与三个已知的SM家族混合足够小的第四代重夸克形成强子。在QCD求和规则的框架下，我们计算了含有两个第四代夸克或一个第四族夸克和一个已知第三族SM夸克的介子的质量和衰变常数.在计算中，我们考虑了两个胶子凝聚图作为非微扰贡献。当第四族夸克被底夸克或魅夸克取代时，所得结果简化为已知的$\bar b b$和$\bar c c$夸克偶素的质量和衰变常数.
英文摘要：
The heavy fourth generation of quarks that have sufficiently small mixing with the three known SM families form hadrons. In the present work, we calculate the masses and decay constants of mesons containing either both quarks from the fourth generation or one from fourth family and the other from known third family SM quarks in the framework of the QCD sum rules. In the calculations, we take into account two gluon condensate diagrams as nonperturbative contributions. The obtained results reduce to the known masses and decay constants of the $\bar b b$ and $\bar c c$ quarkonia when the fourth family quark is replaced by the bottom or charm quark.
Tenth-order lepton g-2: Contribution of some fourth-order radiative corrections to the sixth-order g-2 containing light-by-light-scattering subdiagrams
We present the general form of a universal soft-collinear distribution operator to compute the soft-virtual cross-section to next-to-next-to-next-to-next-to-leading order (N$^4$LO) in QCD for a process with any number of final state colorless particles in hadron colliders. By acting this universal operator on the pure virtual corrections, which need to be computed explicitly for a process, the soft-virtual cross-section can be obtained. The operator is constructed by exploiting the factorization and renormalization group evolution of amplitudes in QCD, and the universality of soft gluon contri…
Correlations of conserved charges, i.e., the baryon number, electric charge and the strangeness, have been calculated at finite temperature and chemical potential up to the fourth order. The calculations are done in a 2+1 flavor low energy effective theory, where quantum and thermal fluctuations are encoded through the evolution of flow equations within the functional renormalization group approach. Strangeness neutrality and a fixed ratio of the electric charge to the baryon number density are implemented throughout the computation. We find that higher-order correlations carry more sensitive …
We study the $θ$-vacuum of QCD using two-flavor chiral perturbation theory ($χ$PT) in the presence of a uniform, background magnetic field calculating the magnetic field-dependent free energy density, the topological density, the topological susceptibility and the fourth cumulant at one-loop order. We find that the topological susceptibility is enhanced by the magnetic field while the fourth topological cumulant is diminished at weak fields and enhanced at larger fields when $θ=0$. However, in the QCD vacuum with $θ\neq 0$, the topological susceptibility can be either monotonically enhanced or…
We study the topological susceptibility and the fourth cumulant of the QCD vacuum in the presence of a uniform, background magnetic field in two-and-three flavor QCD finding novel, model-independent sum rules relating the shift in the topological susceptibility due to the background field to the shift in the quark condensates, and the shift in the fourth cumulant to the shifts in the quark condensates and susceptibilities
K_1(1270)-K_1(1400) mixing and the fourth generation SM effects in B-->K_1l^+l^- decays
The implications of the fourth generation quarks in the B--> K_{1} (1270,1400)l^{+}l^{-} with l=mu, tau decays are studied, where the mass eigenstates K_{1} (1270) and K_{1} (1400) are the mixture of ^{1}{P}_{1} and ^{3}{P}_{1} states with the mixing angle θ_{K}. In this context, we have studied various observables like branching ratio (BR), forward backward asymmetry ( A_{FB} ) and longitudinal and transverse helicity fractions ( f_{L,T} ) of K_{1} meson in B--> K_{1} l^{+}l^{-} decays. To study these observables, we have used the Light Cone QCD sum rules form factors and set the mixing angle…
The spectra of some 0++ four-quark states, which are composed of \bar qq pairs, are calculated in QCD. The light four-quark states are calculated using the traditional sum rules while four-quark states containing one heavy quark are computed in HQET. For constructing the interpolating currents, different couplings of the color and spin inside the \bar qq pair are taken into account. It is found that the spin and color combination has little effect on the mass of the four-quark states.
$B \to K \etap$ decays in the SM with fourth generation fermions
利用微扰QCD（pQCD）因子分解方法，计算了含有第四代费米子（SM 4）的标准模型（SM）中由包含$\tp$夸克的圈图引起的四个$B \to K \etap$衰变的新物理贡献.在所考虑的SM 4参数空间内，我们发现：（a）SM和SM 4的次领先阶（next-to-leading分支比，NLO）pQCD预言与实验数据在一个标准差内基本一致;（b）对于$Br(B \to K η)$，第四代贡献的加入可以有效地改善理论预言与实验数据的一致性;（c）对于$Br(B \to K \etar)$，由于$\tp$环引起的衰减与数据不符;（d）对所考虑衰变的CP破坏不对称性的新物理修正仅为10%左右。
