Electromagnetic Form Research Articles

Nucleon Electromagnetic Form Factors at Large Momentum Transfer from Lattice QCD

Nucleon Electromagnetic Form Factors at Large Momentum Transfer from Lattice QCD

Multipole expansion for the electron-nucleus scattering at high energies in the unified electroweak theory

The paper presents the multipole expansion for the electron-nucleus scattering cross section at high energies within the framework of the unified electroweak theory. The electroweak currents of the nucleus are expanded into the simple components with definite angular momenta, called the multipole form factors. The multipole expansion of the cross section is a consequence of the above expansion. Besides the familiar electromagnetic form factors, there are also the vector and axial form factors, respectively, related to weak interactions. To determine multipole form factors, general formulas for the calculation of reduced matrix elements are established using the fractional parentage coefficient method and the multiparticle shell model. Calculation of them enables us to obtain more detailed information about the nuclear structure and elucidate the role played by the weak interaction in the high-energy reaction mechanisms.

Momentum dependence of mixing in the pion vector form factor and its effect on * *Supported in part by the Fundamental Research Funds for the Central Universities (FRF-BR-19-001A), and the National Natural Science Foundation of China (11975028, 11974043)

The inclusion of the mixing effect is essential for a precise description of the pion electromagnetic form factor in the process, which quantifies the two-pion contribution to the anomalous magnetic moment of muon . In this study, we analyze the momentum dependence of mixing by considering loop contributions at the next-to-leading order in expansion within the framework of resonance chiral theory. We revisit a previous study [Y. H. Chen, D. L. Yao, and H. Q. Zheng, Commun. Theor. Phys. 69, 1 (2018)] and consider the contribution arising from the kaon mass splitting in the kaon loops and latest experimental data. We perform two types of fits (with momentum-independent or momentum-dependent mixing amplitude) to describe and data within the energy region of 600900 MeV and decay width of . Furthermore, we compare their results. Our findings indicate that the momentum-independent and momentum-dependent mixing schemes provide appropriate descriptions of the data. However, the momentum-dependent scheme exhibits greater self-consistency, considering the reasonable imaginary part of the mixing matrix element obtained. Regarding the contribution to the anomalous magnetic moment of the muon, , the results obtained from the fits considering the momentum-dependent mixing amplitude are in good agreement with those obtained without incorporating the momentum dependence of mixing, within the margin of errors. Furthermore, based on the fitted values of the relevant parameters, we observe that the decay width of is predominantly influenced by the mixing effect.

An Assessment of Pseudoscalar and Vector Meson Electromagnetic Form Factors

An Assessment of Pseudoscalar and Vector Meson Electromagnetic Form Factors

Multi-objective parametric optimization of driver-based electromagnetic sheet metal forming of SS304 using AA6061-T6 driver

This study uses statistical techniques to optimize the electromagnetic forming process for driver-based sheet metal forming with a flat coil. AA6061T6 sheet was used as a driver to form SS304 sheets. The optimization of maximum elongation, die fitting, maximum Lorentz force, and peak current was carried out. The results were verified through simulation which were in close agreement with the experimental results. The most influential factor was the voltage (C.R of 72.97%), followed by coil gap and SS304 sheet thickness (7.99 and 6.07%, respectively).

Study pion distribution amplitudes from the electromagnetic form factor by data-driven dispersion relation

We study the pion electromagnetic form factor in the modulus squared dispersion relation, and do the model independent extraction of the chiral mass embedded in the sub-leading twist light-cone distribution amplitude. The motivation of this work is the recent measurement of timelike form factor in the resonant regions, which makes up the piece lacking solid QCD-based calculation. With the perturbative QCD calculation up to next-to-leading-order of strong coupling and twist four level of meson distribution amplitudes, we obtain the chiral mass of pion meson as m_0^pi (1 , textrm{GeV}) = 1.31^{+0.27}_{-0.30} , textrm{GeV}. Due to the chiral enhancement contribution from the sub-leading twist distribution amplitudes in the perturbative QCD calculation, we can not extract the lowest Gegenbauer moments of pion from the study of electromagnetic form factor. This problem could be settled down with the foresee Belle-II and BESIII measurement of the transition form factor especially in the large momentum transfers regions.

The Dual Energetic State of Living Organisms: Life. death and restitution

Our initial study demonstrated the release of a replicate cell from a dwarf form of Stentor coeurleus that had undergone apoptosis, i.e., programmed cell death. The replicate separated from the moribund cell and faded into the ambient environment. In the present series of experiments actively mobile, transparent, dwarf cells and algae fragments were returned from the ambient state into sealed deep well slides containing cell free protozoa medium. Ancillary experiments provided evidence that these cells displayed electromagnetic energy. Further observation over several days showed a progressive transformation of the dwarf cell by accruing inclusions to a senescent state and eventual encysted state. We hypothesize that these unicellular cells and algae fragment consisted of metabolic and electromagnetic energetic forms that can be separated at the life/death interface and returned from the ambient environment by electromagnetic energy. Restitution of the metabolic form and senescent is the final process.

Valence quark, sea, and gluon content of the pion from the parton distribution functions and the electromagnetic form factor

Valence quark, sea, and gluon content of the pion from the parton distribution functions and the electromagnetic form factor

Pion observables calculated in Minkowski and Euclidean spaces with Ansätze for quark propagators

We study two quark--propagator meromorphic Ans\"atze that admit clear connection between calculations in Euclidean space and Minkowski spacetime. The connection is established through a modified Wick rotation in momentum space, where the integration contour along the imaginary axis is adequately deformed. The Ans\"atze were previously proposed in the literature and fitted to Euclidean lattice QCD data. The generalized impulse approximation is used to calculate the pion transition form factor and electromagnetic form factor, correcting an earlier result. The pion decay constant and distribution amplitude are also calculated. The latter is used to deduce the asymptotic behavior of the form factors. Such an asymptotic behavior is compared with those obtained directly from the generalized impulse approximation and the causes of differences are pointed out.

Contribution of nuclear excitation electromagnetic form factors in C12 and O16 to the Coulomb sum rule

We report on empirical parameterizations of longitudinal and transverse nuclear excitation electromagnetic form factors in ${\rm ^{12}C}$ and ${\rm ^{16}O}$. We extract the contribution of nuclear excitations to the Normalized Inelastic Coulomb Sum Rule (\csr) as a function of momentum transfer $\bf q$ and find that it is significant (0.29$\pm$0.030 at $\bf q$= 0.22 GeV). The total contributions of nuclear excitations to $S_L({\bf q})$ in ${\rm ^{12}C}$ and ${\rm ^{16}O}$ are found to be equal within the uncertainties. Since the cross sections for nuclear excitations are significant, the radiative tails from nuclear excitations should be included in precise calculations of radiative corrections to quasielastic electron scattering at low $\bf q$ and deep-inelastic electron scattering at large energy transfers $\nu$. The parameterizations also serve as a benchmark in testing theoretical modeling of cross sections for excitation of nuclear states in electron and neutrino interactions on nuclear targets at low energies.

Generalized parton distributions at zero skewness

We present a new determination of the generalized parton distributions (GPDs) with their uncertainties at zero skewness, $ \xi =0 $, through a simultaneous analysis of all available experimental data of the nucleon electromagnetic form factors (FFs), nucleon charge and magnetic radii, proton axial FFs (AFFs) and wide-angle Compton scattering (WACS) cross sections for the first time, and we investigate whether there is any tension between these data. This can be considered the most comprehensive analysis of GPDs at $ \xi=0 $ performed so far. We show that such an analysis provides the simultaneous determination of three kinds of GPDs, namely $ H^q $, $ \widetilde{H}^q $ and $ E^q $, considering also the sea-quark contributions. As a result, we find that the inclusion of the WACS and AFF data at larger values of the momentum transfer squared $ Q^2=-t $ can put new constraints on GPDs and change them drastically in some cases. We show that there is a considerable tension between the WACS and the proton magnetic form factor ($ G_M^p $) data, especially at larger values of $ -t $. However, we indicate that the results for the gravitational FF $ M_2 $ and the proton total angular momentum $ J^p $ calculated using the extracted GPDs are in relatively good agreement with the light-cone QCD sum rules (LCSRs) and lattice QCD predictions when the sea-quark contributions are considered and both WACS and $ G_M^p $ data are included in the analyses simultaneously.

Toy model to understand the oscillatory behavior in timelike nucleon form factors

To understand the oscillatory behavior exhibited in the timelike electromagnetic form factors of nucleons, we propose a toy model based on the Jost function of the $N\bar N$ pair into the timelike form factors with the help of the distorted-wave Born approximation. By constructing a simple square-well potential reflecting the final-state interaction of $N\bar N$, we naturally represent the damped oscillatory phenomenon in the timelike electromagnetic form factors of nucleons. Especially, our study reveals that the ``period" of the oscillation is approximately determined by the Yukawa interaction range $1/m_\pi$. Other possible potentials are also discussed. The threshold enhancements of the cross sections for $e^+e^-\to n\bar n$, $\Lambda\bar\Lambda$, and $\Lambda_c\bar\Lambda_c$ can also be understand within this scenario.

Effect of die conductivity on electromagnetic forming of tube

Electromagnetic forming (EMF) is a high-speed forming technology that uses electromagnetic forces to deform materials. In this process, the capacitor bank stores energy and it is discharged through the coil; here small part of stored energy is utilized, and the remaining part is wasted through losses. The current loss is significant. It can be in the form of loss in coil, die, fixtures, etc. It has been observed that the range of efficiency of the EMF process varies between 10 and 40%. Therefore, the present work explores into reducing the losses by using a suitable die material to improve the efficiency of the EMF process. Here, the effect of die material on the deformation of Al tube is studied. For this study, two die of same geometry and different materials, namely nylon and steel, are used. It is observed that the effect of die material plays important role in the EMF process. Almost 5% increase in deformation is observed with nylon die compared to steel die at the same discharge energy. The FE based simulations are carried out and results are validated experimentally with 94% agreement.

Analysis of high velocity forming of metallic tubes

Metal forming is vital in many manufacturing industries for resizing and reshaping of raw metallic tubes and sheets. Conventional forming processes like forging, rolling, tube drawing and extrusion are associated with high-cost complex tools which are applicable for specific shape and size. High velocity deformation process utilizes impact energy for forming and deformation takes place at high velocity. This paper analyses the high velocity forming of 6061 aluminium tubes, formed under electromagnetic force. Numerical simulation is used to understand dynamic conditions of electromagnetic compressive forming.

Simulation of Electromagnetic Forming Process and Optimization of Geometric Parameters of Perforated Al Sheet Using RSM

Electromagnetic forming (EMF) is a kind of high-speed forming technology that can be useful for materials like aluminum. EMF helps to overcome the limitations of traditional forming. Due to this ability, the use of EMF in automotive applications has risen in recent years. The application of finite element software packages such as ANSYS 22 gives numerical modelling capabilities to simulate the EMF process and to design the forming process. Hence, the aim of this research work is to build and study the three-dimensional finite element model for the electromagnetic forming process and analyze the geometric parameters influencing the deformation of the perforated sheet with a design of experiments (DOE) approach. The finite element simulation is used in two stages. In the first stage, the electromagnetic force or Lorentz force striking the workpiece (i.e., Al sheet) is predicted using the ANSYS 22 Emag module. In the second stage, the predicted Lorentz force is then applied on an Al sheet to calculate the sheet deformation. The deformation of the sheet is predicted for different combinations of the geometric parameters of the sheet, such as open area percentage, ligament ratio (LR) and size of the hole, using ANSYS 22 Structural. In the DOE, response surface methodology (RSM) is used by considering the geometric parameters of perforated sheet such as open area percentage, ligament ratio (LR) and size of the hole. To minimize the number of experiments, an RSM model named central composite design (CCD) is employed. Further, the optimization study finds that the maximum deformation 0.0435 mm is calculated for the optimized combination of 25% open area, 0.14 LR and 4 mm hole size.

Measurements of the Electric and Magnetic Form Factors of the Neutron for Timelike Momentum Transfer.

We present the first measurements of the electric and magnetic form factors of the neutron in the timelike (positive q^{2}) region as function of four-momentum transfer. We explored the differential cross sections of the reaction e^{+}e^{-}→n[over ¯]n with data collected with the BESIII detector at the BEPCII accelerator, corresponding to an integrated luminosity of 354.6 pb^{-1} in total at twelve center-of-mass energies between sqrt[s]=2.0-2.95 GeV. A relative uncertainty of 18% and 12% for the electric and magnetic form factors, respectively, is achieved at sqrt[s]=2.3935 GeV. Our results are comparable in accuracy to those from electron scattering in the comparable spacelike region of four-momentum transfer. The electromagnetic form factor ratio R_{em}≡|G_{E}|/|G_{M}| is within the uncertainties close to unity. We compare our result on |G_{E}| and |G_{M}| to recent model predictions, and the measurements in the spacelike region to test the analyticity of electromagnetic form factors.

Unpolarized generalized parton distributions of light and heavy vector mesons

We study the leading-twist unpolarized generalized parton distributions (GPDs) of light and heavy vector mesons, i.e., the $\ensuremath{\rho}$, $J/\ensuremath{\psi}$, and $\mathrm{\ensuremath{\Upsilon}}$, at zero skewness. An ansatz incorporating the zero-mode contribution is introduced to modify the light front overlap representation of GPDs. The leading Fock-state light front wave functions of vector mesons from Dyson-Schwinger and Bethe-Salpeter equations approach are then employed to study the meson GPDs. The light front spatial distribution of valence quarks within vector mesons is then studied with the impact parameter dependent GPD. We also investigate the electromagnetic and gravitational form factors, which are the first and second Mellin moments of the GPDs. The light-cone mass radius of $\ensuremath{\rho}$ is determined to be 0.30 fm, close to a recent Nambu-Jona-Lasinio model prediction of 0.32 fm. For $J/\ensuremath{\psi}$ and $\mathrm{\ensuremath{\Upsilon}}$, they are predicted to be 0.151 fm and 0.089 fm respectively.

Gauge Invariance of Quantum Electrodynamics of Multi-Electron Atoms

The proof of the gauge invariance of the quantum electrodynamics of photons and electrons does not apply directly to the quantum electrodynamics of photons, electrons, and nuclei, since the multi-electron atoms belong to the space of asymptotic states of the extended theory. We indicate two possible ways to circumvent this problem and prove, using a fairly general model for the description of nucleon–nucleon interaction in nuclei, the gauge invariance of the masses and electromagnetic form factors of multi-electron atoms in all orders of perturbation theory.

1−+ hybrid meson in J/ψ radiative decays from lattice QCD

We present the first theoretical prediction of the production rate of $1^{-+}$ light hybrid meson $\eta_1$ in $J/\psi$ radiative decays. In the $N_f=2$ lattice QCD formalism with the pion mass $m_\pi\approx 350$ MeV, the related electromagnetic multipole form factors are extracted from the three-point functions that involve necessarily quark annihilation diagrams, which are calculated through the distillation method. The partial width of $J/\psi\to \gamma \eta_1$ is determined to be $2.29(77)~\mathrm{eV}$ at the $\eta_1$ mass $m_{\eta_1}=2.23(4)$ GeV. If $\eta_1$ corresponds to the recently observed $\eta_1(1855)$ in the process $J/\psi\to \gamma\eta_1(1855)\to \gamma \eta\eta'$ by BESIII, then the branching fraction $\mathrm{Br}(J/\psi\to \gamma\eta_1(1855))$ is estimated to be $6.2(2.2)\times 10^{-5}$, which implies $\mathrm{Br}(\eta_1(1855)\to \eta\eta')\sim 4.3\%$.

The electromagnetic Sigma-to-Lambda transition form factors with coupled-channel effects in the space-like region

Using dispersion theory, the electromagnetic Sigma-to-Lambda transition form factors are expressed as the product of the pion electromagnetic form factor and the Sigma {bar{varLambda }}rightarrow pi pi scattering amplitudes with the latter estimated from SU(3) chiral perturbation theory including the baryon decuplet as explicit degrees of freedom. The contribution of the K{bar{K}} channel is also taken into account and the pi pi –K{bar{K}} coupled-channel effect is included by means of a two-channel Muskhelishvili–Omnès representation. It is found that the electric transition form factor shows a significant shift after the inclusion of the K{bar{K}} channel, while the magnetic transition form factor is only weakly affected. However, the K{bar{K}} effect on the electric form factor is obscured by the undetermined coupling h_A in the three-flavor chiral Lagrangian. The error bands of the Sigma-to-Lambda transition form factors from the uncertainties of the couplings and low-energy constant in three-flavor chiral perturbation theory are estimated by a bootstrap sampling method.