We argue that the renormalization factors for nonlocal quark-antiquark and gluon operators at space-like and time-like separations connected by a Wilson line coincide to all orders in perturbation theory. We calculate the anomalous dimensions and renormalization constants of quark-antiquark and gluon operators to three- and two-loop accuracy, respectively, and also compute vacuum expectation values of these operators to three-loop accuracy.
The complete set of relations, which mutually express the spacelike and timelike kernel functions for the hadronic vacuum polarization contribution to the muon anomalous magnetic moment $a^{\text{HVP}}_μ$ in terms of each other, is obtained. By making use of the derived relations the explicit expression for the next-to-leading order spacelike kernel function, which enters the representation for $a^{\text{HVP}}_μ$ involving the hadronic vacuum polarization function, is obtained. The corresponding next-to-leading order spacelike kernel function, which appears in the representation for $a^{\text{…
We investigate the $(π^0,η,η')\toγ^*γ$ transitions both for the spacelike region and the timelike region using the light-front quark model (LFQM). In particular, we present the new direct method to explore the timelike region without resorting to mere analytic continuation from the spacelike region to the timelike region. Our direct calculation in timelike region shows the complete agreement not only with the analytic continuation result from the spacelike region but also with the result from the dispersion relation between the real and imaginary parts of the form factor. For the low energy re…
Some form factors of ground-state hadrons with spin might show a zero crossing at spacelike momenta of electron-hadron scattering. In the timelike region of hadron-antihadron production by electron-positron collisions the form factors become complex. When the hadrons decay, the relative phases between form factors can be measured by the angular distributions of their decay products. Using analyticity and the QCD high-energy limits for constraint-free form factors and for helicity amplitudes, we show how a single zero crossing in the spacelike region is related to the high-energy limit of the p…
This addendum provides results complementary to those obtained in [J. Phys. G49, 055001 (2022)]. Specifically, an equivalent form of the relation, which binds together the "spacelike" kernel functions for the hadronic vacuum polarization contribution to the muon anomalous magnetic moment $a^{\text{HVP}}_μ$, is obtained. It is shown that the infrared limiting value of the "spacelike" and "timelike" kernel functions, which enter the representations for $a^{\text{HVP}}_μ$ involving the Adler function and the $R$-ratio, is identical to the corresponding QED contribution to the muon anomalous magne…
We present complete calculations of the electromagnetic form factors of the $Ω^-$ in the spacelike region and in the timelike region. The four elastic form factors: electric charge ($G_{E0}$), magnetic dipole ($G_{M1}$), electric quadrupole ($G_{E2}$) and magnetic octupole ($G_{M3}$), are estimated within the covariant spectator quark model, in terms of the square momentum transfer $q^2$. The free parameters of the $Ω^-$ wave function, including a $S$-wave state and two independent $D$-wave states radial wave functions and the admixture coefficients are fixed by the comparison with the lattice…
Based on the recently measurements of the $e^{+} e^{-} \to Σ^{+} \barΣ^{-}$ and $e^{+} e^{-} \to Σ^{-} \barΣ^{+}$ processes, the electromagnetic form factors of the hyperon $Σ^+$ and $Σ^-$ in the timelike region are investigate by using the vector meson dominance model. We have included the contributions from the $ρ$, $ω$ and $ϕ$ mesons. The model parameters are determined with the BESIII experimental data on the timelike effective form factors $|G_{\rm eff}|$ of $Σ^{+}$ and $Σ^{-}$ for center-of-mass energy from 2.3864 to 3.02 GeV. Then, we analytically continue the electromagnetic form facto…
Two-Loop Spacelike Splitting Amplitudes in Full-Color QCD
CERN, Theoretical Physics Department（欧洲核子研究中心理论物理部）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；Key Laboratory for Particle Astrophysics and Cosmology (MOE)（粒子天体物理与宇宙学重点实验室（教育部））
The energy-energy-correlator (EEC) observable in $e^+e^-$ annihilation measures the energy deposited in two detectors as a function of the angle between the detectors. The collinear limit, where the angle between the two detectors approaches zero, is of particular interest for describing the substructure of jets produced at hadron colliders as well as in $e^+e^-$ annihilation. We derive a factorization formula for the leading power asymptotic behavior in the collinear limit of a generic quantum field theory, which allows for the resummation of logarithmically enhanced terms to all orders by re…
