We derive the leading two-pion exchange contributions to the two-nucleon electromagnetic current operator in the framework of chiral effective field theory using the method of unitary transformation. Explicit results for the current and charge densities are given in momentum and coordinate space.
The electromagnetic form factor of proton is studied following our previous calculation of the anomalous magnetic moment. The non-perturbative term is incorporated to correct the $Q^2$ dependence.
A gauge invariant unitary theory for pion photoproduction
Ward-Takahashi恒等式对于光生振幅的规范不变性至关重要。在这里，我们证明了酉性，特别是包含的$πN$和$γπN$阈值平等的基础上产生的光生振幅，满足两体酉性和广义沃德高桥身份。最终振幅是反应$πN\rightarrowπN$和$γN\rightarrowπN$的一组耦合通道积分方程的解。%数据可根据要求从作者处获得，%电子邮件：phchv@pippin.cc.flinders.edu.au %提交至Physical Review C
Pion photoproduction amplitudes are calculated from a set of equations that have been derived by coupling an external photon to all places in a dressed pion-nucleon vertex. The calculation is consistent with gauge invariance, charge conservation, unitarity and covariance. To provide input to the photoproduction amplitude, a photon-nucleon vertex is calculated from a set of equations derived by complete attachment of photons to a dressed nucleon propagator. We check the accuracy of this vertex by extracting its nucleon electromagnetic form factors.
Pion photoproduction off the proton in a gauge-invariant chiral unitary framework
我们在一个明显规范不变的手征么正扩展的手征微扰理论中研究质子光生π介子。在第一步中，我们考虑介子重子散射考虑到所有的次主导级接触相互作用。得到的低能常数由s波π-核子散射和反应pi- p --> eta n的低能数据拟合确定。为了评估理论上的不确定性，我们执行两种不同的拟合策略。在确定了低能常数后，我们分析了π介子和η光生的s波多极振幅E0+的数据。这些都是无参数的预测，因为两个新的低能常数是由中子和质子的磁矩决定的。
Electromagnetic Corrections to the One-Pion-Exchange Potential
在手征微扰理论的框架内计算了一π交换势的导阶电磁环修正。这些修正产生了一个有效的核子-核子势，$V_{πγ}$，它补充了OPEP和核子-核子库仑势之和。这个潜在的是电荷依赖和它的建设被证明是规范不变。潜在的$V_{πγ}$已包括在NP数据的奈梅亨分波分析中。一个特定的重整化方案的选择，导致一个可以忽略不计的变化，在带电的piNN耦合常数和NP 1 S 0散射长度和有效范围。
The formation of charged pion condensate under parallel electromagnetic fields is studied within the two-flavor Nambu--Jona-Lasinio model. The technique of Schwinger proper time method is extended to explore the quantity locating in the off-diagonal flavor space, i.e., charged pion. We obtain the associated effective potential as a function of the strength of the electromagnetic fields and find out that it contains a sextic term which possibly induce weakly first order phase transition. Dependence of pion condensation on model parameters is investigated.
Within an isospin- and momentum-dependent transport model, we investigate the necessity of selfconsistent calculations for the electromagnetic field in probing the nuclear symmetry energy using pion observables in heavy-ion collisions at intermediate energies. To this end, we perform the $^{96}$Ru + $^{96}$Ru collisions at 400 MeV/nucleon with two calculations scenarios for the electromagnetic field including the selfconsistent calculation and the most used Liénard-Wiechert formula, while the latter is a simplified one of the complete Liénard-Wiechert formula by neglecting the radiation field …
Leading-order Corrections of a Dynamical Model for Electromagnetic Pion Production Reactions
利用么正变换方法，导出了Phys.Rev.C54，2660（1996）中建立的一个电磁π介子产生反应动力学模型的有效哈密顿量的首阶修正.由此产生的能量无关的重子质量和γ N -> Delta顶点相互作用的单圈修正与核子和Delta的结构，并已计算内的组成夸克模型。我们发现，对γ N -> Delta的磁M1跃迁的单圈修正很小，而它们对E2和库仑C2跃迁的贡献与散射态的π云效应的贡献相反。我们的结果进一步表明，从提取的经验E2和C2形状因子中确定N和Delta组分夸克波函数的非球形L=2分量需要严格和完整的介子云效应计算。我们还发现，对非共振π介子产生算符的单圈修正可以解决描述近阈值γ p -> pi^0 p反应的困难。讨论了未来可能的发展。
We report on ongoing work to determine the pion-cloud contribution to the electromagnetic $N\rightarrowΔ$ transition form factors. The starting point is an $SU(6)$ spin-flavor symmetric constituent-quark model with instantaneous confinement that is augmented by dynamical pions which couple directly to the quarks. This system is treated in a relativistically invariant way within the framework of point-form quantum mechanics using a multichannel formulation. The first step is to determine the electromagnetic form factors of the bare particles that consist only of three quarks. These form factors…
"Observations on the possible electromagnetic nature of nucleon interactions and pions" -- historical manuscript from 1969 by B. W. Ninham and C. Pask
Centre of Excellence ENSEMBLE3 Sp. z o. o.（ENSEMBLE3卓越中心有限责任公司）；Chemical and Biological Systems Simulation Lab, Centre of New Technologies, University of Warsaw（华沙大学新技术中心化学与生物系统模拟实验室）；Department of Chemical and Geological Sciences and CSGI University of Cagliari（卡利亚里大学化学与地质科学系及CSGI）
We construct analytic (3+1)-dimensional inhomogeneous and topologically non-trivial pion systems using chiral perturbation theory. We discuss the effect of isospin asymmetry with vanishing electromagnetic interactions as well as some particular configurations with non-vanishing electromagnetic interactions. The inhomogeneous configurations of the pion fields are characterized by a non-vanishing topological charge that can be identified with baryons surrounded by a cloud of pions. This system supports a topologically protected persistent superflow. When the electromagnetic field is turned on th…
The two-photon-exchange (TPE) effects in the process $e^+e^- \rightarrow π^+π^-$ at large momentum transfer are discussed within the perturbative QCD (pQCD). The contributions from the twist-2 and twist-3 distribution amplitudes (DAs) of pion are considered in the estimation. Different with the results under the one-photon-exchange (OPE) approximation, the TPE effects result in an asymmetry of the differential cross section on the scattering angle. The precise measurement of this asymmetry by the further experiment is an precise test of pQCD at large momentum transfer. The time-like electromag…
We investigate the pion electromagnetic half off-shell form factors, which parametrize the matrix element of the charged pion electromagnetic current with one leg off-mass-shell and the other leg on-mass-shell, using an exactly solvable manifestly covariant model of a $(3+1)$ dimensional fermion field theory. The model provides a 3D imaging of the two off-shell pion form factors $F_1$ and $F_2$ as a function of $(Q^2,t)$, which are related to each other satisfying the Ward-Takahashi identity. The normalization of the renormalized charge form factor $F_1$ is fixed by $F_1(Q^2=0, t=m^2_π)=1$ whi…
We present our calculation of electromagnetic effects, induced by the spectator charge on Feynman-$x_F$ distributions of charged pions in peripheral $Pb+Pb$ collisions at CERN SPS energies, including realistic initial space-time-momentum conditions for pion emission. The calculation is performed in the framework of our simplified implementation of the fire-streak model, adopted to the production of both $π^-$ and $π^+$ mesons. Isospin effects are included to take into account the asymmetry in production of $π^+$ and $π^-$ at high rapidity. A comparison to a simpler model from the literature is…
