Letters to Nature

Nature 429, 638-642 (10 June 2004) | doi:10.1038/nature02589; Received 23 January 2004; Accepted 21 April 2004

A precision measurement of the mass of the top quark

DØ CollaborationV. M. Abazov1, B. Abbott2, A. Abdesselam3, M. Abolins4, V. Abramov5, B. S. Acharya6, D. L. Adams7, M. Adams8, S. N. Ahmed9, G. D. Alexeev1, A. Alton10, G. A. Alves11, Y. Arnoud12, C. Avila13, V. V. Babintsev5, L. Babukhadia14, T. C. Bacon15, A. Baden16, S. Baffioni17, B. Baldin18, P. W. Balm19, S. Banerjee6, E. Barberis20, P. Baringer21, J. Barreto11, J. F. Bartlett18, U. Bassler22, D. Bauer23, A. Bean21, F. Beaudette3, M. Begel24, A. Belyaev25, S. B. Beri26, G. Bernardi22, I. Bertram27, A. Besson12, R. Beuselinck15, V. A. Bezzubov5, P. C. Bhat18, V. Bhatnagar26, M. Bhattacharjee14, G. Blazey28, F. Blekman19, S. Blessing25, A. Boehnlein18, N. I. Bojko5, T. A. Bolton29, F. Borcherding18, K. Bos19, T. Bose30, A. Brandt31, G. Briskin32, R. Brock4, G. Brooijmans30, A. Bross18, D. Buchholz33, M. Buehler8, V. Buescher34, V. S. Burtovoi5, J. M. Butler35, F. Canelli24, W. Carvalho36, D. Casey4, H. Castilla-Valdez37, D. Chakraborty28, K. M. Chan24, S. V. Chekulaev5, D. K. Cho24, S. Choi38, S. Chopra7, D. Claes39, A. R. Clark40, B. Connolly25, W. E. Cooper18, D. Coppage21, S. Crépé-Renaudin12, M. A. C. Cummings28, D. Cutts32, H. da Motta11, G. A. Davis24, K. De31, S. J. de Jong9, M. Demarteau18, R. Demina24, P. Demine41, D. Denisov18, S. P. Denisov5, S. Desai14, H. T. Diehl18, M. Diesburg18, S. Doulas20, L. V. Dudko42, L. Duflot3, S. R. Dugad6, A. Duperrin17, A. Dyshkant28, D. Edmunds4, J. Ellison38, J. T. Eltzroth31, V. D. Elvira18, R. Engelmann14, S. Eno16, G. Eppley43, P. Ermolov42, O. V. Eroshin5, J. Estrada24, H. Evans30, V. N. Evdokimov5, T. Ferbel24, F. Filthaut9, H. E. Fisk18, M. Fortner28, H. Fox33, S. Fu30, S. Fuess18, E. Gallas18, A. N. Galyaev5, M. Gao30, V. Gavrilov44, R. J. Genik II27, K. Genser18, C. E. Gerber8, Y. Gershtein32, G. Ginther24, B. Gómez13, P. I. Goncharov5, K. Gounder18, A. Goussiou45, P. D. Grannis14, H. Greenlee18, Z. D. Greenwood46, S. Grinstein47, L. Groer30, S. Grünendahl18, M. W. Grünewald48, S. N. Gurzhiev5, G. Gutierrez18, P. Gutierrez2, N. J. Hadley16, H. Haggerty18, S. Hagopian25, V. Hagopian25, R. E. Hall49, C. Han10, S. Hansen18, J. M. Hauptman50, C. Hebert21, D. Hedin28, J. M. Heinmiller8, A. P. Heinson38, U. Heintz35, M. D. Hildreth45, R. Hirosky51, J. D. Hobbs14, B. Hoeneisen52, J. Huang23, Y. Huang10, I. Iashvili38, R. Illingworth15, A. S. Ito18, M. Jaffré3, S. Jain2, R. Jesik15, K. Johns53, M. Johnson18, A. Jonckheere18, H. Jöstlein18, A. Juste18, W. Kahl29, S. Kahn7, E. Kajfasz17, A. M. Kalinin1, D. Karmanov42, D. Karmgard45, R. Kehoe4, S. Kesisoglou32, A. Khanov24, A. Kharchilava45, B. Klima18, J. M. Kohli26, A. V. Kostritskiy5, J. Kotcher7, B. Kothari30, A. V. Kozelov5, E. A. Kozlovsky5, J. Krane50, M. R. Krishnaswamy6, P. Krivkova54, S. Krzywdzinski18, M. Kubantsev29, S. Kuleshov44, Y. Kulik18, S. Kunori16, A. Kupco55, V. E. Kuznetsov38, G. Landsberg32, W. M. Lee25, A. Leflat42, F. Lehner18,61, C. Leonidopoulos30, J. Li31, Q. Z. Li18, J. G. R. Lima28, D. Lincoln18, S. L. Linn25, J. Linnemann4, R. Lipton18, A. Lucotte12, L. Lueking18, C. Lundstedt39, C. Luo23, A. K. A. Maciel28, R. J. Madaras40, V. L. Malyshev1, V. Manankov42, H. S. Mao56, T. Marshall23, M. I. Martin28, S. E. K. Mattingly32, A. A. Mayorov5, R. McCarthy14, T. McMahon57, H. L. Melanson18, A. Melnitchouk32, A. Merkin42, K. W. Merritt18, C. Miao32, H. Miettinen43, D. Mihalcea28, N. Mokhov18, N. K. Mondal6, H. E. Montgomery18, R. W. Moore4, Y. D. Mutaf14, E. Nagy17, M. Narain35, V. S. Narasimham6, N. A. Naumann9, H. A. Neal10, J. P. Negret13, S. Nelson25, A. Nomerotski18, T. Nunnemann18, D. O'Neil4, V. Oguri36, N. Oshima18, P. Padley43, K. Papageorgiou8, N. Parashar46, R. Partridge32, N. Parua14, A. Patwa14, O. Peters19, P. Pétroff3, R. Piegaia47, B. G. Pope4, H. B. Prosper25, S. Protopopescu7, M. B. Przybycien33,61, J. Qian10, S. Rajagopalan7, P. A. Rapidis18, N. W. Reay29, S. Reucroft20, M. Ridel3, M. Rijssenbeek14, F. Rizatdinova29, T. Rockwell4, C. Royon41, P. Rubinov18, R. Ruchti45, B. M. Sabirov1, G. Sajot12, A. Santoro36, L. Sawyer46, R. D. Schamberger14, H. Schellman33, A. Schwartzman47, E. Shabalina8, R. K. Shivpuri58, D. Shpakov20, M. Shupe53, R. A. Sidwell29, V. Simak55, V. Sirotenko18, P. Slattery24, R. P. Smith18, G. R. Snow39, J. Snow57, S. Snyder7, J. Solomon8, Y. Song31, V. Sorín47, M. Sosebee31, N. Sotnikova42, K. Soustruznik54, M. Souza11, N. R. Stanton29, G. Steinbrück30, D. Stoker59, V. Stolin44, A. Stone8, D. A. Stoyanova5, M. A. Strang31, M. Strauss2, M. Strovink40, L. Stutte18, A. Sznajder36, M. Talby17, W. Taylor14, S. Tentindo-Repond25, T. G. Trippe40, A. S. Turcot7, P. M. Tuts30, R. Van Kooten23, V. Vaniev5, N. Varelas8, F. Villeneuve-Seguier17, A. A. Volkov5, A. P. Vorobiev5, H. D. Wahl25, Z.-M. Wang14, J. Warchol45, G. Watts60, M. Wayne45, H. Weerts4, A. White31, D. Whiteson40, D. A. Wijngaarden9, S. Willis28, S. J. Wimpenny38, J. Womersley18, D. R. Wood20, Q. Xu10, R. Yamada18, T. Yasuda18, Y. A. Yatsunenko1, K. Yip7, J. Yu31, M. Zanabria13, X. Zhang2, B. Zhou10, Z. Zhou50, M. Zielinski24, D. Zieminska23, A. Zieminski23, V. Zutshi28, E. G. Zverev42 & A. Zylberstejn41 for DØ Collaboration (Participants are listed in alphabetical order.)

  1. Joint Institute for Nuclear Research, P O Box 79, 141980 Dubna, Russia;
  2. University of Oklahoma, Department of Physics and Astronomy, Norman, Oklahoma 73019, USA;
  3. Laboratoire de l'Accélérateur Linéaire, IN2P3-CNRS, BP 34, Batiment 200, F-91898 Orsay, France;
  4. Michigan State University, Department of Physics and Astronomy, East Lansing, Michigan 48824, USA;
  5. Institute for High Energy Physics, 142284 Protvino, Russia;
  6. Tata Institute of Fundamental Research, School of Natural Sciences, Homi Bhabha Rd, Mumbai 400005, India;
  7. Brookhaven National Laboratory, Physics Department, Bldg 510C, Upton, New York 11973, USA;
  8. University of Illinois at Chicago, Department of Physics, 845 W. Taylor, Chicago, Illinois 60607, USA;
  9. University of Nijmegen/NIKHEF, P O Box 9010, NL-6500 GL Nijmegen, The Netherlands;
  10. University of Michigan, Department of Physics, 500 E. University Avenue, Ann Arbor, Michigan 48109, USA;
  11. LAFEX, Centro Brasileiro de Pesquisas Físicas, Rua Dr Xavier Sigaud, 150, 22290-180 Rio de Janeiro, Brazil;
  12. Laboratoire de Physique Subatomique et de Cosmologie, IN2P3-CNRS, Université de Grenoble 1, 53 Avenue des Martyrs, F-38026 Grenoble, France;
  13. Universidad de los Andes, Department de Fisica, HEP Group, Apartado Aereo 4976, Bogotá, Colombia;
  14. State University of New York, Department of Physics and Astronomy, Stony Brook, New York 11794, USA;
  15. Imperial College London, Department of Physics, Prince Consort Road, London SW7 2BW, UK;
  16. University of Maryland, Department of Physics, College Park, Maryland 20742, USA;
  17. CPPM, IN2P3-CNRS, Université de la Méditerranée, 163 Avenue de Luminy, F-13288 Marseille, France;
  18. Fermi National Accelerator Laboratory, P O Box 500, Batavia, Illinois 60510, USA;
  19. FOM-Institute NIKHEF and University of Amsterdam/NIKHEF, P O Box 41882, 1009 DB Amsterdam, The Netherlands;
  20. Northeastern University, Department of Physics, Boston, Massachusetts 02115, USA;
  21. University of Kansas, Department of Physics and Astronomy, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045, USA;
  22. LPNHE, Universités Paris VI and VII, IN2P3-CNRS, 4 Place Jussieu, Tour 33, F-75252 Paris, France;
  23. Indiana University, Department of Physics, 727 E. 3rd St, Bloomington, Indiana 47405, USA;
  24. University of Rochester, Department of Physics and Astronomy, Rochester, New York 14627, USA;
  25. Florida State University, Department of Physics 4350, Tallahassee, Florida 32306, USA;
  26. Panjab University, Department of Physics, Chandigarh 160014, India;
  27. Lancaster University, Department of Physics, Lancaster LA1 4YB, United Kingdom;
  28. Northern Illinois University, Department of Physics, DeKalb, Illinois 60115, USA;
  29. Kansas State University, Department of Physics, Manhattan, Kansas 66506, USA;
  30. Columbia University, Department of Physics, 538 W. 120th St, New York, New York 10027, USA;
  31. University of Texas, Department of Physics, Box 19059, Arlington, Texas 76019, USA;
  32. Brown University, Department of Physics, 182 Hope St, Providence, Rhode Island 02912, USA;
  33. Northwestern University, Department of Physics and Astronomy, 2145 Sheridan Road, Evanston, Illinois 60208, USA;
  34. Universität Freiburg, Physikalisches Institut, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany;
  35. Boston University, Department of Physics, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA;
  36. Universidade do Estado do Rio de Janeiro, Instituto de Física, Rua São Francisco Xavier, 524, 20559-900 Rio de Janeiro, Brazil;
  37. CINVESTAV, Departamento de Física, P O Box 14-740, 07000 Mexico City, Mexico;
  38. University of California, Department of Physics, Riverside, California 92521, USA;
  39. University of Nebraska, Department of Physics and Astronomy, Lincoln, Nebraska 68588, USA;
  40. Lawrence Berkeley National Laboratory and University of California, 1 Cyclotron Road, Berkeley, California 94720, USA;
  41. DAPNIA/Service de Physique des Particules, CEA, Saclay, F-91191 Gif-sur-Yvette, France;
  42. Moscow State University, Department of Physics, Vorobjovy Gory, 119899 Moscow, Russia;
  43. Rice University, Bonner Nuclear Lab, P O Box 1892, Houston, Texas 77005, USA;;
  44. Institute for Theoretical and Experimental Physics, B. Cheremushkinskaya ul. 25, 117259 Moscow, Russia;
  45. University of Notre Dame, Department of Physics, Notre Dame, Indiana 46556, USA;
  46. Louisiana Tech University, Department of Physics, Ruston, Louisiana 71272, USA;;
  47. Universidad de Buenos Aires, Departamento de Física, FCEN, Pabellón 1, Ciudad Universitaria, 1428 Buenos Aires, Argentina;
  48. University College Dublin, Department of Experimental Physics, Faculty of Science, Belfield, Dublin 4, Ireland;
  49. California State University, Department of Physics, 2345 E. San Ramon Avenue, Fresno, California 93740, USA;
  50. Iowa State University, Department of Physics, High Energy Physics Group, Ames, Iowa 50011, USA;
  51. University of Virginia, Department of Physics, Charlottesville, Virginia 22901, USA;
  52. Universidad San Francisco de Quito, P O Box 17-12-841, Quito, Ecuador;
  53. University of Arizona, Department of Physics, P O Box 210081, Tucson, Arizona 85721, USA;
  54. Institute of Particle and Nuclear Physics, Center for Particle Physics, Faculty of Mathematics and Physics, Charles University in Prague, V Holesovickach 2, CZ-18000 Prague 8, Czech Republic;
  55. Institute of Physics of the Academy of Sciences of the Czech Republic, Center for Particle Physics, Na Slovance 2, CZ-18221 Prague 8, Czech Republic;
  56. Institute of High Energy Physics, P O Box 918, Beijing 100039, China;
  57. Langston University, Department of Mathematics, Langston, Oklahoma 73050, USA;
  58. Delhi University, Department of Physics and Astrophysics, Delhi 110007, India;
  59. University of California, Department of Physics and Astronomy, 4129 Frederick Reines Hall, Irvine, California 92697, USA;
  60. University of Washington, Department of Physics, P O Box 351560, Seattle, Washington 98195, USA.
  61. Present addresses: University of Zurich, Zurich, Switzerland (F.L.); Institute of Nuclear Physics, Krakow, Poland (M.B.P.)

The standard model of particle physics contains parameters—such as particle masses—whose origins are still unknown and which cannot be predicted, but whose values are constrained through their interactions. In particular, the masses of the top quark (M t) and W boson (M W)1 constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. A precise measurement of M t can therefore indicate where to look for the Higgs, and indeed whether the hypothesis of a standard model Higgs is consistent with experimental data. As top quarks are produced in pairs and decay in only about 10-24 s into various final states, reconstructing their masses from their decay products is very challenging. Here we report a technique that extracts more information from each top-quark event and yields a greatly improved precision (of plusminus 5.3 GeV/c 2) when compared to previous measurements2. When our new result is combined with our published measurement in a complementary decay mode3 and with the only other measurements available2, the new world average for M t becomes4 178.0 plusminus 4.3 GeV/c 2. As a result, the most likely Higgs mass increases from the experimentally excluded5 value6 of 96 to 117 GeV/c 2, which is beyond current experimental sensitivity. The upper limit on the Higgs mass at the 95% confidence level is raised from 219 to 251 GeV/c 2.

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