Evidence for production of single top quarks

被引:89
作者
Abazov, V. M. [1 ,44 ]
Abbott, B. [86 ]
Abolins, M. [76 ]
Acharya, B. S. [36 ]
Adams, M. [62 ]
Adams, T. [60 ]
Aguilo, E. [7 ,8 ,9 ,10 ]
Ahn, S. H. [38 ]
Ahsan, M. [70 ]
Alexeev, G. D. [1 ,44 ]
Alkhazov, G. [48 ]
Alton, A. [75 ]
Alverson, G. [74 ]
Alves, G. A. [3 ]
Anastasoaie, M. [43 ]
Ancu, L. S. [43 ]
Andeen, T. [64 ]
Anderson, S. [56 ]
Anzelc, M. S. [64 ]
Aoki, M. [61 ]
Arnoud, Y. [18 ]
Arov, M. [71 ]
Arthaud, M. [23 ]
Askew, A. [60 ]
Asman, B. [49 ,50 ,51 ,52 ]
Assis Jesus, A. C. S. [4 ]
Atramentov, O. [60 ]
Avila, C. [12 ]
Ay, C. [31 ]
Badaud, F. [17 ]
Baden, A. [72 ]
Bagby, L. [61 ]
Baldin, B. [61 ]
Bandurin, D. V. [70 ]
Banerjee, P. [36 ]
Banerjee, S. [36 ]
Barberis, E. [74 ]
Barfuss, A. -F. [19 ]
Bargassa, P. [91 ]
Baringer, P. [69 ]
Barreto, J. [3 ]
Bartlett, J. F. [61 ]
Bassler, U. [23 ]
Bauer, D. [54 ]
Beale, S. [7 ,8 ,9 ,10 ]
Bean, A. [69 ]
Begalli, M. [4 ]
Begel, M. [84 ]
Belanger-Champagne, C. [49 ,50 ,51 ,52 ]
Bellantoni, L. [61 ]
机构
[1] Joint Inst Nucl Res, Dubna, Russia
[2] Univ Buenos Aires, Buenos Aires, DF, Argentina
[3] Ctr Brasileiro Pesquisas Fis, LAFEX, Rio De Janeiro, Brazil
[4] Univ Estado Rio de Janeiro, BR-20550011 Rio De Janeiro, Brazil
[5] Univ Fed ABC, Santo Andre, Brazil
[6] Univ Estadual Paulista, Inst Fis Teor, BR-01405 Sao Paulo, Brazil
[7] Univ Alberta, Edmonton, AB, Canada
[8] Simon Fraser Univ, Burnaby, BC V5A 1S6, Canada
[9] York Univ, Toronto, ON M3J 2R7, Canada
[10] McGill Univ, Montreal, PQ, Canada
[11] Univ Sci & Technol China, Hefei 230026, Peoples R China
[12] Univ Los Andes, Bogota, Colombia
[13] Charles Univ Prague, Ctr Particle Phys, Prague, Czech Republic
[14] Czech Tech Univ, CR-16635 Prague, Czech Republic
[15] Acad Sci Czech Republ, Inst Phys, Ctr Particle Phys, Prague, Czech Republic
[16] Univ San Francisco, Quito, Ecuador
[17] Univ Blaise Pascal, IN2P3, CNRS, LPC, Clermont, France
[18] Univ Grenoble 1, IN2P3, CNRS, LPSC,Inst Natl Polytech Grenoble, F-38041 Grenoble, France
[19] Univ Mediterranee, CNRS, IN2P3, CPPM, Marseille, France
[20] Univ Paris 11, CNRS, IN2P3, LAL, Orsay, France
[21] Univ Paris 06, CNRS, IN2P3, LPNHE, Paris, France
[22] Univ Paris 07, CNRS, IN2P3, LPNHE, Paris, France
[23] CEA, DAPNIA, Serv Phys Particules, Saclay, France
[24] Univ Strasbourg, IPHC, Strasbourg, France
[25] Univ Haute Alsace, CNRS, IN2P3, Strasbourg, France
[26] Univ Lyon 1, IPNL, CNRS, IN2P3, F-69622 Villeurbanne, France
[27] Univ Lyon, Lyon, France
[28] Rhein Westfal TH Aachen, Phys Inst A 3, Aachen, Germany
[29] Univ Bonn, Inst Phys, D-5300 Bonn, Germany
[30] Univ Freiburg, Inst Phys, Freiburg, Germany
[31] Johannes Gutenberg Univ Mainz, Inst Phys, D-6500 Mainz, Germany
[32] Univ Munich, Munich, Germany
[33] Univ Wuppertal, Fachbereich Phys, Wuppertal, Germany
[34] Panjab Univ, Chandigarh 160014, India
[35] Univ Delhi, Delhi 110007, India
[36] Tata Inst Fundamental Res, Mumbai 400005, Maharashtra, India
[37] Univ Coll Dublin, Dublin 2, Ireland
[38] Korea Univ, Korea Detector Lab, Seoul, South Korea
[39] Sungkyunkwan Univ, Suwon, South Korea
[40] CINVESTAV, Mexico City 14000, DF, Mexico
[41] NIKHEF H, FOM Inst, NL-1009 DB Amsterdam, Netherlands
[42] Univ Amsterdam, NIKHEF, Amsterdam, Netherlands
[43] Radboud Univ Nijmegen, NIKHEF, NL-6525 ED Nijmegen, Netherlands
[44] Joint Inst Nucl Res, Dubna, Russia
[45] Inst Theoret & Expt Phys, Moscow 117259, Russia
[46] Moscow MV Lomonosov State Univ, Moscow, Russia
[47] Inst High Energy Phys, Protvino, Russia
[48] Petersburg Nucl Phys Inst, St Petersburg, Russia
[49] Stockholm Univ, S-10691 Stockholm, Sweden
[50] Royal Inst Technol, Stockholm, Sweden
来源
PHYSICAL REVIEW D | 2008年 / 78卷 / 01期
基金
瑞典研究理事会; 加拿大自然科学与工程研究理事会; 巴西圣保罗研究基金会; 英国科学技术设施理事会;
关键词
D O I
10.1103/PhysRevD.78.012005
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron p (p) over bar collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top-quark partner that is always produced from strong-coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top-quark production has been searched for in ever larger data sets. In this analysis, we select events from a 0.9 fb(-1) data set that have an electron or muon and missing transverse energy from the decay of a W boson from the top-quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W + jets and t (t) over bar events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix-element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top-quark production of sigma(p (p) over bar -> tb + X, tqb + X) = 4.7 +/- 1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top-quark production. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa quark mixing matrix element that describes the Wtb coupling and find vertical bar V(tb)f(1)(L)vertical bar = 1.31(-0.21)(+0.25), where f(1)(L) is a generic vector coupling. This model-independent measurement translates into 0.68 <vertical bar V-tb vertical bar <= 1 at the 95% C.L. in the standard model.
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页数:47
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