Measurement of the Ratios of Branching Fractions B(B_s⁰->D_s^-π⁺)/B(B⁰->D⁻π⁺) and B(B⁺->D⁰π⁺)/B(B⁰->D⁻π

Article

Reference

Measurement of the Ratios of Branching Fractions B(B

->D

π

)/B(B

->D

π

) and B(B

->D

π

)/B(B

->D

π

)

CDF Collaboration

CAMPANELLI, Mario (Collab.), et al .

Abstract

We report an observation of the decay B0s→D−sπ+ in pp collisions at s√=1.96  TeV using 115   pb−1 of data collected by the CDF II detector at the Fermilab Tevatron. We observe 83±11(stat) B0s→D−sπ+ candidates, representing a large increase in statistics over previous measurements and the first observation of this decay at a pp collider. We present the first

measurement of the relative branching fraction

B(B0s→D−sπ+)/B(B0→D−π+)=1.32±0.18(stat)±0.38(syst). We also measure B(B+→D0π+)/B(B0→D−π+)=1.97±0.10(stat)±0.21(syst), which is consistent with previous measurements

CDF Collaboration, CAMPANELLI, Mario (Collab.), et al . Measurement of the Ratios of Branching Fractions B(B

->D

π

)/B(B

->D

π

) and B(B

->D

π

)/B(B

->D

π

). Physical Review Letters , 2006, vol. 96, no. 19, p. 191801

DOI : 10.1103/PhysRevLett.96.191801

Available at:

http://archive-ouverte.unige.ch/unige:38319

Disclaimer: layout of this document may differ from the published version.

1 / 1

Measurement of the Ratios of Branching Fractions B B

! D

= B B

! D

and B B

! D

= B B

! D

A. Abulencia,²³D. Acosta,¹⁷J. Adelman,¹³T. Affolder,¹⁰T. Akimoto,⁵³M. G. Albrow,¹⁶D. Ambrose,¹⁶S. Amerio,⁴² D. Amidei,³³A. Anastassov,⁵⁰K. Anikeev,¹⁶A. Annovi,⁴⁴J. Antos,¹M. Aoki,⁵³G. Apollinari,¹⁶J.-F. Arguin,³² T. Arisawa,⁵⁵A. Artikov,¹⁴W. Ashmanskas,¹⁶A. Attal,⁸F. Azfar,⁴¹P. Azzi-Bacchetta,⁴²P. Azzurri,⁴⁴N. Bacchetta,⁴² H. Bachacou,²⁸W. Badgett,¹⁶A. Barbaro-Galtieri,²⁸V. E. Barnes,⁴⁶B. A. Barnett,²⁴S. Baroiant,⁷V. Bartsch,³⁰G. Bauer,³¹

F. Bedeschi,⁴⁴S. Behari,²⁴S. Belforte,⁵²G. Bellettini,⁴⁴J. Bellinger,⁵⁷A. Belloni,³¹E. Ben-Haim,¹⁶D. Benjamin,¹⁵ A. Beretvas,¹⁶J. Beringer,²⁸T. Berry,²⁹A. Bhatti,⁴⁸M. Binkley,¹⁶D. Bisello,⁴²M. Bishai,¹⁶R. E. Blair,²C. Blocker,⁶

K. Bloom,³³B. Blumenfeld,²⁴A. Bocci,⁴⁸A. Bodek,⁴⁷V. Boisvert,⁴⁷G. Bolla,⁴⁶A. Bolshov,³¹D. Bortoletto,⁴⁶ J. Boudreau,⁴⁵S. Bourov,¹⁶A. Boveia,¹⁰B. Brau,¹⁰C. Bromberg,³⁴E. Brubaker,¹³J. Budagov,¹⁴H. S. Budd,⁴⁷S. Budd,²³

K. Burkett,¹⁶G. Busetto,⁴²P. Bussey,²⁰K. L. Byrum,²S. Cabrera,¹⁵M. Campanelli,¹⁹M. Campbell,³³F. Canelli,⁸ A. Canepa,⁴⁶D. Carlsmith,⁵⁷R. Carosi,⁴⁴S. Carron,¹⁵M. Casarsa,⁵²A. Castro,⁵P. Catastini,⁴⁴D. Cauz,⁵² M. Cavalli-Sforza,³A. Cerri,²⁸L. Cerrito,⁴¹S. H. Chang,²⁷J. Chapman,³³Y. C. Chen,¹M. Chertok,⁷G. Chiarelli,⁴⁴ G. Chlachidze,¹⁴F. Chlebana,¹⁶I. Cho,²⁷K. Cho,²⁷D. Chokheli,¹⁴J. P. Chou,²¹P. H. Chu,²³S. H. Chuang,⁵⁷K. Chung,¹²

W. H. Chung,⁵⁷Y. S. Chung,⁴⁷M. Ciljak,⁴⁴C. I. Ciobanu,²³M. A. Ciocci,⁴⁴A. Clark,¹⁹D. Clark,⁶M. Coca,¹⁵ A. Connolly,²⁸M. E. Convery,⁴⁸J. Conway,⁷B. Cooper,³⁰K. Copic,³³M. Cordelli,¹⁸G. Cortiana,⁴²A. Cruz,¹⁷J. Cuevas,¹¹ R. Culbertson,¹⁶D. Cyr,⁵⁷S. DaRonco,⁴²S. D’Auria,²⁰M. D’onofrio,¹⁹D. Dagenhart,⁶P. de Barbaro,⁴⁷S. De Cecco,⁴⁹ A. Deisher,²⁸G. De Lentdecker,⁴⁷M. Dell’Orso,⁴⁴S. Demers,⁴⁷L. Demortier,⁴⁸J. Deng,¹⁵M. Deninno,⁵D. De Pedis,⁴⁹ P. F. Derwent,¹⁶C. Dionisi,⁴⁹J. Dittmann,⁴P. DiTuro,⁵⁰C. Do¨rr,²⁵A. Dominguez,²⁸S. Donati,⁴⁴M. Donega,¹⁹P. Dong,⁸ J. Donini,⁴²T. Dorigo,⁴²S. Dube,⁵⁰K. Ebina,⁵⁵J. Efron,³⁸J. Ehlers,¹⁹R. Erbacher,⁷D. Errede,²³S. Errede,²³R. Eusebi,⁴⁷ H. C. Fang,²⁸S. Farrington,²⁹I. Fedorko,⁴⁴W. T. Fedorko,¹³R. G. Feild,⁵⁸M. Feindt,²⁵J. P. Fernandez,⁴⁶R. Field,¹⁷ G. Flanagan,³⁴L. R. Flores-Castillo,⁴⁵A. Foland,²¹S. Forrester,⁷G. W. Foster,¹⁶M. Franklin,²¹J. C. Freeman,²⁸Y. Fujii,²⁶

I. Furic,¹³A. Gajjar,²⁹M. Gallinaro,⁴⁸J. Galyardt,¹²J. E. Garcia,⁴⁴M. Garcia Sciverez,²⁸A. F. Garfinkel,⁴⁶C. Gay,⁵⁸ H. Gerberich,²³E. Gerchtein,¹²D. Gerdes,³³S. Giagu,⁴⁹P. Giannetti,⁴⁴A. Gibson,²⁸K. Gibson,¹²C. Ginsburg,¹⁶ K. Giolo,⁴⁶M. Giordani,⁵²M. Giunta,⁴⁴G. Giurgiu,¹²V. Glagolev,¹⁴D. Glenzinski,¹⁶M. Gold,³⁶N. Goldschmidt,³³

J. Goldstein,⁴¹G. Gomez,¹¹G. Gomez-Ceballos,¹¹M. Goncharov,⁵¹O. Gonza´lez,⁴⁶I. Gorelov,³⁶A. T. Goshaw,¹⁵ Y. Gotra,⁴⁵K. Goulianos,⁴⁸A. Gresele,⁴²M. Griffiths,²⁹S. Grinstein,²¹C. Grosso-Pilcher,¹³U. Grundler,²³ J. Guimaraes da Costa,²¹C. Haber,²⁸S. R. Hahn,¹⁶K. Hahn,⁴³E. Halkiadakis,⁴⁷A. Hamilton,³²B-Y. Han,⁴⁷R. Handler,⁵⁷ F. Happacher,¹⁸K. Hara,⁵³M. Hare,⁵⁴S. Harper,⁴¹R. F. Harr,⁵⁶R. M. Harris,¹⁶K. Hatakeyama,⁴⁸J. Hauser,⁸C. Hays,¹⁵ H. Hayward,²⁹A. Heijboer,⁴³B. Heinemann,²⁹J. Heinrich,⁴³M. Hennecke,²⁵M. Herndon,⁵⁷J. Heuser,²⁵D. Hidas,¹⁵

C. S. Hill,¹⁰D. Hirschbuehl,²⁵A. Hocker,¹⁶A. Holloway,²¹S. Hou,¹M. Houlden,²⁹S.-C. Hsu,⁹B. T. Huffman,⁴¹ R. E. Hughes,³⁸J. Huston,³⁴K. Ikado,⁵⁵J. Incandela,¹⁰G. Introzzi,⁴⁴M. Iori,⁴⁹Y. Ishizawa,⁵³A. Ivanov,⁷B. Iyutin,³¹

E. James,¹⁶D. Jang,⁵⁰B. Jayatilaka,³³D. Jeans,⁴⁹H. Jensen,¹⁶E. J. Jeon,²⁷M. Jones,⁴⁶K. K. Joo,²⁷S. Y. Jun,¹² T. R. Junk,²³T. Kamon,⁵¹J. Kang,³³M. Karagoz-Unel,³⁷P. E. Karchin,⁵⁶Y. Kato,⁴⁰Y. Kemp,²⁵R. Kephart,¹⁶U. Kerzel,²⁵

V. Khotilovich,⁵¹B. Kilminster,³⁸D. H. Kim,²⁷H. S. Kim,²⁷J. E. Kim,²⁷M. J. Kim,¹²M. S. Kim,²⁷S. B. Kim,²⁷ S. H. Kim,⁵³Y. K. Kim,¹³M. Kirby,¹⁵L. Kirsch,⁶S. Klimenko,¹⁷M. Klute,³¹B. Knuteson,³¹B. R. Ko,¹⁵H. Kobayashi,⁵³

K. Kondo,⁵⁵D. J. Kong,²⁷J. Konigsberg,¹⁷A. Korytov,¹⁷A. V. Kotwal,¹⁵A. Kovalev,⁴³J. Kraus,²³I. Kravchenko,³¹ M. Kreps,²⁵A. Kreymer,¹⁶J. Kroll,⁴³N. Krumnack,⁴M. Kruse,¹⁵V. Krutelyov,⁵¹S. E. Kuhlmann,²Y. Kusakabe,⁵⁵ S. Kwang,¹³A. T. Laasanen,⁴⁶S. Lai,³²S. Lami,⁴⁸S. Lami,⁴⁸S. Lammel,¹⁶M. Lancaster,³⁰R. L. Lander,⁷K. Lannon,³⁸

A. Lath,⁵⁰G. Latino,⁴⁴I. Lazzizzera,⁴²C. Lecci,²⁵T. LeCompte,²J. Lee,⁴⁷J. Lee,⁴⁷S. W. Lee,⁵¹R. Lefe`vre,³ N. Leonardo,³¹S. Leone,⁴⁴S. Levy,¹³J. D. Lewis,¹⁶K. Li,⁵⁸C. Lin,⁵⁸C. S. Lin,¹⁶M. Lindgren,¹⁶E. Lipeles,⁹T. M. Liss,²³

A. Lister,¹⁹D. O. Litvintsev,¹⁶T. Liu,¹⁶Y. Liu,¹⁹N. S. Lockyer,⁴³A. Loginov,³⁵M. Loreti,⁴²P. Loverre,⁴⁹R.-S. Lu,¹ D. Lucchesi,⁴²P. Lujan,²⁸P. Lukens,¹⁶G. Lungu,¹⁷L. Lyons,⁴¹J. Lys,²⁸R. Lysak,¹E. Lytken,⁴⁶P. Mack,²⁵ D. MacQueen,³²R. Madrak,¹⁶K. Maeshima,¹⁶P. Maksimovic,²⁴G. Manca,²⁹F. Margaroli,⁵R. Marginean,¹⁶C. Marino,²³

A. Martin,⁵⁸M. Martin,²⁴V. Martin,³⁷M. Martı´nez,³T. Maruyama,⁵³H. Matsunaga,⁵³M. E. Mattson,⁵⁶R. Mazini,³² P. Mazzanti,⁵K. S. McFarland,⁴⁷D. McGivern,³⁰P. McIntyre,⁵¹P. McNamara,⁵⁰R. McNulty,²⁹A. Mehta,²⁹ S. Menzemer,³¹A. Menzione,⁴⁴P. Merkel,⁴⁶C. Mesropian,⁴⁸A. Messina,⁴⁹M. von der Mey,⁸T. Miao,¹⁶N. Miladinovic,⁶

J. Miles,³¹R. Miller,³⁴J. S. Miller,³³C. Mills,¹⁰M. Milnik,²⁵R. Miquel,²⁸S. Miscetti,¹⁸G. Mitselmakher,¹⁷ A. Miyamoto,²⁶N. Moggi,⁵B. Mohr,⁸R. Moore,¹⁶M. Morello,⁴⁴P. Movilla Fernandez,²⁸J. Mu¨lmensta¨dt,²⁸

A. Mukherjee,¹⁶M. Mulhearn,³¹Th. Muller,²⁵R. Mumford,²⁴P. Murat,¹⁶J. Nachtman,¹⁶S. Nahn,⁵⁸I. Nakano,³⁹ A. Napier,⁵⁴D. Naumov,³⁶V. Necula,¹⁷C. Neu,⁴³M. S. Neubauer,⁹J. Nielsen,²⁸T. Nigmanov,⁴⁵L. Nodulman,²

O. Norniella,³T. Ogawa,⁵⁵S. H. Oh,¹⁵Y. D. Oh,²⁷T. Okusawa,⁴⁰R. Oldeman,²⁹R. Orava,²²K. Osterberg,²² C. Pagliarone,⁴⁴E. Palencia,¹¹R. Paoletti,⁴⁴V. Papadimitriou,¹⁶A. Papikonomou,²⁵A. A. Paramonov,¹³B. Parks,³⁸

S. Pashapour,³²J. Patrick,¹⁶G. Pauletta,⁵²M. Paulini,¹²C. Paus,³¹D. E. Pellett,⁷A. Penzo,⁵²T. J. Phillips,¹⁵ G. Piacentino,⁴⁴J. Piedra,¹¹K. Pitts,²³C. Plager,⁸L. Pondrom,⁵⁷G. Pope,⁴⁵X. Portell,³O. Poukhov,¹⁴N. Pounder,⁴¹

F. Prakoshyn,¹⁴A. Pronko,¹⁶J. Proudfoot,²F. Ptohos,¹⁸G. Punzi,⁴⁴J. Pursley,²⁴J. Rademacker,⁴¹A. Rahaman,⁴⁵ A. Rakitin,³¹S. Rappoccio,²¹F. Ratnikov,⁵⁰B. Reisert,¹⁶V. Rekovic,³⁶N. van Remortel,²²P. Renton,⁴¹M. Rescigno,⁴⁹ S. Richter,²⁵F. Rimondi,⁵K. Rinnert,²⁵L. Ristori,⁴⁴W. J. Robertson,¹⁵A. Robson,²⁰T. Rodrigo,¹¹E. Rogers,²³S. Rolli,⁵⁴ R. Roser,¹⁶M. Rossi,⁵²R. Rossin,¹⁷C. Rott,⁴⁶A. Ruiz,¹¹J. Russ,¹²V. Rusu,¹³D. Ryan,⁵⁴H. Saarikko,²²S. Sabik,³² A. Safonov,⁷W. K. Sakumoto,⁴⁷G. Salamanna,⁴⁹O. Salto,³D. Saltzberg,⁸C. Sanchez,³L. Santi,⁵²S. Sarkar,⁴⁹K. Sato,⁵³

P. Savard,³²A. Savoy-Navarro,¹⁶T. Scheidle,²⁵P. Schlabach,¹⁶E. E. Schmidt,¹⁶M. P. Schmidt,⁵⁸M. Schmitt,³⁷ T. Schwarz,³³L. Scodellaro,¹¹A. L. Scott,¹⁰A. Scribano,⁴⁴F. Scuri,⁴⁴A. Sedov,⁴⁶S. Seidel,³⁶Y. Seiya,⁴⁰A. Semenov,¹⁴

F. Semeria,⁵L. Sexton-Kennedy,¹⁶I. Sfiligoi,¹⁸M. D. Shapiro,²⁸T. Shears,²⁹P. F. Shepard,⁴⁵D. Sherman,²¹ M. Shimojima,⁵³M. Shochet,¹³Y. Shon,⁵⁷I. Shreyber,³⁵A. Sidoti,⁴⁴P. Sinervo,³²A. Sisakyan,¹⁴J. Sjolin,⁴¹A. Skiba,²⁵

A. J. Slaughter,¹⁶K. Sliwa,⁵⁴D. Smirnov,³⁶J. R. Smith,⁷F. D. Snider,¹⁶R. Snihur,³²M. Soderberg,³³A. Soha,⁷ S. Somalwar,⁵⁰V. Sorin,³⁴J. Spalding,¹⁶F. Spinella,⁴⁴P. Squillacioti,⁴⁴M. Stanitzki,⁵⁸A. Staveris-Polykalas,⁴⁴ R. St. Denis,²⁰B. Stelzer,⁸O. Stelzer-Chilton,³²D. Stentz,³⁷J. Strologas,³⁶D. Stuart,¹⁰J. S. Suh,²⁷A. Sukhanov,¹⁷

K. Sumorok,³¹H. Sun,⁵⁴T. Suzuki,⁵³A. Taffard,²³R. Tafirout,³²R. Takashima,³⁹Y. Takeuchi,⁵³K. Takikawa,⁵³ M. Tanaka,²R. Tanaka,³⁹M. Tecchio,³³P. K. Teng,¹K. Terashi,⁴⁸S. Tether,³¹J. Thom,¹⁶A. S. Thompson,²⁰ E. Thomson,⁴³P. Tipton,⁴⁷V. Tiwari,¹²S. Tkaczyk,¹⁶D. Toback,⁵¹K. Tollefson,³⁴T. Tomura,⁵³D. Tonelli,⁴⁴ M. To¨nnesmann,³⁴S. Torre,⁴⁴D. Torretta,¹⁶S. Tourneur,¹⁶W. Trischuk,³²R. Tsuchiya,⁵⁵S. Tsuno,³⁹N. Turini,⁴⁴ F. Ukegawa,⁵³T. Unverhau,²⁰S. Uozumi,⁵³D. Usynin,⁴³L. Vacavant,²⁸A. Vaiciulis,⁴⁷S. Vallecorsa,¹⁹A. Varganov,³³

E. Vataga,³⁶G. Velev,¹⁶G. Veramendi,²³V. Veszpremi,⁴⁶T. Vickey,²³R. Vidal,¹⁶I. Vila,¹¹R. Vilar,¹¹I. Vollrath,³² I. Volobouev,²⁸F. Wu¨rthwein,⁹P. Wagner,⁵¹R. G. Wagner,²R. L. Wagner,¹⁶W. Wagner,²⁵R. Wallny,⁸T. Walter,²⁵ Z. Wan,⁵⁰M. J. Wang,¹S. M. Wang,¹⁷A. Warburton,³²B. Ward,²⁰S. Waschke,²⁰D. Waters,³⁰T. Watts,⁵⁰M. Weber,²⁸

W. C. Wester III,¹⁶B. Whitehouse,⁵⁴D. Whiteson,⁴³A. B. Wicklund,²E. Wicklund,¹⁶H. H. Williams,⁴³P. Wilson,¹⁶ B. L. Winer,³⁸P. Wittich,⁴³S. Wolbers,¹⁶C. Wolfe,¹³S. Worm,⁵⁰T. Wright,³³X. Wu,¹⁹S. M. Wynne,²⁹A. Yagil,¹⁶ K. Yamamoto,⁴⁰J. Yamaoka,⁵⁰Y. Yamashita.,³⁹C. Yang,⁵⁸U. K. Yang,¹³W. M. Yao,²⁸G. P. Yeh,¹⁶J. Yoh,¹⁶K. Yorita,¹³

T. Yoshida,⁴⁰I. Yu,²⁷S. S. Yu,⁴³J. C. Yun,¹⁶L. Zanello,⁴⁹A. Zanetti,⁵²I. Zaw,²¹F. Zetti,⁴⁴ X. Zhang,²³J. Zhou,⁵⁰and S. Zucchelli⁵

(CDF Collaboration)

1Institute of Physics, Academia Sinica, Taipei, Taiwan 11529, Republic of China

2Argonne National Laboratory, Argonne, Illinois 60439, USA

3Institut de Fisica d’Altes Energies, Universitat Autonoma de Barcelona, E-08193, Bellaterra (Barcelona), Spain

4Baylor University, Waco, Texas 76798, USA

5Istituto Nazionale di Fisica Nucleare, University of Bologna, I-40127 Bologna, Italy

6Brandeis University, Waltham, Massachusetts 02254, USA

7University of California, Davis, Davis, California 95616, USA

8University of California, Los Angeles, Los Angeles, California 90024, USA

9University of California, San Diego, La Jolla, California 92093, USA

10University of California, Santa Barbara, Santa Barbara, California 93106, USA

11Instituto de Fisica de Cantabria, CSIC-University of Cantabria, 39005 Santander, Spain

12Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA

13Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, USA

14Joint Institute for Nuclear Research, RU-141980 Dubna, Russia

15Duke University, Durham, North Carolina 27708, USA

16Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA

17University of Florida, Gainesville, Florida 32611, USA

18Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, I-00044 Frascati, Italy

19University of Geneva, CH-1211 Geneva 4, Switzerland

20Glasgow University, Glasgow G12 8QQ, United Kingdom

191801-2

21Harvard University, Cambridge, Massachusetts 02138, USA

22Division of High Energy Physics, Department of Physics, University of Helsinki and Helsinki Institute of Physics, FIN-00014, Helsinki, Finland

23University of Illinois, Urbana, Illinois 61801, USA

24The Johns Hopkins University, Baltimore, Maryland 21218, USA

25Institut fu¨r Experimentelle Kernphysik, Universita¨t Karlsruhe, 76128 Karlsruhe, Germany

26High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305, Japan

27Center for High Energy Physics: Kyungpook National University, Taegu 702-701; Seoul National University, Seoul 151-742;

and SungKyunKwan University, Suwon 440-746, Korea

28Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

29University of Liverpool, Liverpool L69 7ZE, United Kingdom

30University College London, London WC1E 6BT, United Kingdom

31Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

32Institute of Particle Physics: McGill University, Montre´al, Canada H3A 2T8;

and University of Toronto, Toronto, Canada M5S 1A7

33University of Michigan, Ann Arbor, Michigan 48109, USA

34Michigan State University, East Lansing, Michigan 48824, USA

35Institution for Theoretical and Experimental Physics, ITEP, Moscow 117259, Russia

36University of New Mexico, Albuquerque, New Mexico 87131, USA

37Northwestern University, Evanston, Illinois 60208, USA

38The Ohio State University, Columbus, Ohio 43210, USA

39Okayama University, Okayama 700-8530, Japan

40Osaka City University, Osaka 588, Japan

41University of Oxford, Oxford OX1 3RH, United Kingdom

42University of Padova, Istituto Nazionale di Fisica Nucleare, Sezione di Padova-Trento, I-35131 Padova, Italy

43University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

44Istituto Nazionale di Fisica Nucleare Pisa, Universities of Pisa, Siena and Scuola Normale Superiore, I-56127 Pisa, Italy

45University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA

46Purdue University, West Lafayette, Indiana 47907, USA

47University of Rochester, Rochester, New York 14627, USA

48The Rockefeller University, New York, New York 10021, USA

49Istituto Nazionale di Fisica Nucleare, Sezione di Roma 1, University di Roma ‘‘La Sapienza,’’ I-00185 Roma, Italy

50Rutgers University, Piscataway, New Jersey 08855, USA

51Texas A&M University, College Station, Texas 77843, USA

52Istituto Nazionale di Fisica Nucleare, University of Trieste/ Udine, Italy

53University of Tsukuba, Tsukuba, Ibaraki 305, Japan

54Tufts University, Medford, Massachusetts 02155, USA

55Waseda University, Tokyo 169, Japan

56Wayne State University, Detroit, Michigan 48201, USA

57University of Wisconsin, Madison, Wisconsin 53706, USA

58Yale University, New Haven, Connecticut 06520, USA (Received 5 August 2005; published 17 May 2006) We report an observation of the decayB⁰_s !D_sinppcollisions atps

1:96 TeVusing115 pb¹ of data collected by the CDF II detector at the Fermilab Tevatron. We observe8311statB⁰_s !D_s candidates, representing a large increase in statistics over previous measurements and the first observation of this decay at appcollider. We present the first measurement of the relative branching fractionBB⁰_s ! D_s=BB⁰!D 1:320:18stat 0:38syst. We also measureBB!D⁰=BB⁰! D 1:970:10stat 0:21syst, which is consistent with previous measurements.

DOI:10.1103/PhysRevLett.96.191801 PACS numbers: 13.25.Hw, 14.40.Nd

B⁰_s-B⁰_s oscillation is expected to occur in the standard model of particle physics. Measurement of the oscillation frequency, when combined with that forB⁰-B⁰oscillation, tests the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix. A deviation from unitarity could arise from a variety of new physics effects [1].B⁰_s meson oscillations have yet to be directly observed, with a lower limit (95% C.L.) on the oscillation frequency cur-

rently at 14:5 ps¹ [2]. For comparison, the average B meson lifetime is of the order of 1 ps, and theB⁰oscillation frequency is0:5 ps¹. This lower limit implies that excel- lent proper time resolution is required to observe the oscillation. In semileptonic B⁰_s decays, the proper time measurement is degraded due to the undetected neutrino.

Fully reconstructed hadronic B⁰_s decays such as B⁰_s! D_s do not suffer from this problem [3]. Obtaining a

large sample of such decays is an important first step toward measuringB⁰_s mixing.

In addition, the measurement of the branching ratio of B⁰_s !D_s decay along with that of B⁰ !D and B!D⁰can be used to studyBmeson decay mecha- nisms. As shown in Fig. 1, B⁰_s!D_s decay proceeds only at tree level while theB⁰ andB modes have addi- tional, nontree, contributions. Therefore, measurements of ratios of branching fractions of these decays can, in prin- ciple, isolate contributions from the different decay dia- grams [4].

To date, a fewB⁰_s !D_s events have been observed [5,6] ineecollisions at LEP.Bfactories, while running at the 4S resonance, do not produce B⁰_s mesons.

However, large samples of B⁰_s are produced at the Tevatron. The ability to trigger on displaced vertices allows the upgraded collider detector at Fermilab (CDF II) to collect large samples of fully reconstructed B⁰_s decay modes.

In this Letter, we present an observation ofB⁰_s!D_s decays and a measurement of the ratios of branching fractions ofB⁰_s !D_sandB!D⁰relative to the branching fraction ofB⁰!Ddecays. We use a sam- ple of fully reconstructedB!D decays corresponding to115 pb¹ ofpp collisions at

ps

1:96 TeVcollected by the CDF II detector at the Fermilab Tevatron between February 2002 and January 2003. Charge conjugate modes are implied throughout this Letter.

The components of the CDF II detector relevant to this analysis are described briefly below; a more complete description can be found elsewhere [7]. We use tracks reconstructed by both the central outer tracker (COT) and the silicon microstrip detector (SVX II) in the rangejj 1 [8], where is the pseudorapidity defined as lntan=2and is the polar angle with respect to the proton beam direction. The SVX II detector consists of double-sided silicon strip sensors arranged in five cylindri- cal shells with radii between 2.5 and 10.6 cm [9].

Surrounding the SVX II is the COT [10], an open-cell drift chamber that has an inner (outer) radius of 40 (137) cm.

The COT has 96 layers, organized in 8 superlayers with alternating superlayers of axial and 2 stereo readout.

TheBdecays used in this analysis are selected with a three- level trigger system. At Level 1, charged tracks are recon- structed in the COT axial superlayers by a hardware pro- cessor, the eXtremely fast tracker (XFT) [11]. This trigger

requires two oppositely charged tracks with transverse momenta p_T 2 GeV=c and scalar sum p_T1p_T2 5:5 GeV=c. At Level 2, the silicon vertex trigger (SVT) [12] associates SVX IIr’position measurements with XFT tracks. This provides a precise measurement of the track impact parameter,d₀, which is defined as the projec- tion of a track’s distance of closest approach to the beam line onto the transverse plane. The resolution of the impact parameter measurement is 50m, which includes ap- proximately 30m contribution from the transverse beam size. Hadronic decays of heavy flavor particles are selected by requiring two tracks with 120md₀ 1000 m. The two trigger tracks must have an opening angle in the transverse plane satisfying 2 j’j 90 and must satisfy the requirement L_xy>200m, where L_xyis defined as the distance in the transverse plane from the beam line to the two-track vertex projected onto the two-track momentum vector. A complete event reconstruc- tion is performed at Level 3, and the Level 1 and Level 2 requirements are confirmed. Since events satisfying the displaced vertex trigger are dominated by the decays of promptly produced charm, the largest background toB! Ddecays results from combining a promptDmeson with an unrelated track from the event.

Reconstruction ofBmeson candidates begins by select- ing Dmeson candidates. We reconstruct the followingD meson decay modes: D⁰!K,D!Kand D_s ! followed by !KK. We exploit the narrow!KKresonance in theD_s decays to greatly suppress background by requiring 1010 MeV=c²<

mKK<1028 MeV=c². No particle identification is used in this analysis. All particle hypotheses consistent with the candidate decay structure are attempted. The track combinations which comprise a D meson candidate are required to originate from a common vertex. An additional track withp_T >1:6 GeV=candRD; _B<1:5is added and assigned a pion mass to reconstruct the B meson

candidate. We define R

²’²

p , where ’

and are the azimuthal angle and pseudorapidity of the pion with respect to the direction of the D meson candidate. The selection requirements are optimized to yield the largestS=

SB

p for each of the decays. In the optimization procedure, the number of signal events (S) is estimated using a Monte Carlo simulation, while the num- ber of background events (B) is estimated using sidebands of theBmeson mass spectra reconstructed in data.

We require theBmeson candidate tracks to be consistent with the following constraints: the Dmeson tracks origi- nate from a common vertex, the momentum of the D meson points back, in three dimensions, to the remaining B meson candidate track, and the invariant mass of theD meson decay products is consistent with the world average of the corresponding Dmeson mass [2]. We also require that at least two of theB meson daughter tracks are con- sistent with the trigger requirements. The combinatorial FIG. 1. Different Feynman diagrams which contribute toB!

Ddecays.

191801-4

background is strongly reduced by requiring that L^B_xy>

400m and L_xyB!D>150m, where the latter refers to theL_xyof theDmeson decay vertex with respect to theBmeson decay vertex. The impact parameter of the B meson momentum with respect to the beam axis is required to be less than80mto assure that theBmeson candidate originates from the primary vertex. The invariant mass distributions ofB⁰_s,B, andB⁰meson candidates are shown in Fig. 2. The prominent peak at each expectedB meson mass establishesB!Ddecay signals, including our observation ofB⁰_s!D_s.

We measure the following ratio:

BB⁰_s!D_s

BB⁰!D NB⁰_s NB⁰

B⁰ B⁰_s

f_d f_s

BD !K BD_s !B!KK

(1) whereNB⁰_sandNB⁰are the signal yields,f_d=f_sis the ratio of fragmentation fractions forB⁰andB⁰_smesons, and B⁰=B⁰_sis the ratio of trigger and reconstruction effi- ciencies. Equation (1) also applies to the B!D⁰ mode, with terms forB⁰_sdecays replaced by those relevant

to B decays. There are three components to the ratio of branching fractions measurement: the ratio of B meson yields obtained from fits to the invariant mass spectra, the ratio of signal efficiencies obtained from Monte Carlo simulation, and the product of previously measured pro- duction and branching fractions.

In our analysis, we use Monte Carlo simulation to de- termine shapes of mass spectra and relative efficiencies.

The Monte Carlo generation proceeds as follows. Trans- verse momentum and rapidity distributions of single b quarks are generated based on calculations using next-to- leading-order perturbative QCD [13].B meson kinematic distributions are obtained by simulating Peterson fragmen- tation [14] on quark-level distributions. Additional frag- mentation particles, correlated b-b production and the underlying event structure are not simulated. B meson decays are simulated using EvtGen [15]. The simulation of the CDF II detector and trigger is based upon aGEANT 3

description [16] that includes effects of time variation of the beam position and hardware configuration of the SVX II and SVT.

The yield of B mesons is extracted from the invariant mass spectra using a binned ² fit, as shown in Fig. 2.

There are three contributions to the background shape used in the fit. The combinatorial background component is modeled with a linear combination of a linear and exponential distribution. The shape of background due to Cabibbo-suppressed B!DK decay is modeled by a Gaussian and is shown as shaded distributions in Figs. 2(a) –2(c). Backgrounds due to partially recon- structed B decays contribute to the low mass side of the signal peak and are modeled by inclusive B!DX Monte Carlo simulation. The structures in the region close to the signal are due toB!Ddecays, where a photon or a⁰from theD decay is not reconstructed. The decay of the polarizedDproduces the double-peaked structure.

As an example of the various contributing backgrounds, Fig. 2(d) shows the invariant mass spectrum forB!DX Monte Carlo reconstructed asB!D⁰. In the fit to the data mass spectrum, the fractions of combinatorial back- ground and partially reconstructedB’s are allowed to float in the fit. The ratio of Cabibbo-suppressedB!DKback- ground to the corresponding signal is fixed to the world average ratio of branching fractions, with the trigger and reconstruction efficiencies of the two modes taken into account. The fitted yields of B⁰!D, B!D⁰, and B⁰_s !D_s decays are 111843stat, 1260 42statand8311statevents, respectively.

Trigger and reconstruction efficiencies for B⁰; B, and B⁰_s decays are determined using Monte Carlo simula- tion. The trigger efficiency differs among the three B meson decay modes due to differences in decay kine- matics (e.g., opening angle distributions) which arise from the different masses and spins of the intermediate and final state particles. The ratios of efficiencies are

2] Mass [GeV/c π+

Ds

5.0 5.5 6.0

2 Entries per 20 MeV/c

0 5 10 15 20 25 30 35

2] Mass [GeV/c

-π+

Ds

5.0 5.5 6.0

2 Entries per 20 MeV/c

0 5 10 15 20 25 30

35 (a)

2] Mass [GeV/c π⁺

D-

5.0 5.5 6.0

2Entries per 10 MeV/c

0 50 100 150 200 250

2] Mass [GeV/c π

D-

5.0 5.5 6.0

2Entries per 10 MeV/c

0 50 100 150 200

250 (b)

2] Mass [GeV/c π+

D0

5.0 5.5 6.0

2Entries per 10 MeV/c

0 50 100 150 200 250 300

2] Mass [GeV/c π

D0

5.0 5.5 6.0

2Entries per 10 MeV/c

0 50 100 150 200 250

300 (c)

2] Mass [GeV/c π+

D0

5.0 5.5 6.0

2 Entries per 10 MeV/c

0 20 40 60 80 100 120

other B decays π+ D*- 0→ B

π+ D*0 +→ B

K+ D0 +→ B

π+ D0

→ B+

2] Mass [GeV/c π+

D0

5.0 5.5 6.0

2 Entries per 10 MeV/c

0 20 40 60 80 100 120

Simulation

(d)

FIG. 2 (color online). Invariant mass spectra for (a) D_s, (b)D, and (c) D⁰ for data, with² fits overlaid. The main background under the signal peak is combinatorial, mod- eled with a combination of a linear and exponential function.

The shaded peak corresponds toB!DKdecays, and is mod- eled with a Gaussian. The additional background component in the low mass region is due to partially reconstructedBdecays.

This background component is modeled using shapes deter- mined by inclusiveB!DXMonte Carlo simulations. A sample Monte Carlo mass distribution forB!D⁰events is shown in (d). Contributions from different sources in (d) are ordered by peak position, from right to left.

B⁰=B 0:7080:010 and B⁰=B⁰_s 0:9030:012, where the uncertainties are due to the limited statistics of Monte Carlo samples.

World average values [2] are used for the various branching fractions in Eq. (1). In terms ofB meson pro- duction, we assume f_df_u, consistent with previous measurement [17]. The B⁰_s=B⁰ production fraction used in this analysis is the world average value, f_s=f_d 0:2700:029, currently dominated by LEP measure- ments. The ratio of fragmentation fractions may be differ- ent in a hadron collider environment than in ee collisons. However, the ratio of fragmentation fractions measured by CDF [17] is consistent with the LEP results.

Many systematic uncertainties cancel in the measure- ment of ratios of branching fractions due to the similarity of final state kinematics. Systematic uncertainties come from three main sources: fitting the invariant mass distri- butions to obtain signal yields, determination of the ratio of efficiencies, and uncertainties on external inputs. The con- tribution to the systematic uncertainty from externally measured quantities is calculated by propagating world average uncertainties. Systematic uncertainties on the sig- nal yields are determined by comparing the fitted yields after changing the invariant mass region of the fit and varying the background shape within the range allowed by theB!DX Monte Carlo statistics and world average uncertainties on the branching fractions of participatingB decays. Systematic uncertainties on the ratio of efficiencies come from physics sources such as the choice of p_T spectrum or meson lifetime, and detector sources such as inaccuracies in the XFT and SVT hardware simulation.

The uncertainty due to a given source is estimated by the shift of the ratio of efficiencies when the effect of that source is modified in the Monte Carlo simulation. The effect of the choice ofBmesonp_T spectrum is estimated by reweighting the Monte Carlo simulation to match the measuredBhadronp_T spectrum [7]. Since the trigger and

analysis selection only accept events in which theBmeson is displaced from the primary interaction point, the effi- ciencies depend upon the B and D meson lifetimes. To estimate uncertainties due toBandDmeson lifetimes, the Monte Carlo simulation is reweighted with different life- times within the world average uncertainties. Because of the different specific ionization ofandKin the COT, kaons are 6% less efficient in satisfying the XFT require- ments [18]. The Monte Carlo simulation is reweighted to reproduce this effect. To estimate the uncertainty due to imperfections in simulating the signal selection require- ment efficiencies, we compare efficiencies between Monte Carlo simulation and sideband subtracted B and B⁰signal for every selection requirement separately. In the case of the B=B⁰ branching fraction ratio measurement, there is an additional systematic uncertainty associated with the fact that theB⁰ decay has four tracks in the final state while B has only three. We infer the corrections and systematic uncertainties due to the fourth track by comparing trigger and reconstruction efficiencies in data and Monte Carlo simulations for semileptonic B! DlX; D!D⁰decays between theD⁰ !K andKfinal states.

The systematic uncertainties are summarized in Table I.

The total systematic uncertainty is obtained by adding individual contributions in quadrature. Using Eq. (1), we obtain the following values for the ratios of branching fractions:

BB⁰_s!D_s

BB⁰!D 1:320:18stat 0:10syst 0:34BR 0:14PR; (2) BB!D⁰

BB⁰!D 1:970:10stat 0:15syst

0:14BR; (3)

where BR and PR refer to the uncertainty on the ratio ofD meson branching fractions andB⁰_s meson production rela- tive to B⁰, respectively. Under the assumption of isospin invariance, our measurement of the ratio BB! D⁰=BB⁰ !D is consistent with the world av- erage [2]. This provides a high statistics cross-check of the measurement procedure.

In conclusion, we have presented the first observation of B⁰_s!D_s decays in pp collisions, and the first mea- surement of theB⁰_s!D_sbranching fraction relative to theB⁰ !Dbranching fraction. The precision of this measurement is currently not adequate to separate the contributions of different decay diagrams [4]. We expect the measurement precision to improve as world average values ofDmeson branching fractions andBmeson pro- duction fractions improve.

We thank the Fermilab staff and the technical staffs of the participating institutions for their vital contributions.

TABLE I. Summary of relative systematic uncertainties.

Effect B⁰s=B⁰[%] B=B⁰ [%]

fitNB⁰_s; B 4.5 2.0

fitNB⁰ 2.3 2.3

B_pT spectrum 2.6 1.5

trigger simulation 1.6 0.2

selection simulation 4.0 4.0

⁰mass cut 0.2 not applicable

B=B⁰_s meson lifetime 2.0 0.4

D⁰=D_s meson lifetime 0.1 0.1

B⁰ meson lifetime 0.4 0.4

Dmeson lifetime <0:1 <0:1

fourth track accept not applicable 5.2

Total 7.4 7.4

191801-6

This work was supported by the U.S. Department of Energy and National Science Foundation; the Italian Istituto Nazionale di Fisica Nucleare; the Ministry of Education, Culture, Sports, Science and Technology of Japan; the Natural Sciences and Engineering Research Council of Canada; the National Science Council of the Republic of China; the Swiss National Science Foun- dation; the A. P. Sloan Foundation; the Bundesmini- sterium fu¨r Bildung und Forschung, Germany; the Korean Science and Engineering Foundation and the Korean Research Foundation; the Particle Physics and Astronomy Research Council and the Royal Society, UK;

the Russian Foundation for Basic Research; the Comisio´n Interministerial de Ciencia y Tecnologı´a, Spain; in part by the European Community’s Human Potential Programme under Contract No. HPRN-CT-2002-00292; and the Academy of Finland.

[1] A. J. Buraset al., Phys. Lett. B500, 161 (2001).

[2] S. Eidelmanet al., Phys. Lett. B592, 1 (2004).

[3] K. Anikeevet al., Fermilab Report No. FERMILAB-PUB- 01-197 (2001).

[4] A. K. Leibovich, Z. Ligeti, I. W. Stewart, and M. B. Wise, Phys. Lett. B586, 337 (2004).

[5] D. Buskulicet al.(ALEPH Collaboration), Phys. Lett. B 311, 425 (1993).

[6] R. Akerset al.(OPAL Collaboration), Phys. Lett. B337, 196 (1994).

[7] D. Acosta et al.(CDF Collaboration), Phys. Rev. D71, 032001 (2005).

[8] CDF II uses a cylindrical coordinate system in which’is the azimuthal angle, r is the radius from the nominal beamline, y points up, andz points in the proton beam direction with the origin at the center of the detector. The transverse plane is the plane perpendicular to thezaxis. A superconducting magnet provides a nearly uniform 1.4 T axial field in which charged particles are reconstructed.

[9] A. Sillet al., Nucl. Instrum. Methods Phys. Res., Sect. A 447, 1 (2000).

[10] T. Affolderet al., Nucl. Instrum. Methods Phys. Res., Sect.

A526, 249 (2004).

[11] E. J. Thomson et al., IEEE Trans. Nucl. Sci. 49, 1063 (2002).

[12] W. Ashmanskaset al., Nucl. Instrum. Methods Phys. Res., Sect. A518, 532 (2004).

[13] P. Nason, S. Dawson, and R. K. Ellis, Nucl. Phys.B303, 607 (1988).

[14] C. Peterson, D. Schlatter, I. Schmitt, and P. M. Zerwas, Phys. Rev. D27, 105 (1983).

[15] D. J. Lange, Nucl. Instrum. Methods Phys. Res., Sect. A 462, 152 (2001).

[16] R. Brun, R. Hagelberg, M. Hansroul, and J. C. Lassalle, CERN Reports No. CERN-DD-78-2-REV and No. CERN- DD-78-2.

[17] T. Affolderet al.(CDF Collaboration), Phys. Rev. Lett.84, 1663 (2000).

[18] D. Acostaet al.(CDF Collaboration), Phys. Rev. Lett.94, 122001 (2005).