Cross-section, vector-polarization, and tensor-polarization distributions are calculated for the reactions $e^+ e^- \rightarrow \bar{p}p$ and $e^+ e^- \rightarrow \barΛ Λ$. Each reaction requires six characteristic functions that are bilinear in the, possibly complex, electromagnetic form factors, denoted $G_E(P^2)$ and $G_M(P^2)$, of $p$ and $Λ$. For the hyperon reaction also the joint-decay distributions of $Λ$ and $\barΛ$ are calculated. Their knowledge allow a complete determination of the hyperon electromagnetic form factors, without measuring hyperon spins. We explain how this is done in practice. For some tensor-polarization components our results are in conflict with previously repeatedly published distributions.
In present work, we investigated $K^{-}+\, ^{3}\mathrm{He}$ reaction at low energies. The coupled-channel Faddeev AGS equations were solved for $\bar{K}Nd-πΣ{d}$ three-body system in momentum representation to extract the scattering amplitudes. To trace the signature of the $Λ$(1405) resonance in the $πΣ$ invariant mass, the deuteron energy spectrum for $K^{-}+\,^{3}\mathrm{He}\rightarrowπΣ{d}$ reaction was obtained. Different types of $\bar{K}N-πΣ$ potentials based on phenomenological and chiral SU(3) approaches were used. As a remarkable result of this investigation, it was found that the de…
Three-body calculations of $K\bar{K}N$ system with quantum numbers $I=1/2$, $J^π=(\frac{1}{2})^{+}$ were performed. Using separable potentials for two-body interactions, we calculated the $πΣ$ mass spectra for the $(\bar{K}N)_{I=0}+K^{+}\rightarrow(πΣ)^{0}K^{+}$ reaction on the basis of three-body Alt-Grassberger-Sandhas equations in the momentum representation. In this regard, different types of $\bar{K}N-πΣ$ potentials based on phenomenological and chiral SU(3) approach are used. The possibility to observe the trace of $Λ(1405)$ resonance in $(πΣ)^{0}$ mass spectra was studied. Using the $χ^…
A method to extract the polarization of $Ω$ hyperons produced via the strong interaction is presented. Assuming they are spin 3/2 particles, the corresponding spin density matrix can be written in terms of seven non-zero polarization parameters, all retrievable from the angular distribution of the decay products. Moreover by considering the full decay chain $Ω\rightarrow ΛK\rightarrow pπK$ the magnitude of the asymmetry parameters $β_Ω$ and $γ_Ω$ can be obtained. This method, applied here to the specific $Ω$ case, can be generalized to any weakly decaying hyperon and is perfectly suited for th…
Cross section of the neutron capture reaction $n+p\rightarrow d+γ$ at threshold was calculated with different realistic $^{3}S_{1}$ deuteron and $^{1}S_{0}$ $np$ scattering wave functions stemming from Nijmegen-II, JISP16, Paris, Idaho and Moscow (with forbidden states) potentials. It is found that this reaction with thermal neutrons may be described without a contribution of meson exchange currents.
In this work, we make a theoretical study on the $p \bar p \rightarrow Λ\barΛη$ reaction for antiproton beam energy from threshold to 4GeV within an effective Lagrangian approach and isobar model. By assuming this reaction is dominated by the excitation of $Λ$ and $\bar Λ$ resonances in intermediate states, we calculate the total cross sections and give the predictions of the angular distribution and invariant mass spectrum of final particles. In particular, we discuss the possibility to verify the existence of a narrow $Λ$ resonance found in the process of $K^- p\to ηΛ$ in the present reactio…
Resonance model study on $K^+ N \rightarrow K N η$ near threshold
利用共振模型研究了$K^+ N \rightarrow K N η$反应，假定这些反应在阈值附近受$N^*(1535)$的激发控制.发现超子交换图和$ρ$交换图对这些反应的贡献最大。因此，这些反应可能是研究$N^*(1535)$与$KΛ$、$KΣ$和$Nρ$通道偶联的好地方。我们表明，最终粒子的角分布提供了有用的信息有关的不同机制的$N^*(1535)$激发，这可能是有用的，为未来的实验分析这些反应。
We investigate the charmed baryon production reaction $p\bar{p}\rightarrowΛ_c\barΛ_c$ in an effective Lagrangian approach. Besides the $t$-channel $D^0$ and $D^{*0}$ mesons exchanges, the $s$-channel $Y(4630)$ meson exchange is taken into account. For the total cross sections, the $D^0$ and $D^{*0}$ mesons provide minor background contributions, while the $Y(4630)$ state gives a clear peak structure with the magnitude of 10 $μ$b at center of mass energy 4.63 GeV. Basing on the results, we suggest that the reaction of $p\bar{p}\rightarrowΛ_c\barΛ_c$ can be used to search for the $1^{--}$ charmo…
The $\bar{K} N \rightarrow K Ξ$ reaction in coupled channel chiral models up to next-to-leading order
本文采用次领先阶的手征SU（3）拉格朗日量，在耦合道中实现么正化，研究了奇异度S=-1扇区中s波中的介子-重子相互作用.拉格朗日的参数已被安装到一个大的实验数据在不同的两体通道，特别注意的$\bar{K} N \rightarrow K Ξ$反应，这是特别敏感的非线性光学条款。为了改进$KΞ$产生通道中的模型，唯象地考虑了高自旋超子共振$Σ(2030)$和$Σ(2250)$的影响.
The $Λ(1405)$ resonance production reaction is investigated within the framework of the coupled-channels Alt-Grassberger-Sandhas (AGS) equations. We perform full three-body calculations for the $\bar{K}NN-πYN$ amplitudes on the physical real energy axis and investigate how the signature of the $Λ(1405)$ appears in the cross sections of the $K^-d\rightarrow πΣn$ reactions, also in view of the planned E31 experiment at J-PARC. Two types of meson-baryon interaction models are considered: an energy-dependent interaction based on chiral $SU(3)$ effective field theory, and an energy-independent vers…
Collective reaction paths for fusion reactions, $^{16}$O+$α$ $\rightarrow$ $^{20}$Ne and $^{16}$O+$^{16}$O $\rightarrow$ $^{32}$S, are microscopically determined, on the basis of the adiabatic self-consistent collective coordinate (ASCC) method. The collective path is maximally decoupled from other intrinsic degrees of freedom. The reaction paths turn out to deviate from those obtained with standard mean-field calculations with constraints on quadrupole and octupole moments. The potentials and inertial masses defined in the ASCC method are calculated along the reaction paths. The sub-barrier f…
The lowest-lying resonance in the QCD spectrum is the $0^{++}$ isoscalar $σ$ meson, also known as the $f_0(500)$. We augment SU(2) chiral perturbation theory ($χ$PT) by including the $σ$ meson as an additional explicit degree of freedom, as proposed by Soto, Talavera, and Tarrús and others. In this effective field theory, denoted $χ$PT$_S$, the $σ$ meson's well-established mass and decay width are not sufficient to properly renormalize its self energy. At $\mathcal{O}(p^4)$ another low-energy constant appears in the dressed $σ$-meson propagator; we adjust it so that the isoscalar pion-pion sca…
The reaction $e^+e^-\rightarrow Λ^+_c\barΛ^-_c$ is investigated at energies close to the threshold with emphasis on the role played by the $X(4630)$ resonance. The interaction in the final $Λ^+_c \barΛ^-_c$ system, constructed within chiral effective field theory and supplemented by a pole diagram that represents a bare $X(4630)$ resonance, is taken into account rigorously. The pole parameters of the $X(4630)$ are extracted and found to be compatible with the ones of the $X(4660)$ resonance that have been established in the reaction $e^+e^- \to π^+π^-ψ(2S)$. The actual result for the $X(4630)$…
Partial-wave analysis of $\bar K N$ scattering reactions
我们通过单能分波分析研究了两体反应$\bar K N\rightarrow \bar K N$、$\bar K N\rightarrow πΛ$和$\bar K N\rightarrow πΣ$。能量范围1480 - 2100 MeV。因此，提取的这些反应的分波振幅的多通道能量依赖模型满足的分波$S$矩阵的么正性的约束。我们得到了很好的预测微分截面，极化，极化截面，和截面这些反应从一个全球性的能量依赖的解决方案。
We report on the calculation of first-order QED corrections for the $γp\rightarrow l^+l^-p^{\prime}$ process. An upcoming experiment at MAMI (Mainz) aims to compare the cross sections of muon- and electron-pair production in this reaction to test lepton universality. Precise knowledge of the electromagnetic radiative corrections is needed for these measurements. As a first step, we present the leading QED radiative corrections in the soft-photon approximation when accounting for the finite lepton mass. For the kinematics at MAMI, we find corrections of the percent level for muons, and of order…
In this paper, we study the polarization of the $Λ(1405)$ in the $γp \rightarrow K^+ πΣ$ reaction within an effective Lagrangian approach and isobar model. In our model, the $Λ(1405)$ is excited through the t-channel $K/K^*$ exchanges and u-channel hyperon exchange. Compared to previous studies, we also include the contribution from a contact term, which is necessary for our model to interpret the polarization of the $Λ(1405)$. In addition, we also discuss the possibility to verify the proposed two-pole structure of the $Λ(1405)$ using the polarization data. We find that the polarization of th…
The $K^- p \rightarrow ηΛ$ reaction in an effective Lagrangian model
我们报告的理论研究的$K^- p \to ηΛ$反应阈值附近使用有效的拉格朗日方法。考虑了$s-$通道$Λ(1670)$、$t-$通道$K^*$和$u-$通道质子极图的作用。我们表明，总的截面数据是很好地再现。然而，仅考虑$s-$波$Λ(1670)$态以及$t-$和$u-$通道的背景贡献并不足以描述$K^- p \to ηΛ$反应角分布中的碗状结构，这表明在某些能量区域应该存在对该反应有贡献的较高分波.事实上，如果我们考虑来自$D_{03}$共振的贡献，我们可以描述碗结构，然而，需要相当小的宽度（$\sim 2$ MeV）的这种共振。
The $η$ mesic nucleus is considered to be one of the interesting exotic many body systems and has been studied since 1980's theoretically and experimentally. Recently, the formation of the $η$ mesic nucleus in the fusion reactions of the light nuclei such as $d + d \rightarrow (η+ α) \rightarrow X$ has been proposed and the experiments have been performed by WASA-at-COSY. We develop a theoretical model to evaluate the formation rate of the $η$ mesic nucleus in the fusion reactions and show the calculated results. We find that the $η$ bound states could be observed in the reactions in cases wit…
The determination of the Argonne National Laboratory-Osaka University (ANL-Osaka) Partial-Wave Amplitudes (PWA) of $πN$ and $γN$ Reactions is reviewed. The predicted PWA are presented on a web page (https://www.phy.anl.gov/theory/research/anl-osaka-pwa). The formulas are given for using the predicted PWA to calculate the cross sections of (1) meson-baryon ($MB$) scattering $MB \rightarrow M'B'$ with $MB, M'B'= πN, ηN, KΛ, KΣ$, (2) two-pion production $πN \rightarrow πΔ, ρN, σN \rightarrow ππN$, (3) Meson photoproduction $γN \rightarrow πN, ηN, KΛ, KΣ$, (4) Pion electroproduction $N(e,e'π)N$, (…
A combined analysis of the reactions $π^-p\rightarrow K^0Λ$ and $ηn$ is carried out with a chiral quark model. The data in the center-of-mass (c.m.) energy range from threshold up to $W\simeq 1.8$ GeV are reasonably described. For $π^-p\rightarrow K^0Λ$, it is found that $N(1535)S_{11}$ and $N(1650)S_{11}$ paly crucial roles near threshold. The $N(1650)S_{11}$ resonance contributes to the reaction through configuration mixing with $N(1535)S_{11}$. The constructive interference between $N(1535)S_{11}$ and $N(1650)S_{11}$ is responsible for the peak structure around threshold in the total cross …
Sequential decays of the triple strange process $\bar{p} p \rightarrow \barΩ^{+} Ω^{-} \rightarrow K^{+} \barΛ K^{-} Λ\rightarrow K^{+} \bar{p} π^{+} K^{-} p π^{-}$: a model-independent approach
本文开发了一种模型无关的不可约张量形式论，用于分析 PANDA 实验中 $\ar{p}p$ 碰撞产生 $\arΩΩ$ 及其三奇异衰变过程，给出了密度矩阵与 Fano 统计张量表达式，并推导了初始与最终系统产生截面之间的关系。
A simple exactly solvable model is proposed for describing the decays $Υ(4S) \rightarrow B^0\bar B^0$ and $Υ(4S) \rightarrow B^+B^-$. Our predictions agree with available experimental data. Using this model, we analyze the Coulomb effects in the spectra of these decays. It is shown that the frequently used assumption of factorization of Coulomb effects is not fulfilled. The Coulomb interaction leads to the difference in the positions and heights of the peaks corresponding to the charged and neutral modes. As a result, the ratio of probability of $Υ(4S)\rightarrow B^+B^-$ decay and $Υ(4S) \righ…
Inspired by the observation of the pentaquark states $P_{c}(4312),P_{c}(4440)$ and $P_{c}(4457)$ at LHCb, photoproduction of these three $P_{c}$ states via the interaction $γp\rightarrow J/ψp$ is investigated in an effective Lagrangian approach. The $t$-channel Pomeron exchange diffractive process is considered as the main background for the $J/ψ$ photoproduction. The numerical results show that the theoretical cross section, which is calculated by assuming a branching ratio $Br[P_{c}\rightarrow J/ψp]\simeq 3\%$, is consistent with the existing experimental data of the $ γp\rightarrow J/ψp$ pr…
The ratio of di-lepton production cross sections on a proton, using the $γp\rightarrow l^+ l^- p$ process, above and below di-muon production threshold allows to extract the effective lepton-proton interaction, which is required to be identical for electrons and muons if lepton universality is exact. To test for a scenario of broken universality at the percent level, of the size which could explain the different proton charge radii extracted from electron scattering and from muonic hydrogen spectroscopy, we evaluate all one-loop QED corrections to this process, including the full lepton mass d…
The $f_{1}(1420)$ productions via pion and kaon induced reactions on a proton target are investigated in an effective Lagrangian approach. Two treatments of the $t$-channel Born term, the Feynman model and the Regge model, are introduced to calculate the total and differential cross sections of the $π^{-}p\rightarrow f_{1}(1420)n$ and $K^{-}p\rightarrow f_{1}(1420)Λ$ reactions. The numerical results indicate that the experimental data of the total cross section of the $π^{-}p\rightarrow f_{1}(1420)n$ reaction can be reproduced in both the Feynman and the Regge models. Based on the parameters d…
The astrophysical S-factor and reaction rate of the direct capture process $α+d$ $\rightarrow$ $^6$Li + $γ$, as well as the abundance of the $^6$Li element are estimated in a three-body model. The initial state is factorized into the deuteron bound state and the $α+d$ scattering state. The final nucleus $^6$Li(1+) is described as a three-body bound state $α+n+p$ in the hyperspherical Lagrange-mesh method. Corrections to the asymptotics of the overlap integral in the S- and D-waves have been done for the E2 S-factor. The isospin forbidden E1 S-factor is calculated from the initial isosinglet st…
With a combined analysis of data on $Υ(5S)\rightarrow h_b(1P,2P)π^+π^-$ and $Υ(5S)\rightarrow B^{(\ast)}\bar B^{(\ast)}π$ in an effective field theory approach, we determine resonance parameters of $Z_b$ states in two scenarios. In one scenario we assume that $Z_b$ states are pure molecular states, while in the other one we assume that $Z_b$ states contain compact components. We find that the present data favor that there should be some compact components inside $Z_b^{(\prime)}$ associated with the molecular components. By fitting the invariant mass spectra of $Υ(5S)\rightarrow h_b(1P,2P)π^+π^…
