Measurement of the t C22 t production cross section in 2fb C01 of pC22p collisions at ??? s p ? 1:96 TeV using lepton plus jets events with soft muon b tagging T. Aaltonen, 24 J. Adelman, 14 T. Akimoto, 56 B. A ? lvarez Gonza?lez, 12,t S. Amerio, 44a,44b D. Amidei, 35 A. Anastassov, 39 A. Annovi, 20 J. Antos, 15 G. Apollinari, 18 A. Apresyan, 49 T. Arisawa, 58 A. Artikov, 16 W. Ashmanskas, 18 A. Attal, 4 A. Aurisano, 54 F. Azfar, 43 P. Azzurri, 47a,47b W. Badgett, 18 A. Barbaro-Galtieri, 29 V.E. Barnes, 49 B.A. Barnett, 26 V. Bartsch, 31 G. Bauer, 33 P.-H. Beauchemin, 34 F. Bedeschi, 47a D. Beecher, 31 S. Behari, 26 G. Bellettini, 47a,47b J. Bellinger, 60 D. Benjamin, 17 A. Beretvas, 18 J. Beringer, 29 A. Bhatti, 51 M. Binkley, 18 D. Bisello, 44a,44b I. Bizjak, 31,y R.E. Blair, 2 C. Blocker, 7 B. Blumenfeld, 26 A. Bocci, 17 A. Bodek, 50 V. Boisvert, 50 G. Bolla, 49 D. Bortoletto, 49 J. Boudreau, 48 A. Boveia, 11 B. Brau, 11,b A. Bridgeman, 25 L. Brigliadori, 44a C. Bromberg, 36 E. Brubaker, 14 J. Budagov, 16 H.S. Budd, 50 S. Budd, 25 S. Burke, 18 K. Burkett, 18 G. Busetto, 44a,44b P. Bussey, 22 A. Buzatu, 34 K.L. Byrum, 2 S. Cabrera, 17,v C. Calancha, 32 M. Campanelli, 36 M. Campbell, 35 F. Canelli, 14,18 A. Canepa, 46 B. Carls, 25 D. Carlsmith, 60 R. Carosi, 47a S. Carrillo, 19,o S. Carron, 34 B. Casal, 12 M. Casarsa, 18 A. Castro, 6a,6b P. Catastini, 47a,47c D. Cauz, 55a,55b V. Cavaliere, 47a,47c M. Cavalli-Sforza, 4 A. Cerri, 29 L. Cerrito, 31,p S.H. Chang, 28 Y.C. Chen, 1 M. Chertok, 8 G. Chiarelli, 47a G. Chlachidze, 18 F. Chlebana, 18 K. Cho, 28 D. Chokheli, 16 J.P. Chou, 23 G. Choudalakis, 33 S.H. Chuang, 53 K. Chung, 13 W.H. Chung, 60 Y.S. Chung, 50 T. Chwalek, 27 C.I. Ciobanu, 45 M.A. Ciocci, 47a,47c A. Clark, 21 D. Clark, 7 G. Compostella, 44a M.E. Convery, 18 J. Conway, 8 M. Cordelli, 20 G. Cortiana, 44a,44b C.A. Cox, 8 D.J. Cox, 8 F. Crescioli, 47a,47b C. Cuenca Almenar, 8,v J. Cuevas, 12,t R. Culbertson, 18 J.C. Cully, 35 D. Dagenhart, 18 M. Datta, 18 T. Davies, 22 P. de Barbaro, 50 S. De Cecco, 52a A. Deisher, 29 G. De Lorenzo, 4 M. Dell?Orso, 47a,47b C. Deluca, 4 L. Demortier, 51 J. Deng, 17 M. Deninno, 6a P.F. Derwent, 18 G.P. di Giovanni, 45 C. Dionisi, 52a,52b B. Di Ruzza, 55a,55b J.R. Dittmann, 5 M. D?Onofrio, 4 S. Donati, 47a,47b P. Dong, 9 J. Donini, 44a T. Dorigo, 44a S. Dube, 53 J. Efron, 40 A. Elagin, 54 R. Erbacher, 8 D. Errede, 25 S. Errede, 25 R. Eusebi, 18 H.C. Fang, 29 S. Farrington, 43 W.T. Fedorko, 14 R.G. Feild, 61 M. Feindt, 27 J.P. Fernandez, 32 C. Ferrazza, 47a,47d R. Field, 19 G. Flanagan, 49 R. Forrest, 8 M.J. Frank, 5 M. Franklin, 23 J.C. Freeman, 18 I. Furic, 19 M. Gallinaro, 52a J. Galyardt, 13 F. Garberson, 11 J.E. Garcia, 21 A.F. Garfinkel, 49 K. Genser, 18 H. Gerberich, 25 D. Gerdes, 35 A. Gessler, 27 S. Giagu, 52a,52b V. Giakoumopoulou, 3 P. Giannetti, 47a K. Gibson, 48 J.L. Gimmell, 50 C.M. Ginsburg, 18 N. Giokaris, 3 M. Giordani, 55a,55b P. Giromini, 20 M. Giunta, 47a,47b G. Giurgiu, 26 V. Glagolev, 16 D. Glenzinski, 18 M. Gold, 38 N. Goldschmidt, 19 A. Golossanov, 18 G. Gomez, 12 G. Gomez-Ceballos, 33 M. Goncharov, 33 O. Gonza?lez, 32 I. Gorelov, 38 A.T. Goshaw, 17 K. Goulianos, 51 A. Gresele, 44a,44b S. Grinstein, 23 C. Grosso-Pilcher, 14 R.C. Group, 18 U. Grundler, 25 J. Guimaraes da Costa, 23 Z. Gunay-Unalan, 36 C. Haber, 29 K. Hahn, 33 S.R. Hahn, 18 E. Halkiadakis, 53 B.-Y. Han, 50 J.Y. Han, 50 F. Happacher, 20 K. Hara, 56 D. Hare, 53 M. Hare, 57 S. Harper, 43 R.F. Harr, 59 R.M. Harris, 18 M. Hartz, 48 K. Hatakeyama, 51 C. Hays, 43 M. Heck, 27 A. Heijboer, 46 J. Heinrich, 46 C. Henderson, 33 M. Herndon, 60 J. Heuser, 27 S. Hewamanage, 5 D. Hidas, 17 C.S. Hill, 11,d D. Hirschbuehl, 27 A. Hocker, 18 S. Hou, 1 M. Houlden, 30 S.-C. Hsu, 29 B.T. Huffman, 43 R.E. Hughes, 40 U. Husemann, 61 M. Hussein, 36 J. Huston, 36 J. Incandela, 11 G. Introzzi, 47a M. Iori, 52a,52b A. Ivanov, 8 E. James, 18 D. Jang, 13 B. Jayatilaka, 17 E.J. Jeon, 28 M.K. Jha, 6a S. Jindariani, 18 W. Johnson, 8 M. Jones, 49 K.K. Joo, 28 S.Y. Jun, 13 J.E. Jung, 28 T.R. Junk, 18 T. Kamon, 54 D. Kar, 19 P.E. Karchin, 59 Y. Kato, 42,m R. Kephart, 18 J. Keung, 46 V. Khotilovich, 54 B. Kilminster, 18 D.H. Kim, 28 H.S. Kim, 28 H.W. Kim, 28 J.E. Kim, 28 M.J. Kim, 20 S.B. Kim, 28 S.H. Kim, 56 Y.K. Kim, 14 N. Kimura, 56 L. Kirsch, 7 S. Klimenko, 19 B. Knuteson, 33 B.R. Ko, 17 K. Kondo, 58 D.J. Kong, 28 J. Konigsberg, 19 A. Korytov, 19 A.V. Kotwal, 17 M. Kreps, 27 J. Kroll, 46 D. Krop, 14 N. Krumnack, 5 M. Kruse, 17 V. Krutelyov, 11 T. Kubo, 56 T. Kuhr, 27 N.P. Kulkarni, 59 M. Kurata, 56 S. Kwang, 14 A.T. Laasanen, 49 S. Lami, 47a S. Lammel, 18 M. Lancaster, 31 R.L. Lander, 8 K. Lannon, 40,s A. Lath, 53 G. Latino, 47a,47c I. Lazzizzera, 44a,44b T. LeCompte, 2 E. Lee, 54 H.S. Lee, 14 S.W. Lee, 54,u S. Leone, 47a J.D. Lewis, 18 C.-S. Lin, 29 J. Linacre, 43 M. Lindgren, 18 E. Lipeles, 46 T.M. Liss, 25 A. Lister, 8 D.O. Litvintsev, 18 C. Liu, 48 T. Liu, 18 N.S. Lockyer, 46 A. Loginov, 61 M. Loreti, 44a,44b L. Lovas, 15 D. Lucchesi, 44a,44b C. Luci, 52a,52b J. Lueck, 27 P. Lujan, 29 P. Lukens, 18 G. Lungu, 51 L. Lyons, 43 J. Lys, 29 R. Lysak, 15 D. MacQueen, 34 R. Madrak, 18 K. Maeshima, 18 K. Makhoul, 33 T. Maki, 24 P. Maksimovic, 26 S. Malde, 43 S. Malik, 31 G. Manca, 30,f A. Manousakis-Katsikakis, 3 F. Margaroli, 49 C. Marino, 27 C.P. Marino, 25 A. Martin, 61 V. Martin, 22,l M. Mart??nez, 4 R. Mart??nez-Ballar??n, 32 T. Maruyama, 56 P. Mastrandrea, 52a T. Masubuchi, 56 M. Mathis, 26 M.E. Mattson, 59 P. Mazzanti, 6a K.S. McFarland, 50 P. McIntyre, 54 R. McNulty, 30,k A. Mehta, 30 P. Mehtala, 24 A. Menzione, 47a P. Merkel, 49 C. Mesropian, 51 T. Miao, 18 N. Miladinovic, 7 R. Miller, 36 C. Mills, 23 M. Milnik, 27 A. Mitra, 1 G. Mitselmakher, 19 H. Miyake, 56 N. Moggi, 6a C.S. Moon, 28 R. Moore, 18 M.J. Morello, 47a,47b J. Morlock, 27 P. Movilla Fernandez, 18 J. Mu?lmensta?dt, 29 A. Mukherjee, 18 Th. Muller, 27 R. Mumford, 26 P. Murat, 18 M. Mussini, 6a,6b J. Nachtman, 18 Y. Nagai, 56 A. Nagano, 56 J. Naganoma, 56 K. Nakamura, 56 I. Nakano, 41 A. Napier, 57 V. Necula, 17 J. Nett, 60 C. Neu, 46,w PHYSICAL REVIEW D 79, 052007 (2009) 1550-7998=2009=79(5)=052007(25) 052007-1 C211 2009 The American Physical Society M.S. Neubauer, 25 S. Neubauer, 27 J. Nielsen, 29,h L. Nodulman, 2 M. Norman, 10 O. Norniella, 25 E. Nurse, 31 L. Oakes, 43 S.H. Oh, 17 Y.D. Oh, 28 I. Oksuzian, 19 T. Okusawa, 42 R. Orava, 24 K. Osterberg, 24 S. Pagan Griso, 44a,44b E. Palencia, 18 V. Papadimitriou, 18 A. Papaikonomou, 27 A.A. Paramonov, 14 B. Parks, 40 S. Pashapour, 34 J. Patrick, 18 G. Pauletta, 55a,55b M. Paulini, 13 C. Paus, 33 T. Peiffer, 27 D.E. Pellett, 8 A. Penzo, 55a T.J. Phillips, 17 G. Piacentino, 47a E. Pianori, 46 L. Pinera, 19 K. Pitts, 25 C. Plager, 9 L. Pondrom, 60 O. Poukhov, 16,a N. Pounder, 43 F. Prakoshyn, 16 A. Pronko, 18 J. Proudfoot, 2 F. Ptohos, 18,j E. Pueschel, 13 G. Punzi, 47a,47b J. Pursley, 60 J. Rademacker, 43,d A. Rahaman, 48 V. Ramakrishnan, 60 N. Ranjan, 49 I. Redondo, 32 P. Renton, 43 M. Renz, 27 M. Rescigno, 52a S. Richter, 27 F. Rimondi, 6a,6b L. Ristori, 47a A. Robson, 22 T. Rodrigo, 12 T. Rodriguez, 46 E. Rogers, 25 S. Rolli, 57 R. Roser, 18 M. Rossi, 55a R. Rossin, 11 P. Roy, 34 A. Ruiz, 12 J. Russ, 13 V. Rusu, 18 B. Rutherford, 18 H. Saarikko, 24 A. Safonov, 54 W.K. Sakumoto, 50 O. Salto?, 4 L. Santi, 55a,55b S. Sarkar, 52a,52b L. Sartori, 47a K. Sato, 18 A. Savoy-Navarro, 45 P. Schlabach, 18 A. Schmidt, 27 E.E. Schmidt, 18 M.A. Schmidt, 14 M.P. Schmidt, 61,a M. Schmitt, 39 T. Schwarz, 8 L. Scodellaro, 12 A. Scribano, 47a,47c F. Scuri, 47a A. Sedov, 49 S. Seidel, 38 Y. Seiya, 42 A. Semenov, 16 L. Sexton-Kennedy, 18 F. Sforza, 47a A. Sfyrla, 25 S.Z. Shalhout, 59 T. Shears, 30 P.F. Shepard, 48 M. Shimojima, 56,r S. Shiraishi, 14 M. Shochet, 14 Y. Shon, 60 I. Shreyber, 37 A. Sidoti, 47a P. Sinervo, 34 A. Sisakyan, 16 A.J. Slaughter, 18 J. Slaunwhite, 40 K. Sliwa, 57 J.R. Smith, 8 F.D. Snider, 18 R. Snihur, 34 A. Soha, 8 S. Somalwar, 53 V. Sorin, 36 J. Spalding, 18 T. Spreitzer, 34 P. Squillacioti, 47a,47b M. Stanitzki, 61 R. St. Denis, 22 B. Stelzer, 34 O. Stelzer-Chilton, 34 D. Stentz, 39 J. Strologas, 38 G.L. Strycker, 35 D. Stuart, 11 J.S. Suh, 28 A. Sukhanov, 19 I. Suslov, 16 T. Suzuki, 56 A. Taffard, 25,g R. Takashima, 41 Y. Takeuchi, 56 R. Tanaka, 41 M. Tecchio, 35 P.K. Teng, 1 K. Terashi, 51 J. Thom, 18,i A.S. Thompson, 22 G.A. Thompson, 25 E. Thomson, 46 P. Tipton, 61 P. Ttito-Guzma?n, 32 S. Tkaczyk, 18 D. Toback, 54 S. Tokar, 15 K. Tollefson, 36 T. Tomura, 56 D. Tonelli, 18 S. Torre, 20 D. Torretta, 18 P. Totaro, 55a,55b S. Tourneur, 45 M. Trovato, 47a S.-Y. Tsai, 1 Y. Tu, 46 N. Turini, 47a,47c F. Ukegawa, 56 S. Vallecorsa, 21 N. van Remortel, 24,c A. Varganov, 35 E. Vataga, 47a,47d F. Va?zquez, 19,o G. Velev, 18 C. Vellidis, 3 M. Vidal, 32 R. Vidal, 18 I. Vila, 12 R. Vilar, 12 T. Vine, 31 M. Vogel, 38 I. Volobouev, 29,u G. Volpi, 47a,47b P. Wagner, 46 R.G. Wagner, 2 R.L. Wagner, 18 W. Wagner, 27,x J. Wagner-Kuhr, 27 T. Wakisaka, 42 R. Wallny, 9 S.M. Wang, 1 A. Warburton, 34 D. Waters, 31 M. Weinberger, 54 J. Weinelt, 27 W.C. Wester III, 18 B. Whitehouse, 57 D. Whiteson, 46,g A.B. Wicklund, 2 E. Wicklund, 18 S. Wilbur, 14 G. Williams, 34 H.H. Williams, 46 P. Wilson, 18 B.L. Winer, 40 P. Wittich, 18,i S. Wolbers, 18 C. Wolfe, 14 T. Wright, 35 X. Wu, 21 F. Wu?rthwein, 10 S. Xie, 33 A. Yagil, 10 K. Yamamoto, 42 J. Yamaoka, 17 U.K. Yang, 14,q Y.C. Yang, 28 W.M. Yao, 29 G.P. Yeh, 18 J. Yoh, 18 K. Yorita, 58 T. Yoshida, 42,n G.B. Yu, 50 I. Yu, 28 S.S. Yu, 18 J.C. Yun, 18 L. Zanello, 52a,52b A. Zanetti, 55a X. Zhang, 25 Y. Zheng, 9,e and S. Zucchelli 6a,6b (CDF Collaboration) 1 Institute of Physics, Academia Sinica, Taipei, Taiwan 11529, Republic of China 2 Argonne National Laboratory, Argonne, Illinois 60439, USA 3 University of Athens, 157 71 Athens, Greece 4 Institut de Fisica d?Altes Energies, Universitat Autonoma de Barcelona, E-08193, Bellaterra (Barcelona), Spain 5 Baylor University, Waco, Texas 76798, USA 6a Istituto Nazionale di Fisica Nucleare Bologna, I-40127 Bologna, Italy 6b University of Bologna, I-40127 Bologna, Italy 7 Brandeis University, Waltham, Massachusetts 02254, USA 8 University of California, Davis, Davis, California 95616, USA 9 University of California, Los Angeles, Los Angeles, California 90024, USA 10 University of California, San Diego, La Jolla, California 92093, USA 11 University of California, Santa Barbara, Santa Barbara, California 93106, USA 12 Instituto de Fisica de Cantabria, CSIC-University of Cantabria, 39005 Santander, Spain 13 Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA 14 Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, USA 15 Comenius University, 842 48 Bratislava, Slovakia; Institute of Experimental Physics, 040 01 Kosice, Slovakia 16 Joint Institute for Nuclear Research, RU-141980 Dubna, Russia 17 Duke University, Durham, North Carolina 27708, USA 18 Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA 19 University of Florida, Gainesville, Florida 32611, USA 20 Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, I-00044 Frascati, Italy 21 University of Geneva, CH-1211 Geneva 4, Switzerland 22 Glasgow University, Glasgow G12 8QQ, United Kingdom T. AALTONEN et al. PHYSICAL REVIEW D 79, 052007 (2009) 052007-2 23 Harvard University, Cambridge, Massachusetts 02138, USA 24 Division of High Energy Physics, Department of Physics, University of Helsinki and Helsinki Institute of Physics, FIN-00014, Helsinki, Finland 25 University of Illinois, Urbana, Illinois 61801, USA 26 The Johns Hopkins University, Baltimore, Maryland 21218, USA 27 Institut fu?r Experimentelle Kernphysik, Universita?t Karlsruhe, 76128 Karlsruhe, Germany 28 Center 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 29 Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA 30 University of Liverpool, Liverpool L69 7ZE, United Kingdom 31 University College London, London WC1E 6BT, United Kingdom 32 Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, E-28040 Madrid, Spain 33 Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA 34 Institute 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 35 University of Michigan, Ann Arbor, Michigan 48109, USA 36 Michigan State University, East Lansing, Michigan 48824, USA 37 Institution for Theoretical and Experimental Physics, ITEP, Moscow 117259, Russia 38 University of New Mexico, Albuquerque, New Mexico 87131, USA 39 Northwestern University, Evanston, Illinois 60208, USA 40 The Ohio State University, Columbus, Ohio 43210, USA 41 Okayama University, Okayama 700-8530, Japan 42 Osaka City University, Osaka 588, Japan 43 University of Oxford, Oxford OX1 3RH, United Kingdom 44a Istituto Nazionale di Fisica Nucleare, Sezione di Padova-Trento, I-35131 Padova, Italy 44b University of Padova, I-35131 Padova, Italy 45 LPNHE, Universite Pierre et Marie Curie/IN2P3-CNRS, UMR7585, Paris, F-75252 France 46 University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA 47a Istituto Nazionale di Fisica Nucleare Pisa, I-56127 Pisa, Italy 47b University of Pisa, I-56127 Pisa, Italy 47c University of Siena, I-56127 Pisa, Italy m Visitor from University of Fukui, Fukui City, Fukui Prefecture, Japan 910-0017. l Visitor from University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom. k Visitor from University College Dublin, Dublin 4, Ireland. j Visitor from University of Cyprus, Nicosia CY-1678, Cyprus. i Visitor from Cornell University, Ithaca, NY 14853, USA. h Visitor from University of California Santa Cruz, Santa Cruz, CA 95064, USA. g Visitor from University of California Irvine, Irvine, CA 92697, USA. f Visitor from Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari, 09042 Monserrato (Cagliari), Italy. e Visitor from Chinese Academy of Sciences, Beijing 100864, China. d Visitor from University of Bristol, Bristol BS8 1TL, United Kingdom. c Visitor from Universiteit Antwerpen, B-2610 Antwerp, Belgium. b Visitor from University of Massachusetts Amherst, Amherst, MA 01003, USA. y On leave from J. Stefan Institute, Ljubljana, Slovenia. x Visitor from Bergische Universita?t Wuppertal, 42097 Wuppertal, Germany. w Visitor from University of Virginia, Charlottesville, VA 22904, USA. v Visitor from IFIC (CSIC-Universitat de Valencia), 46071 Valencia, Spain. u Visitor from Texas Tech University, Lubbock, TX 79609, USA. t Visitor from University de Oviedo, E-33007 Oviedo, Spain. s Visitor from University of Notre Dame, Notre Dame, IN 46556, USA. r Visitor from Nagasaki Institute of Applied Science, Nagasaki, Japan. q Visitor from University of Manchester, Manchester M13 9PL, United Kingdom. p Visitor from Queen Mary, University of London, London, E1 4NS, United Kingdom. o Visitor from Universidad Iberoamericana, Mexico D.F., Mexico. n Visitor from Kinki University, Higashi-Osaka City, Japan 577-8502. a Deceased. MEASUREMENT OF THE t C22 t PRODUCTION CROSS ... PHYSICAL REVIEW D 79, 052007 (2009) 052007-3 47d Scuola Normale Superiore, I-56127 Pisa, Italy 48 University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA 49 Purdue University, West Lafayette, Indiana 47907, USA 50 University of Rochester, Rochester, New York 14627, USA 51 The Rockefeller University, New York, New York 10021, USA 52a Istituto Nazionale di Fisica Nucleare, Sezione di Roma 1, I-00185 Roma, Italy 52b Sapienza Universita` di Roma, I-00185 Roma, Italy 53 Rutgers University, Piscataway, New Jersey 08855, USA 54 Texas A&M University, College Station, Texas 77843, USA 55a Istituto Nazionale di Fisica Nucleare Trieste/Udine, I-34100 Trieste, Italy 55b University of Trieste/Udine, I-33100 Udine, Italy 56 University of Tsukuba, Tsukuba, Ibaraki 305, Japan 57 Tufts University, Medford, Massachusetts 02155, USA 58 Waseda University, Tokyo 169, Japan 59 Wayne State University, Detroit, Michigan 48201, USA 60 University of Wisconsin, Madison, Wisconsin 53706, USA 61 Yale University, New Haven, Connecticut 06520, USA (Received 26 January 2009; published 20 March 2009) We present a measurement of the t C22 t production cross section in pC22p collisions at ??? s p ? 1:96 TeV using events containing a high transverse momentum electron or muon, three or more jets, and missing transverse energy. Events consistent with t C22 t decay are found by identifying jets containing candidate heavy-flavor semileptonic decays to muons. The measurement uses a CDF run II data sample corre- sponding to 2fb C01 of integrated luminosity. Based on 248 candidate events with three or more jets and an expected background of 79:5C65:3 events, we measure a production cross section of 9:1C61:6pb. DOI: 10.1103/PhysRevD.79.052007 PACS numbers: 13.85.Ni, 13.85.Qk, 14.65.Ha I. INTRODUCTION Top quark pair production in hadronic collisions in the standard model (SM) proceeds via either quark-antiquark annihilation or through gluon-gluon fusion. At the Fermilab Tevatron collider, with a center-of-mass energy of 1.96 TeV, the production is expected to be dominated by quark-antiquark annihilation. For a top mass of 175 GeV=c 2 the theoretical cross section is calculated to be 6:6C60:6pb[1] and decreases by approximately 0.2 pb for each 1 GeV=c 2 increase in the top mass over the range 170 GeV=c 2 2:1) in azimuth and ranges from 0.1 to 0.64 units of C17 (corresponding to a nearly constant 2.7 C14 change in polar angle). The electromagnetic calorimeters are instru- mented with proportional and scintillating strip detectors that measure the transverse profile of electromagnetic showers at a depth corresponding to the shower maximum. Behind the central calorimeter are four layers of central muon drift chambers (CMU) covering j C17 j <0:6. The calorimeter provides approximately 1 m of steel shielding. Behind an additional 60 cm of steel in the central region sit an additional four layers of muon drift chambers (CMP) arranged in a box-shaped layout around the central detec- tor. Central muon extension (CMX) chambers, which are arrayed in a conical geometry, provide muon detection for the region 0:6< j C17 j <1:0 with between four and six layers of drift chamber, depending on zenith angle. The CMX chambers covering from 225 C14 to 315 C14 in azimuth are knownasthe??miniskirt??whilethosecovering from75 C14 to 105 C14 in azimuth are known as the ??keystone.?? The re- mainder of the CMX chambers are referred to as the ??arches.?? The muon chambers measure the coordinate of hits in the drift direction, x, via a drift time measurement and a calibrated drift velocity, and for CMU and CMX, the longitudinal coordinate, z. The longitudinal coordinate is measured in CMU by comparing the pulse heights, en- coded in time over threshold, of pulses at opposite ends of the sense wire. In CMX, the conical geometry provides a small stereo angle from which the z coordinate of track segments can be measured. Reconstructed track segments in CMU and CMP have a maximum of 4 hits, and in CMX a maximum of 6 hits. FIG. 1. Elevation view of the CDF II detector. MEASUREMENT OF THE t C22 t PRODUCTION CROSS ... PHYSICAL REVIEW D 79, 052007 (2009) 052007-5 III. DATA SAMPLE AND EVENT SELECTION This analysis is based on an integrated luminosity of 2034C6120 pb C01 [7](1993 pb C01 with the CMX detector operational) collected with the CDF II detector between March 2002 and May 2007. A. Kinematic selection The triggering and off-line event selection used in this analysis are nearly identical to that used in the previous analysis described in [4]. For completeness we reproduce the basic trigger and selection criteria here and highlight the few differences. CDF II employs a threelevel trigger system, the first two consisting of special purpose hardware and the third con- sisting of afarmof commoditycomputers.Triggers forthis analysis are based on selecting high transverse momentum electrons and muons. The electron sample is triggered as follows: At the first trigger level, events are selected by requiring a track with P T >8 GeV=c matched to an elec- tromagnetic calorimeter tower with E T >8 GeV and little energy in the hadronic calorimeter behind it. At the second trigger level, calorimeter energy clusters are assembled, and the track found at the first level must be matched to an electromagnetic cluster with E T >16 GeV. At the third level, off-line reconstruction is performed and an electron candidate with E T >18 GeV is required. The muon sam- ple trigger begins at the first trigger level with a track with P T >4 GeV=c matched to hits in the CMU and CMP chambers or a track with P T >8 GeV=c matched to hits in the CMX chambers. At the second level a track with P T >8 GeV=c is required in the event for all but the first few percent of the integrated luminosity, for which triggers at the first level were fed directly to the third level trigger. At the third trigger level a reconstructed track with P T > 18 GeV=c is required to be matched to the muon chamber hits. From the inclusive lepton data set produced by the electron and muon triggers described above, we select off line an inclusive W plus jets candidate sample by requiring a reconstructed isolated electron with E T >20 GeV or muon with P T >20 GeV=c, E6 T >30 GeV and at least 1 jet with E T >20 GeV and j C17 j <2:0. We define an isolation parameter, I, as the calorimeter energy in a cone of C1R C17 ????????????????????????? C1C17 2 ?C1C30 2 p <0:4 around the lepton (not including the lepton energy itself) divided by the E T (P T ) of the lepton. We select isolated electrons (muons) by requiring I<0:1. Electrons and muons satisfying these criteria are called the ??primary lepton.?? Jets are identified using a fixed-cone algorithm with a cone size of C1R ? 0:4 and are constrained to originate at the pC22p collision vertex. Their energies are corrected to account for detector re- sponse variations in C17, drifts in calorimeter gain, nonline- arity of calorimeter energy response, multiple interactions in an event, and for energy loss in uninstrumented regions of the detector. These corrections bring the jet energies, on average, back to the sum P T of the particles in the jet cone, but not all the way back to the parton energy. This is slightly different from the previous analysis [4] where the correction was done only for response variations in C17, gain drifts, and multiple interactions. The jet counting threshold in that analysis was E T >15 GeV, which corresponds roughly to the E T >20 GeV used here with the additional corrections. The missing transverse energy is corrected to account for the shifts in jet energies due to the jet correc- tions above, and the E6 T threshold has been raised from 20 GeVin the previous analysis to 30 GeV here, consistent with the change in jet corrections. Z boson candidate events are rejected by removing events in which a second, sameflavor, oppositesignisolatedlepton,togetherwiththe primary lepton, makes an invariant mass between 76 and 106 GeV=c 2 . The acceptance of these selection criteria for t C22 t events is discussed in Sec. V. The t C22 t signal region consists of W candidate events with 3 or more jets, while the W ?1 and W ?2 jet events provide a control sample with little signal contamination. The data set selected above is dominated by QCD pro- duction of W bosons with multiple jets. As a first stage of background reduction, we define a total event transverse energy, H T , as the scalar sum of the electron E T or muon P T , E6 T and jet E T for jets with E T >8 GeV and j C17 j < 2:4. Figure 2 shows a comparison between the H T distri- butions for simulated t C22 t and W ?jets events with at least 3 jets. For 3 or more jet events, we require H T >200 GeV. This requirement rejects approximately 30% of the back- ground while retaining approximately 99% of the t C22 t signal. NoH T requirement is made for the control region of 1- and 2-jet events. [GeV] T H 0 50 100 150 200 250 300 350 400 450 500 Arbitrary Units tt W+jets Overflow Bin FIG. 2 (color online). The distribution of H T for simulated t C22 t and W ?jets events with at least three jets. T. AALTONEN et al. PHYSICAL REVIEW D 79, 052007 (2009) 052007-6 B. Muon tagging Even after the H T requirement is imposed, the expected signal to background ratio in W?C213 jet events is about 1:7. To further improve the signal to background ratio, events with one or more b-jets are identified by searching inside jets for semileptonic decays of b-hadrons into muons. The algorithm for identifying such candidate b-jets is known as soft-lepton tagging or ??SLTC22?? and a jet with a candidate semileptonic b decay to a muon is a ??tagged?? jet. The SLTC22algorithm is described in detail in Ref. [4]. We review here only its basic features. Muon identification at CDF relies on the presence of a track segment (??stub??) in the muon chambers, matched to a track in the central trackingsystem. The soft muon tagger is basedon aC31 2 function that uses all available information about the match between the extrapolated COT track and the muon stub to require that the deviations be consistent with the multiple Coulomb scattering expected for a muon traversing the CDF calorimeter. The algorithm begins by selecting ??taggable?? tracks. A track is declared taggable ifit containsatleast 3 axial and 2 stereo COT superlayers that have at least 5 hits each. To obtain some rejection for decays in flight (DIF), the impact parameter, d 0 , of the track with respect to the beam line, is required to be less than 2 mm. The track is further required to originatewithin 60cm of the center of thedetector along the beam direction. Finally, the track must have aP T above an approximate range-out threshold of 3:0 GeV=c and extrapolate to within a fiducial volume at the muon cham- bers that extends 3C27 MS outside of the physical edges of the chambers, where C27 MS is the deviation expected from mul- tiple Coulomb scattering at the track P T . Matching between the extrapolated COT track and the muon stub is done using the following observables (??matching variables??): the extrapolated position along the muon chamber drift direction (x), the longitudinal coordinate along the chamber wires (z) when such infor- mation is available, and the extrapolated slope (C30 L ). Tracks in the COT are paired with stubs based on the best match in x, which must be less than 50 cm for a track-stub pair to become a muon candidate. We refer to the difference between the extrapolated and measured positions in x and z as C1x and C1z, respectively, and between the extrapolated and measured slope as C1C30 L . The distributions of these variables over an ensemble of events are referred to as the ??matching distributions.?? Candidate muons are selected with the SLTC22 algorithm by constructing a global C31 2 quantity, L, based on a com- parison of the measured matching variables with their expectations. The first step in constructing L is taking a sum, Q, of individual C31 2 variables: Q ? X n i?1 ?X i C0C22 i ? 2 C27 2 i ; (1) where C22 i and C27 i are, respectively, the expected mean and width of the distribution of the matching variable X i . The sum is taken over n selected variables as described below. We construct L, by normalizing Q according to L ? ?QC0n? ?????????????? var?Q? p ; (2) where the variance, var?Q?, is calculated using the full covariance matrix for the selected variables. The normal- ization is chosen to make L independent of the number of variables n. The selected variables are the full set of matching var- iables,C1x,C1z,andC1C30 L intheCMU,CMP, andCMXwith the following two exceptions: The CMP chambers do not provide a measurement of the longitudinal coordinate z, and matching in C30 L is not included for stubs in the muon chambers that have only three hits. Because of their sig- nificantly poorer resolution, track segments reconstructed only in the CMU or only in the CMP chambers with only three hits are rejected (if the SLTC22 candidate has stubs in both CMU and CMP, then a stub with only three hits is allowed). These two exceptions are a new feature of the algorithm,sincethepreviouspublication,thatreduceback- grounds from hadronic punchthrough with a negligible effect on the efficiency. Note that a muon that traverses both the CMU and the CMP chambers yields two sets of matching measurements in x and C30 L and one z matching measurement, and is referred to as a CMUP muon. All available matching variables are used in the calculation of L for a given muon candidate. As described in Ref. [4], the expected means and widths in Eq. (1) are parametrized as a function of the P T of the muon using J=c and W and Z bosons in the data. We use the same parametrization described there. The efficiency has been remeasured, from the data, using the full data set for this analysis. Using J=c events only, we measure the efficiency as a function of the quantity L defined in Eq. (2) (the efficiency measurement is described in detail in Sec. VB). The efficiency plateaus at a value of j L jC20 3:5, and we there- fore use this requirement to define an SLTC22 tag. Beginning with theW ?jets candidate data set, selected as described in Sec. IIIA, we require that at least one jet in each event has an SLTC22tag. A jet is determined to have an SLTC22 tag if a candidate muon with j L jC20 3:5 is found within a cone of C1R<0:6 centered on the jet axis. When theprimary leptonis a muon,the eventis rejected whenthe SLTC22 has opposite charge to the primary muon and to- gether with that muon has an invariant mass between 8 and 11 GeV=c 2 or between 70 and 110 GeV=c 2 . This rejects events in which an C7 orZboson decays to a pair of muons, one of which becomes the primary lepton while the other ends up in a jet and is tagged by the SLTC22 algorithm. Whether the primary is an electron or a muon, events where the invariant mass is less than 5 GeV=c 2 are also removed to prevent sequential double-semileptonic MEASUREMENT OF THE t C22 t PRODUCTION CROSS ... PHYSICAL REVIEW D 79, 052007 (2009) 052007-7 b ! c ! s decays (where the primary lepton and the SLTC22 tag are from these semileptonic decays, rather than the primary lepton being from the decay of a W boson) from entering the sample, as well as events with a J=c decay. We further reject events as candidate radiative Drell-Yan and Z bosons if the tagged jet has an electromagnetic energy fraction above 0.8 and only one track with >1:0 GeV=c within a cone of C1R ? 0:4 about the jet axis. Three levels of selection are defined in this analysis. Events that pass the kinematic cuts and the dilepton and radiative-Z vetoes, but do not necessarily have an SLTC22-taggable track in them, comprise the ??pretag?? sample. Pretag events that have an SLTC22-taggable track (P T >3 GeV=c, passing quality cuts, pointing to the muon chambers) within C1R<0:6 of a jet with E T > 20 GeV are called taggable events. Finally, the subset of SLTC22-taggable events that have at least one SLTC22-tagged jet are called tagged events. C. Selected event samples Table I shows the number of pretagged, taggable, and tagged events in the electron and muon channels in this data set as a function of jet multiplicity. IV. MONTE CARLO DATA SETS The detector acceptance of t C22 t events is modeled using PYTHIA v6.216 [8] and HERWIG v.6.510 [9]. This analysis uses the former for the final cross section estimate and the latter to estimate the systematics resulting in the modeling oft C22 tproduction and decay. The PYTHIA event generator has been tuned using jet data to better model the effects of multiple interactions and remnants from the breakup of the proton and antiproton. The generators are used with the CTEQ5L parton distribution functions [10]. Decays of b- and c-hadrons are modeled using EVTGEN [11]. Events with a W boson produced in association with multiple jets are modeled using ALPGEN v2.1 [12], with parton showering provided by PYTHIA v6.326 and HF hadron decays handled by EVTGEN. ALPGEN calculates exact matrix elements at leading order for a large set of parton level processes in QCD and electroweak interac- tions. The showering in PYTHIA may result in multiple ALPGEN samples covering the same phase space. These overlaps are removed using a jet-parton matching algo- rithm along with a jet-based heavy-flavor overlap removal algorithm [13]. Estimates of backgrounds from diboson production (WW, WZ, and ZZ) and Drell-Yan=Z ! C28C28 are derived using PYTHIA. Drell-Yan to C22C22 events are modeled using ALPGEN with PYTHIA showering while single-top produc- tion is modeled with MADEVENT [14], also with PYTHIA showering. The CDF II detector simulation reproduces the response of the detector to particles produced in pC22p collisions. The detector geometry database used in the simulation is the same as that used for reconstruction of the collision data. Details of the CDF II simulation can be found in [15]. V. EFFICIENCY FOR IDENTIFYING t C22 t EVENTS The efficiency for identifying t C22 t events in this analysis is factorized into the geometric times kinematic acceptance and the SLTC22 tagging efficiency. The acceptance is eval- uatedassumingatopmassof175 GeV=c 2 andincludesthe branching fraction to leptons, which is assumed to have the SM value. The tagging efficiency is the efficiency for SLTC22 tagging at least one jet in events that pass the geometric and kinematic selection. Each piece is described below. A. Geometric and kinematic acceptance The acceptance of t C22 t events in this analysis is measured in PYTHIA and then corrected, using measurements from thedata,foreffectsthatarenotsufficientlywellmodeledin the simulation: the lepton trigger efficiencies, the fraction of the pC22p luminous region well contained in the CDF detector (i.e., the z-vertex cut efficiency), and track recon- struction and lepton identification efficiencies. The effi- ciency of thez-vertex cut,j z 0 j <60 cm, is measured from minimum-bias triggered events to be ?96:3C60:2?%. The correction factor for the difference between the track re- construction efficiencies in data and simulation is 1:014C6 0:002. Events in the Monte Carlo (MC) samples are not required to pass any trigger, so the acceptance is multiplied by lepton trigger efficiency. The lepton trigger and identi- fication efficiencies, measured using the unbiased leg of Z boson decays to electrons and muons, and the correction TABLE I. Summary of event counts for 2fb C01 of CDF run II data for the event selection described in Secs. IIIA and IIIB. 1 jet 2 jets 3 jets C21 4 jets C21 3 jets Electrons Pretag 79348 13068 1615 660 2275 SLTC22 taggable 43005 10479 1518 648 2166 SLTC22 tagged 519 224 85 64 149 CMUP muons Pretag 38165 6320 719 325 1044 SLTC22 taggable 20162 4921 673 312 985 SLTC22 tagged 224 105 41 34 75 CMX muons Pretag 23503 3672 422 162 584 SLTC22 taggable 12428 2864 396 160 556 SLTC22 tagged 149 55 16 8 24 Electrons?muons Pretag 141016 23060 2756 1147 3903 SLTC22 taggable 75595 18264 2587 1120 3707 SLTC22 tagged 892 384 142 106 248 T. AALTONEN et al. PHYSICAL REVIEW D 79, 052007 (2009) 052007-8 factors for each of the primary lepton types are shown in Table II. The raw acceptance is defined as the number of pretag events divided by the total number of t C22 t events in the PYTHIA sample. The acceptance, after correcting for the differences between data and simulation, is shown in Table III as a function of the number of identified jets. B. Efficiency of the SLTC22 algorithm The efficiency of the SLTC22 algorithm is measured from the data using samples of J=c and Z decays triggered on a single muon. The tagger is applied to the nontrigger muon (probeleg).Ifbothlegspassthetrigger,onlyoneofthemis used. To reduce background in the Z sample, the leg that is not used to measure efficiency is required to be isolated and to be consistent with being a minimum ionizing par- ticle in the calorimeter. We correct for the remaining background using the invariant mass regions outside the Z mass window (??sidebands??). The efficiency of the SLTC22 is defined as C15 ? No. of tagged muons No. of taggable muon tracks with a stub : (3) TABLE II. Summary of lepton trigger and identification efficiencies. Quantity Electron CMUP muon CMX muon Trigger efficiency 0:966C60:005 0:917C60:005 0:925C60:007 Lepton ID efficiency (data) 0:789C60:004 0:829C60:006 0:893C60:006 Lepton ID efficiency (MC) 0:806C60:001 0:896C60:001 0:916C60:002 Lepton ID correction 0:978C60:005 0:926C60:007 0:975C60:007 TABLE III. Acceptance fort C22 tevents as a function of jet multiplicity from the PYTHIA Monte Carlo sample, after data/MC corrections described in the text. In the combined acceptance we account for the fact that the CMX detector was not operating early in run II. The uncertainties listed are statistical only. 1 jet 2 jets 3 jets C21 4 jets C21 3 jets Electron (%) 0:163C60:002 0:858C60:004 1:63C60:01 2:08C60:01 3:71C60:01 CMUP muon (%) 0:088C60:001 0:472C60:003 0:909C60:004 1:142C60:005 2:05C60:01 CMX muon (%) 0:042C60:001 0:219C60:002 0:414C60:003 0:532C60:003 0:946C60:004 Combined (%) 0:292C60:002 1:544C60:005 2:946C60:008 3:743C60:009 6:69C60:01 [GeV/c] T p 10 Efficiency [%] 50 55 60 65 70 75 80 85 90 95 100 |<0.6 region?| FIG. 3 (color online). The SLTC22 efficiency for CMU/CMP as a function of P T measured from J=c and Z data for j L j <3:5. The solid line is the fit to the data and the dashed lines indicate the uncertainty on the fit. [GeV/c] T p 10 Efficiency [%] 50 55 60 65 70 75 80 85 90 95 100 |>0.6 region?| FIG. 4 (color online). The SLTC22 efficiency for CMX arches (circles) and miniskirt/keystone (triangles) as a function of P T measured from J=c and Z data for j L j <3:5. The solid curves are the fits to the data and the dashed lines indicate the un- certainties on the fits. MEASUREMENT OF THE t C22 t PRODUCTION CROSS ... PHYSICAL REVIEW D 79, 052007 (2009) 052007-9 The requirement in the denominator that the taggable muon track has a stub in the requisite muon chambers decouples the muon reconstruction efficiency, which is accounted for separately, from the efficiency of the tagger. Figures 3 and 4 show the efficiency for tagging muons with j L jC20 3:5 as a function of muon P T from both J=c and Z data. The decrease in efficiency with increasing P T is due, primarily, to non-Gaussian tails in the resolution functions. These efficiency data are fit to functional forms [4] shown as the curves in the data. The dotted curves are those obtained by varying the fit parameters by C61C27. Although the efficiency measurement is dominated by isolated muons, we donotexpectthat itwill dependon theisolation of the muon because the muon chambers are well shielded from the inner detector. We have checked this assumption by measuring the efficiency as a function of the number of nearby tracks and found no dependence. The efficiency for SLTC22 tagging a t C22 t event is measured for Monte Carlo events that pass the geometric and kine- matic selection. We model the SLTC22 tagging in these events by tagging muons from semileptonic HF decay with a probability given by the efficiencies in Figs. 3 and 4. Events withouta??real??muontagof thistype can stillbe SLTC22 tagged through a mistag. Mistags in t C22 t events are included by applying the ??mistag matrix??described in the following section, and are included as part of the signal efficiency. The SLTC22 tagging efficiency in t C22 t events is given in Table IV. VI. PREDICTING THE NUMBER OF TAGS FROM LIGHT-QUARK JETS As a prelude to the evaluation of the backgrounds to the t C22 t signal we describe a new method, developed for this analysis, for predicting the number of SLTC22 tags that come from light-quark jets. We refer to these as mistags, and they result from a combination of hadronic punch- through of the calorimeter and muon steel, and hadronic decays in flight. To predict the number of mistags in our sample we use a track-basedmistagprobabilitythatisafunctionoftrackP T and C17. We use reconstructed D C3 and C3 0 to identify a clean sample of pions, kaons, and protons and measure the probability per taggable track, in 8 bins of P T and 9 bins of C17, for each to satisfy the SLTC22j L j <3:5 requirement. Details of the reconstruction technique, the measurement of the tagging probabilities, and the assembly and testing of the two-dimensional (8C29) mistag matrix are de- scribed in what follows. A. Data samples To identify kaons and pions we reconstruct D C3? ! D 0 C25 ? ! K C0 C25 ? C25 ? decays, and their charge conjugates. This data set is collected using a two-track trigger that requires two oppositely charged tracks with P T C21 2 GeV=c. The tracks are also required to have a scalar sum P T1 ?P T2 C21 5:5 GeV=c, an opening angle between them of 2 C14 C20jC1C30jC2090 C14 , and originate from a displaced vertex. A sample of protons is obtained by reconstructing C3 ! pC25 C0 decays. These events are collected using another two- tracktriggersimilarto theone describedabove, but withan opening angle requirement of 20 C14 C20jC1C30jC20135 C14 and the invariant mass of the track pair (assumed to be pions) required to be 4 GeV=c 2 C20 M?C25;C25?C207 GeV=c 2 . B. Event reconstruction We apply the following track quality criteria in the reconstruction of both D C3 [16] and C3 0 [17] decays: (i) the number of COTaxial superlayers withC21 5 hits is C21 3; (ii) the number of COT stereo superlayers withC21 5 hits is C21 2; (iii) the track has jz 0 jC2060 cm. TheD C3 reconstruction then proceeds through the exami- nation of the mass difference C1m ? m?KC25C25?C0m?KC25? with the following criteria: (i) the kaon must have opposite charge to each of the two pions; (ii) jC1z 0 jC205cmbetween any two tracks; (iii) the soft pion from the D C3 ! D 0 C25 decay must have P T C21 0:5 GeV=c; (iv) the kaon and pion from the D 0 decay must each have P T C21 2 GeV=c; (v) the kaon and pion tracks must have impact parame- ter, jd 0 jC200:2cm; (vi) jm?KC25?C0m?D 0 ?j C20 0:03 GeV=c 2 ; TABLE IV. t C22 t event tagging efficiency for SLT muons as a function of jet multiplicity from the PYTHIA Monte Carlo sample. The lepton category refers to the primary lepton. The average tagging efficiency is determined by weighting each channel by the acceptance and luminosity for each channel. The listed uncertainties are statistical only. 1 jet 2 jets 3 jets C21 4 jets C21 3 jets Electron (%) 7:0C60:311:4C60:212:9C60:114:9C60:114:0C60:1 CMUP muon (%) 5:6C60:310:7C60:211:8C60:114:1C60:113:1C60:1 CMX muon (%) 6:7C60:511:2C60:312:3C60:214:2C60:213:4C60:2 Average (%) 6:5C60:211:2C60:112:5C60:114:6C60:113:6C60:1 T. AALTONEN et al. PHYSICAL REVIEW D 79, 052007 (2009) 052007-10 ] 2 ) [GeV/c?)-M(K??M(K 0.14 0.145 0.15 0.155 0.16 2 Number of Candidates / 0.0001 GeV/c 0 10000 20000 30000 40000 50000 < 4 GeV/c T p?3 GeV/c ] 2 ) [GeV/c?)-M(K??M(K 0.14 0.145 0.15 0.155 0.16 2 Number of Candidates / 0.0001 GeV/c 0 10000 20000 30000 40000 50000 < 5 GeV/c T p?4 GeV/c ] 2 ) [GeV/c?)-M(K??M(K 0.14 0.145 0.15 0.155 0.16 2 Number of Candidates / 0.0001 GeV/c 0 5000 10000 15000 20000 25000 30000 35000 < 6 GeV/c T p?5 GeV/c ] 2 ) [GeV/c?)-M(K??M(K 0.14 0.145 0.15 0.155 0.16 2 Number of Candidates / 0.0001 GeV/c 0 5000 10000 15000 20000 25000 30000 < 8 GeV/c T p?6 GeV/c ] 2 ) [GeV/c?)-M(K??M(K 0.14 0.145 0.15 0.155 0.16 2 Number of Candidates / 0.0001 GeV/c 0 2000 4000 6000 8000 10000 12000 < 12 GeV/c T p?8 GeV/c ] 2 ) [GeV/c?)-M(K??M(K 0.14 0.145 0.15 0.155 0.16 2 Number of Candidates / 0.0001 GeV/c 0 200 400 600 800 1000 1200 1400 1600 1800 < 17 GeV/c T p?12 GeV/c ] 2 ) [GeV/c?)-M(K??M(K 0.14 0.145 0.15 0.155 0.16 2 Number of Candidates / 0.0001 GeV/c 0 50 100 150 200 250 300 < 22 GeV/c T p?17 GeV/c ] 2 ) [GeV/c?)-M(K??M(K 0.14 0.145 0.15 0.155 0.16 2 Number of Candidates / 0.0001 GeV/c 0 10 20 30 40 50 60 70 80 22 GeV/c? T p FIG. 5 (color online). The m?KC25C25?C0m?KC25? distribution for D C3C6 ! D 0 C25 C6 , D 0 ! K C7 C25 C6 candidates in different SLTC22-track-P T bins. The line in each plot represents the fit to the sideband regions. MEASUREMENT OF THE t C22 t PRODUCTION CROSS ... PHYSICAL REVIEW D 79, 052007 (2009) 052007-11 (vii) At least one of the tracks (K or C25) from the D 0 must be SLTC22 taggable (including having P T C21 3 GeV=c). As shown in Fig. 5, a clean D C3 signal is obtained for the right-sign C1m distribution. The reconstruction of C3 decays requires the following criteria: (i) the pion and proton must have opposite charge; (ii) jC1z 0 jC202cmbetween the two tracks; (iii) the C31 2 of the vertex fit must be C20 10; (iv) the vertex must have L xy C21 0:5cm, where L xy is defined as the projection onto the net momentum direction, in the rC0C30 plane, of the vector pointing from the primary to the secondary vertex; (v) the proton P T is greater than the pion P T ; (vi) the pion must have P T C21 0:4 GeV=c; (vii) the proton must have jd 0 jC200:2cm; (viii) the proton must be SLTC22 taggable (including having P T C21 3 GeV=c). Figure 6 shows the invariant mass distribution in the pC25 mass hypothesis. We define a signal region for D C3 and C3 0 decays as well as sideband regions for each. We measure the sideband- subtracted tagging probability for K, C25, and p tracks using ] 2 ) [GeV/c?M(p 1.09 1.1 1.11 1.12 1.13 1.14 1.15 1.16 1.17 2 Number of Candidates / 0.0005 GeV/c 5000 10000 15000 20000 25000 30000 < 4 GeV/c T p? 3 GeV/c ] 2 ) [GeV/c?M(p 1.09 1.1 1.11 1.12 1.13 1.14 1.15 1.16 1.17 2 Number of Candidates / 0.0005 GeV/c 2000 4000 6000 8000 10000 < 5 GeV/c T p? 4 GeV/c ] 2 ) [GeV/c?M(p 1.09 1.1 1.11 1.12 1.13 1.14 1.15 1.16 1.17 2 Number of Candidates / 0.0005 GeV/c 500 1000 1500 2000 2500 3000 3500 < 6 GeV/c T p? 5 GeV/c ] 2 ) [GeV/c?M(p 1.09 1.1 1.11 1.12 1.13 1.14 1.15 1.16 1.17 2 Number of Candidates / 0.0005 GeV/c 400 600 800 1000 1200 1400 1600 1800 2000 < 8 GeV/c T p? 6 GeV/c ] 2 ) [GeV/c?M(p 1.09 1.1 1.11 1.12 1.13 1.14 1.15 1.16 1.17 2 Number of Candidates / 0.0005 GeV/c 300 400 500 600 700 800 < 12 GeV/c T p? 8 GeV/c ] 2 ) [GeV/c?M(p 1.09 1.1 1.11 1.12 1.13 1.14 1.15 1.16 1.17 2 Number of Candidates / 0.0005 GeV/c 80 100 120 140 160 180 200 220 240 12 GeV/c? T p FIG. 6 (color online). The m?pC25? distribution for C3 0 ! pC25 candidates in different SLTC22-track-P T bins. The line in each plot represents the fit to the sideband regions. T. AALTONEN et al. PHYSICAL REVIEW D 79, 052007 (2009) 052007-12 events in the signal, corrected for the enhanced probabil- ities in the sidebands. The sideband regions have a higher SLTC22 per track tag probability because they are enriched in HF as a result of the two-track trigger described above. The signal and sideband regions are given in Table Vand the sideband subtraction is done using the fits [5] shown in Figs. 5 and 6. The tag probabilities before and after side- band subtraction are shown as a function of P T in Fig. 7. We note that there are systematic uncertainties due to the choice of fit functions and, in particular, the quality of the fits in the sideband regions. These systematics, and all others associated with the construction of the mistag ma- trix, are evaluated by testing the predictive power of the matrix on a variety of independent data samples, as de- scribed in Sec. VIIIB. The mistag matrix is designed to predict SLTC22 tags that arise from both hadronic punchthrough and decays in flight. When a pion or a kaon from a D C3 decays in flight, the track may be poorly reconstructed causing the recon- structed mass to fall outside of the signal region defined in Table V. We measure the size of this effect usingD C3 decays in a Monte Carlo sample and make a correction. The correction factor is calculated in three bins in P T (limited by the Monte Carlo sample size) and shown in Table VI. Full details of the calculation of the correction factor are given in [5]. C. The mistag matrix At this point we have SLTC22 tag probabilities for tracks from C25, K, and p, corrected for backgrounds (sideband subtracted) and for a bias against C25 and K decays in flight. What remains is to assemble these separate SLTC22 tag probabilities into a full mistag matrix that can be used to predict the number of tags in light-flavor jets in W ?jets events. To assemble the final mistag matrix, we take a weighted sum of the individual C25, K, and p matrices as follows: M ij ? W C25 C1M C25 ij ?W K C1M K ij ?W p C1M p ij ; (4) where M ij is the entry in the ith P T and jth C17 bins of the final matrix and M C25 ij , M K ij , and M p ij are the corresponding entries in the C25, K, and p matrices. The weights W C25 ? 71:9%, W K ? 15:6%, and W p ? 12:5% are taken from the taggable-track particle content of light-quark jets in ALPGEN W ?jets Monte Carlo events. Figure 8 shows the final tag probability for the eight P T bins (integrated over C17) and the nine C17 bins (integrated over P T ). The features in the C17 distribution are due to the profile of TABLE V. Mass windows used in determining the status of a D C3 or C3 0 candidate. Region Mass window (MeV=c 2 ) D C3 signal 142:42160:20C60:04 0:16C60:04 75:6C62:61:09C60:14 3?4 0:99C60:09 0:77C60:08 10:2C61:31:04C60:02 K 4?6 0:65C60:06 0:51C60:06 10:8C61: :02C60:02 >60:39C60:05 0:23C60:04 18:2C61:81:05C60:02 T. AALTONEN et al. PHYSICAL REVIEW D 79, 052007 (2009) 052007-14 cantly larger tag rate than true W events. The enhanced tag rate arises due to the contribution of b C22 b events to the QCD background and because of the correlation between the tag rate and measuredE6 T in events in which theE6 T arises from jet mismeasurement or semileptonic HF decay rather than from a neutrino in a W boson decay. In order to avoid doublecountingwe correct theestimate oftags inW ?jets events by (1C0F QCD ), where F QCD is the QCD multijet fraction in the W ?jets candidate sample. A. Mistags The background due to mistags is evaluated using the track-based mistag matrix described in Sec. VI. To predict the number of events from W ?jets with at least 1 mistag, we apply the mistag matrix to all pretag events according to N Wjtag raw ? X events C20 1C0 Y N trk i?1 ?1C0P?P Ti ;C17 i ?? C21 ; (5) where the sum runs over each event in the pretag sample, and the product is over each taggable track in the event. P?P Ti ;C17 i ? is the probability from the mistag matrix for tagging the ith track with parameters P Ti and C17 i . Note that the sum over the events in Eq. (5) includes any t C22 t events that are in the pretag sample. We correct for the resulting overestimate of the background at the final stage of the cross section calculation (see Sec. IX). It also includes W ?HF events, diboson events, etc. Therefore mistags from these backgrounds are included here. Tags from muons resulting from the decay of HF hadrons or W or Z bosons in these backgrounds are calculated separately us- ing Monte Carlo simulations, as described in Secs. VIIB and VIIE. To avoid any double counting the Monte Carlo estimates of the contributions from these backgrounds do not include any mistags. A fraction, F QCD , of the events in the signal region are QCD events for which the background is estimated sepa- rately. Therefore, we correct the prediction of Eq. (5) according to N Wjtag corr ??1C0F QCD ?C1N Wjtag raw : (6) The background estimate from the application of the mistag matrix is shown in Table VII. We list here both the raw prediction and that corrected by (1C0F QCD ). The calculation of F QCD is described in Sec. VIIC1. B. W ?heavy flavor The evaluation of background tags from the semilep- tonic decays of HF quarks in Wb C22 b, WcC22c, and Wcevents is done using the ALPGEN Monte Carlo program. We deter- mine the fraction of W ?jets events that contain heavy flavor at the pretag level, F HF , and the tagging efficiency, C15 HF , for these events and then normalize the total to the number of W ?jets events seen in the data. The final prediction of the number of tags from W ?heavy-flavor events is N HF ??1C0F QCD C0F other ?C1N pretag C1F HF C1C15 HF ; (7) where F QCD is the fraction of QCD events in the pretag sample and F other is the fraction of other, non-W ?jets backgrounds. As with the mistag prediction, correction for t C22 t in the pretag sample is done as part of the final cross section calculation. This procedure is used because the theory cross sections for the Wb C22 b, WcC22c, and Wc processes have large uncer- tainties, whereas the uncertainties on the fraction of events with heavy-flavor jets are smaller. This procedure follows that used in [3]. The HF fractions of events in the W ?jets sample are determined by measuring the fractions in Monte Carlo events and then scaling those fractions by a multiplicative factor of 1:15C60:35, determined by comparing measured HF fractions in inclusive jet data with those predicted by ALPGEN. The ALPGEN HF fractions, broken down according to the number of b-orc-jets, are shown in Table VIII. In addition to the uncertainty on the HF-fraction scaling, an additional uncertainty on the ALPGEN fractions is determined by varying the ALPGEN generator parameters such as Q 2 and the quark masses. The Monte Carlo sample is also employed to determine the efficiency for tagging a muon from a semileptonic heavy-flavor decay in W ?heavy-flavor events. As with the t C22 t tagging efficiency described in Sec. V, tags are assigned based on the SLTC22 tagging efficiency measured in the data (Figs. 3 and 4). The results are shown in Table VIII. Note that we do not include here the additional efficiency that arises from mistags in real HF jets, because this is included in the mistag evaluation given in Table VII. Armed with these HF fractions and tagging efficiencies, the number of tagged events from W ?HF is evaluated TABLE VII. Summary of background estimate from mistags in W ?jets events. These numbers include a contribution from t C22 t events in the W ?jets sample that is removed in the final cross section calculation, as described in Sec. IX. 1 jet 2 jet 3 jets C21 4 jets C21 3 jets N Wjtag raw 641:0C632:0 238:0C612:055:0C62:832:7C61:687:5C64:4 N Wjtag corr 622:0C631:0 226:0C612:053:0C62:731:4C61:684:5C64:3 MEASUREMENT OF THE t C22 t PRODUCTION CROSS ... PHYSICAL REVIEW D 79, 052007 (2009) 052007-15 according to Eq. (7). The results are given in the last line of Table VIII. C. QCD background The background due to tags in QCD events that enter the signal sample is estimated by calculating the fraction of QCD events in theW ?jets data and applying the standard mistag matrix times a multiplicative factor. The multipli- cative factor is required because the tagging rate of QCD events that enter the pretag sample is higher than the corresponding tagging rate for W ?jets events. 1. The QCD fraction The fraction of QCD events before SLTC22 tagging is determined using the isolation,I (see Sec. IIIA), andE6 T of eventswithhigh-P T leptonsandjets.Undertheassumption that I and E6 T are uncorrelated for QCD events, the number of QCD events in the t C22 t signal region can be found by extrapolation from the nonsignal regions N QCD D ? N C N A N B ; (8) where region D, the signal region, and regions A, B, and C are defined according to region A: E6 T <20 GeV; I>0:2; region B: E6 T <20 GeV; I<0:1; region C: E6 T >30 GeV; I>0:2; region D: E6 T >30 GeV; I<0:1: The event counts used in Eq. (8) are corrected for Monte Carlo predictions of the number of W ?jets and t C22 t events in regions A, B, and C. The QCD fraction F QCD is then given by N QCD D divided by the total number of events in region D. The QCD fractions are given in Table IX. To evaluate the accuracy of the E6 T -I prediction, two complementary regions in the plane are defined as region E: E6 T <20 GeV; 0:130 GeV; 0:1200 GeV for T Require H FIG. 11 (color online). The expected background and observed tags in W ?1, 2, 3, and 4-or-more jets events. The expected t C22 t contribution is normalized to the measured cross section. [GeV] T Tagged Jet E 0 20 40 60 80 100 120 140 160 180 200 Number of tagged jets / 5 GeV 0 50 100 150 200 250 300 Number of tagged jets / 5 GeV Data Mistags ,Wcc,WcbWb QCD Other backgrounds = 9.1 pb tt ? scaled to tt uncertaintiestBackground+t W + 1,2 jets Overflow Bin [GeV] T Tagged Jet E 0 20 40 60 80 100 120 140 160 180 200 Number of tagged jets / 5 GeV 0 5 10 15 20 25 30 35 40 Number of tagged jets / 5 GeV Data = 9.1 pb tt ? scaled to tt Mistags ,Wcc,WcbWb QCD Other backgrounds uncertaintiestBackground+t 3 jets?W + Overflow Bin FIG. 12. Comparison of the jet E T distributions for tagged jets and for expectations from mistags, W ?heavy-flavor, QCD and t C22 t events. The upper plot is for W ?1- and 2-jet events and the lower plot for W ?3-or-more-jets events. TABLE XVI. Summary of components of the denominator for the cross section calculation. The t C22 tacceptance and tagging efficiency for 3-or-more-jets events is determined using the PYTHIA Monte Carlo simulation. Electrons CMUP muons CMX muons Acc. no tag (%) 3:71C60:01C60:21 2:05C60:01C60:14 0:946C60:004C60:050 Event tagging eff. (%) 14:02C60:08C60:72 13:07C60:10C60:67 13:38C60:16C60:68 Acc. with tag (%) 0:520C60:003C60:039 0:268C60:002C60:022 0:127C60:002C60:009 Luminosity (pb C01 ) 2033:6C6119:6 2033:6C6119:6 1992:5C6117:2 Denominator (pb C01 ) 10:58C60:07C60:80C60:62 7:97C60:06C60:49C60:47 Total denominator (pb C01 ) 18:56C60:09?stat?C60:94?sys?C61:09?lum? T. AALTONEN et al. PHYSICAL REVIEW D 79, 052007 (2009) 052007-22 Figure 11 shows, in bins of the number of jets in W ? jets candidates, the expected number of tagged background and t C22 t (normalized to the measured cross section) events together with the number of observed SLTC22 tags. In Figs. 12?14 we examine a few kinematic features of the taggedevents.In eachcase thedata are comparedto the expected backgrounds plus t C22 t, normalized to the measured cross section. The agreement between data and expectation is good. The only slight exceptions are a few bins at lowE T in the W?C213 jet events in Fig. 12, where the number of observed tags exceeds somewhat the expectation. This is consistent with the excess seen in the low E T jet data in Table XIII, which is folded into the systematic uncertainty on the measurement. X. CONCLUSIONS Using 2fb C01 of integrated luminosity collected by the CDF II detector, we have measured the total cross section for t C22 t production in pC22p collisions with a center-of-mass energy, ??? s p ? 1:96 TeV. The measurement begins by se- lecting a data set of W ?jets candidates. We separate [GeV/c] T Tagged SLT P 0 5 10 15 20 25 30 35 40 Number of tagged SLT / 2 GeV/c 0 50 100 150 200 250 300 350 400 450 Number of tagged SLT / 2 GeV/c Data Mistags ,Wcc,WcbWb QCD Other backgrounds = 9.1 pb tt ? scaled to tt uncertaintiestBackground+t W + 1,2 jets Overflow Bin [GeV/c] T Tagged SLT P 0 5 10 15 20 25 30 35 40 Number of tagged SLT / 2 GeV/c 0 10 20 30 40 50 60 70 Number of tagged SLT / 2 GeV/c Data = 9.1 pb tt ? scaled to tt Mistags ,Wcc,WcbWb QCD Other backgrounds uncertaintiestBackground+t 3 jets?W + Overflow Bin FIG. 13. P T of the SLTC22 tags compared with expectations from backgrounds and t C22 t. The upper plot is for W ?1- and 2-jet events and the lower plot for W?C213-jet events. [GeV/c] rel T Tagged SLT P 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Number of tagged SLT / 0.25 GeV/c 0 50 100 150 200 250 300 350 400 450 Number of tagged SLT / 0.25 GeV/c Data Mistags ,Wcc,WcbWb QCD Other backgrounds = 9.1 pb tt ? scaled to tt uncertaintiestBackground+t W + 1,2 jets Overflow Bin [GeV/c] rel T Tagged SLT P 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Number of tagged SLT / 0.25 GeV/c 0 10 20 30 40 50 60 70 Number of tagged SLT / 0.25 GeV/c Data = 9.1 pb tt ? scaled to tt Mistags ,Wcc,WcbWb QCD Other backgrounds uncertaintiestBackground+t 3 jets?W + Overflow Bin FIG. 14. The distribution of P T relative to the jet axis (P T rel ) for tags in data, compared with expectations from backgrounds plus t C22 t. The upper plot is for 1- and 2-jet events and the lower plot for C21 3-jet events. MEASUREMENT OF THE t C22 t PRODUCTION CROSS ... PHYSICAL REVIEW D 79, 052007 (2009) 052007-23 signal from background by identifying candidate semilep- tonic decays of b-hadrons into muons. This technique was first published in Ref. [4]. This measurement is an update that uses 10 times the amount of data of the previous measurement and a new technique for evaluating the domi- nant background (see Sec. VI) of misidentifying a jet from a light-flavor quark as one containing a b-hadron. The measured t C22 t cross section is C27?pC22p ! t C22 tX??9:1C61:1 ?1:0 C00:9 C60:6pb; (15) consistent with the expectation of 6:7 ?0:7 C00:9 pb for standard model production and decay of top quark pairs with a mass of 175 GeV=c 2 . The measurement agrees well with other CDF measurements of the t C22 t production cross section [24], as well as with the most recent publications from D0 [25]. Assuming the cross section increases 0.2 pb for every 1 GeV=c 2 decrease in the top mass, then at the world average top mass of 172:4 GeV=c 2 the theoretical cross section is approximately 7.2 pb. Using a linear fit to the mass dependence, the measured cross section was esti- mated at the world average top mass and is found to be 8:9C61:6pb. The kinematic distributions of the tagged sample are also consistent with standard model expecta- tions. The observed number of tags in W ?1- and 2-jet events is in excellent agreement with expectations from background, indicating that the backgrounds are well understood. ACKNOWLEDGMENTS 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 the 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 Bundesminis- terium 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, UK; 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 the Programa Consolider-Ingenio 2010, Spain; the Slovak R&D Agency; and the Academy of Finland. [1] M. Cacciari et al., J. High Energy Phys. 09 (2008) 127; N. Kidonakis and R. Vogt, Phys. Rev. D 78, 074005 (2008); S. Moch and P. Uwer, Nucl. Phys. B, Proc. Suppl. 183,75 (2008). [2] We use a ?z;C30;C18? coordinate system where the z-axis is in the direction of the proton beam, and C30 and C18 are the azimuthal and polar angles, respectively. The pseudora- pidity, C17, is defined as C0ln?tan C18 2 ?. The transverse momen- tum of a charged particle is P T ? PsinC18, where P represents the measured momentum of the charged- particle track. The analogous quantity using calorimeter energies, defined as E T ? EsinC18, is called transverse energy. The missing transverse energy is defined as E6 T ? C0j P i E i T ^n i j where E i T is the magnitude of the transverse energy contained in each calorimeter tower i in the pseu- dorapidity region j C17 j <3:6 and ^n i is the direction unit vector of the tower in the plane transverse to the beam direction. [3] A. Abulencia et al. (CDF Collaboration), Phys. Rev. Lett. 97, 082004 (2006); D. Acosta et al. (CDF Collaboration), Phys. Rev. D 71, 052003 (2005). [4] D. Acosta et al. (CDF Collaboration), Phys. Rev. D 72, 032002 (2005). [5] Ulysses Allen Grundler, Ph.D. thesis, University of Illinois at Urbana-Champaign, Urbana, IL, 2008, FERMILAB- THESIS-2008-27. [6] The CDF II Detector Technical Design Report No. Fermilab-Pub-96/390-E; D. Acosta et al., Phys. Rev. D 71, 052003 (2005). [7] S. Klimenko, J. Konigsberg, and T.M. Liss, Fermilab Report No. Fermilab-FN-0741. [8] T. Sjostrand et al., Comput. Phys. Commun. 135, 238 (2001). [9] G. Corcella et al., J. High Energy Phys. 01 (2001) 10. [10] H.L. Lai et al., Eur. Phys. J. C 12, 375 (2000). [11] D.J. Lange et al., Nucl. Instrum. Methods Phys. Res., Sect. A 462, 152 (2001). [12] M. Mangano et al., J. High Energy Phys. 07 (2003) 1. [13] Daniel Sherman, Ph.D. thesis, Harvard University. [14] F. Maltoni and T. Stelzer, J. High Energy Phys. 02 (2003) 27. [15] E. Gerchtein and M. Paulini, ECONF C0303241, TUMT005 (2003), arXiv:physics/0306031. [16] D. Acosta et al. (CDF Collaboration), Phys. Rev. Lett. 91, 241804 (2003); A. Abulencia et al. (CDF Collaboration), Phys. Rev. D 74, 031109 (2006). [17] A. Abulencia et al. (CDF Collaboration), Phys. Rev. Lett. 98, 122001 (2007). [18] J.M. Campbell and R.K. Ellis, Phys. Rev. D 60, 113006 (1999). The ZZ cross section of 3.4 pb is appropriate for the PYTHIA Monte Carlo sample we use that includes events with one off-shell Z. The value is arrived at by T. AALTONEN et al. PHYSICAL REVIEW D 79, 052007 (2009) 052007-24 normalizing the PYTHIA sample to the Campbell and Ellis cross section of 1.58 pb for two on-shell Z bosons. [19] D. Acosta et al. (CDF Collaboration), Phys. Rev. Lett. 94, 091803 (2005). [20] Z. Sullivan, Phys. Rev. D 70, 114012 (2004). [21] A.D. Martin, R.G. Roberts, W.J. Stirling, and R.S. Thorne, Eur. Phys. J. C 4, 463 (1998). [22] J. Pumplin et al., J. High Energy Phys. 07 (2002) 012. [23] A. Bhatti et al., Nucl. Instrum. Methods Phys. Res., Sect. A 566, 375 (2006). [24] The CDF Collaboration, CDF Conference note 9448 (2008), http://www-cdf.fnal.gov/physics/new/top/ confNotes/. [25] V.M. Abazov et al. (D0 Collaboration), Phys. Rev. Lett. 100, 192003 (2008); 100, 192004 (2008). MEASUREMENT OF THE t C22 t PRODUCTION CROSS ... PHYSICAL REVIEW D 79, 052007 (2009) 052007-25