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- Schael, S, et al.
(författare)
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Precision electroweak measurements on the Z resonance
- 2006
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 5. |
- Thulin, Mats, 1948-, et al.
(författare)
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Ambilobea, a new genus from Madagascar, the position of Aucoumea, and comments on the tribal classification of the frankincense and myrrh family (Burseraceae)
- 2008
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 26:04-mar, s. 218-229
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Tidskriftsartikel (refereegranskat)abstract
- Phylogenetic analyses of 46 species, representing all tribes and 14 out of 18 recognized genera of Burseraceae, are performed using nuclear ETS and plastid rps16 sequences. Boswellia madagascariensis, the only Malagasy species of this genus, is shown to belong to a clade comprising all sampled members of the current tribe Canarieae plus Triomma, whereas other species of Boswellia (including the type, B. serrata) form a clade that is strongly supported as sister to Garuga. A new genus, Ambilobea, is proposed for B. madagascariensis and the new combination A. madagascariensis is made. Ambilobea differs from Boswellia s. s. by being dioecious and by having valvate petals and, furthermore, is unique in the family by its winged tips to the petioles, by having pyrenes that remain attached to the detached valves of the fruit at dehiscence, and by its long-spinose pollen grains. Aucoumea, a monotypic central African rain forest genus, is strongly supported as sister to a clade with the arid-adapted Bursera and Commiphora. Boswellia s. s. and Garuga form a clade characterized by having hermaphroditic flowers. The relationships within Burseraceae emerging from this and previous phylogenetic studies are, on several points, in conflict with current tribal delimitation. The following suggestions for a new tribal classification of Burseraceae are made: 1) Beiselia, sister to the rest of the family, needs to be placed in a tribe of its own, Beiselieae, trib. nov., 2) Protieae should be restricted to Crepidospermum, Protium and Tetragastris, although generic rearrangements seem to be needed within this tribe, 3) Bursereae should be restricted to Aucoumea, Bursera and Commiphora, but generic rearrangements are needed in the Bursera-Commiphora complex, 4) the remaining genera, Ambilobea, Boswellia, Canarium, Dacryodes, Garuga, Haplolobus, Pseudodacryodes, Rosselia, Santiria, Scutinanthe, Trattinnickia and Triomma, are probably best placed in a broadly circumscribed Garugeae.
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