As a quark and an antiquark cannot be isolated, the intrinsic motion of a composite $q \bar q$ system in its lowest-energy states lies predominantly in 1+1 dimensions, as in an open string with the quark and the antiquark at its two ends. Accordingly, we study the lowest-energy states of an open string $q\bar q$ system in QCD and QED in 1+1 dimensions. We show that $π^0, η$, and $η'$ can be adequately described as open string $q\bar q$ QCD mesons. By extrapolating into the $q\bar q$ QED sector in which a quark and an antiquark interact with the QED interaction, we find an open string isoscalar $I(J^π)$=$0(0^-)$ QED meson state at 17.9$\pm$1.5 MeV and an isovector $(I(J^π)$=$1(0^-), I_3$=0) QED meson state at 36.4$\pm$3.8 MeV. The predicted masses of the isoscalar and isovector QED mesons are close to the masses of the hypothetical X17 and E38 particles observed recently, making them good candidates for these particles. The decay products of QED mesons may show up as excess $e^+e^-$ and $γγ$ pairs in the anomalous soft photon phenomenon associated with hadron productions in high-energy hadron-proton collisions and $e^+$-$e^-$ annihilations. Measurements of the invariant masses of excess $e^+e^-$ and $γγ$ pairs will provide tests for the existence of the open string $q\bar q$ QED mesons. An assembly of gravitating QED mesons are expected to emit electron-positron pairs and/or gamma rays and their decay energies and lifetimes will be modified by their gravitational binding energies. Consequently, a self-gravitating isoscalar QED meson assembly whose mass $M$ and radius $R$ satisfy $(M/M_\odot)/(R/R_\odot) \gtrsim 4.71 \times 10^5$ will not produce electron-positron pairs nor gamma rays and may be a good candidate for the primordial dark matter.
Schwinger's boson solution for massless fermions in QED in 1+1D has been applied and generalized to quarks interacting in QED and QCD interactions, leading to stable and confined open-string QED and QCD boson excitations of the quark-QCD-QED system in 1+1D. Just as the open-string QCD excitations in 1+1D can be the idealization of QCD mesons with a flux tube in 3+1D, so the open-string QED excitations in 1+1D may likewise be the idealization of QED mesons with masses in the tens of MeV region, corresponding possibly to the anomalous X17 and E38 particles observed recently. A further search for…
We present a lattice analysis of the light pseudoscalar mesons with consideration for the mixing between the flavour-neutral states $π^0$, $η$ and $η^\prime$. We extract the masses and flavour compositions of the pseudoscalar meson nonet in $n_f=1+1+1$ lattice QCD+QED around an SU(3)-flavour symmetric point, and observe flavour-symmetry features of the extracted data, along with preliminary extrapolation results for the flavour compositions at the physical point. A key result of this work is the observed mass splitting between the $π^0$ and $η$ on our ensembles, which is found to exhibit behav…
We study the stability of a hypothetical QED neutron, which consists of a color-singlet system of two $d$ quarks and a $u$ quark interacting with the QED interaction. As a quark cannot be isolated, the intrinsic motion of the three quarks in the lowest-energy state may lie predominantly in 1+1 dimensions, as in a $d$-$u$-$d$ open string. The attractive $d$-$u$ and $u$-$d$ QED interactions may overcome the weaker repulsive $d$-$d$ QED interaction to bind the three quarks together. We examine the QED neutron in a phenomenological three-body problem in 1+1 dimensions with an effective interaction…
The Wigner Function of Produced Particles in String Fragmentation
我们证明了具有横向禁闭的QCD 4可以近似紧化为具有横向夸克质量$m_{{}_T}$的QCD 2，该质量通过求解一组耦合的横向本征值方程得到。在一个强耦合和大量的口味的限制，QCD 2进一步承认Schwinger QED 2型玻色化的解决方案。因此，我们通过研究Schwinger QED 2中产生的玻色子的Wigner函数，从唯象上研究弦碎裂中产生的粒子的时空动力学，它模仿了量子色动力学中弦碎裂的许多特征。我们发现，粒子的动量在不同地区的快度平台产生的初始时刻的弦碎裂的夸克拉远离反夸克在高能量，在纵向空间-动量-时间有序的弦碎裂的经典图片。
Heavy ion collisions provide a unique probe of the quark-gluon plasma properties. The role of partonic degrees of freedom in p-Pb collisions at $\sqrt{s_{NN}}$ = 5 TeV by studying the production cross section is studied. Experimental observable like the number of K$_S$ mesons is sensitive to the kinematic properties of the reaction. Our results demonstrate the importance of angular distribution for the partonic degrees of freedom in hadronization process.
The dynamics of quarks and gauge fields in the lowest energy states in QCD and QED interactions is studied by compactifying the (3+1)D space-time to the (1+1)D space-time with cylindrical symmetry and by combining Schwinger's longitudinal confinement in (1+1)D with Polyakov's transverse confinement in (2+1)D. Using the action integral, we separate out the transverse and longitudinal degrees of freedom. By solving the derived transverse and longitudinal equations, we study the QCD and QED collective excitations. In addition to the well known QCD low-energy states, we find stable collective QED …
We construct the D4/D8 brane configuration in the Witten-Sakai-Sugimoto model by introducing a pair of heavy flavour brane with a heavy-light open string. The multiplets created by the heavy-light string acquire mass due to the finite separation of the heavy and light flavour branes thus they could be identified as the heavy-light meson fields in this model. On the other hand the glueball field is identified as the gravitational fluctuations carried by the close string in the bulk, so this model is able to describe the interaction of glueball and heavy-light meson through the open-close string…
