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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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| 2. |
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| 3. |
- Martinez, EA, et al.
(författare)
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Incidence of unilateral fertilizations after low dose deep intrauterine insemination in spontaneously ovulating sows under field conditions
- 2006
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Ingår i: Reproduction in domestic animals. - : Wiley-Blackwell. - 0936-6768 .- 1439-0531. ; 41:1, s. 41-47
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Tidskriftsartikel (refereegranskat)abstract
- A new procedure for non-surgical deep intrauterine insemination (DUI) in unrestrained sows hormonally induced to ovulate, has been reported. In comparison with standard artificial insemination (AI), with this procedure, the sperm numbers inseminated can be reduced 20-fold without reducing the reproductive performance of these hormonally treated sows. The present study evaluated, using two experiments, the reproductive performance applying 20-fold different sperm numbers per AI dose using DUI or standard AI in spontaneously ovulating sows, under field conditions. In experiment 1, AI was applied to crossbred sows at 12, 24 and 36 h after onset of spontaneous oestrus using one of the following two regimes: (i) DUI (treatment) with 0.15 x 10(9) fresh boar spermatozoa in 5 ml of Beltsville thawing solution (BTS) extender (n = 95), and (ii) standard cervical AI (control) with 2.85 x 10(9) fresh spermatozoa in 95 ml of BTS extender (n = 95). The farrowing rates of the two groups of sows were statistically similar (NS). However, a decrease (p less than 0.002) in litter size and the total number of pigs born alive was observed in sows inseminated with the DUI procedure. In experiment 2, 42 post-weaned oestrus sows were inseminated following the same design described for experiment 1 during spontaneous oestrus. On day 6 after onset of oestrus, the proximal segment of the uterine horns of the sows were flushed under surgery to retrieve eventual embryos and evaluate the success of fertilization per cornua (e.g. occurrence of effective uni- vs bilateral sperm transport rendering uni- or bilateral, complete or partial fertilization). Retrieved embryos were assessed for cleavage and number of accessory spermatozoa. Although identical overall pregnancy rates were achieved in both insemination groups, the percentage of sows with partial bilateral fertilization and unilateral fertilization was markedly higher (p less than 0.05) in the DUI group (35%) compared with the control (standard AI) group (5%), with a consequent lower (p less than 0.001) percentage of viable early embryos after DUI. The number of accessory spermatozoa in the zona pellucida of the embryos was highly variable, but higher (p less than 0.001) in control animals than in DUI-AI. No accessory spermatozoa were found in oocytes retrieved from sows depicting unilateral fertilization. In conclusion, DUI in spontaneously ovulating sows with 0.15 x 10(9) spermatozoa renders similar farrowing rates but a lower litter size compared with use of standard AI with a 20-fold higher sperm dose. The lower litter size ought to be related to a decreased distribution of spermatozoa after DUI leading to a higher incidence of partial bilateral and unilateral fertilization.
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