Elaborating on the four-dimensional helicity scheme, we propose a pure four-dimensional formulation (FDF) of the
d
-dimensional regularization of one-loop scattering amplitudes. In our formulation ...particles propagating inside the loop are represented by massive internal states regulating the divergences. The latter obey Feynman rules containing multiplicative selection rules which automatically account for the effects of the extra-dimensional regulating terms of the amplitude. We present explicit representations of the polarization and helicity states of the four-dimensional particles propagating in the loop. They allow for a complete, four-dimensional, unitarity-based construction of
d
-dimensional amplitudes. Generalized unitarity within the FDF does not require any higher-dimensional extension of the Clifford and the spinor algebra. Finally we show how the FDF allows for the recursive construction of
d
-dimensional one-loop integrands, generalizing the four-dimensional open-loop approach.
We report on the calculation of the cross section for Higgs boson production in association with three jets via gluon fusion, at next-to-leading-order (NLO) accuracy in QCD, in the infinite top-mass ...approximation. After including the complete NLO QCD corrections, we observe a strong reduction in the scale dependence of the result, and an increased steepness in the transverse momentum distributions of both the Higgs boson and the leading jets. The results are obtained with the combined use of GOSAM, SHERPA, and the MADDIPOLE-MADEVENT framework.
Spike fertility index (SF) has been proposed as a promising trait to be used as a selection criterion in wheat breeding programs aimed at increasing grain yield, but no actual evidence of its ...successful application has been reported. In this study, 146 recombinant inbred lines derived from a cross between ‘Baguette 10’ and ‘Klein Chajá’, Argentinean spring bread wheat cultivars with contrasting SF, were evaluated during three crop seasons (2013, 2014 and 2015) at Balcarce, Argentina. Grain yield, grain number/m
2
, grain weight, and SF were measured at maturity. Changes in grain yield (i.e., responses to selection) after application of different selection strategies, including different selection criteria and selection intensities, were determined. Significant correlations were observed between grain number and grain yield, SF and grain yield, and SF and grain weight. Analysis of SF variance components showed a significant genotype × environment interaction, but it represented only 9% of the total variation, whereas 51% of the variation was genetic, resulting in a high narrow-sense heritability (0.84). The use of SF as a selection criterion, either solely or in combination with selection for high yield, increased yield, resulting in higher and more stable yields than if selecting for high yield alone. Our findings support the use of spike fertility index as a selection criterion for increasing genetic progress and stability of yield in bread wheat breeding programs.
Fusarium head blight (FHB) remains a devastating disease in bread wheat (
Triticum aestivum
L.). Genetic resistance to FHB is complex; aside from active physiological resistance, plant developmental ...and morphological traits indirectly affect disease progression and provide a passive resistance mechanism. Here, the relationship between FHB Type II resistance and spike architecture traits was evaluated in a recombinant inbred line (RIL) population of bread wheat in field experiments during two crop seasons under a completely randomized block design with two replications. Point inoculation was carried out at anthesis of each RIL. Disease severity at 21 days post inoculation (dpi), area under the disease progress curve (AUDPC) comprising severity measurements at 12, 17 and 21 dpi, rachis length, spike density, number of spikelets per spike, number of florets per spike and number of florets per spikelet were determined. The population showed significant variation for all traits. Heritability was moderate-high for FHB severity (0.69) and AUDPC (0.63) and high for spike architecture traits (0.74–0.92). FHB severity at 21 dpi and AUDPC were significantly associated with number of florets per spike
r
= 0.38 (
P
< 0.001) and
r
= 0.31 (
P
< 0.01) respectively and with the number of florets per spikelet
r
= 0.28 (
P
< 0.01) and
r
= 0.27 (
P
< 0.05) respectively, reflecting a greater spread of the fungus in spikes with higher floret number. These results suggest that the number of florets per spike and per spikelet should be considered in FHB resistance breeding efforts, because selection of lines with higher number of florets could lead to a correlated selection response towards increased FHB levels under field conditions.
Grain yield in bread wheat is often tightly associated with grain number/m2. In turn, spike fertility (SF), i.e., the quotient between grain number and spike chaff dry weight, accounts for a great ...proportion of the variation in grain number among cultivars. In order to examine the potential use of SF as a breeding target, (1) variation for the trait was assessed in six datasets combining commercial cultivars under different environmental conditions, (2) trait heritability was estimated in a set of F1 hybrids derived from controlled crosses between cultivars with contrasting SF and (3) SF distribution pattern was analysed in two F2 segregating populations. Analysis of commercial cultivars revealed considerable variation for SF, under both optimal and sub-optimal conditions. In addition, genotypic variation was consistently larger than genotype × environment interaction variation in all datasets. Narrow sense heritability, estimated by the mid-parent-offspring regression of 20 F1 hybrids and their respective parents, was 0·63. Data from two F2 populations exhibited bell-shaped and symmetric frequency distributions of SF, with a SF mean intermediate between the parental values. Substantial transgressive segregation was detected in both F2 populations. In conclusion, SF appears to be a heritable trait with predominantly additive effects. This warrants further investigation on the feasibility of using SF as an early selection criterion in wheat breeding programs aimed at increasing grain yield.
We present the calculation of the cross section for Higgs boson production in association with a top quark pair plus one jet, at next-to-leading-order accuracy in QCD. All mass dependence is retained ...without recurring to any approximation. After including the complete next-to-leading-order QCD corrections, we observe a strong reduction in the scale dependence of the result. We also show distributions for the invariant mass of the top quark pair, with and without the additional jet, and for the transverse momentum and the pseudorapidity of the Higgs boson. Results for the virtual contributions are obtained with a novel reduction approach based on integrand decomposition via the Laurent expansion, as implemented in the library, NINJA. Cross sections and differential distributions are obtained with an automated setup which combines the GOSAM and SHERPA frameworks.
We present the calculation of the NLO QCD corrections to the associated production of a Higgs boson and two jets, in the infinite top-mass limit. We discuss the technical details of the computation ...and we show the numerical impact of the radiative corrections on several observables at the LHC. The results are obtained by using a fully automated framework for fixed order NLO QCD calculations based on the interplay of the packages GoSam and Sherpa. The evaluation of the virtual corrections constitutes an application of the d-dimensional integrand-level reduction to theories with higher dimensional operators. We also present first results for the one-loop matrix elements of the partonic processes with a quark-pair in the final state, which enter the hadronic production of a Higgs boson together with three jets in the infinite top-mass approximation.
FormCalc 7 Agrawal, S; Hahn, T; Mirabella, E
Journal of physics. Conference series,
01/2012, Letnik:
368, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We present additions and improvements in Version 7 of FormCalc, most notably analytic tensor reduction, choice of OPP methods, and MSSM initialization via FeynHiggs, as well as a parallelized Cuba ...library for numerical integration.
Many extensions of the Standard Model involve two Higgs doublet fields to break the electroweak symmetry, leading to the existence of three neutral and two charged Higgs particles. In particular, ...this is the case of the Minimal Supersymmetric extension of the Standard Model, the MSSM. A very important parameter is tanβ defined as the ratio of the vacuum expectation value of the two Higgs doublets. In this Letter we focus on the left–right asymmetry in the production of polarised top quarks in association with charged Higgs bosons at the LHC. This quantity allows for a theoretically clean determination of tanβ. In the MSSM, the asymmetry remains sensitive to the strong and electroweak radiative corrections and, thus, to the superparticle spectrum. Some possible implications of these results are discussed.
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