Observation of New Charmless Decays of Bottom Hadrons

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Reference

Observation of New Charmless Decays of Bottom Hadrons

CDF Collaboration

CLARK, Allan Geoffrey (Collab.), et al.

Abstract

We search for new charmless decays of neutral b hadrons to pairs of charged hadrons, using 1  fb−1 of data collected by the CDF II detector at the Fermilab Tevatron. We report the first

observation of the B0s→K−π+ decay and measure

B(B0s→K−π+)=(5.0±0.7(stat)±0.8(syst))×10−6. We also report the first observation of charmless b-baryon decays, and measure B(Λ0b→pπ−)=(3.5±0.6(stat)±0.9(syst))×10−6 and B(Λ0b→pK−)=(5.6±0.8(stat)±1.5(syst))×10−6. No evidence is found for other modes, and we set the limit B(B0s→π+π−)

CDF Collaboration, CLARK, Allan Geoffrey (Collab.), et al . Observation of New Charmless Decays of Bottom Hadrons. Physical Review Letters , 2009, vol. 103, no. 03, p. 031801

DOI : 10.1103/PhysRevLett.103.031801

Available at:

http://archive-ouverte.unige.ch/unige:38601

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

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Observation of New Charmless Decays of Bottom Hadrons

T. Aaltonen,²⁴J. Adelman,¹⁴T. Akimoto,⁵⁶B. A´ lvarez Gonza´lez,^12,rS. Amerio,^44b,44aD. Amidei,³⁵A. Anastassov,³⁹ A. Annovi,²⁰J. Antos,¹⁵G. Apollinari,¹⁸A. Apresyan,⁴⁹T. Arisawa,⁵⁸A. Artikov,¹⁶W. Ashmanskas,¹⁸A. Attal,⁴

A. Aurisano,⁵⁴F. Azfar,⁴³P. Azzurri,^47d,47aW. Badgett,¹⁸A. Barbaro-Galtieri,²⁹V. E. Barnes,⁴⁹B. A. Barnett,²⁶ V. Bartsch,³¹G. Bauer,³³P.-H. Beauchemin,³⁴F. Bedeschi,^47aD. Beecher,³¹S. Behari,²⁶G. Bellettini,^47b,47aJ. Bellinger,⁶⁰

D. Benjamin,¹⁷A. Beretvas,¹⁸J. Beringer,²⁹A. Bhatti,⁵¹M. Binkley,¹⁸D. Bisello,^44b,44aI. Bizjak,^31,wR. E. Blair,² C. Blocker,⁷B. Blumenfeld,²⁶A. Bocci,¹⁷A. Bodek,⁵⁰V. Boisvert,⁵⁰G. Bolla,⁴⁹D. Bortoletto,⁴⁹J. Boudreau,⁴⁸ A. Boveia,¹¹B. Brau,^11,bA. Bridgeman,²⁵L. Brigliadori,^44aC. Bromberg,³⁶E. Brubaker,¹⁴J. Budagov,¹⁶H. S. Budd,⁵⁰

S. Budd,²⁵S. Burke,¹⁸K. Burkett,¹⁸G. Busetto,^44b,44aP. Bussey,²²A. Buzatu,³⁴K. L. Byrum,²S. Cabrera,^17,t C. Calancha,³²M. Campanelli,³⁶M. Campbell,³⁵F. Canelli,^14,18 A. Canepa,⁴⁶B. Carls,²⁵D. Carlsmith,⁶⁰R. Carosi,^47a S. Carrillo,^19,mS. Carron,³⁴B. Casal,¹²M. Casarsa,¹⁸A. Castro,^6b,6aP. Catastini,^47c,47aD. Cauz,^55b,55aV. Cavaliere,^47c,47a M. Cavalli-Sforza,⁴A. Cerri,²⁹L. Cerrito,^31,nS. H. Chang,²⁸Y. C. Chen,¹M. Chertok,⁸G. Chiarelli,^47aG. Chlachidze,¹⁸ F. Chlebana,¹⁸K. Cho,²⁸D. Chokheli,¹⁶J. P. Chou,²³G. Choudalakis,³³S. H. Chuang,⁵³K. Chung,¹³W. H. Chung,⁶⁰

Y. S. Chung,⁵⁰T. Chwalek,²⁷C. I. Ciobanu,⁴⁵M. A. Ciocci,^47c,47aA. Clark,²¹D. Clark,⁷G. Compostella,^44a M. E. Convery,¹⁸J. Conway,⁸M. Cordelli,²⁰G. Cortiana,^44b,44aC. A. Cox,⁸D. J. Cox,⁸F. Crescioli,^47b,47a C. Cuenca Almenar,^8,tJ. Cuevas,^12,rR. Culbertson,¹⁸J. C. Cully,³⁵D. Dagenhart,¹⁸M. Datta,¹⁸T. Davies,²² P. de Barbaro,⁵⁰S. De Cecco,^52aA. Deisher,²⁹G. De Lorenzo,⁴M. Dell’Orso,^47b,47aC. Deluca,⁴L. Demortier,⁵¹J. Deng,¹⁷ M. Deninno,^6aP. F. Derwent,¹⁸G. P. di Giovanni,⁴⁵C. Dionisi,^52b,52aB. Di Ruzza,^55b,55aJ. R. Dittmann,⁵M. D’Onofrio,⁴

S. Donati,^47b,47aP. Dong,⁹J. Donini,^44aT. Dorigo,^44aS. Dube,⁵³J. Efron,⁴⁰A. Elagin,⁵⁴R. Erbacher,⁸D. Errede,²⁵ S. Errede,²⁵R. Eusebi,¹⁸H. C. Fang,²⁹S. Farrington,⁴³W. T. Fedorko,¹⁴R. G. Feild,⁶¹M. Feindt,²⁷J. P. Fernandez,³²

C. Ferrazza,^47d,47aR. Field,¹⁹G. Flanagan,⁴⁹R. Forrest,⁸M. J. Frank,⁵M. Franklin,²³J. C. Freeman,¹⁸I. Furic,¹⁹ M. Gallinaro,^52aJ. Galyardt,¹³F. Garberson,¹¹J. E. Garcia,²¹A. F. Garfinkel,⁴⁹K. Genser,¹⁸H. Gerberich,²⁵D. Gerdes,³⁵

A. Gessler,²⁷S. Giagu,^52b,52aV. Giakoumopoulou,³P. Giannetti,^47aK. Gibson,⁴⁸J. L. Gimmell,⁵⁰C. M. Ginsburg,¹⁸ N. Giokaris,³M. Giordani,^55b,55aP. Giromini,²⁰M. Giunta,^47b,47aG. Giurgiu,²⁶V. Glagolev,¹⁶D. Glenzinski,¹⁸M. Gold,³⁸

N. Goldschmidt,¹⁹A. Golossanov,¹⁸G. Gomez,¹²G. Gomez-Ceballos,³³M. Goncharov,³³O. Gonza´lez,³²I. Gorelov,³⁸ A. T. Goshaw,¹⁷K. Goulianos,⁵¹A. Gresele,^44b,44aS. Grinstein,²³C. Grosso-Pilcher,¹⁴R. C. Group,¹⁸U. Grundler,²⁵

J. Guimaraes da Costa,²³Z. Gunay-Unalan,³⁶C. Haber,²⁹K. Hahn,³³S. R. Hahn,¹⁸E. Halkiadakis,⁵³B.-Y. Han,⁵⁰ J. Y. Han,⁵⁰F. Happacher,²⁰K. Hara,⁵⁶D. Hare,⁵³M. Hare,⁵⁷S. Harper,⁴³R. F. Harr,⁵⁹R. M. Harris,¹⁸M. Hartz,⁴⁸ K. Hatakeyama,⁵¹C. Hays,⁴³M. Heck,²⁷A. Heijboer,⁴⁶J. Heinrich,⁴⁶C. Henderson,³³M. Herndon,⁶⁰J. Heuser,²⁷ S. Hewamanage,⁵D. Hidas,¹⁷C. S. Hill,^11,dD. Hirschbuehl,²⁷A. Hocker,¹⁸S. Hou,¹M. Houlden,³⁰S.-C. Hsu,²⁹ B. T. Huffman,⁴³R. E. Hughes,⁴⁰U. Husemann,⁶¹M. Hussein,³⁶J. Huston,³⁶J. Incandela,¹¹G. Introzzi,^47aM. Iori,^52b,52a

A. Ivanov,⁸E. James,¹⁸D. Jang,¹³B. Jayatilaka,¹⁷E. J. Jeon,²⁸M. K. Jha,^6aS. Jindariani,¹⁸W. Johnson,⁸M. Jones,⁴⁹ K. K. Joo,²⁸S. Y. Jun,¹³J. E. Jung,²⁸T. R. Junk,¹⁸T. Kamon,⁵⁴D. Kar,¹⁹P. E. Karchin,⁵⁹Y. Kato,⁴²R. Kephart,¹⁸

J. Keung,⁴⁶V. Khotilovich,⁵⁴B. Kilminster,¹⁸D. H. Kim,²⁸H. S. Kim,²⁸H. W. Kim,²⁸J. E. Kim,²⁸M. J. Kim,²⁰ S. B. Kim,²⁸S. H. Kim,⁵⁶Y. K. Kim,¹⁴N. Kimura,⁵⁶L. Kirsch,⁷S. Klimenko,¹⁹B. Knuteson,³³B. R. Ko,¹⁷K. Kondo,⁵⁸ D. J. Kong,²⁸J. Konigsberg,¹⁹A. Korytov,¹⁹A. V. Kotwal,¹⁷M. Kreps,²⁷J. Kroll,⁴⁶D. Krop,¹⁴N. Krumnack,⁵M. Kruse,¹⁷

V. Krutelyov,¹¹T. Kubo,⁵⁶T. Kuhr,²⁷N. P. Kulkarni,⁵⁹M. Kurata,⁵⁶S. Kwang,¹⁴A. T. Laasanen,⁴⁹S. Lami,^47a S. Lammel,¹⁸M. Lancaster,³¹R. L. Lander,⁸K. Lannon,^40,qA. Lath,⁵³G. Latino,^47c,47aI. Lazzizzera,^44b,44aT. LeCompte,²

E. Lee,⁵⁴H. S. Lee,¹⁴S. W. Lee,^54,sS. Leone,^47aJ. D. Lewis,¹⁸C.-S. Lin,²⁹J. Linacre,⁴³M. Lindgren,¹⁸E. Lipeles,⁴⁶ A. Lister,⁸D. O. Litvintsev,¹⁸C. Liu,⁴⁸T. Liu,¹⁸N. S. Lockyer,⁴⁶A. Loginov,⁶¹M. Loreti,^44b,44aL. Lovas,¹⁵ D. Lucchesi,^44b,44aC. Luci,^52b,52aJ. Lueck,²⁷P. Lujan,²⁹P. Lukens,¹⁸G. Lungu,⁵¹L. Lyons,⁴³J. Lys,²⁹R. Lysak,¹⁵ D. MacQueen,³⁴R. Madrak,¹⁸K. Maeshima,¹⁸K. Makhoul,³³T. Maki,²⁴P. Maksimovic,²⁶S. Malde,⁴³S. Malik,³¹ G. Manca,^30,fA. Manousakis-Katsikakis,³F. Margaroli,⁴⁹C. Marino,²⁷C. P. Marino,²⁵A. Martin,⁶¹V. Martin,^22,l M. Martı´nez,⁴R. Martı´nez-Balları´n,³²T. Maruyama,⁵⁶P. Mastrandrea,^52aT. Masubuchi,⁵⁶M. Mathis,²⁶M. E. Mattson,⁵⁹ P. Mazzanti,^6aK. S. McFarland,⁵⁰P. McIntyre,⁵⁴R. McNulty,^30,kA. Mehta,³⁰P. Mehtala,²⁴A. Menzione,^47aP. Merkel,⁴⁹

C. Mesropian,⁵¹T. Miao,¹⁸N. Miladinovic,⁷R. Miller,³⁶C. Mills,²³M. Milnik,²⁷A. Mitra,¹G. Mitselmakher,¹⁹ H. Miyake,⁵⁶N. Moggi,^6aC. S. Moon,²⁸R. Moore,¹⁸M. J. Morello,^47b,47aJ. Morlock,²⁷P. Movilla Fernandez,¹⁸ J. Mu¨lmensta¨dt,²⁹A. Mukherjee,¹⁸Th. Muller,²⁷R. Mumford,²⁶P. Murat,¹⁸M. Mussini,^6b,6aJ. Nachtman,¹⁸Y. Nagai,⁵⁶

A. Nagano,⁵⁶J. Naganoma,⁵⁶K. Nakamura,⁵⁶I. Nakano,⁴¹A. Napier,⁵⁷V. Necula,¹⁷J. Nett,⁶⁰C. Neu,^46,u

M. S. Neubauer,²⁵S. Neubauer,²⁷J. Nielsen,^29,hL. Nodulman,²M. Norman,¹⁰O. Norniella,²⁵E. Nurse,³¹L. Oakes,⁴³ S. H. Oh,¹⁷Y. D. Oh,²⁸I. Oksuzian,¹⁹T. Okusawa,⁴²R. Orava,²⁴K. Osterberg,²⁴S. Pagan Griso,^44b,44aE. Palencia,¹⁸ V. Papadimitriou,¹⁸A. Papaikonomou,²⁷A. A. Paramonov,¹⁴B. Parks,⁴⁰S. Pashapour,³⁴J. Patrick,¹⁸G. Pauletta,^55b,55a M. Paulini,¹³C. Paus,³³T. Peiffer,²⁷D. E. Pellett,⁸A. Penzo,^55aT. J. Phillips,¹⁷G. Piacentino,^47aE. Pianori,⁴⁶L. Pinera,¹⁹

K. Pitts,²⁵C. Plager,⁹L. Pondrom,⁶⁰O. Poukhov,^16,aN. Pounder,⁴³F. Prakoshyn,¹⁶A. Pronko,¹⁸J. Proudfoot,² F. Ptohos,^18,jE. Pueschel,¹³G. Punzi,^47b,47aJ. Pursley,⁶⁰J. Rademacker,^43,dA. Rahaman,⁴⁸V. Ramakrishnan,⁶⁰ N. Ranjan,⁴⁹I. Redondo,³²P. Renton,⁴³M. Renz,²⁷M. Rescigno,^52aS. Richter,²⁷F. Rimondi,^6b,6aL. Ristori,^47a A. Robson,²²T. Rodrigo,¹²T. Rodriguez,⁴⁶E. Rogers,²⁵S. Rolli,⁵⁷R. Roser,¹⁸M. Rossi,^55aR. Rossin,¹¹P. Roy,³⁴ A. Ruiz,¹²J. Russ,¹³V. Rusu,¹⁸H. Saarikko,²⁴A. Safonov,⁵⁴W. K. Sakumoto,⁵⁰O. Salto´,⁴L. Santi,^55b,55aS. Sarkar,^52b,52a

L. Sartori,^47aK. Sato,¹⁸A. Savoy-Navarro,⁴⁵P. Schlabach,¹⁸A. Schmidt,²⁷E. E. Schmidt,¹⁸M. A. Schmidt,¹⁴ M. P. Schmidt,^61,aM. Schmitt,³⁹T. Schwarz,⁸L. Scodellaro,¹²A. Scribano,^47c,47aF. Scuri,^47aA. Sedov,⁴⁹S. Seidel,³⁸ Y. Seiya,⁴²A. Semenov,¹⁶L. Sexton-Kennedy,¹⁸F. Sforza,^47aA. Sfyrla,²⁵S. Z. Shalhout,⁵⁹T. Shears,³⁰P. F. Shepard,⁴⁸

M. Shimojima,^56,pS. Shiraishi,¹⁴M. Shochet,¹⁴Y. Shon,⁶⁰I. Shreyber,³⁷A. Sidoti,^47aP. Sinervo,³⁴A. Sisakyan,¹⁶ A. J. Slaughter,¹⁸J. Slaunwhite,⁴⁰K. Sliwa,⁵⁷J. R. Smith,⁸F. D. Snider,¹⁸R. Snihur,³⁴A. Soha,⁸S. Somalwar,⁵³V. Sorin,³⁶

J. Spalding,¹⁸T. Spreitzer,³⁴P. Squillacioti,^47c,47aM. Stanitzki,⁶¹R. St. Denis,²²B. Stelzer,³⁴O. Stelzer-Chilton,³⁴ D. Stentz,³⁹J. Strologas,³⁸G. L. Strycker,³⁵D. Stuart,¹¹J. S. Suh,²⁸A. Sukhanov,¹⁹I. Suslov,¹⁶T. Suzuki,⁵⁶A. Taffard,^25,g

R. Takashima,⁴¹Y. Takeuchi,⁵⁶R. Tanaka,⁴¹M. Tecchio,³⁵P. K. Teng,¹K. Terashi,⁵¹R. Tesarek,¹⁸J. Thom,^18,i A. S. Thompson,²²G. A. Thompson,²⁵E. Thomson,⁴⁶P. Tipton,⁶¹P. Ttito-Guzma´n,³²S. Tkaczyk,¹⁸D. Toback,⁵⁴

S. Tokar,¹⁵K. Tollefson,³⁶T. Tomura,⁵⁶D. Tonelli,¹⁸S. Torre,²⁰D. Torretta,¹⁸P. Totaro,^55b,55aS. Tourneur,⁴⁵ M. Trovato,^47aS.-Y. Tsai,¹Y. Tu,⁴⁶N. Turini,^47c,47aF. Ukegawa,⁵⁶S. Vallecorsa,²¹N. van Remortel,^24,cA. Varganov,³⁵ E. Vataga,^47d,47aF. Va´zquez,^19,mG. Velev,¹⁸C. Vellidis,³M. Vidal,³²R. Vidal,¹⁸I. Vila,¹²R. Vilar,¹²T. Vine,³¹M. Vogel,³⁸

I. Volobouev,^29,sG. Volpi,^47b,47aP. Wagner,⁴⁶R. G. Wagner,²R. L. Wagner,¹⁸W. Wagner,^27,vJ. Wagner-Kuhr,²⁷ T. Wakisaka,⁴²R. Wallny,⁹S. M. Wang,¹A. Warburton,³⁴D. Waters,³¹M. Weinberger,⁵⁴J. Weinelt,²⁷W. C. Wester III,¹⁸

B. Whitehouse,⁵⁷D. Whiteson,^46,gA. B. Wicklund,²E. Wicklund,¹⁸S. Wilbur,¹⁴G. Williams,³⁴H. H. Williams,⁴⁶ P. Wilson,¹⁸B. L. Winer,⁴⁰P. Wittich,^18,iS. Wolbers,¹⁸C. Wolfe,¹⁴T. Wright,³⁵X. Wu,²¹F. Wu¨rthwein,¹⁰S. Xie,³³ A. Yagil,¹⁰K. Yamamoto,⁴²J. Yamaoka,¹⁷U. K. Yang,^14,oY. C. Yang,²⁸W. M. Yao,²⁹G. P. Yeh,¹⁸J. Yoh,¹⁸K. Yorita,⁵⁸

T. Yoshida,⁴²G. B. Yu,⁵⁰I. Yu,²⁸S. S. Yu,¹⁸J. C. Yun,¹⁸L. Zanello,^52b,52aA. Zanetti,^55aX. Zhang,²⁵ Y. Zheng,^9,eand S. Zucchelli^6b,6a

(CDF Collaboration)

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

2Argonne National Laboratory, Argonne, Illinois 60439, USA

3University of Athens, 157 71 Athens, Greece

4Institut de Fisica d’Altes Energies, Universitat Autonoma de Barcelona, E-08193, Bellaterra (Barcelona), Spain

5Baylor University, Waco, Texas 76798, USA

6aIstituto Nazionale di Fisica Nucleare Bologna, I-40127 Bologna, Italy

6bUniversity of Bologna, I-40127 Bologna, Italy

7Brandeis University, Waltham, Massachusetts 02254, USA

8University of California, Davis, Davis, California 95616, USA

9University of California, Los Angeles, Los Angeles, California 90024, USA

10University of California, San Diego, La Jolla, California 92093, USA

11University of California, Santa Barbara, Santa Barbara, California 93106, USA

12Instituto de Fisica de Cantabria, CSIC-University of Cantabria, 39005 Santander, Spain

13Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA

14Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, USA

15Comenius University, 842 48 Bratislava, Slovakia; Institute of Experimental Physics, 040 01 Kosice, Slovakia

16Joint Institute for Nuclear Research, RU-141980 Dubna, Russia

17Duke University, Durham, North Carolina 27708, USA

18Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA

19University of Florida, Gainesville, Florida 32611, USA

20Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, I-00044 Frascati, Italy

21University of Geneva, CH-1211 Geneva 4, Switzerland

22Glasgow University, Glasgow G12 8QQ, United Kingdom

23Harvard University, Cambridge, Massachusetts 02138, USA

031801-2

24Division of High Energy Physics, Department of Physics, University of Helsinki and Helsinki Institute of Physics, FIN-00014, Helsinki, Finland

25University of Illinois, Urbana, Illinois 61801, USA

26The Johns Hopkins University, Baltimore, Maryland 21218, USA

27Institut fu¨r Experimentelle Kernphysik, Universita¨t Karlsruhe, 76128 Karlsruhe, Germany

28Center for High Energy Physics: Kyungpook National University, Daegu 702-701, Korea;

Seoul National University, Seoul 151-742, Korea;

Sungkyunkwan University, Suwon 440-746, Korea;

Korea Institute of Science and Technology Information, Daejeon, 305-806, Korea;

Chonnam National University, Gwangju, 500-757, Korea

29Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

30University of Liverpool, Liverpool L69 7ZE, United Kingdom

31University College London, London WC1E 6BT, United Kingdom

32Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, E-28040 Madrid, Spain

33Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

34Institute of Particle Physics: McGill University, Montre´al, Que´bec, Canada H3A 2T8;

Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6;

University of Toronto, Toronto, Ontario, Canada M5S 1A7;

and TRIUMF, Vancouver, British Columbia, Canada V6T 2A3

35University of Michigan, Ann Arbor, Michigan 48109, USA

36Michigan State University, East Lansing, Michigan 48824, USA

37Institution for Theoretical and Experimental Physics, ITEP, Moscow 117259, Russia

38University of New Mexico, Albuquerque, New Mexico 87131, USA

39Northwestern University, Evanston, Illinois 60208, USA

40The Ohio State University, Columbus, Ohio 43210, USA

41Okayama University, Okayama 700-8530, Japan

42Osaka City University, Osaka 588, Japan

43University of Oxford, Oxford OX1 3RH, United Kingdom

44aIstituto Nazionale di Fisica Nucleare, Sezione di Padova-Trento, I-35131 Padova, Italy

44bUniversity of Padova, I-35131 Padova, Italy

45LPNHE, Universite Pierre et Marie Curie/IN2P3-CNRS, UMR7585, Paris, F-75252 France

46University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

47aIstituto Nazionale di Fisica Nucleare Pisa, I-56127 Pisa, Italy

47bUniversity of Pisa, I-56127 Pisa, Italy

47cUniversity of Siena, I-56127 Pisa, Italy

47dScuola Normale Superiore, I-56127 Pisa, Italy

48University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA

49Purdue University, West Lafayette, Indiana 47907, USA

50University of Rochester, Rochester, New York 14627, USA

51The Rockefeller University, New York, New York 10021, USA

52aIstituto Nazionale di Fisica Nucleare, Sezione di Roma 1, I-00185 Roma, Italy

52bSapienza Universita` di Roma, I-00185 Roma, Italy

53Rutgers University, Piscataway, New Jersey 08855, USA

54Texas A&M University, College Station, Texas 77843, USA

55aIstituto Nazionale di Fisica Nucleare Trieste/Udine, I-34100 Trieste, Italy

55bUniversity of Trieste/Udine, I-33100 Udine, Italy

56University of Tsukuba, Tsukuba, Ibaraki 305, Japan

57Tufts University, Medford, Massachusetts 02155, USA

58Waseda University, Tokyo 169, Japan

59Wayne State University, Detroit, Michigan 48201, USA

60University of Wisconsin, Madison, Wisconsin 53706, USA

61Yale University, New Haven, Connecticut 06520, USA (Received 22 December 2008; published 17 July 2009)

We search for new charmless decays of neutralbhadrons to pairs of charged hadrons, using1 fb¹of data collected by the CDF II detector at the Fermilab Tevatron. We report the first observation of the B⁰s !K^þdecay and measureBðB⁰s !K^þÞ ¼ð5:00:7ðstatÞ 0:8ðsystÞÞ10⁶. We also report the first observation of charmless b-baryon decays, and measure Bð⁰_b!pÞ ¼ð3:50:6ðstatÞ 0:9ðsystÞÞ10⁶ andBð⁰_b!pKÞ ¼ð5:60:8ðstatÞ 1:5ðsystÞÞ10⁶. No evidence is found for other modes, and we set the limitBðB⁰s !^þÞ<1:210⁶at 90% C.L.

DOI:10.1103/PhysRevLett.103.031801 PACS numbers: 13.25.Hw, 14.40.Nd

Two-body nonleptonic charmless decays of b hadrons are among the most widely studied processes in flavor physics. The variety of open channels involving similar final states provides crucial experimental information to improve the accuracy of effective models of strong inter- action dynamics. The quark-level transitionb!umakes decay amplitudes sensitive to, the least known angle of the quark-mixing (Cabibbo-Kobayashi-Maskawa, CKM) matrix. Significant contributions from higher-order (‘‘pen- guin’’) transitions provide sensitivity to the possible pres- ence of new physics in internal loops, if the observed decay rates are inconsistent with expectations.

Rich experimental data are currently available forB^þ and B⁰ mesons, produced in large quantities in ð4SÞ decays [1], while much less is experimentally known about the charmless decay modes of theB⁰_s, which are expected to exhibit an equally rich phenomenology. Information fromB⁰_sdecays is needed to better constrain the phenome- nological models of hadronic amplitudes in heavy flavor decays. This would lead to increased precision in compar- ing data to predictions, allowing extraction of CKM pa- rameters from non-tree-level amplitudes [2] and greater sensitivity to new physics contributions.

Of the possibleB⁰s decay modes into pairs of charmless pseudoscalar mesons, only B⁰s!K^þK has been ob- served to date [3]. TheB⁰s !K^þmode is of particular interest, because its branching fraction is sensitive to the CKM angle[4] and the current experimental bound [3] is lower than most predictions [5–7].

A measurement of the branching fraction of theB⁰_s ! ^þ mode, along with the B⁰ !K^þK mode, would allow a determination of the strength of penguin- annihilation amplitudes [8], which is currently poorly known and a source of significant uncertainty in many calculations [6]. The present search is sensitive to both modes. Two-body charmless decays are also expected from bottom baryons. The modes⁰_b!pK and⁰_b!p are predicted to have measurable branching fractions, of order 10⁶ [9], and, in addition to the interest in their observation, must be considered as a possible background to the rareB⁰_s andB⁰ modes being investigated.

In this Letter we report the results of a search for rare decays of neutral bottom hadrons into a pair of charged charmless hadrons (p,K, or), performed in1 fb¹ofpp collisions at ffiffiffi

ps

¼1:96 TeV, collected by the upgraded Collider Detector (CDF II) at the Fermilab Tevatron. We report the first observation of modesB⁰s !K^þ,⁰_b ! pK, and ⁰_b!p, and measure their relative branch- ing fractions [10].

CDF II is a multipurpose magnetic spectrometer sur- rounded by calorimeters and muon detectors [11,12]. The resolution on transverse momentum of charged particles is

_pT=p²_T 0:15%=ðGeV=cÞ, corresponding to a typical mass resolution of22 MeV=c²for our signals. The specific ionization energy loss (dE=dx) of charged particles can be measured from the charge collected by the drift chamber (COT), and provides 1:5 separation between kaons and pions with momenta greater than2 GeV=c. The data were collected by a three-level trigger system [13], using a set of requirements specifically aimed at selecting two-pronged B decays [3]. Two opposite-charge particles are required, with reconstructed transverse momenta p_T1, p_T2>

2 GeV=c, the scalar sum p_T1þp_T2>5:5 GeV=c, and an azimuthal opening angle <135. The impact pa- rameterd(distance of closest approach to the beam line) of the two tracks is required to be0:1< d <1:0 mm, reduc- ing the light-quark background by 2 orders of magnitude while preserving about half of the signal. An opening- angle requirement 20< <135, preferentially se- lects two-body B decays over multibody decays with 97% efficiency and further reduces background. Each track pair is then used to form aBcandidate, which is required to have an impact parameterdB<140mand to have trav- eled a distanceL_T >200min the transverse plane. The overall acceptance of the trigger selection is 2% forb hadrons withp_T>4 GeV=candjj<1.

The offline selection is based on a more accurate deter- mination of the same quantities used in the trigger, with the addition of two further observables: the isolation (I_B) of the Bcandidate [14], and the quality of the three-dimensional fit (²with 1 d.o.f.) of the decay vertex of theBcandidate.

Requiring a large value ofIBreduces the background from light-quark jets, and a low²reduces the background from decays of different long-lived particles within the event, owing to the good resolution of the SVX detector in the zdirection. The selection is optimized for detection of the B⁰s!K^þ mode. Maximal sensitivity for both discov- ery and limit setting is achieved with a single choice of selection requirements [15] by minimizing the variance of the estimate of the branching fraction in the absence of signal [16]. The variance is evaluated by performing the full measurement procedure on simulated samples contain- ing background and all signals from the known modes, but noB⁰_s !K^þsignal. The background fraction for each selection is determined from data by extrapolating the mass sidebands of the signal, and the signal yield is pre- dicted by a detailed detector simulation. This procedure yields the final selection: IB>0:525, ²<5, d >

120m,dB<60m, andLT>350m.

No more than oneB candidate per event is found after this selection, and a mass (m) is assigned to each, using a charged pion mass assignment for both decay products.

The resulting mass distribution is shown in Fig.1. A large peak is visible, dominated by the overlapping contributions

031801-4

of the B⁰ !K^þ, B⁰ !^þ, and B⁰s !K^þK modes as seen in Ref. [3]. A B⁰!K^þK signal would appear as an enhancement around 5:18 GeV=c², while signals for the other modes of this search are expected at masses higher than the main peak (5:33–5:55 GeV=c²).

Backgrounds include misreconstructed multibody b-hadron decays (physics background) and random pairs of charged particles (combinatorial background).

We used an unbinned likelihood fit, incorporating kine- matic (kin) and particle identification (PID) information, to determine the fraction of each individual mode in our sample. The likelihood for theith event is

Li¼ ð1bÞX

j

fjL^kin_j L^PID_j þbðfpL^kinp L^PIDp

þ ð1fpÞL^kin_c L^PID_c Þ; (1) where the indexjruns over all signal modes, and the index

‘‘p’’ (‘‘c’’) labels the physics (combinatorial) background terms. Thefjare the signal fractions to be determined by the fit, together with the background fraction parametersb andfp.

The kinematic information is summarized by three loosely correlated observables: (a) the massm; (b) the signed momentum imbalance¼ ð1p1=p2Þq1, where p1(p2) is the lower (higher) of the particle momenta, and q1is the sign of the charge of the particle of momentump1; (c) the scalar sum of particle momenta ptot¼p1þp2. The above variables allow evaluation of the invariant

mass m₁₂ of a candidate for any mass assignment of the decay products (m₁,m₂), using the equation

m²₁₂¼m²2m²þm²₁þm²₂2 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi p²₁þm²

q ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

p²₂þm² q

þ2 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi p²₁þm²₁

q ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

p²₂þm²₂ q

; (2)

wherep1 ¼^1jj_2jjptot,p2¼_2jj¹ ptot.

We used the mass sidebands in data (m2

½5:00;5:12 [ ½5:6;6:2 GeV=c²) to obtain the kinematic distributions of backgrounds [16]. The mass distribution of the combinatorial background is parametrized by an exponential function, while the physics background is modeled by an ARGUS function [17] convoluted with a Gaussian resolution function. In order to ensure the relia- bility of the search for small signals in the vicinity of larger peaks, the shapes of the mass distributions assigned to each signal have been modeled in detail, including momentum dependence and non-Gaussian resolution tails from a full detector simulation, and the effects of soft photon radiation in the final state [16,18]. This resolution model describes very accurately the observed shape of the D⁰ !K^þ signal in a sample of 1:510⁶ D^þ!D^0þ decays, collected with a similar trigger selection. The D^þ! D^0þ sample was also used to calibrate the dE=dx re- sponse of the drift chamber to kaons and pions, using the charge of the pion fromD^þdecay to identify theD⁰decay products. ThedE=dxresponse of protons was determined from a sample of about 124 000 ⁰ !p decays. The model of the background allows for pion, kaon, proton, and electron components, whose fractions are determined by the fit. Muons are indistinguishable from pions with the available 10% fractional dE=dx resolution and are there- fore incorporated into the pion component.

From the signal fractions returned by the likelihood fit we calculate the signal yields shown in Table I. The significance of each signal is evaluated as the ratio of the yield observed in data, and its total uncertainty (statistical and systematic) as determined from a simulation where the size of that signal is set to zero. This evaluation assumes a Gaussian distribution of yield estimates, supported by the results obtained from repeated fits to simulated samples.

We obtain significant signals for the B⁰_s !K^þ mode (8:2), and for the ⁰_b!p (6:0) and ⁰_b!pK TABLE I. Yields and significances of rare mode signals. The first quoted uncertainty is statistical, the second is systematic.

Mode Ns Significance

B⁰s !K^þ 2303416 8:2

B⁰s !^þ 261614 <3 B⁰!K^þK 612535 <3

⁰_b !pK 1562011 11:5

⁰_b !p 1101816 6:0

] c

mass [GeV/

π π Invariant

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 2

c Candidates per 20 MeV/

102

103

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 102

103

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 102

103

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 102

103

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 102

103

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 102

103

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 102

103

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 102

103

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 102

103

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 102

103

] c

π π Invariant

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 2

c Candidates per 20 MeV/

102

103

π-

K+

→ B0

K-

K+

→

s

B0

π-

π+

→ B0

π+

K-

→

s

B0

pK-

→

b

Λ0

π-

→p

b

Λ0

K-

K+

→ B0

π-

π+

→

s

B0

combinatorial backg.

decays B multibody data

total

FIG. 1 (color online). Mass distribution of the 8286 recon- structed candidates. The charged pion mass is assigned to both tracks. The total projection and projections of each signal and background component of the likelihood fit are overlaid on the data distribution. Signals and multibodyBbackground compo- nents are shown stacked on the combinatorial background com- ponent.

(11:5) modes. No evidence is found for the modesB⁰s ! ^þorB⁰ !K^þK, in agreement with expectations of significantly smaller branching fractions.

To avoid large uncertainties associated with production cross sections and absolute reconstruction efficiency, we measure all branching fractions relative to the B⁰ ! K^þ mode. Results are listed in Table II. Frequentist upper limits [21] at the 90% C.L. are quoted for the unseen modes. For the measurement of⁰_bbranching fractions, the additional requirementpTð⁰_bÞ>6 GeV=cwas applied to allow easy comparison with other⁰_bmeasurements at the Tevatron, which are only available above this threshold [19,22]. This additional requirement lowers the⁰_byields by about 20%.

The raw fractions returned by the fit were corrected for the differences in selection efficiencies between different modes, which range from 8% to 40% for the measurements of b mesons and ⁰_b branching fractions, respectively.

These corrections were determined from detailed detector simulation, with the following exceptions that were mea- sured from data: the momentum-averaged relative isolation efficiency betweenB⁰s and B⁰,1:000:03, has been de- termined from fully reconstructed samples of B⁰s ! J=c, and B⁰ !J=cK⁰ decays [16]; the difference in efficiency for triggering on kaons and pions due to the different specific ionization in the COT (a 5% effect) was measured from a sample ofD^þ!K^þþ decays triggered on two tracks, using the unbiased third track [23].

Possible differences in efficiency of the isolation require- ment between B⁰ and ⁰_b, and in the trigger efficiency between kaons and protons, were taken into account in the systematic uncertainties.

The dominant contributions to the systematic uncer- tainty are the uncertainty on the combinatorial background model and the uncertainty on the dE=dx calibration and parametrization. Other contributions come from trigger efficiencies, physics background shape and kinematics,b hadron masses and lifetimes, and the possible polarization of⁰_bdecays. Details of the systematic uncertainties can be found in Ref. [16].

Absolute branching fractions are also quoted in TableII, by normalizing to world-average values of production fractions and BðB⁰!K^þÞ [20]. The branching frac- tion measured for theB⁰s !K^þmode is consistent with the previous upper limit (<5:610⁶at 90% C.L.), based on a subsample of the current data [3]. This agrees with the prediction in Ref. [24], but it is lower than most other predictions [5,6,25]. The B⁰s!^þ upper limit im- proves and supersedes the previous best limit [3]. The present measurement ofBðB⁰ !K^þKÞ is in agreement with other existing measurements and has a similar reso- lution [20], but the resulting upper limit is weaker due to the observed central value. The sensitivity to both B⁰! K^þKandB⁰_s !^þ is now close to the upper end of the theoretically expected range [5–7,26]. We also report the first branching fraction measurements of charmlessb

decays. They are significantly lower than the previous upper limit of 2:310⁵ [27], and in reasonable agree- ment with predictions [9], thus excluding the possibility of large [Oð10²Þ] enhancements from R-parity violating supersymmetric scenarios [28]. Their ratio can be deter- mined directly from our data with greater accuracy than the individual values. For this purpose, the additional p_T>

6 GeV=crequirement is not necessary, and we can exploit the full sample size, obtaining Bð⁰_b!pÞ=Bð⁰_b! pKÞ ¼0:660:140:08, in good agreement with the predicted range 0.60–0.62 [9].

In summary, we have searched for rare charmless decay modes of neutralbhadrons into pairs of charged hadrons in CDF data. We report the first observation of the modes B⁰s!K^þ, ⁰_b!p, and ⁰_b!pK, and measure their relative branching fractions. We set upper limits on the unobserved modesB⁰!K^þK andB⁰s !^þ.

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

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 TABLE II. Measured relative branching fractions of rare modes. The ratiof=fd is pT dependent [19], and is defined here as f=fd¼ðpp!⁰_bX;pT>6 GeV=c;jj<1Þ=ðpp!B⁰X;pT>6 GeV=c;jj<1Þ. Absolute branching fractions were de- rived by normalizing to the current world-average valueBðB⁰!K^þÞ ¼ ð19:40:6Þ 10⁶, and assuming the average values at high energy for the production fractions:fs=fd ¼0:2760:034, andf=fd¼0:2300:052[20]. The first quoted uncertainty is statistical, the second is systematic.

Mode RelativeB AbsoluteBð10⁶Þ

B⁰s !K^{þ f}_f^s_d^BðB_BðB^0s0^!K!K^þþÞÞ¼0:0710:0100:007 5:00:70:8

B⁰s !^{þ f}_f^s_d^BðB_BðB^0s0!K^!þþÞÞ¼0:0070:0040:005 0:490:280:36(<1:2at 90% C.L.) B⁰!K^þK ^BðB_BðB⁰0^!K!K^þþKÞ^Þ¼0:0200:0080:006 0:390:160:12(<0:7at 90% C.L.) ⁰_b!pK ^f_{fd BðB}^Bð0^0b!K^!pKþÞÞ¼0:0660:0090:008 5:60:81:5

⁰_b!p ^f_{fd BðB}^Bð0^0b!K^!pþÞÞ¼0:0420:0070:006 3:50:60:9

031801-6

Council of Canada; the National Science Council of the Republic of China; the Swiss National Science Founda- tion; the A. P. Sloan Foundation; the Bundesministerium fu¨r Bildung und Forschung, Germany; the Korean Science and Engineering Foundation and the Korean Research Foundation; the Science and Technology Facilities Council and the Royal Society, U.K.; the Institut National de Physique Nucleaire et Physique des Particules/CNRS; the Russian Foundation for Basic Research; the Ministerio de Ciencia e Innovacio´n, and Programa Consolider-Ingenio 2010, Spain; the Slovak R&D Agency; and the Academy of Finland.

aDeceased.

bVisitor from University of Massachusetts Amherst, Amherst, MA 01003, USA.

cVisitor from Universiteit Antwerpen, B-2610 Antwerp, Belgium.

dVisitor from University of Bristol, Bristol BS8 1TL, United Kingdom.

eVisitor from Chinese Academy of Sciences, Beijing 100864, China.

fVisitor from Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari, 09042 Monserrato (Cagliari), Italy.

gVisitor from University of California Irvine, Irvine, CA 92697, USA.

hVisitor from University of California, Santa Cruz, Santa Cruz, CA 95064, USA.

iVisitor from Cornell University, Ithaca, NY 14853, USA.

jVisitor from University of Cyprus, Nicosia CY-1678, Cyprus.

kVisitor from University College Dublin, Dublin 4, Ireland.

lVisitor from University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.

mVisitor from Universidad Iberoamericana, Mexico D.F., Mexico.

nVisitor from Queen Mary, University of London, London, E1 4NS, United Kingdom.

oVisitor from University of Manchester, Manchester M13 9PL, United Kingdom.

pVisitor from Nagasaki Institute of Applied Science, Nagasaki, Japan.

qVisitor from University of Notre Dame, Notre Dame, IN 46556, USA.

rVisitor from University de Oviedo, E-33007 Oviedo, Spain.

sVisitor from Texas Tech University, Lubbock, TX 79409, USA.

tVisitor from IFIC (CSIC-Universitat de Valencia), 46071 Valencia, Spain.

uVisitor from University of Virginia, Charlottesville, VA 22904, USA.

vVisitor from Bergische Universita¨t Wuppertal, 42097 Wuppertal, Germany.

wOn leave from J. Stefan Institute, Ljubljana, Slovenia.

[1] B. Aubertet al.(BABARCollaboration), Phys. Rev. D75, 012008 (2007); S.-W. Lin et al. (Belle Collaboration), Phys. Rev. Lett. 99, 121601 (2007); A. Bornheim et al.

(CLEO Collaboration), Phys. Rev. D68, 052002 (2003).

[2] R. Fleischer, Phys. Lett. B459, 306 (1999); A. Soni and D. A. Suprun, Phys. Rev. D75, 054006 (2007).

[3] A. Abulenciaet al.(CDF Collaboration), Phys. Rev. Lett.

97, 211802 (2006).

[4] M. Gronau and J. L. Rosner, Phys. Lett. B 482, 71 (2000).

[5] J.-F. Sun, G.-H. Zhu, and D.-S. Du, Phys. Rev. D 68, 054003 (2003).

[6] M. Beneke and M. Neubert, Nucl. Phys. B675, 333 (2003).

[7] A. Aliet al., Phys. Rev. D76, 074018 (2007); X.-Q. Yu, Y. Li, and C.-D. Lu, Phys. Rev. D71, 074026 (2005);72, 119903(E) (2005).

[8] A. J. Buras, R. Fleischer, S. Recksiegel, and F. Schwab, Nucl. Phys.B697, 133 (2004).

[9] R. Mohanta, A. K. Giri, and M. P. Khanna, Phys. Rev. D 63, 074001 (2001).

[10] Throughout this Letter, C conjugate modes are implied and branching fractions indicateCPaverages.

[11] D. Acosta et al.(CDF Collaboration), Phys. Rev. D71, 032001 (2005); A. Sill (CDF Collaboration), Nucl.

Instrum. Methods Phys. Res., Sect. A 447, 1 (2000); A.

Affolderet al., Nucl. Instrum. Methods Phys. Res., Sect. A 453, 84 (2000); T. Affolderet al., Nucl. Instrum. Methods Phys. Res., Sect. A526, 249 (2004).

[12] CDF II uses a cylindrical coordinate system in whichis the azimuthal angle,ris the radius from the nominal beam line, 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.

[13] E. Thomson et al., IEEE Trans. Nucl. Sci. 49, 1063 (2002); R. Downing et al., Nucl. Instrum. Methods Phys. Res., Sect. A 570, 36 (2007); B. Ashmanskas et al., Nucl. Instrum. Methods Phys. Res., Sect. A 518, 532 (2004).

[14] Isolation is defined as IB¼pTðBÞ=ðp_TðBÞ þP

ipTiÞ, where pTðBÞ is the transverse momentum of the B candidate, and the sum runs over all other tracks within a cone of radius 1, in - space around the B flight direction.

[15] G. Punzi, eConf C030908, MODT002 (2003).

[16] M. J. Morello, Ph.D. thesis, Scuola Normale Superiore, Pisa [Fermilab Report No. FERMILAB-THESIS-2007-57, 2007].

[17] Defined asme^cAðm=mAÞ2 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 ðm=mAÞ²

p , form<

mA. The cutoff mA and the coefficient cA were free parameters in our fit. See H. Albrecht et al. (ARGUS Collaboration), Phys. Lett. B241, 278 (1990).

[18] E. Baracchini and G. Isidori, Phys. Lett. B 633, 309 (2006).

[19] T. Aaltonenet al.(CDF Collaboration), Phys. Rev. D79, 032001 (2009).

[20] C. Amsleret al., Phys. Lett. B667, 1 (2008).

[21] G. J. Feldman and R. D. Cousins, Phys. Rev. D57, 3873 (1998).

[22] A. Abulenciaet al.(CDF Collaboration), Phys. Rev. Lett.

98, 122002 (2007).

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

[24] A. R. Williamson and J. Zupan, Phys. Rev. D74, 014003 (2006);74, 039901(E) (2006).

[25] C.-W. Chiang, M. Gronau, and J. L. Rosner, Phys. Lett. B 664, 169 (2008).

[26] Y. Li, C.-D. Lu, Z.-J. Xiao, and X.-Q. Yu, Phys. Rev. D70, 034009 (2004).

[27] D. Acosta et al.(CDF Collaboration), Phys. Rev. D72, 051104 (2005).

[28] R. Mohanta, Phys. Rev. D63, 056006 (2001).

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