Stimulated by the newly observed charged hidden-charm state $Z_{cs}(3985)^-$ by BESIII Collaboration, $Z_{cs}(4000)^+$, $Z_{cs}(4220)^+$ and the excited $B_s^0$ states by LHCb Collaboration, a full calculation including masses and decay widths is emerged in the chiral quark model. For $Z_{cs}$ states, we assign quantum numbers $I(J^P)=\frac{1}{2}(1^+)$ and quark composition $c\bar{c}s\bar{u}$ according to the experiment. For $B_s^0$ states, systematically investigations are performed with $I(J^P)=0(0^+), 0(1^+), 0(2^+)$ both in 2-body $b\bar{s}$ and 4-body $b\bar{s}q\bar{q}~(q=u~\rm{or}~d)$ systems. Each tetraquark calculation takes all structures including meson-meson, diquark-antidiquark and all possible color configurations into account. Among the numerical techniques to solve the 2-body and 4-body Schr{ö}dinger equation, the spatial wave functions are expanded in series of Gaussian basis functions for high precision, which is the way Gaussian expansion method so called. Our results indicate that the low-lying states of 4-quark system are all higher than the corresponding thresholds either for $c\bar{c}s\bar{u}$ or for $b\bar{s}q\bar{q}$ systems. With the help of the real scaling method, we found two resonance states with masses of 4023 MeV and 4042 MeV for $c\bar{c}s\bar{u}$ system. The state $c\bar{c}s\bar{u}(4042)$ has a consistent mass and decay width with the recent observed state $Z_{cs}(3985)^-$. For $b\bar{s}q\bar{q}$ system with $J=0$, some resonance states are also found. The newly observed excited $B_s^0$ states can be accommodated in the chiral quark model as $2S$ or $1D$ states, and the mixing with four-quark states are also needed to be considered.
We derive the chiral effective Lagrangian for excited heavy-light mesons from QCD under proper approximations. We focus on the chiral partners with $j_l^P=\frac{3}{2}^+$ and $j_l^P=\frac{3}{2}^-$ which amounts to ($1^+,2^+$) and ($1^-,2^-$) states respectively. The low energy constants including the masses of the chiral partners are calculated. The calculated spectrum for the excited mesons are found roughly consistent with experimental data. In addition, our results indicate that quantum numbers of $B_J(5970)$ can be identified with $1^-$ or $2^-$.
We study the conjectured "Insensitivity to Chiral Symmetry Breaking" in the highly excited light baryon spectrum. While the experimental spectrum is being measured at JLab and CBELSA/TAPS, this insensitivity remains to be computed theoretically in detail. As the only existing option to have both confinement, highly excited states and chiral symmetry, we adopt the truncated Coulomb gauge formulation of QCD, considering a linearly confining Coulomb term. Adopting a systematic and numerically intensive variational treatment up to 12 harmonic oscillator shells we are able to access several angular…
The charge form factor and charge radius of neutron are investigated in the perturbative chiral quark model (PCQM) with considering both the ground and excited states in the quark propagator. A Cornell-like potential is extracted in accordance with the predetermined ground state quark wavefunction, and the excited quark states are derived by solving the Dirac equation with the extracted PCQM potential numerically. The study reveals that the contributions of the excited quark states are considerably influential in the charge form factor and charge radius of neutron as expected, and the total re…
We interpret the recent ATLAS multi-jet search results using 20.3 fb-1 data at sqrt(s)=8 TeV in the context of searching for excited quarks. Within the effective field theory framework, using the null results of that search, our analysis shows that the excited quark mass below 5 TeV can be excluded at the 95% confidence level. Our analysis also indicates that when the validation of effective field theory is considered, the limit can be largely compromised.
We present a detailed study of the production and decay of the excited quark at the QCD next-to-leading order (NLO) level at the Large Hadron Collider, using the narrow width approximation and helicity amplitudes method. We find that the QCD NLO corrections can tighten the constraints on the model parameters and reduce the scale dependencies of the total cross sections. We discuss the signals of the excited quark production with decay mode $q^{\ast}\rightarrow qγ$ and $q^{\ast}\rightarrow qg$, and present several important kinematic distributions. Moreover, we give the upper limits of the exci…
Potential discovery, observation and exclusion limits of excited $u$ and $d$ quarks with gamma+jet final state are researched at the multi-TeV scale colliders, FCC and S$pp$C in this work. Both colliders, FCC and S$pp$C, show that excited $u$ and $d$ quarks could be discovered up to 42.1 TeV and 55.2 TeV for $u^\star$, 30.3 TeV and 39.4 TeV for $d^\star$ and 42.3 TeV and 55.5 TeV mass values for degenerate case (m$_{u^\star}$ = m$_{d^\star}$), respectively. Determination of excited quarks compositeness scale is examined, which will be up to multi-PeV level. Beside these analysis, free paramete…
We argue that three-quark excited states naturally group into quartets, split into two parity doublets, and that the mass splittings between these parity partners decrease higher up in the baryon spectrum. This decreasing mass difference can be used to probe the running quark mass in the mid-infrared power-law regime. A measurement of masses of high-partial wave Delta* resonances should be sufficient to unambiguously establish the approximate degeneracy. We test this concept with the first computation of excited high-j baryon masses in a chirally invariant quark model.
A convergence of the valence quark self-energies in the 1S, 2S, $1P_{1/2}$, $1P_{3/2}$ orbits induced by pion and gluon field configurations, is shown in the frame of a relativistic chiral quark model. It is shown that in order to reach a convergence, one needs to include contribution of the intermediate quark and anti-quark states with the total momentum up to $j=25/2$. It is argued that a restriction to the lowest mode when estimating the self-energy is not good approximation.
The effect of transverse gluons on the chiral symmetry patterns of excited mesons is studied in a Coulomb gauge QCD model. The linear rising static quark-antiquark potential and the transverse gluon propagator known from lattice studies are input into the model. The non-perturbative quark propagator, which enters the meson bound state equations, is derived from the Dyson--Schwinger equations and a complete set of mesons for general spin quantum number is presented. From analyzing the bound state equations for large spins it is demonstrated, that chiral and axial symmetry are restored. In this …
The parton model relations in conjunction with quark-hadron duality in deep inelastic scattering suggests an asymptotic dominance of quark-diquark type of baryonic excited states with a radial Regge uniformly distributed mass squared spectrum $M_{n}^2 = μ^2 n + M_0^2$. We argue that this points to a lineary quark-diquark confining potential. We analyze the radial ($n$) and angular-momentum ($J$) Regge trajectories for all light-quark states with baryon number one listed in the 2016 edition of the Particle Data Tables. The parameters of the mass squared trajectories are obtained by linear regre…
Resonant production of excited $u$ and $d$ quarks at the Future Circular Collider and Super proton-proton Collider have been researched. Dominant jet-jet decay mode has been considered. It is shown that FCC and SppC have great potential for discovery of excited $u$ ($d$) quark: up to 44.1 (36.3) and 58.4 (47.8) TeV masses, respectively. For degenerate case (M$_{u^{\star}}$ = M$_{d^{\star}}$), these values are 45.9 and 60.9 TeV, respectively. This discovery will also afford an opportunity to determine the compositeness scale up to multi-PeV level.
The pseudoscalar and vector excited mesons in the U(3)*U(3) chiral model
构造了一个手征U（3）*U（3）拉格朗日量，它除了包含通常的介子场外，还包含它们的第一径向激发。拉格朗日量是由玻色化的Nambu-Jona-Lasinio夸克模型与可分离的非局域相互作用，与形状因子对应的3维基态和激发态波函数。手征对称性的自发破缺由NJL能隙方程控制。用五种不同的形状因子描述了π介子、K介子和矢量介子九重态的第一径向激发。每个形状因子仅包含一个任意参数。计算了这些介子态的质量和弱衰变常数$F_{π'}, F_K and F_{K'}$。
We point out that the determination of the leptonic decay width of radially-excited quarkonia is strongly dependent on the position of the node typical of these excitations. We suggest that this feature could be related with the longstanding rho-pi puzzle.
The COMPASS collaboration, as a part of their hadron spectroscopy program, is going to measure the radiative decay widths of light-quark mesons via the Primakoff reactions. In this letter we study the photon couplings of light-quark q qbar states in the covariant oscillator quark model and evaluate the transition rates for {rho(770), b_1(1235), a_1(1260), a_2(1320), pi_2(1670), rho_3(1690), rho(1700)}^pm to pi^pm gamma, which are expected to be measured by the COMPASS. Such photon couplings could be useful not only for understanding the internal structures of observed light-quark mesons and th…
The complete spectrum of $c\bar{b}$ states is obtained in a phenomenological non relativistic quark model(NRQM), which consists of a confinement potential and one gluon exchange potential (OGEP) as effective quark - antiquark potential. We make predictions for the radiative decay (E1 and M1) widths and weak decay widths of $c\bar{b}$ states in the framework of NRQM formalism.
Recently we developed a numerical technique to compute chiral symmetry breaking at T=0 with different current quark masses m0, including the current quark masses of the six standard flavours u, d, s, c, b, t. We also fitted from Lattice QCD data the quark-antiquark string tension sigma dependence on temperature T. We now utilize sigma(T) to further upgrade the chiral invariant and confinement quark model to finite temperatures T =/= 0. We study the quark mass at finite T and obtain the corresponding chiral crossover at T=Tc. The quark mass critical curve has a shape similar, but not identical,…
We solve the Bethe-Salpeter equation (BSE) for a system of a heavy quark-antiquark pair interacting with a Poincare invariant generalization of screened linear confining potential. In order to get reliable description the Lorentz scalar confining interaction is complemented by the effective one gluon exchange. Within presented model we reasonably reproduce all known radial excitations of the vector charmonia. We have found that $J/Ψ$ is the only charmonium left bellow naive quark-antiquark threshold $2m_c$, while the all excited states are situated above this threshold. We develop a method whi…
