Phys. Rev. D
80,
052001
(2009)
[24 pages]
Search for the neutral current top quark decay t→Zc using the ratio of Z-boson+4 jets to W-boson+4 jets production
T. Aaltonen et al. CDF Collaboration
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T. Aaltonen24, J. Adelman14, T. Akimoto56, B. Álvarez González12,m, S. Amerio44b,44a, D. Amidei35, A. Anastassov39, A. Annovi20, J. Antos15, G. Apollinari18, A. Apresyan49, T. Arisawa58, A. Artikov16, W. Ashmanskas18, A. Attal4, A. Aurisano54, F. Azfar43, P. Azzurri47b,47a, W. Badgett18, A. Barbaro-Galtieri29, V. E. Barnes49, B. A. Barnett26, V. Bartsch31, G. Bauer33, P.-H. Beauchemin34, F. Bedeschi47a, D. Beecher31, S. Behari26, G. Bellettini47b,47a, J. Bellinger60, D. Benjamin17, A. Beretvas18, J. Beringer29, A. Bhatti51, M. Binkley18, D. Bisello44b,44a, I. Bizjak31,r, R. E. Blair2, C. Blocker7, B. Blumenfeld26, A. Bocci17, A. Bodek50, V. Boisvert50, G. Bolla49, D. Bortoletto49, J. Boudreau48, A. Boveia11, B. Brau11,†, A. Bridgeman25, L. Brigliadori44a, C. Bromberg36, E. Brubaker14, J. Budagov16, H. S. Budd50, S. Budd25, S. Burke18, K. Burkett18, G. Busetto44b,44a, P. Bussey22, A. Buzatu34, K. L. Byrum2, S. Cabrera17,o, C. Calancha32, M. Campanelli36, M. Campbell35, F. Canelli14,18, A. Canepa46, B. Carls25, D. Carlsmith60, R. Carosi47a, S. Carrillo19,h, S. Carron34, B. Casal12, M. Casarsa18, A. Castro6b,6a, P. Catastini47c,47a, D. Cauz55b,55a, V. Cavaliere47c,47a, M. Cavalli-Sforza4, A. Cerri29, L. Cerrito31,i, S. H. Chang28, Y. C. Chen1, M. Chertok8, G. Chiarelli47a, G. Chlachidze18, F. Chlebana18, K. Cho28, D. Chokheli16, J. P. Chou23, G. Choudalakis33, S. H. Chuang53, K. Chung13, W. H. Chung60, Y. S. Chung50, T. Chwalek27, C. I. Ciobanu45, M. A. Ciocci47c,47a, A. Clark21, D. Clark7, G. Compostella44a, M. E. Convery18, J. Conway8, M. Cordelli20, G. Cortiana44b,44a, C. A. Cox8, D. J. Cox8, F. Crescioli47b,47a, C. Cuenca Almenar8,o, J. Cuevas12,m, R. Culbertson18, J. C. Cully35, D. Dagenhart18, M. Datta18, T. Davies22, P. de Barbaro50, S. De Cecco52a, A. Deisher29, G. De Lorenzo4, M. Dell’Orso47b,47a, C. Deluca4, L. Demortier51, J. Deng17, M. Deninno6a, P. F. Derwent18, G. P. di Giovanni45, C. Dionisi52b,52a, B. Di Ruzza55b,55a, J. R. Dittmann5, M. D’Onofrio4, S. Donati47b,47a, P. Dong9, J. Donini44a, T. Dorigo44a, S. Dube53, J. Efron40, A. Elagin54, R. Erbacher8, D. Errede25, S. Errede25, R. Eusebi18, H. C. Fang29, S. Farrington43, W. T. Fedorko14, R. G. Feild61, M. Feindt27, J. P. Fernandez32, C. Ferrazza47d,47a, R. Field19, G. Flanagan49, R. Forrest8, M. J. Frank5, M. Franklin23, J. C. Freeman18, H. J. Frisch14, I. Furic19, M. Gallinaro52a, J. Galyardt13, F. Garberson11, J. E. Garcia21, A. F. Garfinkel49, K. Genser18, H. Gerberich25, D. Gerdes35, A. Gessler27, S. Giagu52b,52a, V. Giakoumopoulou3, P. Giannetti47a, K. Gibson48, J. L. Gimmell50, C. M. Ginsburg18, N. Giokaris3, M. Giordani55b,55a, P. Giromini20, M. Giunta47b,47a, G. Giurgiu26, V. Glagolev16, D. Glenzinski18, M. Gold38, N. Goldschmidt19, A. Golossanov18, G. Gomez12, G. Gomez-Ceballos33, M. Goncharov33, O. González32, I. Gorelov38, A. T. Goshaw17, K. Goulianos51, A. Gresele44b,44a, S. Grinstein23, C. Grosso-Pilcher14, R. C. Group18, U. Grundler25, J. Guimaraes da Costa23, Z. Gunay-Unalan36, C. Haber29, K. Hahn33, S. R. Hahn18, E. Halkiadakis53, B.-Y. Han50, J. Y. Han50, F. Happacher20, K. Hara56, D. Hare53, M. Hare57, S. Harper43, R. F. Harr59, R. M. Harris18, M. Hartz48, K. Hatakeyama51, C. Hays43, M. Heck27, A. Heijboer46, B. Heinemann29, J. Heinrich46, C. Henderson33, M. Herndon60, J. Heuser27, S. Hewamanage5, D. Hidas17, C. S. Hill11,§, D. Hirschbuehl27, A. Hocker18, S. Hou1, M. Houlden30, S.-C. Hsu29, B. T. Huffman43, R. E. Hughes40, U. Husemann61, M. Hussein36, J. Huston36, J. Incandela11, G. Introzzi47a, M. Iori52b,52a, A. Ivanov8, E. James18, D. Jang13, B. Jayatilaka17, E. J. Jeon28, M. K. Jha6a, S. Jindariani18, W. Johnson8, M. Jones49, K. K. Joo28, S. Y. Jun13, J. E. Jung28, T. R. Junk18, T. Kamon54, D. Kar19, P. E. Karchin59, Y. Kato42,f, R. Kephart18, J. Keung46, V. Khotilovich54, B. Kilminster18, D. H. Kim28, H. S. Kim28, H. W. Kim28, J. E. Kim28, M. J. Kim20, S. B. Kim28, S. H. Kim56, Y. K. Kim14, N. Kimura56, L. Kirsch7, S. Klimenko19, B. Knuteson33, B. R. Ko17, K. Kondo58, D. J. Kong28, J. Konigsberg19, A. Korytov19, A. V. Kotwal17, M. Kreps27, J. Kroll46, D. Krop14, N. Krumnack5, M. Kruse17, V. Krutelyov11, T. Kubo56, T. Kuhr27, N. P. Kulkarni59, M. Kurata56, S. Kwang14, A. T. Laasanen49, S. Lami47a, S. Lammel18, M. Lancaster31, R. L. Lander8, K. Lannon40,l, A. Lath53, G. Latino47c,47a, I. Lazzizzera44b,44a, T. LeCompte2, E. Lee54, H. S. Lee14, S. W. Lee54,n, S. Leone47a, J. D. Lewis18, C.-S. Lin29, J. Linacre43, M. Lindgren18, E. Lipeles46, A. Lister8, D. O. Litvintsev18, C. Liu48, T. Liu18, N. S. Lockyer46, A. Loginov61, M. Loreti44b,44a, L. Lovas15, D. Lucchesi44b,44a, C. Luci52b,52a, J. Lueck27, P. Lujan29, P. Lukens18, G. Lungu51, L. Lyons43, J. Lys29, R. Lysak15, D. MacQueen34, R. Madrak18, K. Maeshima18, K. Makhoul33, T. Maki24, P. Maksimovic26, S. Malde43, S. Malik31, G. Manca30,††, A. Manousakis-Katsikakis3, F. Margaroli49, C. Marino27, C. P. Marino25, A. Martin61, V. Martin22,e, M. Martínez4, R. Martínez-Ballarín32, T. Maruyama56, P. Mastrandrea52a, T. Masubuchi56, M. Mathis26, M. E. Mattson59, P. Mazzanti6a, K. S. McFarland50, P. McIntyre54, R. McNulty30,d, A. Mehta30, P. Mehtala24, A. Menzione47a, P. Merkel49, C. Mesropian51, T. Miao18, N. Miladinovic7, R. Miller36, C. Mills23, M. Milnik27, A. Mitra1, G. Mitselmakher19, H. Miyake56, N. Moggi6a, C. S. Moon28, R. Moore18, M. J. Morello47b,47a, J. Morlock27, P. Movilla Fernandez18, J. Mülmenstädt29, A. Mukherjee18, Th. Muller27, R. Mumford26, P. Murat18, M. Mussini6b,6a, J. Nachtman18, Y. Nagai56, A. Nagano56, J. Naganoma56, K. Nakamura56, I. Nakano41, A. Napier57, V. Necula17, J. Nett60, C. Neu46,p, M. S. Neubauer25, S. Neubauer27, J. Nielsen29,a, L. Nodulman2, M. Norman10, O. Norniella25, E. Nurse31, L. Oakes43, S. H. Oh17, Y. D. Oh28, I. Oksuzian19, T. Okusawa42, R. Orava24, K. Osterberg24, S. Pagan Griso44b,44a, E. Palencia18, V. Papadimitriou18, A. Papaikonomou27, A. A. Paramonov14, B. Parks40, S. Pashapour34, J. Patrick18, G. Pauletta55b,55a, M. Paulini13, C. Paus33, T. Peiffer27, D. E. Pellett8, A. Penzo55a, T. J. Phillips17, G. Piacentino47a, E. Pianori46, L. Pinera19, K. Pitts25, C. Plager9, L. Pondrom60, O. Poukhov16,*, N. Pounder43, F. Prakoshyn16, A. Pronko18, J. Proudfoot2, F. Ptohos18,c, E. Pueschel13, G. Punzi47b,47a, J. Pursley60, J. Rademacker43,§, A. Rahaman48, V. Ramakrishnan60, N. Ranjan49, I. Redondo32, P. Renton43, M. Renz27, M. Rescigno52a, S. Richter27, F. Rimondi6b,6a, L. Ristori47a, A. Robson22, T. Rodrigo12, T. Rodriguez46, E. Rogers25, S. Rolli57, R. Roser18, M. Rossi55a, R. Rossin11, P. Roy34, A. Ruiz12, J. Russ13, V. Rusu18, B. Rutherford18, H. Saarikko24, A. Safonov54, W. K. Sakumoto50, O. Saltó4, L. Santi55b,55a, S. Sarkar52b,52a, L. Sartori47a, K. Sato18, A. Savoy-Navarro45, P. Schlabach18, A. Schmidt27, E. E. Schmidt18, M. A. Schmidt14, M. P. Schmidt61,*, M. Schmitt39, T. Schwarz8, L. Scodellaro12, A. Scribano47c,47a, F. Scuri47a, A. Sedov49, S. Seidel38, Y. Seiya42, A. Semenov16, L. Sexton-Kennedy18, F. Sforza47a, A. Sfyrla25, S. Z. Shalhout59, T. Shears30, P. F. Shepard48, M. Shimojima56,k, S. Shiraishi14, M. Shochet14, Y. Shon60, I. Shreyber37, A. Sidoti47a, P. Sinervo34, A. Sisakyan16, A. J. Slaughter18, J. Slaunwhite40, K. Sliwa57, J. R. Smith8, F. D. Snider18, R. Snihur34, A. Soha8, S. Somalwar53, V. Sorin36, J. Spalding18, T. Spreitzer34, P. Squillacioti47c,47a, M. Stanitzki61, R. St. Denis22, B. Stelzer34, O. Stelzer-Chilton34, D. Stentz39, J. Strologas38, G. L. Strycker35, D. Stuart11, J. S. Suh28, A. Sukhanov19, I. Suslov16, T. Suzuki56, A. Taffard25,‡‡, R. Takashima41, Y. Takeuchi56, R. Tanaka41, M. Tecchio35, P. K. Teng1, K. Terashi51, J. Thom18,b, A. S. Thompson22, G. A. Thompson25, E. Thomson46, P. Tipton61, P. Ttito-Guzmán32, S. Tkaczyk18, D. Toback54, S. Tokar15, K. Tollefson36, T. Tomura56, D. Tonelli18, S. Torre20, D. Torretta18, P. Totaro55b,55a, S. Tourneur45, M. Trovato47a, S.-Y. Tsai1, Y. Tu46, N. Turini47c,47a, F. Ukegawa56, S. Vallecorsa21, N. van Remortel24,‡, A. Varganov35, E. Vataga47d,47a, F. Vázquez19,h, G. Velev18, C. Vellidis3, M. Vidal32, R. Vidal18, I. Vila12, R. Vilar12, T. Vine31, M. Vogel38, I. Volobouev29,n, G. Volpi47b,47a, P. Wagner46, R. G. Wagner2, R. L. Wagner18, W. Wagner27,q, J. Wagner-Kuhr27, T. Wakisaka42, R. Wallny9, S. M. Wang1, A. Warburton34, D. Waters31, M. Weinberger54, J. Weinelt27, W. C. Wester, III18, B. Whitehouse57, D. Whiteson46,‡‡, A. B. Wicklund2, E. Wicklund18, S. Wilbur14, G. Williams34, H. H. Williams46, P. Wilson18, B. L. Winer40, P. Wittich18,b, S. Wolbers18, C. Wolfe14, T. Wright35, X. Wu21, F. Würthwein10, S. Xie33, A. Yagil10, K. Yamamoto42, J. Yamaoka17, U. K. Yang14,j, Y. C. Yang28, W. M. Yao29, G. P. Yeh18, J. Yoh18, K. Yorita58, T. Yoshida42,g, G. B. Yu50, I. Yu28, S. S. Yu18, J. C. Yun18, L. Zanello52b,52a, A. Zanetti55a, X. Zhang25, Y. Zheng9,**, and S. Zucchelli6b,6a (CDF Collaboration)
1Institute of Physics, Academia Sinica, Taipei, Taiwan 11529, Republic of China
2Argonne National Laboratory, Argonne, Illinois 60439
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
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 für Experimentelle Kernphysik, Universität 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, USA
34Institute of Particle Physics: McGill University, Montréal, Québec, 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 Università di Roma, I-00185 Roma, Italy
53Rutgers University, Piscataway, New Jersey 08855
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 4 May 2009; published 8 September 2009
We have used the Collider Detector at Fermilab (CDF-II) to search for the flavor-changing neutral-current (FCNC) top-quark decay t→Zc using a technique employing ratios of W and Z production, measured in pp̅ data corresponding to an integrated luminosity of 1.52 fb-1. The analysis uses a comparison of two decay chains, pp̅ →tt̅ →WbWb→ℓνbjjb and pp̅ →tt̅ →ZcWb→ℓℓcjjb, to cancel systematic uncertainties in acceptance, efficiency, and luminosity. We validate the modeling of acceptance and efficiency for lepton identification over the multiyear data set using another ratio of W and Z production, in this case the observed ratio of inclusive production of W to Z bosons. To improve the discrimination against standard model backgrounds to top-quark decays, we calculate the top-quark mass for each event with two leptons and four jets assuming it is a tt̅ event with one of the top quarks decaying to Zc. For additional background discrimination we require at least one jet to be identified as originating from a b quark. No significant signal is found and we set an upper limit on the FCNC branching ratio Br(t→Zc) using a likelihood constructed from the ℓℓcjjb top-quark mass distribution and the number of ℓνbjjb events. Limits are set as a function of the helicity of the Z boson produced in the FCNC decay. For 100% longitudinally-polarized Z bosons we find limits of 8.3% and 9.3% (95% C.L.) depending on the assumptions regarding the theoretical top-quark pair production cross section.
© 2009 The American Physical Society
URL:
http://link.aps.org/doi/10.1103/PhysRevD.80.052001
DOI:
10.1103/PhysRevD.80.052001
PACS:
13.85.Rm, 12.60.Cn, 13.85.Qk, 14.65.Ha
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