /CP asymmetry between (ℓ+, ℓ+) and (ℓ−, ℓ−) dilep-tons defined in Eq. 2 and the ACP T /CP asymmetry be-tween (ℓ+_{, ℓ}−_{) dileptons with ∆t > 0 and ∆t < 0 defined} in Eq. 3. T/CP A -0.04 -0.02 0 0.02 0.04 (a)

t| (ps)

∆

|

A

(b)

FIG. 1: (a) AT /CP asymmetry between (ℓ+_{, ℓ}+_{) and (ℓ}−_{, ℓ}−_). A larger charge asymmetry for cascade muons, dominant at small |∆t|, explains the non-flatness of the curve. (b) ACP T /CP asymmetry between (ℓ+_{, ℓ}−_{) dileptons with ∆t > 0} and ∆t < 0.

There are several sources of systematic uncertainty in these measurements. To determine their effect, we vary each source of systematic uncertainty by its known or estimated uncertainty, and take the resulting deviation in the CP parameter as its systematic uncertainty.

For |q/p|, the most important systematic errors are due to uncertainties on electron charge asymmetries. A 1.4×10−3_{deviation of |q/p| is observed by shifting} simul-taneously the electron charge asymmetries by 1.0 × 10−3

which corresponds to the uncertainty estimated with Monte Carlo and control samples. The systematic un-certainty related to the charge asymmetry due to the tracking is estimated by randomly removing a fraction equal to 1.6 × 10−3 _{of the negative tracks from our data} sample. This fraction has been determined from an inde-pendent data control sample. A 1.0 × 10−3 _{deviation of} |q/p| is observed. Similarly, the 1% uncertainty on charge asymmetry for non-BB backgrounds induces a system-atic error of 0.6 × 10−3_.

The widths of the first and second Gaussian of the resolution function for the obc and sbc categories as well as the pseudo-lifetime for the 1d1τ and other categories are varied separately by 10%. This variation is motivated by the comparison of the fitted parameters of the signal resolution function obtained on generic BB Monte Carlo samples and on data being in agreement at 10% level. The fractions of the short-lived and long-lived charmed meson components for obc and sbc are varied by 10 %.

We have also varied the parameters ∆m, τB0 and τ_B±

independently within their known uncertainties [10] and ∆Γ from 10−5 _{to 0.1. Finally, one of the dominant} sys-tematic errors on ∆Γ × Re z is imperfect knowledge of the absolute z scale of the detector and the residual un-certainties in the SVT local alignment, giving an error of 1.2 × 10−3_ps−1_.

TABLE I: Summary of systematic errors for |q/p|, Im z, and ∆Γ × Re z measurements.

Systematic Effects σ(|q/p|) σ(Im z) σ(∆Γ×Re z) (×10−3_{) (×10}−3_{) (×10}−3_ps−1₎ Ch. asym. of non-BB bkg 0.6 0.0 0.0 Ch. asym. in tracking 1.0 0.0 0.0 Ch. asym. of electrons 1.4 0.0 0.0 PDF modeling 0.3 2.5 1.2 Fraction of bkg components 0.2 0.4 0.1 ∆m, τB0, τ_B± and ∆Γ 0.2 1.9 1.1 SVT alignment 0.5 0.6 1.2 Total 1.9 3.2 2.0

For each parameter, the total systematic error is the sum in quadrature of the estimated systematic errors from each source, as summarized in Table I. When we as-sume ∆Γ = 0, the systematic error for Im z is 2.9 × 10−3_. If we compare our results to ∆Γ × Re z = 0.0 and Im z = 0.0 (no CP T violation case), the χ2 _{is 3.25 for} 2 degrees of freedom, which gives a confidence level of 19.7%. Finally, assuming ∆Γ = 0, we obtain Im z = (−3.7 ± 4.6(stat.) ± 2.9(syst.)) × 10−3_.

In summary with the 1999-2004 data (232 × 106 _BB pairs), we have performed a simultaneous likelihood fit of the same-sign and opposite-sign dileptons. We measure the independent parameters governing CP and T

viola-tion, and the CP T and CP violation parameters. The results are

|q/p| − 1 = (−0.8 ± 2.7(stat.) ± 1.9(syst.)) × 10−3, Im z = (−13.9 ± 7.3(stat.) ± 3.2(syst.)) × 10−3_, ∆Γ × Re z = (−7.1 ± 3.9(stat.) ± 2.0(syst.)) × 10−3_ps−1_.

These measurements are a clear improvement over the most precise results previously published [3, 11]. The new measurement of |q/p| is consistent with the Standard Model predictions [4].

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}

institutions 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). 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] J. H. Christenson, J. W. Cronin, V. L. Fitch and R.

Turlay, Phys. Rev. Lett. 13, 138 (1964).

[2] CPLEAR Collaboration, A. Apostolakis et al., Phys. Lett. B 456, 297 (1999).

[3] BABAR_{Collaboration, B. Aubert et al., Phys. Rev. D 70,}

012007 (2004).

[4] M. Beneke et al., Phys. Lett. B 576, 173 (2003); M. Ciuchini et al., JHEP 0308, 031 (2003).

[5] BABAR Collaboration, B. Aubert et al., Nucl. Instr. Methods Phys. Res., Sect. A 479, 1 (2002).

[6] BABAR_{Collaboration, B. Aubert et al., Phys. Rev. Lett.}

88, 231801 (2002).

[7] G. C. Fox and S. Wolfram, Phys. Rev. Lett. 41, 1581 (1978).

[8] BABARCollaboration, B. Aubert et al., Phys. Rev. Lett. 88, 221803 (2002).

[9] BABAR_{Collaboration, B. Aubert et al., Phys. Rev. D 66,}

032003 (2002).

[10] Heavy Flavor Averaging Group, K. Anikeev et al., hep-ex/0505100.

[11] BELLE Collaboration, E. Nakano et al., submitted to Phys. Rev. D , hep-ex/0505017.