Parity violation in elastic electron-nucleon scattering is studied with the basic goal of improving the understanding of electroweak hadronic structure with special emphasis on the strangeness content in the nucleon. Models for the parity-violating (PV) asymmetry are provided and compared with the world data measured at very different kinematics. The effects introduced in the PV asymmetry due to alternative descriptions of the hadronic structure are analyzed in detail. In particular, a wide selection of prescriptions for dealing with the electromagnetic and neutral current weak interaction nucleon form factors, including the most recent ones used in the literature, is considered.
Determining the nonperturbative $s\bar{s}$ content of the nucleon has attracted considerable interest and been the subject of numerous experimental searches. These measurements used a variety of reactions and place important limits on the vector form factors observed in parity-violating (PV) elastic scattering and the parton distributions determined by deep inelastic scattering (DIS). In spite of this progress, attempts to relate information obtained from elastic and DIS experiments have been sparse. To ameliorate this situation, we develop an interpolating model using light-front wave functio…
Motivated by the successes of covariant baryon chiral perturbation theory in one-baryon systems and in heavy-light systems, we study relevance of relativistic effects in hyperon-nucleon interactions with strangeness $S=-1$. In this exploratory work, we follow the covariant framework developed by Epelbaum and Gegelia to calculate the $YN$ scattering amplitude at leading order. By fitting the five low-energy constants to the experimental data, we find that the cutoff dependence is mitigated, compared with the heavy-baryon approach. Nevertheless, the description of the experimental data remains q…
The capabilities of the new version of the Liège Intra-Nuclear Cascade model (INCL++6) are presented in detail. This new version INCL is able to handle strange particles, such as kaons and the $Λ$ particle, and the associated reactions and also allows extending nucleon-nucleon collisions up to about $15-20$ GeV incident energy. Compared to the previous version, new observables can be studied, e.g., kaon, hyperon, and hypernuclei production cross sections (with the use of a suitable de-excitation code) as well as aspects of kaon-induced spallation reactions. The main purpose of this paper is to…
Dense compact objects like neutron stars or black holes have always been one of Gerry Brown's favorite research topics. This is closely related to the effects of strangeness in nuclear physics. Here, we review the chiral Effective Field Theory approach to interactions involving nucleons and hyperons, the possible existence of strange dibaryons, the fate of hyperons in nuclear matter and the present status of three-body forces involving hyperons and nucleons.
Electroproduction of phi meson from proton and the strangeness in the nucleon
我们分析了$uud - s\bar s$团簇模型中阈值附近的过程$e p \to e p ϕ$，作为质子奇异度的探针。我们的考虑是基于相对论谐振子夸克模型，它考虑了强子波函数的洛伦兹收缩效应。我们发现，当奇夸克混合率仅为（3-5）%时，敲除机制与矢量介子主导模型的衍射产生相当，这与非相对论夸克模型预测的（10-20）%相当. $uud$ -和$s\bar s$ -敲除过程的横截面对质子的四动量转移平方有着性质上不同的依赖性，可以通过实验加以区分。本文还简要讨论了在5夸克集团模型中确定质子奇异含量的一种方法。
The scalar strangeness content of the nucleon, characterized by the so-called strangeness-nucleon sigma term, is of fundamental importance in understanding its sea-quark flavor structure. We report a determination of the octet baryon sigma terms via the Feynman-Hellmann theorem by analyzing the latest high-statistics $n_f=2+1$ lattice QCD simulations with covariant baryon chiral perturbation theory up to next-to-next-to-next-to-leading order. In particular, we predict $σ_{πN}=55(1)(4)$ MeV and $σ_{sN}=27(27)(4)$ MeV, while the first error is statistical and the second systematic due to differe…
The behavior of the $ϕ$ meson at finite density is studied, making use of a QCD sum rule approach in combination with the maximum entropy method. It is demonstrated that a possible mass shift of the $ϕ$ in nuclear matter is strongly correlated to the strangeness content of the nucleon, which is proportional to the strange sigma term, $σ_{sN} = m_s \langle N | \overline{s}s | N \rangle$. Our results furthermore show that, depending on the value of $σ_{sN}$, the $ϕ$ meson could receive both a positive or negative mass shift at nuclear matter density. We find that these results depend only weakly…
Recent hydrodynamical simulations of supernova (SN) evolution have highlighted the importance of a thorough control over microscopic physics responsible for such internal processes as neutrino heating. In particular, it has been suggested that modifications to the neutrino-nucleon elastic cross section can potentially play a crucial role in producing successful supernova explosions. One possible source of such corrections can be found in a nonzero value for the nucleon's strange helicity content $Δs$. In the present analysis, however, we show that theoretical and experimental progress over the…
Three-body forces acting on a $Λ$ hyperon in a nuclear medium are investigated, with special focus on the so-called hyperon puzzle in neutron stars. The hyperon-nucleon two-body interaction deduced from SU(3) chiral effective field theory is employed at next-to-leading order. Hyperon-nucleon three-body forces are approximated using saturation by decuplet baryons and are transcribed to density-dependent effective two-body interactions. These together are taken as input in a Brueckner-Bethe-Goldstone equation with explicit treatment of the $ΛN\leftrightarrowΣN$ and $ΛNN\leftrightarrowΣNN$ couple…
