Understanding the structure of d~*(2380) in chiral quark model

The structure and decay properties of d~* have been detailedly investigated in both the chiral SU(3) quark model and the extended chiral SU(3) quark model that describe the energies of baryon ground states and the nucleon-nucleon(NN) scattering data satisfactorily. By performing a dynamical coupled-channels study of the system of ?? and hidden-color channel(CC) with quantum numbers I(J~P) = 0(3~+) in the framework of the resonating group method(RGM), we find that the d~* has a mass of about 2.38-2.42 Ge V and a root-mean-square radius(RMS) of about 0.76-0.88 fm. The channel wave function is extracted by a projection of the RGM wave function onto the physical basis, and the fraction of CC component in the d~* is found to be about 66%-68%, which indicates that the d~* is a hexaquark-dominated exotic state. Based on this scenario the partial decay widths of d~*→dπ~0π~0and d~*→dπ~+π~- are further explicitly evaluated and the total width is then obtained by use of the branching ratios extracted from the measured cross sections of other possible decay channels. Both the mass and the decay width of d~* calculated in this work are compatible with the data(M≈2380 Me V, Γ≈70 Me V) reported by WASA-at-COSY Collaboration.     

Is d a candidate for a hexaquark-dominated exotic state?

We confirm our previous prediction of a d^* state with I(J^P)=0(3⁺) [Phys. Rev. C 60, 045203 (1999)] and report for the first time based on a microscopic calculation that d^* has about 2/3 hidden color (CC) configurations and thus is a hexaquark-dominated exotic state. By performing a more elaborate dynamical coupled-channels investigation of the ΔΔ-CC system within the framework of the resonating group method (RGM) in a chiral quark model, we find that the d^* state has a mass of about 2.38--2.42 GeV, a root-mean-square radius (RMS) of 0.76--0.88 fm, and a CC fraction of 66%--68%. The last may cause a rather narrow width for the d^* which, together with the quantum numbers and our calculated mass, is consistent with the newly observed resonance-like structure (M≈ 2380 MeV, Γ≈ 70 MeV) in double-pionic fusion reactions reported by the WASA-at-COSY Collaboration.     

Is X(3872) a bound state?

All existing experimental evidence for the bound state nature of X(3872) relies on observing its decay products,which are measured with a finite experimental mass resolution that is typically △m≥2 MeV,and much larger than its alleged binding energy,B_X=0.00(18) MeV.On the other hand,we have found recently that there is a clear cancellation in the 1~(++) channel of the invariant DD~*mass around the threshold between continuum and the bound state.This is very much like a similar cancellation in the proton-neutron continuum with the deuteron in the1~(++) channel.Based on comparative fits with a common Tsallis distribution of the experimental cross-sections for prompt production of deuterons and X(3872) in pp collisions with a finite p_T,we find a strong argument for questioning the bound state nature of this state,which also suggests that the large observed production rate could be consistent with a half-bound state.     

Is J~(PC)=3~(-+) molecule possible?

The confirmation of charged charmonium-like states indicates that heavy quark molecules should exist.Here we discuss the possibility of a molecule state with J P C= 3-+. In a one-boson-exchange model investigation for the S wave C = + D* ˉD*2states, one finds that the strongest attraction is in the case J = 3 and I = 0 for bothπ and σ exchanges. Numerical analysis indicates that this hadronic bound state might exist if a phenomenological cutoff parameter around 2.3 Ge V(1.5 Ge V) is reasonable with a dipole(monopole) type form factor in the one-pionexchange model. The cutoff for binding solutions may be reduced to a smaller value once the σ exchange contribution is included. If a state around the D* ˉD*2threshold(≈4472 Me V) in the channel J/ψω(P wave) is observed, the heavy quark spin symmetry implies that it is not a cˉc meson and the J P C are likely to be 3-+.     

Is JPC=3-+ molecule possible?

The confirmation of charged charmonium-like states indicates that heavy quark molecules should exist.Here we discuss the possibility of a molecule state with J P C= 3-+. In a one-boson-exchange model investigation for the S wave C = + D* ˉD*2states, one finds that the strongest attraction is in the case J = 3 and I = 0 for bothπ and σ exchanges. Numerical analysis indicates that this hadronic bound state might exist if a phenomenological cutoff parameter around 2.3 Ge V(1.5 Ge V) is reasonable with a dipole(monopole) type form factor in the one-pionexchange model. The cutoff for binding solutions may be reduced to a smaller value once the σ exchange contribution is included. If a state around the D* ˉD*2threshold(≈4472 Me V) in the channel J/ψω(P wave) is observed, the heavy quark spin symmetry implies that it is not a cˉc meson and the J P C are likely to be 3-+.     

Is Ds（2700） a charmed tetraquark state？

In this article, we assume that the Ds(2700) is a tetraquark state, which consists of a scalar diquark and a vector antidiquark, and calculate its mass with the QCD sum rules. The numerical result indicates that the mass of the vector charmed tetraquark state is about MV = (3.75±0.18) GeV or MV = (3.71±0.15) GeV from different sum rules, which is about 1 GeV larger than the experimental data. Such tetraquark component should be very small in the Ds(2700).     

Exotic vector charmonium and its leptonic decay width

We propose a novel type of interpolating field operator,which manifests the hybrid-like configuration that the charm quark-antiquark pair recoils against gluonic degrees of freedom.A heavy vector charmonium-like state with a mass of 4.33(2) GeV is disentangled from the conventional charmonium states in the quenched approximation.This state has affinity for the hybrid-like operators but couples less to the relevant quark bilinear operator.We also try to extract its leptonic decay constant and give a tentative upper limit that it is less than one tenth of that of J/ψ,which corresponds to a leptonic decay width about dozens of eV.The connection of this state with X(4260) is also discussed.     

Higgs assisted razor search for Higgsinos at a 100 TeV pp collider

A 100 Te V proton-proton collider will be an extremely effective way to probe the electroweak sector of the minimal supersymmetric standard model (MSSM).In this paper,we describe a search strategy for discovering pair-produced Higgsino-like next-to-lightest supersymmetric particles (NLSPs) at a 100 Te V hadron collider that decay to Bino-like lightest supersymmetric particles (LSPs) via intermediate Z and SM Higgs bosons that in turn decay to a pair of leptons and a pair of b-quarks respectively:■.In addition,we examine the potential for machine learning techniques to boost the power of our searches.Using this analysis,Higgsinos up to 1.4 Te V can be discovered at the 5σlevel for Binos with mass of about0.9 Te V using 3000 fb~(-1)of data.Additionally,Higgsinos up to 1.8 Te V can be excluded at 95%C.L.for Binos with mass of about1.4 Te V.This search channel extends the multi-lepton search limits,especially in the region where the mass difference between the Higgsino NLSPs and the Bino LSP is small.     

Antiferromagnetic and topological states in silicene:A mean field study

It has been widely accepted that silicene is a topological insulator, and its gap closes first and then opens again with increasing electric field, which indicates a topological phase transition from the quantum spin Hall state to the band insulator state. However, due to the relatively large atomic spacing of silicene, which reduces the bandwidth, the electron–electron interaction in this system is considerably strong and cannot be ignored. The Hubbard interaction, intrinsic spin orbital coupling(SOC), and electric field are taken into consideration in our tight-binding model, with which the phase diagram of silicene is carefully investigated on the mean field level. We have found that when the magnitudes of the two mass terms produced by the Hubbard interaction and electric potential are close to each other, the intrinsic SOC flips the sign of the mass term at either K or K for one spin and leads to the emergence of the spin-polarized quantum anomalous Hall state.     

Near-threshold η production in pp collisions

We study near-threshold η meson production in pp collisions within an effective Lagrangian approach combined with the isobar model, by allowing for the various intermediate nucleon resonances due to the π, η, and ρ-meson exchanges. It is shown that the ρ-meson exchange is the dominant excitation mechanism for these resonances,and the contribution from the N*(1720) is dominant. The total cross section data can be reasonably reproduced,and the anisotropic angular distributions of the emitted η meson are consistent with experimental measurements.Besides, the invariant mass spectra of pp and pη explain the data well at excess energy of 15 Me V, and are basically consistent with the data at excess energy of 40 Me V. However, our model calculations cannot reasonably account for the two-peak structure in the pη distribution at excess energies of 57 and 72 Me V, which suggests that a more complicated mechanism is needed at higher energy region.     

Symmetry energy at subsaturation densities and the neutron skin thickness of ~(208)Pb

The mass-dependent symmetry energy coefficients asym(A) has been extracted by analysing the heavy nuclear mass differences reducing the uncertainties as far as possible in our previous work.Taking advantage of the obtained symmetry energy coefficient asym(A) and the density profiles obtained by switching off the Coulomb interaction in208 Pb,we calculated the slope parameter L0.11 of the symmetry energy at the density of 0.11 fm-3.The calculated L0.11 ranges from 40.5 Me V to 60.3 Me V.The slope parameter L0.11 of the symmetry energy at the density of 0.11 fm-3is also calculated directly with Skyrme interactions for nuclear matter and is found to have a fine linear relation with the neutron skin thickness of208 Pb,which is the difference of the neutron and proton rms radii of the nucleus.With the linear relation the neutron skin thickness Rn pof208 Pb is predicted to be 0.15–0.21 fm.     

The Ξ~* K and ?η Interaction Within a Chiral Unitary Approach

In this work we study the interaction of the coupled channels ?η and Ξ* ˉK within the chiral unitary approach.The systems under consideration have total isospins 0,strangeness S =-3,and spin 3/2.We study the s wave interaction which implies that the possible resonances generated in the system can have spin-parity JP= 3/2-.The unitary amplitudes in coupled channels develop poles that can be associated with some known baryonic resonances.We find there is a dynamically generated 3/2-? state with mass around 1800 Me V,which is in agreement with the predictions of the five-quark model.     

Shannon information entropies for position-dependent mass Schrdinger problem with a hyperbolic well

The Shannon information entropy for the Schrodinger equation with a nonuniform solitonic mass is evaluated for a hyperbolic-type potential. The number of nodes of the wave functions in the transformed space z are broken when recovered to original space x. The position Sx and momentum S p information entropies for six low-lying states are calculated. We notice that the Sx decreases with the increasing mass barrier width a and becomes negative beyond a particular width a,while the Sp first increases with a and then decreases with it. The negative Sx exists for the probability densities that are highly localized. We find that the probability density ρ(x) for n = 1, 3, 5 are greater than 1 at position x = 0. Some interesting features of the information entropy densities ρs(x) and ρs(p) are demonstrated. The Bialynicki–Birula–Mycielski(BBM)inequality is also tested for these states and found to hold.     

Method for measuring prompt γ-rays generated by D-T neutrons bombarding a depleted uranium spherical shell

The prompt γ-ray spectrum from depleted uranium(DU) spherical shells induced by 14 Me V D-T neutrons is measured. Monte Carlo(MC) simulation gives the largest prompt γ flux with the optimal thickness of the DU spherical shells 3–5 cm and the optimal frequency of neutron pulse 1 MHz. The method of time of flight and pulse shape coincidence with energy(DC-TOF) is proposed, and the subtraction of the background γ-rays discussed in detail. The electron recoil spectrum and time spectrum of the prompt γ-rays are obtained based on a 2 ×2 BC501 A liquid scintillator detector. The energy spectrum and time spectrum of prompt γ-rays are obtained based on an iterative unfolding method that can remove the influence of γ-rays response matrix and pulsed neutron shape.The measured time spectrum and the calculated results are roughly consistent with each other. Experimental promptγ-ray spectrum in the 0.4–3 Me V energy region agrees well with MC simulation based on the ENDF/BVI.5 library,and the discrepancies for the integral quantities of γ-rays of energy 0.4–1 Me V and 1–3 Me V are 9.2% and 1.1%,respectively.     

Equation of state for pure fluids at critical temperature

In this paper, we employ the concept of probability for creating a cavity with diameter d in fluid along with the perturbation and variation approach, and develop an equation of state (EOS) for a hard sphere (HS) and Lennard– Jones (LJ) fluids. A suitable axiomatic form for surface tension S(r) is assumed for the pure fluid, with r as a variable. The function S(r) has an arbitrary parameter m. S(r) = A + B(d/r)/[1 + m(d/r)]. We use the condition in terms of radial distribution function G(λd, η) containing the self-consistent parameter λ and the condition of continuity at r = d/2 to determine A and B. A different EOS can be obtained with a suitable choice of m and the EOS has a lower root-mean-square deviation than that of Barker–Henderson BH2 for LJ fluids.     

Properties of the P_c(4312) pentaquark and its bottom partner

We present an analysis of the newly observed pentaquark P_c(4312)~+ to shed light on its quantum numbers.To do that,the QCD sum rules approach is used.The measured mass of this particle is close to the ∑_c~(++)D~-threshold and has a small width,which supports the possibility of its being a molecular state.We consider an interpolating current in a molecular form and analyze both the positive and negative parity states with spin-1/2.We also consider the bottom counterpart of the state with similar molecular form.Our mass result for the charm pentaquark state supports that the quantum numbers of the observed state are consistent with J~P=1/2~-.     

A high-fidelity memory scheme for quantum data buses

A novel quantum memory scheme is proposed for quantum data buses in scalable quantum computers by using adjustable interaction. Our investigation focuses on a hybrid quantum system including coupled flux qubits and a nitrogen–vacancy center ensemble. In our scheme, the transmission and storage(retrieval) of quantum state are performed in two separated steps, which can be controlled by adjusting the coupling strength between the computing unit and the quantum memory. The scheme can be used not only to reduce the time of quantum state transmission, but also to increase the robustness of the system with respect to detuning caused by magnetic noises. In comparison with the previous memory scheme, about 80% of the transmission time is saved. Moreover, it is exemplified that in our scheme the fidelity could achieve 0.99 even when there exists detuning, while the one in the previous scheme is 0.75.     

Effects of electron–optical phonon interactions on the polaron energy in a wurtzite ZnO/Mg_xZn_(1-x)O quantum well

We investigated the properties of polarons in a wurtzite ZnO/MgxZn1-xO quantum well by adopting a modified Lee–Low–Pines variational method, giving the ground state energy, transition energy, and phonon contributions from various optical-phonon modes to the ground state energy as functions of the well width and Mg composition. In our calculations, we considered the effects of confined optical phonon modes, interface-optical phonon modes, and half-space phonon modes, as well as the anisotropy of the electron effective band mass, phonon frequency, and dielectric constant. Our numerical results indicate that the electron–optical phonon interactions importantly affect the polaronic energies in the ZnO/MgxZn1-xO quantum well. The electron–optical phonon interactions decrease the polaron energies. For quantum wells with narrower wells, the interface optical phonon and half-space phonon modes contribute more to the polaronic energies than the confined phonon modes. However, for wider quantum wells, the total contribution to the polaronic energy mainly comes from the confined modes. The contributions of the various phonon modes to the transition energy change differently with increasing well width. The contribution of the half-space phonons decreases slowly as the QW width increases, whereas the contributions of the confined and interface phonons reach a maximum at d ≈ 5.0 nm and then decrease slowly. However,the total contribution of phonon modes to the transition energy is negative and increases gradually with the QW width of d.As the composition x increases, the total contribution of phonons to the ground state energies increases slowly, but the total contributions of phonons to the transition energies decrease gradually. We analyze the physical reasons for these behaviors in detail.     

Polaron and molecular states of a spin–orbit coupled impurity in a spinless Fermi sea

We investigate the polaron and molecular states of a fermionic atom with one-dimensional spin–orbit coupling(SOC)coupled to a three-dimensional spinless Fermi sea. Because of the interplay among the SOC, Raman coupling and spinselected interatomic interactions, the polaron state induced by the spin–orbit coupled impurity exhibits quite unique features. We find that the energy dispersion of the polaron generally has a double-minimum structure, which results in a finite center-of-mass(c.m.) momentum in the ground state, different from the zero-momentum polarons where SOC are introduced into the majority atoms. By further tuning the parameters such as the atomic interaction strength, a discontinuous transition between the polarons with different c.m. momenta may occur, signaled by the singular behavior of the quasiparticle residue and effective mass of the polaron. Meanwhile, the molecular state as well as the polaron-to-molecule transition is also strongly affected by the Raman coupling and the effective Zeeman field, which are introduced by the lasers generating SOC on the impurity atom. We also discuss the effects of a more general spin-dependent interaction and mass ratio. These results would be beneficial for the study of impurity physics brought by SOC.     

A Gaussian Model for Anisotropic Strange Quark Stars

For studying the anisotropic strange quark stars,we assume that the radial pressure inside an anisotropic star can be obtained simply by isotropic pressure plus an additional Gaussian term with three free parameters(A,μand χ).According to recent observations,a pulsar in a mass range of 1.97±0.04M_⊙ has been measured.Hence,we take this opportunity to set the free parameters of our model.We fix χ by applying boundary and stability conditions and then search the A —μ parameter space for a maximum mass range of 1.9M_⊙ M_(max) 2.1M_⊙.Our results indicate that anisotropy increases the maximum mass M_(max) and also its corresponding radius R for a typical strange quark star.Furthermore,our model shows magnetic field and electric charge increase the anisotropy factor △.In fact,△ has a maximum on the surface and this maximum goes up in the presence of magnetic field and electric charge.Finally,we show that anisotropy can be more effective than either magnetic field or electric charge in raising maximum mass of strange quari stars.