Contributors: bibliotheque, LPSC; Laboratoire de l'Accélérateur Linéaire (LAL); Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS); Laboratoire de Physique Subatomique et de Cosmologie (LPSC); Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS); Centre de Physique des Particules de Marseille (CPPM); Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS); D0; Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA; Univ Michigan, Dept Phys, Ann Arbor, MI 48109 USA; Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA; Joint Inst Nucl Res, Dubna 141980, Russia; Univ Oklahoma, Dept Phys & Astron, Norman, OK 73019 USA; Lab Accelerateur Lineaire, CNRS, IN2P3, F-91898 Orsay, France; Inst High Energy Phys, Protvino 142284, Russia; Tata Inst Fundamental Res, Sch Nat Sci, Bombay 400005, Maharashtra, India; Brookhaven Natl Lab, Dept Phys, Upton, NY 11973 USA; Univ Illinois, Dept Phys, Chicago, IL 60607 USA; Univ Nijmegen, NIKHEF, NL-6500 GL Nijmegen, Netherlands; Ctr Brasileiro Pesquisas Fis, LAFEX, BR-22290180 Rio De Janeiro, Brazil; Univ Grenoble 1, Lab Phys Subatom & Cosmol, CNRS, IN2P3, F-38026 Grenoble, France; Univ Los Andes, Dept Fis, HEP Grp, Bogota, Colombia; SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA; Univ London Imperial Coll Sci Technol & Med, Dept Phys, London SW7 2BW, England; Univ Maryland, Dept Phys, College Pk, MD 20742 USA; Univ Mediterranee, CPPM, CNRS, IN2P3, F-13288 Marseille, France; Fermilab Natl Accelerator Lab, Batavia, IL 60510 USA; FOM, Inst NIKHEF, NL-1009 DB Amsterdam, Netherlands; Univ Amsterdam, NIKHEF, NL-1009 DB Amsterdam, Netherlands; Northeastern Univ, Dept Phys, Boston, MA 02115 USA; Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA; Univ Paris 06, LPNHE, CNRS, IN2P3, F-75252 Paris, France; Univ Paris 07, LPNHE, CNRS, IN2P3, F-75252 Paris, France; Indiana Univ, Dept Phys, Bloomington, IN 47405 USA; Florida State Univ, Dept Phys 4350, Tallahassee, FL 32306 USA; Panjab Univ, Dept Phys, Chandigarh 160014, India; Univ Lancaster, Dept Phys, Lancaster LA1 4YB, England; No Illinois Univ, Dept Phys, De Kalb, IL 60115 USA; Kansas State Univ, Dept Phys, Manhattan, KS 66506 USA; Columbia Univ, Dept Phys, New York, NY 10027 USA; Univ Texas, Dept Phys, Arlington, TX 76019 USA; Brown Univ, Dept Phys, Providence, RI 02912 USA; Northwestern Univ, Dept Phys & Astron, Evanston, IL 60208 USA; Univ Freiburg, Inst Phys, D-79104 Freiburg, Germany; Boston Univ, Dept Phys, Boston, MA 02215 USA; Univ Estado Rio de Janeiro, Inst Fis, BR-20559900 Rio De Janeiro, Brazil; CINVESTAV, Dept Fis, Mexico City 07000, DF, Mexico; Univ Calif Riverside, Dept Phys, Riverside, CA 92521 USA; Univ Nebraska, Dept Phys & Astron, Lincoln, NE 68588 USA; Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA; CEA Saclay, Serv Phys Particules, DAPNIA, F-91191 Gif Sur Yvette, France; Moscow MV Lomonosov State Univ, Dept Phys, Moscow 119899, Russia; Rice Univ, Bonner Nucl Lab, Houston, TX 77005 USA; Inst Theoret & Expt Phys, Moscow 117259, Russia; Univ Notre Dame, Dept Phys, Notre Dame, IN 46556 USA; Louisiana Tech Univ, Dept Phys, Ruston, LA 71272 USA; Univ Buenos Aires, Fac Ciencias Exactas & Nat, Dept Fis, RA-1428 Buenos Aires, DF, Argentina; Natl Univ Ireland Univ Coll Dublin, Fac Sci, Dept Expt Phys, Dublin 4, Ireland; Calif State Univ Fresno, Dept Phys, Fresno, CA 93740 USA; Iowa State Univ, Dept Phys, High Energy Phys Grp, Ames, IA 50011 USA; Univ Virginia, Dept Phys, Charlottesville, VA 22901 USA; Univ San Francisco Quito, Quito, Ecuador; Univ Arizona, Dept Phys, Tucson, AZ 85721 USA; Charles Univ, Fac Math & Phys, Ctr Particle Phys, Inst Nucl & Particle Phys, CZ-18000 Prague 8, Czech Republic; Acad Sci Czech Republ, Inst Phys, Ctr Particle Phys, CZ-18221 Prague 8, Czech Republic; Inst High Energy Phys, Beijing 100039, Peoples R China; Langston Univ, Dept Math, Langston, OK 73050 USA; Univ Delhi, Dept Phys & Astrophys, Delhi 110007, India; Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA; Univ Washington, Dept Phys, Seattle, WA 98195 USA
نبذة مختصرة : The Standard Model of particle physics contains about two dozen parameters - such as particle masses - whose origins are still unknown and cannot be predicted, but whose values are constrained through their interactions. In particular, the masses of the top (t) quark (M_t) and W boson constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. A precise measurement of the top-quark mass can therefore point to where to look for the Higgs, and indeed whether the hypothesis of a SM Higgs is consistent with experimental data. Since top quarks are produced in pairs and decay in only ~10^-24 s into various final states, reconstructing their mass from their decay products is very challenging. Here we report a technique that extracts far more information from each top-quark event and yields a greatly improved precision on the top mass of 5.3 GeV/c^2, compared to previous measurements. When our new result is combined with our published measurement in a complementary decay mode and with the only other measurements available, the new world average for M_t becomes 178.0 +- 4.3 GeV/c^2. As a result, the most likely Higgs mass increases from the experimentally excluded value of 96 GeV/c^2 to 117 GeV/c^2, which is beyond current experimental sensitivity. The upper limit on the Higgs mass at 95% confidence level is raised from 219 GeV/c^2 to 251 GeV/c^2.
For high-resolution version of figures, the article, as appeared in Nature, and related News & Views, see http://www-d0.fnal.gov/Run2Physics/top/public/public.html (8 pages, 4 color figures)
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