排序方式: 共有24条查询结果,搜索用时 31 毫秒
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LHC Higgs Cross Section Working Group A. Denner S. Dittmaier A. Mück G. Passarino M. Spira C. Sturm S. Uccirati M. M. Weber 《The European Physical Journal C - Particles and Fields》2012,72(5):1992
State-of-the-art predictions for the Higgs-boson production cross section via gluon fusion and for all relevant Higgs-boson
decay channels are presented in the presence of a fourth Standard-Model-like fermion generation. The qualitative features
of the most important differences to the genuine Standard Model are pointed out, and the use of the available tools for the
predictions is described. For a generic mass scale of 400−600 GeV in the fourth generation explicit numerical results for
the cross section and decay widths are presented, revealing extremely large electroweak radiative corrections, e.g., to the
cross section and the Higgs decay into WW or ZZ pairs, where they amount to about −50 % or more. This signals the onset of
a non-perturbative regime due to the large Yukawa couplings in the fourth generation. An estimate of the respective large
theoretical uncertainties is presented as well. 相似文献
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A. Bredenstein S. Dittmaier M. Roth 《The European Physical Journal C - Particles and Fields》2004,36(3):341-363
We have constructed a Monte Carlo generator (the corresponding FORTRAN code can be obtained from the authors upon request) for lowest-order predictions for the processes
and
in the standard model and extensions thereof by an effective
coupling as well as anomalous triple and quartic gauge-boson couplings. Polarization is fully supported, and a realistic photon beam spectrum can be taken into account. For the processes
all helicity amplitudes are explicitly given in a compact form. The presented numerical results contain, in particular, a survey of cross sections for representative final states and their comparison to results obtained with the program package Whizard/Madgraph. The impact of a realistic beam spectrum on cross sections and distributions is illustrated. Moreover, the size of various contributions to cross sections, such as from weak charged- or neutral-current, or from strong interactions, is analyzed. Particular attention is paid to W-pair production channels
where we investigate the impact of background diagrams, possible definitions of the W-pair signal, and the issue of gauge-invariance violation caused by finite gauge-boson widths. Finally, the effects of triple and quartic anomalous gauge-boson couplings on cross sections as well as the possibility to constrain these anomalous couplings at future
colliders are discussed.Received: 19 May 2004, Published online: 16 July 2004 相似文献
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Denner Ansgar Dittmaier Stefan Kasprzik Tobias Mück Alexander 《The European Physical Journal C - Particles and Fields》2013,73(2):1-15
The first LHC results seem to disfavor, from the point of view of naturalness, any constrained MSSM realization with universal conditions at the SUSY-breaking scale. A more motivated scenario is given by split-family SUSY, in which the first two generations of squarks are heavy, compatible with a U(2)3 flavor symmetry. We consider this flavor symmetry to be broken at a very high scale and study the consequences at low energies through its RGE evolution. Initial conditions compatible with a split scenario are found, and the preservation of correlations from minimal U(2)3 breaking are checked. The various chiral operators in ΔF=2 processes are analyzed, and we show that, due to LHC gluino bounds, the (LL)(RR) operators cannot always be neglected. Finally, we also study a possible extension of the U(2)3 model compatible with the lepton sector. 相似文献
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S. Dittmaier P. Uwer S. Weinzierl 《The European Physical Journal C - Particles and Fields》2009,59(3):625-646
We report on the calculation of the next-to-leading order QCD corrections to the production of top–antitop-quark pairs in
association with a hard jet at the Tevatron and at the LHC. Results for integrated and differential cross sections are presented.
We find a significant reduction of the scale dependence. In most cases the corrections are below 20% indicating that the perturbative
expansion is well under control. Moreover, the forward–backward charge asymmetry of the top quark, which is analyzed at the
Tevatron, is studied at next-to-leading order. We find large corrections, suggesting that the definition of the observable
has to be refined. 相似文献