We have studied the structure of K- pp by solving this system in a variational treatment, starting from ansatz that Lambda(1405) is a K-p quasi-bound state, Lambda* with mass 1405 MeV/c2. The structure of K-pp reveals a molecular feature, namely, the K- in an "atomic center", Lambda*, plays a key role in producing strong covalent bonding with the other proton. Deeply bound Kbar nuclear systems are formed by this "super-strong" nuclear force due to migrating real bosons, Kbar, a la Heitler-London-Heisenberg, which overcompensates the stiff nuclear incompressibility. Theoretical background of the Lambda (1405) ansatz is discussed in connection with the double-pole picture of Lambda (1405) based on chiral SU(3) dynamics. Detailed analysis reveals single-pole nature of the observable Lambda (1405). There are two kinds of Sigma pi invariant masses experimentally observable, the usual T22 invariant mass and the conversion T21 invariant mass. It is of vital importance to determine whether the Lambda* mass is 1405 MeV or 1420 MeV. The T21 invariant mass from K- absorption at rest in deuteron can provide decisive information about this Lambda* mass problem.
Lambda(1405) poles obtained from pi0-Sigma0 photoproduction data
我们提出了一种策略,以提取的两个$Λ(1405)$极点的位置,最近在不同的能量在杰斐逊实验室的$γp \to K^+ π^0 Σ^0 $反应中测量的实验光生数据。利用手征动力学激发的势函数和自由参数,求解了耦合通道$\bar K N$和$πΣ$在I =0时的Bethe Salpeter方程,并利用I=0时$πΣ\to πΣ$和$\bar K N \to πΣ$散射振幅的线性组合来参数化光核反应的振幅.用一些参数组得到了与数据的良好拟合,通过这些参数组还可以预测$K^- p \to π^0 Σ^0 $反应的截面。这些后来的结果帮助我们在可能的解决方案中做出决定。其结果是,不同的解决方案导致两个极点类似的手征幺正方法中发现的。在最佳结果下,我们发现两个$Λ(1405)$极点在$1385-68i\mev$和$1419-22i\mev$。
Theoretical analysis of Lambda(1405) photoproduction
我们建立了一个描述在λ(1405)区域中γ p -> K^+ π σ反应的模型。该模型包括规范不变的光生机制,和手征幺正模型,给出了包含λ(1405)的再散射振幅。该模型还包含与短程动力学相关的唯象参数,用于拟合数据。我们成功地拟合了最近的CLAS数据,得到了γ p -> K^+ pi Sigma反应中所有电荷态的pi-Sigma不变质量分布(线形)。我们发现手性幺正模型的λ(1405)的高质量极在反应中起着重要的作用。我们还发现非共振背景的贡献是不可忽略的,其相当大的影响移动了几个MeV的λ(1405)峰的位置。这项工作为更全面的分析奠定了基础,在更全面的分析中,同时分析线形和K^+角分布数据,以提取λ(1405)极点。
我们在这里提出的一些结果支持的性质的$Λ(1405)$共振动态产生的介子重子相互作用在耦合通道和两个接近的极点的叠加。我们在$K^- p \to π^0 π^0 Σ^0 $反应中发现了对这一图像的支持,该反应显示出与从$π^- p \to K^0 πΣ$反应获得的不同的形状。我们还呼吁注意的$K^- p \to γπΣ$与$πΣ$在$Λ(1405)$区域,这表明在1420 MeV附近的计算中的窄峰。我们还报告最近的计算的两个$Λ(1405)$状态的辐射衰变和反应,以获得这些衰变模式的信息。最后,我们目前的$pp\to p K^+Λ(1405)$反应最近在ANKE/COSY测量的结果,并与理论结果进行比较。
The Lambda(1405) baryon resonance plays an outstanding role in various aspects in hadron and nuclear physics. It has been considered that the Lambda(1405) resonance is generated by the attractive interaction of the antikaon and the nucleon, as a quasi-bound state below the threshold decaying into the pi Sigma channel. Thus, the structure of Lambda(1405) is closely related to the Kbar N interaction which is the fundamental ingredient to study few-body systems with antikaon. In this paper, after reviewing the basic properties of the Lambda(1405) resonance, we introduce the dynamical coupled-chan…
To understand the nature of two poles for the $Λ(1405)$ state, we revisit the interactions of $\bar{K}N$ and $πΣ$ with their coupled channels, where two-poles structure is found in the second Riemann sheet. We also dynamically generate two poles in the single channel interaction of $\bar{K}N$ and $πΣ$, respectively. Moreover, we make a further study of two poles' properties by evaluating the couplings, the compositeness, the wave functions, and the radii for the interactions of four coupled channels, two coupled channels and the single channel. Our results show that the nature of two poles is …
Physical states are characterised uniquely by their pole positions and the corresponding residues. Accordingly, in those parameters also the nature of the states should be encoded. For bound states (poles on the real $s$-axis below the lowest threshold on the physical sheet) there is an established criterion formulated originally by Weinberg in the 1960s, which allows one to estimate the amount of compact and molecular components in a given state. We demonstrate in this paper that this criterion can be straightforwardly extended to shallow virtual states (poles on the real $s$-axis below the l…
Most of exotic resonances observed in the past decade appear as peak structure near some threshold. These near-threshold phenomena can be interpreted as genuine resonant states or enhanced threshold cusps. Apparently, there is no straightforward way of distinguishing the two structures. In this work, we employ the strength of deep feed-forward neural network in classifying objects with almost similar features. We construct a neural network model with scattering amplitude as input and nature of pole causing the enhancement as output. The training data is generated by an S-matrix satisfying the …
One of the main issues in hadron spectroscopy is to identify the origin of threshold or near-threshold enhancement. Prior to our study, there is no straightforward way of distinguishing even the lowest channel threshold-enhancement of the nucleon-nucleon system using only the cross-sections. The difficulty lies in the proximity of either a bound or virtual state pole to the threshold which creates an almost identical structure in the scattering region. Identifying the nature of the pole causing the enhancement falls under the general classification problem and supervised machine learning using…
Particle scattering is a powerful tool to unveil the nature of various subatomic phenomena. The key quantity is the scattering amplitude whose analytic structure carries the information of the quantum states. In this work, we demonstrate our first step attempt to extract the pole configuration of inelastic scatterings using the deep learning method. Among various problems, motivated by the recent new hadron phenomena, we develop a curriculum learning method of deep neural network to analyze coupled channel scattering problems. We show how effectively the method works to extract the pole config…
We use a near-threshold parameterization with explicit inclusion of the Castillejo-Dalitz-Dyson poles, which is more general than the effective range expansion, to study the bottomonium-like states $Z_b(10610)$ and $Z_b(10650)$. In terms of the partial-wave amplitude, we fit the event number distribution of $B^{(*)}\bar B^*$ system to the experimental data for these resonances from Belle Collaboration. The data could be described very well in our method, which supports the molecular interpretation. Then the relevant physical quantities are obtained, including the $B^{(*)}\bar{B}^*$ scattering …