We carry out a systematic study of the heavy-light meson strong decays in a chiral quark model. For the $S$-wave vectors ($D^*(2007)$, $D^{*\pm}(2010)$), $P$-wave scalars ($D^*_0(2400)$, $B^*_0(5730)$) and tensors ($D^*_2(2460)$, $D^*_{s2}(2573)$), we obtain results in good agreement with the experimental data. For the axial vectors $D_1(2420)$ and $D_1^\prime(2430)$, a state mixing scheme between $1^1P_1$ and $1^3P_1$ is favored with a mixing angle $\phi\simeq-(55\pm 5)^\circ$, which is consistent with previous theoretical predictions. The same mixing scheme also applies to $D_{s1}(2460)$ and $D_{s1}(2536)$ that accounts for the narrow width of the $D_{s1}(2536)$ and its dominant decay into $D^*K$. For $B_1(5725)$ and $B_1^\prime(5732)$, such a mixing explains well the decay width of the former but leads to an even broader $B_1^\prime(5732)$. Predictions for the strange-bottom axial vectors are also made. For the undetermined meson $D^*(2640)$, we find that they fit in well the radially excited state $2^3S_1$ according to its decay mode. The newly observed $D^*_{sJ}(2860)$ strongly favors the $D$-wave excited state $1^3D_3$. For $D^*_{sJ}(2632)$ and $D^*_{sJ}(2690)$, we find they are difficult to fit in any $D_s$ excitations in that mass region, if the experimental data are accurate. Theoretical predictions for decay modes of those unobserved states as multiplets of 2S and 1D waves are also presented, which should be useful for further experimental search for those states.Comment: 14 pages, 6 figures,to appear in PR

Charmed baryon strong decays are studied in a chiral quark model. The data for the decays of $\Lambda^+_c(2593)$, $\Lambda^+_c(2625)$, $\Sigma^{++,+,0}_c$ and $\Sigma^{+,0}_c(2520)$, are accounted for successfully, which allows to fix the pseudoscalar-meson-quark couplings in an effective chiral Lagrangian. Extending this framework to analyze the strong decays of the newly observed charmed baryons, we classify that both $\Lambda_c(2880)$ and $\Lambda_c(2940)$ are $D$-wave states in the N=2 shell; $\Lambda_c(2880)$ could be $|\Lambda_c ^2 D_{\lambda\lambda}{3/2}^+>$ and $\Lambda_c(2940)$ could be $|\Lambda_c ^2 D_{\lambda\lambda}{5/2}^+>$. Our calculation also suggests that $\Lambda_c(2765)$ is very likely a $\rho$-mode $P$-wave excited state in the N=1 shell, and favors a $|\Lambda_c ^4P_\rho 1/2^->$ configuration. The $\Sigma_c(2800)$ favors being a $|\Sigma_c ^2P_\lambda{1/2}^->$ state. But its being $|\Sigma^{++}_c ^4 P_\lambda{5/2}^->$ cannot be ruled out.Comment: 22 pages, 16 tables; typos corrected;version to appear in PR

The strong and radiative decays of the low-lying S -and P-wave Λ c(b) − of the 6 F multiplet have similar strong decay properties. In order to identify them, angular distributions of their decays in either strong decay modes or radiative transitions should be needed.,

In this work, we study the mass spectra of the all-heavy tetraquark systems, i.e., cccc, bbbb, bbcc=ccbb, bccc=ccbc, bcbb=bbbc, and bcbc, within a potential model by including the linear confining potential, Coulomb potential, and spin-spin interactions. It shows that the linear confining potential has important contributions to the masses and is crucial for our understanding of the mass spectra of the all-heavy tetraquark systems. For the all-heavy tetraquarks Q 1 Q 2Q3Q4 , our explicit calculations suggest that no bound states can be formed below the thresholds of any meson pairs ðQ 1Q3 Þ − ðQ 2Q4 Þ or ðQ 1Q4 Þ − ðQ 2Q3 Þ. Thus, we do not expect narrow all-heavy tetraquark states to be existing in experiments.

The strong decay properties of the newly observed states D sJ ð3040Þ, D sJ ð2860Þ, and D sJ ð2710Þ are studied in a constituent quark model with quark-meson effective Lagrangians. We find that the D sJ ð3040Þ could be identified as the low-mass physical state j2P 1 i L (J P ¼ 1 þ ) from the D s ð2 1 P 1 Þ-D s ð2 3 P 1 Þ mixing. The D sJ ð2710Þ is likely to be the low-mass mixed state jðSDÞi L via the 1 3 D 1 -2 3 S 1 mixing. In our model, the D sJ ð2860Þ cannot be assigned to any single state with a narrow width and compatible partial widths to DK and D Ã K. Thus, we investigate a two-state scenario as proposed in the literature. In our model, one resonance is likely to be the 1 3 D 3 (J P ¼ 3 À ), which mainly decays into DK. The other resonance seems to be the j1D 2 0 i H , i.e. the high-mass state in the 1 1 D 2 -1 3 D 2 mixing with J P ¼ 2 À , of which the D Ã K channel is its key decay mode. We also discuss implications arising from these assignments and give predictions for their partner states such as jðSDÞ 0 i H , j2P 0 1 i H , 2 3 P 0 , and 2 3 P 2 , which could be helpful for the search for these new states in future experiments.

Stimulated by the exciting progress in the observation of new bottomonium states, we study the bottomonium spectrum. To calculate the mass spectrum, we adopt a nonrelativistic screened potential model. The radial Schr\"{o}dinger equation is solved with the three-point difference central method, where the spin-dependent potentials are dealt with non-perturbatively. With this treatment, the corrections of the spin-dependent potentials to the wave functions can be included successfully. Furthermore, we calculate the electromagnetic transitions of the $nS$ ($n\leq 4$), $nP$ ($n\leq 3$), and $nD$ ($n\leq 2$) bottomonium states with a nonrelativistic electromagnetic transition operator widely applied to meson photoproduction reactions. Our predicted masses, hyperfine and fine splittings, electromagnetic transition widths and branching ratios of the bottomonium states are in good agreement with the available experimental data. Especially, the EM transitions of $\Upsilon(3S)\to \chi_{b1,2}(1P)\gamma$, which were not well understood in previous studies, can be reasonably explained by considering the corrections of the spin-dependent interactions to the wave functions. We also discuss the observations of the missing bottomonium states by using radiative transitions. Some important radiative decay chains involving the missing bottomonium states are suggested to be observed. We hope our study can provide some useful references to observe and measure the properties of bottomonium mesons in forthcoming experiments.Comment: 14 pages, 1 figure, revised version. To appear in PR

Thermodynamic formulas for investigating systems with density and/or temperature dependent particle masses are generally derived from the fundamental derivation equality of thermodynamics. Various problems in the previous treatments are discussed and modified. Properties of strange quark matter in bulk and strangelets at both zero and finite temperature are then calculated based on the new thermodynamic formulas with a new quark mass scaling, which indicates that low mass strangelets near β equilibrium are multi-quark states with an anti-strange quark, such as the pentaquark (u 2 d 2s ) for baryon nmber 1 and the octaquark (u 4 d 3s ) for dibaryon etc.

Inspired by the newly observed Ξ 0 c states by the LHCb Collaboration, we investigate the OZI-allowed twobody strong decays of the λ-mode 1P wave Ξ ′ c states within the chiral quark model. Our results indicate that: (i) the newly observed states Ξ c (2923) 0 and Ξ c (2939) 0 are good candidates of the λ-mode 1P wave Ξ ′ c states with the spin-parity J P = 3/2 − , namely | 4 P λ 3/2 − and | 2 P λ 3/2 − , respectively. (ii) The another newly observed state Ξ c (2965) 0 mostly corresponds to the λ-mode 1P-wave Ξ ′ c state with the spin-parity J P = 5/2 − , namely | 4 P λ 5/2 − . (iii) For the two λ-mode J P = 1/2 − mixed states, the |P λ 1/2 − 1 is a narrow state with a width of Γ ∼ 15 MeV and mainly decays into Ξ ′ c π; while the |P λ 1/2 − 2 state has a width of Γ ∼ 52 MeV and dominantly decays into Ξ c π and Λ c K channels. If the broad structure around 2880 MeV observed at LHCb arises from the new Ξ 0 c state, this state is very likely to be the |P λ 1/2 − 2 state. m[Ξ c (2939) 0 ] = 2938.55 ± 0.52 MeV, Γ[Ξ c (2939) 0 ] = 10.2 ± 1.9 MeV, m[Ξ c (2965) 0 ] = 2964.88 ± 0.54 MeV, Γ[Ξ c (2965) 0 ] = 14.1 ± 2.2 MeV. As pointed out in Ref. [12], the Ξ c (2930) 0 observed in B − → K − Λ + cΛ −