Double-heavy tetraquarks with strangeness in the chiral quark model

Recently, some progress has been made in the experiments on double-heavy tetraquarks, such as \begin{document}$ T_{cc} $\end{document} reported by the LHCb Collaboration and \begin{document}$ X_{cc\bar{s}\bar{s}} $\end{document} reported by the Belle Collaboration. Coming on the heels of our previous work about \begin{document}$ T_{cc} $\end{document} and \begin{document}$ T_{bb} $\end{document}, we present a study on the bound and resonance states of their companions, \begin{document}$ QQ\bar{q}\bar{s} $\end{document} (\begin{document}$ Q=c,b; q=u, s $\end{document}) tetraquarks with strange flavor in the chiral quark model. Two pictures, meson-meson and diquark-antidiquark ones, and their couplings were considered in our calculations. Isospin violation was neglected herein. Our numerical analysis indicated that the states \begin{document}$ cc\bar{u}\bar{s} $\end{document} with \begin{document}$ \dfrac{1}{2}(1^+) $\end{document} and \begin{document}$ bb\bar{u}\bar{s} $\end{document} with \begin{document}$ \dfrac{1}{2}(1^+) $\end{document} are the most promising stable states against strong interactions. Besides, we found several resonance states for the double-heavy strange tetraquarks with the real scaling method.     

Two alternative versions of strangeness

The concept of strangeness emerged from the low energy phenomenology before the entry of quarks in particle physics. The connection between strangeness and isospin is rather accidental and loose and we recognize later that the definition of strangeness is model-dependent. Indeed, in Gell-Mann's triplet quark model we realize that there is a simple alternative representation of strangeness. When the concept of generations is incorporated into the quark model we find that only the second alternative version of strangeness remains meaningful, whereas the original one does no longer keep its significance.     

Sound velocity in dense stellar matter with strangeness and compact stars

The phase state of dense matter in the intermediate density range (\begin{document}$\sim$\end{document}1-10 times the nuclear saturation density) is both intriguing and unclear and can have important observable effects in the present gravitational wave era of neutron stars. As matter density increases in compact stars, the sound velocity is expected to approach the conformal limit (\begin{document}$c_s/c=1/\sqrt{3}$\end{document}) at high densities and should also fulfill the causality limit (\begin{document}$c_s/c<1$\end{document}). However, its detailed behavior remains a prominent topic of debate. It was suggested that the sound velocity of dense matter could be an important indicator of a deconfinement phase transition, where a particular shape might be expected for its density dependence. In this work, we explore the general properties of the sound velocity and the adiabatic index of dense matter in hybrid stars as well as in neutron stars and quark stars. Various conditions are employed for the hadron-quark phase transition with varying interface tension. We find that the expected behavior of the sound velocity can also be achieved by the nonperturbative properties of the quark phase, in addition to a deconfinement phase transition. Moreover, it leads to a more compact star with a similar mass. We then propose a new class of quark star equation of states, which can be tested by future high-precision radius measurements of pulsar-like objects.     

ss component of the proton and the strangeness magnetic moment

A complete analysis is given of the implications of the empirical indications for a positive strangeness magnetic moment mu(s) of the proton on the possible configurations of the uudss component of the proton. A positive value for mu(s) is obtained in the ss configuration where the uuds subsystem is in an orbitally excited state with [4](FS)[22](F)[22](S) flavor-spin symmetry, which is likely to have the lowest energy. The configurations in which the s is orbitally excited, which include the conventional Kappa(+)lambda(0) configuration, with the exception of that in which the uuds component has spin 2, yield negative values for mu(s). The hidden strangeness analogues of recently proposed quark cluster models for the theta(+) pentaquark give differing signs for mu(s).     

Quark model analysis of strangeness form factors of the proton

The present empirical information on the proton strangeness form factors suggests that the uuds subsystem of the uudsˉ configuration has the flavor spin symmetry [4]_FS[22]_F[22]_S , mixed orbital symmetry [31]_X and that the ˉ is in the ground state. This uudsˉ configuration yields the empirical signs for both the form factors G _E ^s and G _M ^s . Transition matrix elements between the uud and uudsˉ components are significant.     

Domain Wall with Strange Quark Matter in Kaluza-Klein Type Cosmological Model

In this study we have analyzed the Kaluza-Klein type Robertson Walker (RW) cosmological model by considering variable cosmological constant term Λ of the form: , and Λ∼ρ in the presence of strange quark matter with domain wall. The various physical aspects of the model are also discussed.     

Atomic mass,Bjorken variable,and scale dependence of quark transport coefficient in Drell-Yan process for proton incident on nucleus

By means of the nuclear parton distributions determined without the fixed-target Drell-Yan experimental data and the analytic expression of quenching weight based on the BDMPS formalism, next-to-leading order analyses were performed on the Drell-Yan differential cross section ratios from the Fermilab E906 and E866 collaborations. It was found that the results calculated only with the nuclear effects of the parton distribution were not in agreement with the E866 and E906 experimental data. The incoming parton energy loss effect cannot be ignored in the nuclear Drell-Yan reactions. The predicted results indicate that, with the quark transport coefficient as a constant, the suppression due to the target nuclear geometry effect is approximatelybegin{document}$ 16.85 $end{document}% for the quark transport coefficient. It was shown that we should consider the target nuclear geometry effect in studying the Drell-Yan reaction on nuclear targets. On the basis of the Bjorken variable and scale dependence of the quark transport coefficient, the atomic mass dependence was incorporated. The quark transport coefficient was determined as a function of the atomic mass, Bjorken variablebegin{document}$ x_2 $end{document}, and scale begin{document}$ Q^2 $end{document} by the global fit of the experimental data. The determined constant factor begin{document}$ hat{q}_0 $end{document} of the quark transport coefficient is begin{document}$ 0.062pm0.006 $end{document} GeVbegin{document}$ ^2 $end{document}/fm. It was found that the atomic mass dependence has a significant impact on the constant factor begin{document}$ hat{q}_0 $end{document} in the quark transport coefficient in cold nuclear matter.     

高能质子照相的研究进展

高能闪光照相是诊断致密物质内部几何结构和物理特性的最有效技术.高能质子照相在穿透能力、材料识别、空间分辨率等方面都优于X射线照相,已经成为美国先进流体动力学试验装置的优先发展对象.文章详细介绍了高能质子照相方案及其研究进展.     

质子初始位置对激光平面靶相互作用加速质子的影响(英)

为了更细致地理解鞘场质子加速机制,应用2维数值模拟程序Flips2D研究了质子的初始位置对加速以后质子束特性的影响。数值模拟结果表明:质子的初始位置对质子束特性的影响非常明显。质子的出射角与其在横向的初始位置有关,初始位置离激光轴越远,其出射角越大。     

质子初始位置对激光平面靶相互作用加速质子的影响(英)

为了更细致地理解鞘场质子加速机制,应用2维数值模拟程序Flips2D研究了质子的初始位置对加速以后质子束特性的影响。数值模拟结果表明:质子的初始位置对质子束特性的影响非常明显。质子的出射角与其在横向的初始位置有关,初始位置离激光轴越远,其出射角越大。     

Charm diffusion in a pion gas implementing unitarity, chiral and heavy quark symmetries

We compute the charm drag and diffusion coefficients in a hot pion gas, such as is formed in a heavy ion collision after the system cools sufficiently to transit into the hadron phase. We fully exploit heavy quark effective theory (with both D and D^∗ mesons as elementary degrees of freedom during the collision) and chiral perturbation theory, and employ standard unitarization to reach higher temperatures. We find that a certain friction and shear diffusion coefficients are almost p²-independent at a fixed temperature which simplifies phenomenological analysis.At the higher end of reliability of our calculation, , we report a charm relaxation length , in agreement with the model estimate of He, Fries and Rapp.The momentum of a 1 GeV charm quark decreases about 50 MeV per fermi when crossing the hadron phase.     

辐射变色薄膜的质子辐照响应

 用J-2.5质子静电加速器提供的质子束,对研制的一种高灵敏度新型辐射变色膜进行质子辐射响应研究。该变色膜以聚乙烯醇缩聚物为基质,以类丁二炔化合物为有机染色材料,质子能量为2.0 MeV,辐照注量为1.0×10¹⁰～1.0×10¹² cm^-2。用光谱响应测试薄膜的辐射效应显示：变色薄膜颜色由粉红渐变为蓝色, 并随着辐照剂量的增加而逐渐加深;用图像分析仪分析辐照后靶材的光密度发现,图像的光密度随聚焦斑距离的增大而减小;用分光光度计测试其吸收光谱发现,主吸收峰值出现在660 nm附近,且吸收峰处的响应吸光度与质子注量具有较好的线性关系;对新型变色薄膜辐照后持续效应的研究表明,变色膜辐照后续效应微弱,辐照后可以立即测量,且对测量环境变化不敏感。     

β-delayed proton decay of the proton drip-line nucleus 142Ho in the rare-earth region

New β-delayed proton precursor 142Ho was produced via heavy ion induced reaction 106Cd(40Ca, p3n), and identified for the first time by using a He-jet fast tape transport system in combination with "p-γ" coincidence measurements. The β-delayed proton decay of 142Ho was observed and its half life was determined to be (0.4±0.1) s. By fitting the experimental relative branching ratios to final states in the proton daughter nucleus 141Tb and the energy spectrum of β-delayed protons with a statistical model calculation, the ground-state spin of 142Ho was assigned as 5, 6 or 7. Nuclear energy-potential-surface (EPS) calculations were performed using the Woods-Saxon Strutinsky method. The calculated results favored the assignments of 7- to 142Ho. AS the by-products, some γ-transitions in the proton daughter nuclei following the β-delayed proton decays of precursors 139Gd, 140Tb, 142Tb, and 143Dy were reported here for the first time.     

极化海夸克对激发对核子的自旋相关性质的影响

分析各种极化的海夸克对对核子的自旋相关性质的作用. 并试图改进传统模型对质子自旋性质的计算.