Quantum field theory predicts a nonlinear response of the vacuum to strong electromagnetic fields of macroscopic extent.This fundamental tenet has remained experimentally challenging and is yet to be tested in the lab...Quantum field theory predicts a nonlinear response of the vacuum to strong electromagnetic fields of macroscopic extent.This fundamental tenet has remained experimentally challenging and is yet to be tested in the laboratory.A particularly distinct signature of the resulting optical activity of the quantum vacuum is vacuum birefringence.This offers an excellent opportunity for a precision test of nonlinear quantum electrodynamics in an uncharted parameter regime.Recently,the operation of the high-intensity Relativistic Laser at the X-ray Free Electron Laser provided by the Helmholtz International Beamline for Extreme Fields has been inaugurated at the High Energy Density scientific instrument of the European X-ray Free Electron Laser.We make the case that this worldwide unique combination of an X-ray free-electron laser and an ultra-intense near-infrared laser together with recent advances in high-precision X-ray polarimetry,refinements of prospective discovery scenarios and progress in their accurate theoretical modelling have set the stage for performing an actual discovery experiment of quantum vacuum nonlinearity.展开更多
A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion e...A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion elastic and transition form factors. The analysis reveals the following momentum fractions at the scale ζ2:= 2GeV :〈xvalence〉 = 0.48（3）, 〈xglue〉 = 0.41（2）, 〈xsea〉 = 0.11（2）;and despite hardening induced by the emergent phenomenon of dynamical chiral symmetry breaking, the valence-quark distribution function, qπ（x）, exhibits the x ≈ 1 behaviour predicted by quantum chromodynamics（QCD）. After evolution to o ζ = 5.2 GeV, the prediction for qπ（x） matches that obtained using lattice-regularised QCD. This confluence should both stimulate improved analyses of existing data and aid in planning efforts to obtain new data on the pion distribution functions.展开更多
基金funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)under Grants Nos.392856280,416611371,416607684,416702141 and 416708866 within the Research Unit FOR2783/2 and Project-ID 278162697–SFB 1242.
文摘Quantum field theory predicts a nonlinear response of the vacuum to strong electromagnetic fields of macroscopic extent.This fundamental tenet has remained experimentally challenging and is yet to be tested in the laboratory.A particularly distinct signature of the resulting optical activity of the quantum vacuum is vacuum birefringence.This offers an excellent opportunity for a precision test of nonlinear quantum electrodynamics in an uncharted parameter regime.Recently,the operation of the high-intensity Relativistic Laser at the X-ray Free Electron Laser provided by the Helmholtz International Beamline for Extreme Fields has been inaugurated at the High Energy Density scientific instrument of the European X-ray Free Electron Laser.We make the case that this worldwide unique combination of an X-ray free-electron laser and an ultra-intense near-infrared laser together with recent advances in high-precision X-ray polarimetry,refinements of prospective discovery scenarios and progress in their accurate theoretical modelling have set the stage for performing an actual discovery experiment of quantum vacuum nonlinearity.
基金Supported by the Chinese Government’s Thousand Talents Plan for Young ProfessionalsJiangsu Province Hundred Talents Plan for ProfessionalsForschungszentrum Jülich GmbH
文摘A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion elastic and transition form factors. The analysis reveals the following momentum fractions at the scale ζ2:= 2GeV :〈xvalence〉 = 0.48（3）, 〈xglue〉 = 0.41（2）, 〈xsea〉 = 0.11（2）;and despite hardening induced by the emergent phenomenon of dynamical chiral symmetry breaking, the valence-quark distribution function, qπ（x）, exhibits the x ≈ 1 behaviour predicted by quantum chromodynamics（QCD）. After evolution to o ζ = 5.2 GeV, the prediction for qπ（x） matches that obtained using lattice-regularised QCD. This confluence should both stimulate improved analyses of existing data and aid in planning efforts to obtain new data on the pion distribution functions.
