Journal Article

A precision measurement of the mass of the top quark

Bos, K, Abolins, M, Bertram, I, Alves, G A, Da Motta, H, Begel, M, Eltzroth, J T, Blazey, G, Demarteau, M, Avila, C, Edmunds, D, Duflot, L, Bolton, T A, Abazov, V M, Bojko, N I, Chakraborty, D, Demine, P, Diehl, H T, Blekman, F, Boehnlein, A, Crépé-Renaudin, S, Adams, D L, Elvira, V D, Blessing, S, Connolly, B, Buescher, V, Cutts, D, Borcherding, F, Chan, K M, Bean, A, Cummings, M A C, Dugad, S R, Carvalho, W, Doulas, S, Denisov, S P, Babukhadia, L, Abramov, V, Davis, G A, Burtovoi, V S, Bacon, T C, Diesburg, M, Briskin, G, Castilla-Valdez, H, Banerjee, S, Belyaev, A, Chekulaev, S V, Babintsev, V V, Acharya, B S, Cho, D K, Beuselinck, R, Arnoud, Y, Barberis, E, Ahmed, S N, Duperrin, A, Butler, J M, Beri, S B, Bartlett, J F, Baden, A, Cooper, W E, Beaudette, F, Canelli, F, Dyshkant, A, Abdesselam, A, Demina, R, Besson, A, Chopra, S, Casey, D, Dudko, L V, Alton, A, Ellison, J, Clark, A R, Claes, D, Bhatnagar, V, Baffioni, S, De Jong, S J, Bose, T, Bross, A, Brooijmans, G, Bezzubov, V A, Barreto, J, Bhat, P C, Buchholz, D, Bhattacharjee, M, Brandt, A, Denisov, D, Buehler, M, Balm, P W, Adams, M, Baldin, B, Choi, S, Bassler, U, Desai, S, Baringer, P, Brock, R, Abbott, B, Alex

2004

Overview

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 ± 5.3 GeV/ c 2 ) when compared to previous measurements 2 . When our new result is combined with our published measurement in a complementary decay mode 3 and with the only other measurements available 2 , the new world average for M t becomes 4 178.0 ± 4.3 GeV/ c 2 . As a result, the most likely Higgs mass increases from the experimentally excluded 5 value 6 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 .

• Publisher: Nature Publishing Group UK,Nature Publishing,Nature Publishing Group
• Subject: Exact sciences and technology / High Energy Physics - Experiment / Humanities and Social Sciences / letter / multidisciplinary / Physics / Science / Science (multidisciplinary) / The physics of elementary particles and fields