We present the formalism for a new generation of unquenched quark models for baryons in which the effects of quark-antiquark pairs (u anti-u, d anti-d and s anti-s) are taken into account in an explicit form via a microscopic, QCD-inspired, quark-antiquark creation mechaniscm. The present approach is an extension of the flux-tube breaking model of Geiger and Isgur in which now the contributions of quark-antiquark pairs an be studied for any initial baryon and for any flavor of the q anti-q pair. It is shown that the inclusion of q anti-q paris leads to a large contribution of orbital angular momentum to the proton spin.
Decays $D\toπ^+π^-e^+ν_e$ and $D_s\toπ^+ π^-e^+ν_e$ serve as probes that check the existence of constituent $q\bar q$ components in the wave functions of scalar mesons decaying into $π^+π^-$. There exists a great deal of concrete evidence in favor of the exotic four-quark nature of light scalars. At the same time, the further expansion of the area of the $q^2\bar q^2$ model validity for light scalars on ever new processes seems extremely interesting and important. We analyze the BESIII and CLEO data on the decays $D^+\to π^+π^- e^+ν_e$ and $D^+_s\to π^+π^- e^+ν_e$ and show that the results of …
A possibility of existence of a pseudovector-type quark-antiquark condensate in the quark matter and Nambu-Goldstone modes on that condensate in the Nambu-Jona-Lasinio model
Multiple Parton Scattering in Nuclei: Quark-quark Scattering
本文系统地研究了核介质中夸克-夸克（反夸克）双散射对夸克和反夸克碎裂函数的修正，直到\cal{O}（α_{s}^2）$ in deeply inelastic scattering (DIS) off nuclear targets. At the order $ \cal{O}（α_s^2）$, twist-four contributions from quark-quark (antiquark) rescattering also exhibit the Landau-Pomeranchuck-Midgal (LPM) interference feature similar to gluon bremsstrahlung induced by multiple parton scattering. Compared to quark-gluon scattering, the modification, which is dominated by $ t $-channel quark-quark (antiquark) scattering, is only smaller by a factor of $ C_F/C_A=4/9$乘以介质中夸克和胶子的分布比.这种修改对于现实的运动学和有限的介质尺寸是不可忽略的。夸克-反夸克湮灭过程对夸克（反夸克）碎裂函数的修正由介质…
The annihilation of heavy particles close to thermal equilibrium, which plays a prominent role in the chemical equilibration of heavy quarks in the Quark-Gluon Plasma (QGP) as well as in many classic dark matter scenarios, is reexamined. We derive a scattering amplitude that resums near-threshold attractive interaction of the annihilating particles in terms of the non-relativistic scattering $T$-matrix and Green's function, thereby capturing the pertinent Sommerfeld enhancement from both nonperturbative scattering state and bound state solutions. The derived formula is of such generality that …
Diffractive dissociation of gluons into heavy quark-antiquark pairs in proton-proton collisions
我们讨论了胶子衍射离解成重夸克对的问题。这种特殊的机制类似于虚光子衍射分解成夸克，它驱动了低质量衍射或大$β$区域中的衍射深度非弹性粲的产生。在那里，可以理解，有一些保留，根据价重夸克的内容的坡密子。$g p \to Q \bar Q p$的振幅是在碰撞参量和动量空间中导出的。单衍射$p p \to Q \bar Q p X$的截面计算为质子中的基本截面和胶子分布的卷积。计算了LHC名义能量下不同胶子分布的积分截面和粲夸克、底夸克和反夸克的微分分布，如横动量和快度，以及夸克-反夸克不变质量.底部的魅力截面的比例示出和讨论作为几个运动学变量的函数。
In this paper, we study the spatial correlations among quarks and antiquarks produced at mid-rapidity by gluon pair production in the color glass condensate framework. This paper is the first part of a series in which we calculate a complete set of quark/quark, quark/antiquark, and antiquark/antiquark spatial correlation functions in heavy-light ion collisions, with the goal of incorporating their conserved charges into the initial conditions of hydrodynamics. The physical mechanisms captured in this calculation include geometric, entanglement, and interaction-mediated correlations. In this fi…
We study the relaxation time required for the alignment between the spin of a finite-mass quark/antiquark and the thermal vorticity, at finite temperature and baryon chemical potential, in the context of relativistic heavy-ion collisions. The relaxation time is computed as the inverse of the total reaction rate that in turn is obtained from the imaginary part of the quark/antiquark self-energy. We model the interaction between spin and thermal vorticity within the medium by means of a vertex coupling quarks and thermal gluons that, for a uniform temperature, is proportional to the global angul…
We study the transitions between the different color states of a static quark-antiquark pair, singlet and octet, in a thermal medium. This is done non-perturbatively exploiting the infinite mass limit of QCD. This study is interesting because it can be used for future developments within the framework of Effective Field Theories (EFTs) and because it can be combined with other techniques, like lattice QCD or AdS/CFT, to gain non-perturbative information about the evolution of quarkonium in a medium. We also study the obtained expressions in the large $N_{c}$ limit. This allows us to learn less…
The quark and gluon structure of the proton has been under intense experimental and theoretical investigation for five decades. Even for the distributions of the well-studied valence quarks, challenges such as the value of the down quark to up quark ratio at high fractional momenta remain. Much of the sea of quark-antiquark pairs emerges from the splitting of gluons and is well described by perturbative evolution in quantum chromodynamics. However, experiments confirm that there is a non-perturbative component to the sea that is not well understood and hitherto has been difficult to calculate …
