22 research outputs found
Chaos in symmetric phase oscillator networks
No full textCopyright © 2011 American Physical SocietyThis is the final version. Available from the American Physical Society via the DOI in this recordPhase-coupled oscillators serve as paradigmatic models of networks of weakly interacting oscillatory units in physics and biology. The order parameter which quantifies synchronization so far has been found to be chaotic only in systems with inhomogeneities. Here we show that even symmetric systems of identical oscillators may not only exhibit chaotic dynamics, but also chaotically fluctuating order parameters. Our findings imply that neither inhomogeneities nor amplitude variations are necessary to obtain chaos; i.e., nonlinear interactions of phases give rise to the necessary instabilities
and production at the LHC in NNLO QCD
No full textWe consider the production of and pairs at hadron colliders. We report on the complete fully differential computation of radiative corrections at next-to-next-to-leading order (NNLO) in QCD perturbation theory. The calculation includes the leptonic decay of the vector boson with the corresponding spin correlations, off shell effects and final-state photon radiation. We present numerical results for collisions at 7 and 8 TeV and we compare them with available LHC data. In the case of production, the impact of NNLO corrections is generally moderate, ranging from 8% to 18%, depending on the applied cuts. In the case of production, the NNLO effects are more important, and range from 19% to 26%, thereby improving the agreement of the theoretical predictions with the data. As expected, the impact of QCD radiative corrections is significantly reduced when a jet veto is applied
production at the LHC: fiducial cross sections and distributions in NNLO QCD
No full textWe report on the first fully differential calculation for W Z production in hadron collisions up to next-to-next-to-leading order (NNLO) in QCD perturbation theory. Leptonic decays of the W and Z bosons are consistently taken into account, i.e. we include all resonant and non-resonant diagrams that contribute to the process pp → ℓ^{′}^{±} ν ′ ℓ ℓ +X both in the same-flavour (ℓ = ℓ) and the different-flavour (ℓ ≠ ℓ) channel. Fiducial cross sections and distributions are presented in the presence of standard selection cuts applied in the experimental W Z analyses by ATLAS and CMS at centre-of-mass energies of 8 and 13 TeV. As previously shown for the inclusive cross section, NNLO corrections increase the NNLO result by about 10%, thereby leading to an improved agreement with experimental data. The importance of NNLO accurate predictions is also shown in the case of new-physics scenarios, where, especially in high-p categories, their impact can reach . The availability of differential NNLO predictions will play a crucial role in the rich physics programme that is based on precision studies of W Z signatures at the LHC.We report on the first fully differential calculation for production in hadron collisions up to next-to-next-to-leading order (NNLO) in QCD perturbation theory. Leptonic decays of the and bosons are consistently taken into account, i.e. we include all resonant and non-resonant diagrams that contribute to the process both in the same-flavour () and the different-flavour () channel. Fiducial cross sections and distributions are presented in the presence of standard selection cuts applied in the experimental analyses by ATLAS and CMS at centre-of-mass energies of 8 and 13\,TeV. As previously shown for the inclusive cross section, NNLO corrections increase the NLO result by about , thereby leading to an improved agreement with experimental data. The importance of NNLO accurate predictions is also shown in the case of new-physics scenarios, where, especially in high- categories, their impact can reach . The availability of differential NNLO predictions will play a crucial role in the rich physics programme that is based on precision studies of signatures at the LHC
production at the LHC: Fiducial cross sections and distributions in NNLO QCD
No full textWe consider QCD radiative corrections to the production of four charged leptons in the ZZ signal region at the LHC. We report on the complete calculation of the next-to-next-to-leading order (NNLO) corrections to this process in QCD perturbation theory. Numerical results are presented for TeV, using typical selection cuts applied by the ATLAS and CMS collaborations. The NNLO corrections increase the NLO fiducial cross section by about , and they have a relatively small impact on the shape of the considered kinematical distributions. In the case of the distribution of the two Z candidates, the NNLO corrections improve the agreement of the theoretical prediction with the CMS data
Status of diboson production in NNLO QCD
No full textWe present results from the first fully differential next-to-next-to leading order NNLO QCD computation of ZZ production, including off-shell effects, the leptonic decay and non-resonant contributions. We compare theoretical predictions to fiducial cross sections and distributions measured by ATLAS and CMS at 8 TeV and also perform a first comparison with early ATLAS measurements at 13 TeV
Fully-differential NNLO predictions for vector-boson pair production with MATRIX
No full textWe review the computations of the next-to-next-to-leading order (NNLO) QCD corrections to vector-boson pair production processes in proton–proton collisions and their implementation in the numerical code MATRIX. Our calculations include the leptonic decays of W and Z bosons, consistently taking into account all spin correlations, off-shell effects and non-resonant contributions. For massive vector-boson pairs we show inclusive cross sections, applying the respective mass windows chosen by ATLAS and CMS to define Z bosons from their leptonic decay products, as well as total cross sections for stable bosons. Moreover, we provide samples of differential distributions in fiducial phase-space regions inspired by typical selection cuts used by the LHC experiments. For the vast majority of measurements, the inclusion of NNLO corrections significantly improves the agreement of the Standard Model predictions with data
production at hadron colliders in NNLO QCD
No full textWe report on the first computation of the next-to-next-to-leading order (NNLO) QCD corrections to production in proton collisions. We consider both the inclusive production of on-shell pairs at LHC energies and the total rates including off-shell effects of the and bosons. In the off-shell computation, the invariant mass of the lepton pairs from the boson decay is required to be in a given mass window, and the results are compared with the corresponding measurements obtained by the ATLAS and CMS collaborations. The NNLO corrections range from 8% at =7 TeV to 11% at =14 TeV and significantly improve the agreement with the LHC data at =7 and 8 TeV
Zγ production at hadron colliders in NNLO QCD
No full textWe consider the production of Zγ pairs at hadron colliders. We report on the first complete and fully differential computation of radiative corrections at next-to-next-to-leading order in QCD perturbation theory. We present selected numerical results for pp collisions at 7 TeV and compare them to available LHC data. We find that the impact of the NNLO QCD corrections on the fiducial cross section ranges between 4 and 15%, depending on the applied cuts
