Top-Quark Mass Measurement from Dilepton Events at CDF II

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Top-Quark Mass Measurement from Dilepton Events at CDF II

CDF Collaboration

CAMPANELLI, Mario (Collab.), et al.

Abstract

We report a measurement of the top-quark mass using events collected by the CDF II detector from pp collisions at s√=1.96  TeV at the Fermilab Tevatron. We calculate a likelihood function for the top-quark mass in events that are consistent with tt→bℓ−νℓbℓ'+ν′ℓ decays. The likelihood is formed as the convolution of the leading-order matrix element and detector resolution functions. The joint likelihood is the product of likelihoods for each of 33 events collected in 340  pb−1 of integrated luminosity, yielding a top-quark mass Mt=165.2±6.1(stat)±3.4(syst)  GeV/c2. This first application of a matrix-element technique to tt→bℓ+νℓbℓ'−ν¯ℓ′ decays gives the most precise single measurement of Mt in dilepton events.

Combined with other CDF run II measurements using dilepton events, we measure Mt=167.9±5.2(stat)±3.7(syst)  GeV/c2.

CDF Collaboration, CAMPANELLI, Mario (Collab.), et al . Top-Quark Mass Measurement from Dilepton Events at CDF II. Physical Review Letters , 2006, vol. 96, no. 15, p. 152002

DOI : 10.1103/PhysRevLett.96.152002

Available at:

http://archive-ouverte.unige.ch/unige:38321

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

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Top-Quark Mass Measurement from Dilepton Events at CDF II

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,¹⁷K. Kordas,¹⁸A. Korytov,¹⁷A. V. Kotwal,¹⁵A. Kovalev,⁴³J. Kraus,²³ I. Kravchenko,³¹M. Kreps,²⁵A. Kreymer,¹⁶J. Kroll,⁴³N. Krumnack,⁴M. Kruse,¹⁵V. Krutelyov,⁵¹S. E. Kuhlmann,² Y. Kusakabe,⁵⁵S. Kwang,¹³A. T. Laasanen,⁴⁶S. Lai,³²S. Lami,⁴⁸S. Lami,⁴⁸S. Lammel,¹⁶M. Lancaster,³⁰R. L. Lander,⁷ K. Lannon,³⁸A. 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,¹⁶T. Maki,²²P. Maksimovic,²⁴G. Manca,²⁹F. Margaroli,⁵R. Marginean,¹⁶

C. Marino,²³A. Martin,⁵⁸M. Martin,²⁴V. Martin,³⁷M. Martı´nez,³T. Maruyama,⁵³H. Matsunaga,⁵³M. E. Mattson,⁵⁶ R. Mazini,³²P. 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, D. Naumov, V. Necula, C. Neu, M. S. Neubauer, J. Nielsen, T. Nigmanov, L. Nodulman, 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,⁴⁴A. Sill,¹⁶P. Sinervo,³²A. Sisakyan,¹⁴J. Sjolin,⁴¹ A. Skiba,²⁵A. 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,⁴⁴X. Zhang,²³ J. 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

21Harvard University, Cambridge, Massachusetts 02138, USA

152002-2

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, Korea;

Seoul National University, Seoul 151-742, Korea;

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 of Rome ‘‘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 27 December 2005; published 18 April 2006)

We report a measurement of the top-quark mass using events collected by the CDF II detector frompp collisions at

ps

1:96 TeVat the Fermilab Tevatron. We calculate a likelihood function for the top- quark mass in events that are consistent withtt!b‘ _‘b‘⁰⁰_‘decays. The likelihood is formed as the convolution of the leading-order matrix element and detector resolution functions. The joint likelihood is the product of likelihoods for each of 33 events collected in340 pb¹of integrated luminosity, yielding a top-quark mass Mt165:26:1stat 3:4systGeV=c². This first application of a matrix-element technique tott!b‘_‘b‘ ⁰_‘⁰ decays gives the most precise single measurement ofM_t in dilepton events. Combined with other CDF run II measurements using dilepton events, we measureM_t167:9 5:2stat 3:7systGeV=c².

DOI:10.1103/PhysRevLett.96.152002 PACS numbers: 14.65.Ha, 12.15.Ff, 13.85.Ni, 13.85.Qk

Precision measurements of the top-quark massM_tplace constraints on the masses of particles to which the top- quark contributes radiative corrections, including the un- observed Higgs boson [1] and particles in extensions to the standard model [2]. At the Tevatron, top quarks are pri- marily produced in pairs. The dilepton channel, consisting

of the decays tt!b‘ _‘b‘⁰⁰_‘, has a small branching fraction but allows measurements which are less reliant on the calibration of the jet energy scale, the dominant sys- tematic uncertainty, than measurements in channels with hadronic W decays. A discrepancy from other channels could indicate contributions from new processes [3].

The reconstruction of the top-quark mass from dilep- ton events poses a particular challenge as the two neu- trinos from W decays are undetected. Previous measure- ments in this channel [4,5] using run I data have calcu- lated the mass by making several kinematic assumptions and integrating over the remaining unconstrained quan- tity. To extract maximum information from the small sam- ple of dilepton events, we adapt a technique pioneered for the analysis of tt!b‘_‘bq q⁰ decays [6 –10]. This tech- nique uses the leading-order production cross section and a parametrized description of the jet energy resolu- tion. Making minimal kinematic assumptions and integrat- ing over six unconstrained quantities, we obtain per-event likelihoods in top-quark mass which can be directly multi- plied to obtain the joint likelihood from which M_t is determined.

This Letter reports a measurement with data collected by the CDF II detector between March 2002 and August 2004, with an integrated luminosity of 340 pb¹, yielding the most precise single measurement ofM_tin dilepton events, with statistical uncertainty approximately half that of run I measurements [4,5]. We also report a combination of this measurement with other recent measurements using CDF run II data in the dilepton channel.

The CDF II detector [11,12] is an azimuthally and forward-backward symmetric apparatus designed to study pp collisions at the Fermilab Tevatron. It consists of a magnetic spectrometer surrounded by calorimeters and muon chambers. The charged particle tracking system is immersed in a 1.4 T magnetic field parallel to thepandp beams. Calorimeters segmented inandsurround the tracking system and measure the energies of interacting particles. The electromagnetic and hadronic calorimeters are lead-scintillator and iron-scintillator sampling devices.

Drift chambers located outside the central hadron calorim- eters detect muons.

The data are collected with lepton triggers that require events to have an electron or muon withp_T >18 GeV=c.

After off-line reconstruction, we select events with (i) two leptons, each withp_T>20 GeV=c, (ii) significant missing energy transverse to the beam direction (6E_T), and (iii) two jets, each with E_T>15 GeV. The selection is defined as

‘‘DIL’’ in Ref. [13] and was used to measure the cross section in the dilepton channel. These requirements yield 33 events in the sample reported in this Letter.

The probability density for tt decays is expressed as P_sxjM_t, where M_t is the top-quark pole mass and x contains the measured lepton and jet momenta. We cal- culate P_sxjM_t using the theoretical description of the tt production process expressed with respect to x, P_sxjM_t 1=M_tdM_t=dx, where ^d_dx is the dif- ferential cross section andis the total cross section.

To evaluate the probability density, we integrate the leading-order matrix element over quantities which are not directly measured by the detector, i.e., neutrino and quark energies. We assume that lepton momenta are per- fectly measured, that quark angles are perfectly measured by the corresponding jets, and that the two most energetic jets correspond to the b quarks from top-quark decay.

Quark energies, while not directly measured, are esti- mated from the observed energies of the corresponding jets. We define the transfer function Wp; j to be the probability of measuring jet energy jgiven quark energy p. We approximate Wp; j as a sum of two Gaussians fitted to the predicted distribution of quark-jet energy difference from tt events generated with HERWIG [14]

and the CDF II detector simulation [15]. The expression for the probability density at a given mass for a specific event can be written as

P_sxjM_t 1 M_t

Z djMttq_i; p_i;M_tj²Y

jets

Wp_i; j_if_PDFq₁f_PDFq₂; (1)

where the integral is over the momenta of the initial and final state particles,q₁ andq₂ are the incoming momenta, p_i are the outgoing momenta, f_PDFq_i are the parton distribution functions (PDFs) [16], andMttq_i; p_i;M_tis the ttproduction and decay matrix element as defined in Refs. [17,18] for the process qq!tt!b‘_‘b‘ ⁰_‘⁰. While up to 15% ofttpairs at the Tevatron are produced by gluon-gluon fusion (gg!tt), this term can be excluded from the matrix element with negligible effect on the measurement. The term 1=M_t in front of the integral ensures that the normalization condition for the proba- bility densityR

dxP_sxjM_t 1is satisfied. The effect of assumptions and approximations are measured in Monte Carlo experiments of fully realistic events, de- scribed below. Where needed, a correction is taken.

We calculate the probability for the dominant back- ground processes P_bgx and form the generalized per-

event probability density PxjM_t P_sxjM_tp_sM_t P_bg1xp_bg1P_bg2xp_bg2 , wherep_sM_tandp_bgi are determined from the expected fractions of signal and back- ground events, respectively (see Table I). The P_bg are calculated in analogy to Eq. (1), with the background matrix element evaluated numerically using algorithms adapted from the ALPGEN [19] generator. We calculate the probabilities for backgrounds arising from Z=! ee; plus associated jets W 3jets, where one jet is incorrectly identified as a lepton, and WWplus associ- ated jets. Smaller backgrounds, comprising 11% of the expected background, are not modeled. Application of the background probabilities reduces the expected statisti- cal uncertainty by 15%.

The posterior probability density in top-quark mass is the product of a flat Bayesian prior and the joint likelihood, 152002-4

a product of the individual event likelihoods. The mass measurement (M_t) is the mean of the posterior probability, and the statistical uncertainty (M_t) is the standard devia- tion. We calibrate the method using Monte Carlo experi- ments of signal and background events. Signal events are generated withHERWIGfor top-quark masses from 155 to 195 GeV=c². Misidentified leptons are modeled using events from the data, while all other backgrounds are generated using ALPGEN (Z= !ee; ) or PYTHIA

[20] (Z= !; WW; WZ; ZZ) Monte Carlo events.

The numbers of signal and background events in each Monte Carlo experiment are chosen according to Poisson distributions with mean values given in Table I. The esti- mates forttyields take into account the mass dependence of the cross section [21] and acceptance. The response of the method for Monte Carlo experiments with both signal and background is shown in Fig. 1. The response is con-

sistent with a linear dependence on top-quark mass but has a slope that is less than unity due to the incomplete model- ing of background contributions. Corrections M_t! 177:2 M_t178:0=0:84andM_t!M_t=0:84are de- rived from this response and applied to bothM_tandM_t measured in data.

Examining the width of the pull distributions in these Monte Carlo experiments, we find that the statistical un- certainty is underestimated by a factor of 1.51, independent of top-quark mass. This results from simplifying assump- tions described above, made to ensure the computational tractability of the integrals in Eq. (1). The largest effects are from jets which originate from initial or final state radiation rather thanb-quark hadronization, imperfect lep- ton momentum resolution, imperfect jet angle resolution, and unmodeled backgrounds. Correcting by this factor of 1.51, we estimate the mean statistical uncertainty to be 9:4 GeV=c² if M_t178 GeV=c² [22] or 7:8 GeV=c² if M_t165 GeV=c².

We apply the method described in this Letter to the 33 candidate events observed in the data. Including all corrections described above, we measure M_t165:2 6:1stat GeV=c². Figure 2 shows the joint probability density, without systematic uncertainty, for the events in our data set.

The measured statistical uncertainty is consistent with the distribution of statistical uncertainties in Monte Carlo experiments where signal events with M_t165 GeV=c² are chosen according to a Poisson distribution with mean N_tt21:7events. This number of events corresponds to the cross section and acceptance atM_t165 GeV=c². Of

2

] [GeV/c M

155 160 165 170 175 180 185 190 195 2

] [GeV/c M

155 160 165 170 175 180 185 190 195

]

[GeV/c

Mean Measured M

155 160 165 170 175 180 185 190 195

t Herwig t

× s

0)

t-M 178 + (M

± 0.2

=177.2 M0

0.02

± s=0.84

FIG. 1 (color online). Mean measured M_t in Monte Carlo experiments of signal and background events at varying top- quark mass. The solid line is a linear fit to the points.

TABLE I. Expected numbers of signal and background events for a data sample of integrated luminosity of340 pb¹. Other backgrounds are negligible; all numbers have an additional correlated 6% error from uncertainty in the sample luminosity.

Source Events

Expectedtt(M_t178 GeV=c²,6:1 pb) 15:91:4

Expected background 10:51:9

Drell-Yan (Z=) 5:51:3

Misidentified lepton 3:51:4

Diboson (WW=WZ) 1:60:2

Total expected 26:42:3

Run II data 33

2

] [GeV/c M

145 150 155 160 165 170 175 180 185 2

] [GeV/c M

145 150 155 160 165 170 175 180 185

Joint Pobability Density

0 0.005 0.01 0.015

FIG. 2 (color online). Joint posterior probability density as a function of the top-quark mass for the 33 candidate events in data, after all corrections. Systematic uncertainties are not shown.

these Monte Carlo experiments, 17% yielded a statistical uncertainty less than6:1 GeV=c².

There are several sources of systematic uncertainty in our measurement which are summarized in Table II. The largest is due to the uncertainty in the jet energy scale [23], which we estimate at 2:6 GeV=c² by varying the scale within its uncertainty. An uncertainty of 1:2 GeV=c² comes from the limited number of background events available for Monte Carlo experiments. The contribution from uncertainties in the PDFs are estimated by using different PDF sets (CTEQ5L [16] vs MRST72 [24]), differ- ent values of _QCD, varying the eigenvectors of the CTEQ6M [16] set, and varying the initial state contribu- tions of gg and qq; the total corresponding uncertainty added in quadrature is 1:0 GeV=c². Dependence on the Monte Carlo generator is estimated as the difference in the extracted top-quark mass fromPYTHIAevents andHERWIG

events; this amounts to0:8 GeV=c². We observe no differ- ence in the extracted top-quark mass in events from a leading-order and a next-to-leading-order generator [25,26]. We estimate the uncertainty coming from model- ing of the two largest sources of background, Z= and events with a misindentified lepton, to be 0:8 GeV=c². The uncertainty due to imperfect modeling of initial state (ISR) and final state (FSR) QCD radiation is estimated by varying the amount of ISR and FSR in simulated events [27] and is measured to be 0:7 GeV=c² for FSR and 0:5 GeV=c² for ISR. The uncertainty in the mass due to uncertainties in the response correction shown in Fig. 1 is 0:4 GeV=c². The contribution from uncertainties in back- ground composition is estimated by varying the back- ground estimates from Table I within their uncertainties and amounts to0:3 GeV=c². Adding all of these contribu- tions together in quadrature yields a total systematic un- certainty of3:4 GeV=c².

Applications of other dilepton techniques (referred to as

‘‘NWA,’’ ‘‘KIN,’’ and ‘‘PHI’’ in Ref. [28]) using the same CDF run II data yield values consistent with this result. The four results are combined using a standard method [29].

We determine statistical correlations between the measure- ments using Monte Carlo experiments and assume system-

atic uncertainties to be 100% correlated except the few that are method-specific, which are assumed to be uncorrelated.

Table III gives the four dilepton measurements, their sta- tistical correlations, and their weight in the combination.

The NWA method uses looser event selection and thus has a smaller statistical correlation. Correlations significantly less than unity suggest that each method extracts unique information.

Combining the four CDF run II dilepton measurements, we obtain

M_t167:95:2stat 3:7systGeV=c²: This combined result is consistent with the current world average [30] and the single most precise measurement in the leptonjets channel [31].

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 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 Particle Physics and Astronomy Re- search Council and the Royal Society, United Kingdom;

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] The LEP Collaborations, LEP Electroweak Working Group, and SLD Electroweak and Heavy Flavor Groups, Report No. CERN-PH-EP/2004-069.

[2] S. Heinemeyeret al., J. High Energy Phys. 09 (2003) 075.

[3] G. L. Kane and S. Mrenna, Phys. Rev. Lett. 77, 3502 (1996).

[4] B. Abbottet al.(D0 Collaboration), Phys. Rev. Lett.80, 2063 (1998).

t

statistical and systematic errors, their statistical correlations, and the weight of each measurement in the combined result.

Method Result (GeV=c²) Correlation matrix Weight

This Letter 165:2^6:1_6:13:4 1 0.47

NWA [28] 170:7^6:9_6:54:6 0.12 1 0.36 KIN [28] 169:5^7:7_7:24:0 0.40 0.14 1 0.18 PHI [28] 169:7^8:9_9:04:0 0.43 0.25 0.35 1 0.00

Source M_t GeV=c²

Jet energy scale 2.6

Limited background statistics 1.2

PDFs 1.0

Generator 0.8

Background modeling 0.8

FSR modeling 0.7

ISR modeling 0.5

Response correction 0.4

Sample composition uncertainty 0.3

Total 3.4

152002-6

[5] F. Abeet al.(CDF Collaboration), Phys. Rev. Lett.82, 271 (1999).

[6] G. Goldstein, K. Sliwa, and R. H. Dalitz, Phys. Rev. D47, 967 (1993).

[7] K. Kondo, J. Phys. Soc. Jpn.57, 4126 (1988).

[8] J. Estrada, Ph.D. thesis, University of Rochester, 2001.

[9] V. Abazovet al.(D0 Collaboration), Nature (London)429, 638 (2004).

[10] F. Canelli, Ph.D. thesis, University of Rochester, 2003.

[11] D. Acosta et al. (CDF Collaboration), Phys. Rev. D 71, 032001 (2005).

[12] CDF uses a cylindrical coordinate system with thezaxis along the proton beam axis. Pseudorapidity is lntan=2, where is the polar angle and is the azimuthal angle relative to the proton beam direction, whilepT jpjsin,ETEsin.

[13] D. Acostaet al.(CDF Collaboration), Phys. Rev. Lett.93, 142001 (2004).

[14] G. Corcella et al., J. High Energy Phys. 01 (2001) 010, version 6.505.

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

A447, 1 (2000).

[16] J. Pumplinet al., J. High Energy Phys. 07 (2002) 012.

[17] G. Mahlon and S. Parke, Phys. Lett. B411, 173 (1997).

[18] G. Mahlon and S. Parke, Phys. Rev. D55, 7249 (1997).

[19] M. L. Manganoet al., J. High Energy Phys. 07 (2003) 001.

[20] T. Sjo¨strand et al., Comput. Phys. Commun. 135, 238 (2001), version 6.216.

[21] M. Cacciariet al., J. High Energy Phys. 04 (2004) 068.

[22] CDF Collaboration, D0 Collaboration, and Tevatron Electroweak Working Group, hep-ex/0404010.

[23] A. Bhattiet al., hep-ex/0510047 (to be published).

[24] A. D. Martinet al., Eur. Phys. J. C39, 155 (2005).

[25] S. Frixione and B. R. Webber, J. High Energy Phys. 06 (2002) 029.

[26] S. Frixione, P. Nason, and B. R. Webber, J. High Energy Phys. 08 (2003) 007.

[27] A. Abulenciaet al.(CDF Collaboration), Phys. Rev. D73, 032003 (2006).

[28] A. Abulenciaet al.(CDF Collaboration), Phys. Rev. D (to be published).

[29] L. Lyons, D. Gibaut, and P. Clifford, Nucl. Instrum.

Methods Phys. Res., Sect. A270, 110 (1988).

[30] CDF Collaboration, D0 Collaboration, and Tevatron Electroweak Working Group, Report No. FERMILAB- TM-2323-E.

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

96, 022004 (2006).