Scalar Hidden-Charm Tetraquark States with QCD Sum Rules

In this article, we study the masses and pole residues of the pseudoscalar-diquark-pseudoscalar-antidiquark type and vector-diquark-vector-antidiquark type scalar hidden-charm cud(cus) tetraquark states with QCD sum rules by taking into account the contributions of the vacuum condensates up to dimension-10 in the operator product expansion.The predicted masses can be confronted with the experimental data in the future. Possible decays of those tetraquark states are also discussed.     

Analysis of X（1576） as a Tetraquark State with the QCD Sum Rules

We take the viewpoint that X（1576） is the tetraquark state which consists of a scalar diquark and an antiscalar-diquark in relative P-wave, and calculate its mass in the framework of the QCD sum rule approach. The numerical value of the mass mx= （1.66 =k 0.14） GeV is consistent with the experimental data. There might be some tetraquark components in the vector meson X（1576）.     

Exotic ■_s~((*))D~((*)) molecular states and sc■ tetraquark states with J~P=0~+,1~+,2~+

We have calculated the mass spectra for the ■_s~((*))D~((*)) molecular states and sc■ tetraquark states with J~P=0~+,1~+,2~+.The masses of the axial-vector ■_sD~*,■_s~*D molecular states and ■ tetraquark states are predicted to be approximately 3.98 GeV,in good agreement with the mass of Z_(cs)(3985)~- from BESⅢ.In both the molecular and diquark-antidiquark scenarios,our results suggest that there may exist two almost degenerate states,as the strange partners of X(3872) and Z_c(3900).We propose to carefully examine Z_(cs)(3985) in future experiments to verify this.One may also search for more hidden-charm four-quark states with strangeness in not only the open-charm ■_s~((*))D~((*)) channels but also the hidden-charm channels η_cK/K~*,J/ψK/K~*.     

A family of double-beauty tetraquarks: Axial-vector state ■

The spectroscopic parameters and decay channels of the axial-vector tetraquark ■(in what follows,■ are explored using the quantum chromodynamics(QCD) sum rule method.The mass and coupling of this state are calculated using two-point sum rules by taking into account various vacuum condensates,up to 10 dimensions.Our prediction for the mass of this state m=(10215±250) MeV confirms that it is stable with respect to strong and electromagnetic decays and can dissociate to conventional mesons only via weak transformations.We investigate the dominant semileptonic ■ and nonleptonic ■ decays of ■.In these processes,■ is a scalar tetraquark ■ built of a color-triplet diquark and an antidiquark,whereas M is one of the vector mesons ρ~-,K~*(892),D~*(2010)~-,and D_s~(*-).To calculate the partial widths of these decays,we use the QCD three-point sum rule approach and evaluate the weak transition form factors G_i(i=0,1,2,3),which govern these processes.The full width Γ_(full)=(12.9±2.1) × 10~(-8) MeV and the mean lifetime τ=5.1+_(-0.71) ~(+0.99) fs of the tetraquark ■ are computed using the aforementioned weak decays.The obtained information about the parameters of ■ and ■ is useful for experimental investigations of these double-heavy exotic mesons.     

Doubly heavy tetraquarks in an extended chromomagnetic model

Using an extended chromomagnetic model,we perform a systematic study of the masses of doubly heavy tetraquarks.We find that the ground states of the doubly heavy tetraquarks are dominated by the color-triplet ■configuration,which is opposite to that of fully heavy tetraquarks.The combined results suggest that the color-triplet configuration becomes more important when the mass difference between the quarks and antiquarks increases.We find three stable states that lie below the thresholds of two pseudoscalar mesons.They are the I^P=01⁺nnbb tetraquark,I^P=1⁺nncb tetraquark,and J^P=1⁺nsbb tetraquark.     

KN Phase Shifts in Chiral SU（3） Quark Model

The isospin I = 0 and I = 1 kaon-nucleon S and P partial waves phase shifts have been studied in the chiral SU(3) quark model by solving a resonating group method equation. When the parameters of the chiral fields are taken in a reasonable region, the numerical results of S-wave are in good agreement with the experimental data, and the P-wave phase shifts can also be explained qualitatively by the calculation of only central force considered.     

Investigation of the tetraquark states ■ in the improved chromomagnetic interaction model

In the framework of the improved chromomagnetic interaction model, we complete a systematic study of the S-wave tetraquark states ■ ( Q = c, b, and q = u, d, s) with different quantum numbers: J^PC= 0⁽+(+)), 1⁽+(±)),and 2⁽+(+)). The mass spectra of tetraquark states are predicted, and the possible decay channels are analyzed by considering both the angular momentum and C-parity conservation. The recently observed hidden-charm tetraquark states with stra...     

Polarization of plane wave propagating inside elastic hexagonal system solids

Based on the reported physical parameters for hexagonal system solids,we have calculated the effects of anisotropy on polarization of plane P-wave propagation.Herein we report the results of calculations and the newly observed physical phenomena.It is found that,for a given propagation,if the polarization is parallel to the wave vector,so also to the Poynting vector.In such a case,the phase velocity is identical to the energy velocity;the quasi P-wave degenerates to a pure P-wave along the propagation.It is also noted that if the polarization is parallel to the Poynting vector but not to the wave vector,the propagating wave cannot be a pure P-wave.Furthermore,the polarization in a quasi P-wave may deviate from the wave vector for more than 45°,but the deviation from the Poynting vector is always less than 45°.The energy velocity of a quasi SV-wave can be larger than that of the quasi P-wave in some propagation directions,even though the phase velocity of a quasi SV-wave may never be larger than either the phase velocity or energy velocity of the quasi P-wave.Finally,in case of parameters ε=0 and δ*≠0,the polarization of a quasi P-wave has an observed symmetry at a 45°phase angle.The anisotropy of a hexagonal system solid determines if a pure P-wave can be created and what the propagation direction is for a plane wave propagating inside such a hexagonal system solid.     

Branching fractions and direct C P asymmetries of ■_s →K~0h~+h′~-(h(′)=K,π) decays

Motivated by the recent LHCb collaboration measurements of charmless three-body decays of ■s meson, we calculate the branching fractions of ■ s →K0π+π-, ■s→K0K+K-, ■s→K0π+K- and ■s→K0K+π- decay modes using the factorization approach.Both the resonant and nonresonant contributions are studied in detail. For the decays ■s→K0π+π- and ■s→K0K+K-, our results agree well with experimental data, and the former is dominated by the K*, while the latter one is dominated by the nonresonant contribution. Considering the flavor S U(3) symmetry violation, the sum of branching fractions of ■s→K0π+K- and ■s→K0K+π-could accommodate the data well too. It should be noted that both branching fractions are sensitive to the scalar density Kπ|ˉsq|0.Furthermore, the resonant contributions are dominated by the scalar K*0(1430). We hope that these branching fractions could be measured individually in the experiments so as to test the factorization approach and the flavor S U(3) asymmetry. Moreover, the direct C P asymmetries of these decays are also investigated, which could be measured in the running LHCb experiment and Super-b factory in the future.     

A family of double-beauty tetraquarks:Axial-vector state T-bb;(us)

The spectroscopic parameters and decay channels of the axial-vector tetraquark Tho(in what follows,TAV)are explored using the quantum chromodynamics(QCD)sum rule method.The mass and coupling of this state are calculated using two-point sum rules by taking into account various vacuum condensates,up to 10 dimensions.Our prediction for the mass of this state m=(10215±250)MeV confirms that it is stable with respect to strong and electromagnetic decays and can dissociate to conventional mesons only via weak transformations.We investigate the dominant semileptonic■and nonleptonic T AV b:s^-→v10 b:s^-M decays of T AV b:s^-.In these processes,Z-b:s^-is a scalar tetraquark[be][us^-]built of a colo-triplet diquark and an antidiquark,whereas M is one of the vector mesonsρ^-,K^*(892),D^*(2010)^-,and D^*s-.To caleulate the partial w idths of these decays,we use the QCD three-point sum rule approach and evaluate the weak transition form factors Gi(i=0,1,2,3),which govem these processes.The full widthΓfull=(12.9±2.1)×10^-8 MeV and the mean lifetimeτ=5.1+0.99-0.71 fs of the tetraquark TAV are computed us-ing the aforementioned weak decays.The obtained information about the parametersof TAY and Zh,is useful for experimental investigations of these double-heavy exotic mesons.     

Strain effects on optical polarisation properties in (11■2) plane GaN films

We present the theoretical results of the electronic band structure of wurtzite GaN films under biaxial strains in the (11■2)-plane.The calculations are performed by the k · p perturbation theory approach through using the effective-mass Hamiltonian for an arbitrary direction.The results show that the transition energies decrease with the biaxial strains changing from 0.5% to 0.5%.For films of (11■2)-plane,the strains are expected to be anisotropic in the growth plane.Such anisotropic strains give rise to valence band mixing which results in dramatic change in optical polarisation property.The strain can also result in optical polarisation switching phenomena.Finally,we discuss the applications of these properties to the (11■2) plane GaN-based light-emitting diode and lase diode.     

Probing the scale of new physics in the ZZγ coupling at e~+e~- colliders

The Z Zγtriple neutral gauge couplings are absent in the Standard Model(SM)at the tree level.They receive no contributions from dimension-6 effective operators,but can arise from effective operators of dimension-8.We study the scale of new physics associated with such dimension-8 operators that can be probed by measuring the reaction e~+e~-→Zγ followed by ■ decays,at future e~+e~- colliders including the CEPC,FCC-ee,ILC and CLIC.We demonstrate how angular distributions of the final-state mono-photon and leptons can play a key r?le in suppressing SM backgrounds.We further demonstrate that using electron/positron beam polarizations can significantly improve the signal sensitivities.We find that the dimension-8 new physics scale can be probed up to the multiTeV region at such lepton colliders.     

Structure,formation, and decay of ■NN system by Faddeev-AGS calculations

The Faddeev AGS equations for the coupled-channels ■NN-πΣN system with quantum numbers I=1/2 and S=0 are solved. Using separable potentials for the ■N-πΣ interaction, we calculate the transition probability for the(YK)I=0 + N→πΣN reaction. The possibility to observe the trace of the K-pp quasi-bound state in πΣN mass spectra was studied. Various types of chiral-based and phenomenological potentials are used to describe the ■N-πΣ interaction. Finally, we show that we can observe the signature of the K-pp quasi-bound state in the mass spectra, as well as the trace of branch points in the observables.     

Dipion decays of heavy baryons

Compared with the charmed baryons, the bottom baryons are not very well known, either experimentally or theoretically. In this paper, we investigate the dipion strong decays of the P-wave and D-wave excited bottom baryons in the framework of the QPC model. We also extend the same analysis to the charmed baryons.     

Vector hidden-bottom tetraquark candidate: Y(10750)

In this article,we take the scalar diquark and antidiquark operators as the basic constituents,and construct the Cγ_5■γ_5C type tetraquark current to study Y(10750) with the QCD sum rules.The predicted mass M_Y=10.75±0.10 GeV and width Γ_Y=33.60_(-9.45)~(+16.64) MeV support the assignment of Y(10750) as the diquark-antidiquark type vector hidden-bottom tetraquark state,with a relative P-wave between the diquark and antidiquark constituents.     

D-wave excited ■ tetraquark states with JPC=1++ and 1+-

We study the mass spectra of D-wave excited cscs tetraquark states with J^PC=1⁺⁺ and 1^+- in both symmetric ■ and antisymmetric ■ color configurations using the QCD sum rule method.We construct the D-wave diquark-antidiquark type of cscs tetraquark interpolating currents in various excitation structures with(L_λ,L_ρ(l_p1,l_ρ2))=(2,0{0,0)),(1,1{1,0)),(1,1{0,1)),(0,2{1,1)),(0,2{2,0}),(0,2{0,2}).Our results support the interpret...     

Molecular Nature of X(3872) in B0→ K0X (3872) and B+→ K+X (3872) Decays

We investigate the decays of B⁰→ K⁰X(3872) and B⁺→ K⁺X(3872) based on the picture where the X(3872) resonance is strongly coupled to the ■+ c.c. channel. In addition to the decay mechanism where the X(3872) resonance is formed from the ■ pair hadronization with the short-distance interaction, we have also considered the ■ rescattering diagrams in the long-distance scale, where D and ■ are formed from c and ■ separately. Because of the difference of the...     

η_b decay into charmonium in association with c pair

We calculate the inclusive decay rates of ηb into charmonium via double c pairs for S-and P-wave states ηc,J/ψ and χcJ within the framework of non-relativistic QCD(NRQCD) factorization at leading order in αs.Besides calculating the contributions of the color-singlet channels ηb→c[2S+1SL(1)]+c,the effects of c pair in the color-octet configurations are also considered.We find that ηb→c[3S1(8)]+c make a small contribution to Br(ηb→J/ψ(ηc)+c).While in the ηb→χcJ+c case,the color octet contributions are significant,for they are of the same αs4vc5 order as the color-singlet processes.We predict Br(ηb→J/ψ(ηc)+c)=2.99(2.75)×10-5 for S-wave states J/ψ and ηc,and Br(ηb→χcJ+c)=(4.37,3.40,2.83)×10-5(for J =0,1,2) for P-wave states χcJ.In the end,we also find Br(ηb→ cc) is almost saturated by ηb decay into charmonium in association with c pair from the point of view of duality.