S-wave Mesons Research Articles

Why quarkonium hybrid coupling to two S -wave heavy-light mesons is not suppressed

We examine the couplings of quarkonium hybrids to heavy-light meson pairs in the Born-Oppenheimer approximation for QCD. The lowest hybrid multiplets consist of bound states of the Πu and Σu− potentials. We find that the Σu− potential can couple to pairs of S-wave mesons through string breaking, while the Πu potential cannot. From this observation, we derive model-independent selection rules that contradict previous expectations that quarkonium hybrids are forbidden to decay into pairs of S-wave mesons. These Born-Oppenheimer selection rules are consistent with the partial decay widths of the lowest charmonium hybrid with exotic quantum numbers JPC=1−+ recently calculated using lattice QCD. Published by the American Physical Society 2024

Decay constants of B c (nS) and (nS)* *Supported by the National Natural Science Foundation of China (12005060)

The decay constants of the low lying S-wave mesons, i.e. and with , are calculated in the nonrelativistic quark model. The running coupling of the strong interaction is taken into account, and the uncertainties due to varying parameters and losing Lorentz covariance are considered carefully. As a byproduct, the decay constants of the low lying S-wave charmonium and bottomium states are given in the appendixes.

Correction to: Determination of Parameters of a Potential Model for Tetraquark Study by Studying All S-Wave Mesons

Correction to: Determination of Parameters of a Potential Model for Tetraquark Study by Studying All S-Wave Mesons

Determination of Parameters of a Potential Model for Tetraquark Study by Studying All S-Wave Mesons

The masses of low-lying S-wave mesons are evaluated in a constituent quark model (CQM) where the Cornell-like potential and one-gluon exchange spin-spin interaction are employed. To make the model applicable to both the light and heavy quark sectors, we introduce mass-dependent coupling coefficients. There are four free parameters in the model, which are determined by comparing the theoretical results with experimental data. The established model with one set of parameters may be applied to study higher excited meson states as well as multiquark systems in both the light and heavy quark sectors.

B_{(s)} to light tensor meson form factors via LCSR in HQEFT with applications to semileptonic decays

In the present work, the form factors of B_{(s)} to light P-wave tensor mesons (a_2(1320), K^*_2(1430), f_2(1270), f^prime _2(1525)) are calculated via the light cone sum rules (LCSR) in the framework of heavy quark effective field theory (HQEFT). Firstly, the expressions of form factors in terms of the light cone distribution amplitudes (DAs) of tensor mesons are derived via the LCSR at the leading order of heavy quark expansion. It is found that the penguin type form factors can be obtained directly from the corresponding semileptonic ones, which is similar to the case of S-wave mesons. Considering the light tensor meson DAs to twist-3, we give the numerical results of form factors systematically. As applications, we investigate the branching ratios, longitudinal polarization fractions and forward-backward asymmetries of relevant semileptonic decays induced by charged current and flavor changing neutral current (FCNC) separately. Our results may be tested by more precise experiments in the future.

The scalar f_0(500), f_0(980), and a_0(980) resonances and vector mesons in the single Cabibbo-suppressed decays Lambda _c rightarrow p K^+K^- and ppi ^+pi ^-

In the chiral unitary approach, we have studied the single Cabibbo-suppressed decays Lambda _crightarrow pK^+K^- and Lambda _c rightarrow p pi ^+pi ^- by taking into account the s-wave meson–meson interaction as well as the contributions from the intermediate vectors phi and rho ^0. Our theoretical results for the ratios of the branching fractions of Lambda _crightarrow p {bar{K}}^{*0} and Lambda _crightarrow p omega with respect to the one of Lambda _crightarrow p phi are in agreement with the experimental data. Within the picture that the scalar resonances f_0(500), f_0(980), and a_0(980) are dynamically generated from the pseudoscalar-pseudoscalar interactions in s-wave, we have calculated the K^+K^- and pi ^+pi ^- invariant mass distributions respectively for the decays Lambda _crightarrow pK^+K^- and Lambda _crightarrow ppi ^+pi ^-. One can find a broad bump structure for the f_0(500) and a narrow peak for the f_0(980) in the pi ^+pi ^- invariant mass distribution of the decay Lambda _crightarrow ppi ^+pi ^-. For the K^+K^- invariant mass distribution, in addition to the narrow peak for the phi meson, there is an enhancement structure near the K^+K^- threshold mainly due to the contribution from the f_0(980). Both the pi ^+pi ^- and K^+K^- invariant mass distributions are compatible with the BESIII measurement. We encourage our experimental colleagues to measure these two decays, which would be helpful to understand the nature of the f_0(500), f_0(980), and a_0(980).

Semileptonic and nonleptonic weak decays of Λb0

The recent experimental developments require a more precise theoretical study of weak decays of heavy baryon $\Lambda_b^0$. In this work, we provide an updated and systematic analysis of both the semi-leptonic and nonleptonic decays of $\Lambda^0_b$ into baryons $\Lambda^+_c$, $\Lambda$, $p$, and $n$. The diquark approximation is adopted so that the methods developed in the $B$ meson system can be extended into the baryon system. The baryon-to-baryon transition form factors are calculated in the framework of a covariant light-front quark model. The form factors $f_3, ~g_3$ can be extracted and are found to be non-negligible. The semi-leptonic processes of $\Lambda^0_b\to \Lambda^+_c(p)l^-\bar\nu_l$ are calculated and the results are consistent with the experiment. We study the non-leptonic processes within the QCD factorization approach. The decay amplitudes are calculated at the next-to-leading order in strong coupling constant $\alpha_s$. We calculate the non-leptonic decays of $\Lambda^0_b$ into a baryon and a s-wave meson (pseudoscalar or vector) including 44 processes in total. The branching ratios and direct CP asymmetries are predicted. The numerical results are compared to the experimental data and those in the other theoretical approaches. Our results show validity of the diquark approximation and application of QCD factorization approach into the heavy baryon system.

P-wave excited meson photoproduction at the LHeC

As an important sequential work of the S-wave ( ) meson production at the large hadron electron collider (LHeC), we investigate the production of the P-wave excited states (1P1 and 3PJ with J = 0, 1, 2) via photoproduction mechanism within the framework of nonrelativistic QCD at the LHeC. Generally, the process is considered as the main production mechanism at an electron–proton collider due to the large luminosity of the gluon. However, according to our experience on the S-wave meson production at the LHeC, the extrinsic production mechanism, i.e., and , could also provide dominating contributions at low pT region. A careful treatment between these channels is performed and the results on total and differential cross sections, together with main uncertainties are discussed. Taking the quark masses mb = 4.90 ± 0.40 GeV and mc = 1.50 ± 0.20 GeV into account and summing up all the production channels, we expect to accumulate , and events at the LHeC in one operation year with luminosity cm−2 s−1. With such sizable events, it is worth studying the properties of excited P-wave states at the LHeC.

The tetraquark candidate from dynamical lattice QCD simulations

The structure of the tetraquark candidate , which has been experimentally reported in collisions, is studied by s-wave meson–meson coupled-channel scattering on the lattice. The s-wave interactions among the , and channels are derived from (2 + 1)-flavor dynamical QCD simulations at –700 MeV. It is found that the interactions are dominated by the off-diagonal – and – couplings. With the interactions obtained, the s-wave two-body amplitudes and the pole position in –– coupled-channel scattering are calculated. The results show that is not a conventional resonance but a threshold cusp. A semiphenomenological analysis with the coupled-channel interaction to the experimentally observed decay mode is also presented to confirm the conclusion.

Quarkonium production at the LHC: A data-driven analysis of remarkably simple experimental patterns

The LHC quarkonium production data reveal a startling observation: the J/ψ, ψ(2S), χc1, χc2 and ϒ(nS)pT-differential cross sections in the central rapidity region are compatible with one universal momentum scaling pattern. Considering also the absence of strong polarizations of directly and indirectly produced S-wave mesons, we conclude that there is currently no evidence of a dependence of the partonic production mechanisms on the quantum numbers and mass of the final state. The experimental observations supporting this universal production scenario are remarkably significant, as shown by a new analysis approach, unbiased by specific theoretical calculations of partonic cross sections, which are only considered a posteriori, in comparisons with the data-driven results.

Charmed tetraquarks [formula omitted] and [formula omitted] from dynamical lattice QCD simulations

Charmed tetraquarks Tcc=(ccu¯d¯) and Tcs=(csu¯d¯) are studied through the S-wave meson–meson interactions, D–D, K¯–D, D–D⁎ and K¯–D⁎, on the basis of the (2+1)-flavor lattice QCD simulations with the pion mass mπ≃410, 570 and 700 MeV. For the charm quark, the relativistic heavy quark action is employed to treat its dynamics on the lattice. Using the HAL QCD method, we extract the S-wave potentials in lattice QCD simulations, from which the meson–meson scattering phase shifts are calculated. The phase shifts in the isospin triplet (I=1) channels indicate repulsive interactions, while those in the I=0 channels suggest attraction, growing as mπ decreases. This is particularly prominent in the Tcc(JP=1+,I=0) channel, though neither bound state nor resonance are found in the range mπ=410–700 MeV. We make a qualitative comparison of our results with the phenomenological diquark picture.

Decay constants and form factors of s-wave and p-wave mesons in the covariant light-front quark model

We reanalyze the decay constants of s-wave and p-wave mesons and the D, B → M form factors, where M represents a pseudoscalar meson, a vector meson, a scalar meson or an axial vector meson within a covariant light-front quark model. The parameter β for wavefunctions of most of s-wave mesons and that of a few axial-vector mesons are fixed with the latest experimental information, wherever available or using the lattice calculations. The treatment of masses and mixing angles for strange axial vector mesons is improved for the purpose. We extend our analysis to determine the form factors appearing in the Ds, Bs → M transitions, and to the isoscalar final state mesons. Numerical results of the form factors for transitions between a heavy pseudoscalar meson and an s-wave or a p-wave light meson and their momentum dependence are presented in detail. Further, their sensitivity to uncertainties of the β parameters of the initial as well as the final mesons is investigated. Some experimental measurements of the charmed and bottom meson decays are employed to compare the decay constants and transition form factors obtained in this and other works.

Ground State Meson Spectrum in a Relativistic Model with Instanton Induced Interaction

The mass spectrum of the S-wave mesons is considered in the frame work of relativistic harmonic model (RHM). The full Hamiltonian used in the investigation has the Lorentz scalar plus a vector harmonic-oscillator potential, the confined-one-gluon-exchange potential (COGEP) and the instanton-induced quark-antiquark interaction (III). A good description of the mass spectrum is obtained. The respective role of III and COGEP in the S-wave meson spectrum is discussed.

Masses and electroweak properties of light mesons in the relativistic quark model

The masses, pseudoscalar and vector weak decay constants and electromagnetic form factors of light S-wave mesons are studied in the framework of the relativistic quark model based on the quasipotential approach. We use the same model assumptions and parameters as in our previous investigations of heavy meson and baryon properties. The masses and wave functions of the ground state and radially excited π, ρ, K, K* and φ mesons, obtained by solving numerically the relativistic Schrödinger-like equation with the complete relativistic qq̄ potential including both spin-independent and spin-dependent terms, are presented. Novel relativistic expressions for the weak decay constants of the pseudoscalar and vector mesons are derived. It is shown that the intermediate negative-energy quark states give significant contributions which essentially decrease the decay constants bringing them in agreement with experimental data. The electromagnetic form factors of the pion, charged and neutral kaon are calculated in a broad range of the space-like momentum transfer. The corresponding charge radii are determined. All results agree well with the available experimental data.

Open-charm systems in cold nuclear matter

We study the spectral distributions of charmed meson with JP=0− quantum numbers in cold nuclear matter applying a self-consistent and covariant many-body approach established previously for the nuclear dynamics of kaons. At leading orders the computation requires as input the free-space two-body scattering amplitudes only. Our results are based on the s-wave meson–nucleon amplitudes obtained recently in terms of a coupled-channel approach. The amplitudes are characterized by the presence of many resonances in part so far not observed. This gives rise to an intriguing dynamics of charmed mesons in nuclear matter. At nuclear saturation density we predict a pronounced two-mode structure of the D+ mesons with a main branch pushed up by about 32 MeV. The lower branch reflects the coupling to two resonance-hole states that are almost degenerate. For the D− we obtain a single mode pushed up by about 18 MeV relative to the vacuum mode. Most spectacular are the results for the Ds+ meson. The presence of an exotic resonance-hole state gives rise to a rather broad and strongly momentum dependent spectral distribution.

MASSES OF LIGHT MESONS IN THE RELATIVISTIC QUARK MODEL

The masses of the S-wave mesons consisting of the light (u, d, s) quarks are calculated within the constituent quark model. The relativistic Schrödinger-like equation with a confining potential is numerically solved for the complete relativistic [Formula: see text] potential including both spin-independent and spin-dependent terms. The obtained masses of the ground state π, ρ, K, K* and ϕ mesons and their first radial excitations are in a reasonably good overall agreement with experimental data.

The family of strange multiquarks related to the [formula omitted] and [formula omitted

I study the D s ( 2317 ) and D s ( 2457 ) discovered at BaBar, CLEO and Belle, and find that they belong to a class of strange S = − 1 tetraquarks and pentaquarks, which is equivalent to the class of kaonic molecules bound by short range attraction. In this class of hadrons a kaon is strongly trapped by a s-wave meson or baryon. To describe this class of multiquarks the Resonating Group Method is applied to a standard quark model with chiral symmetry breaking, and the short range kaon-meson(baryon) interactions are extracted. A criterion is derived to classify the attractive channels. I conclude that the mesons B s ( 0 + ) , B s ( 1 + ) , and the baryons Ω c c , Ω c b , Ω b b clearly belong to the new hadronic class of the D s ( 2317 ) and D s ( 2457 ) . The hadrons f 0 ( 980 ) , Λ , Σ c , Σ b possibly belong to a related family.

Hybrid configuration content of heavyS-wave mesons

We use the nonrelativistic expansion of QCD (NRQCD) on the lattice to study the lowest hybrid configuration contribution to the ground state of heavy S-wave mesons. Using lowest-order lattice NRQCD to create the heavy-quark propagators, we form a basis of ``unperturbed'' S-wave and hybrid states. We then apply the lowest-order coupling of the quark spin and chromomagnetic field at an intermediate time slice to create ``mixed'' correlators between the S-wave and hybrid states. From the resulting amplitudes, we extract the off-diagonal element of our two-state Hamiltonian. Diagonalizing this Hamiltonian gives us the admixture of a hybrid configuration within the meson ground state. The present effort represents a continuation of previous work: the analysis has been extended to include lattices of varying spacings, source operators having better overlap with the ground states, and the pseudoscalar (along with the vector) channel. Results are presented for bottomonium $(\ensuremath{\Upsilon},{\ensuremath{\eta}}_{b})$ using three different sets of quenched lattices. We also show results for charmonium $(J/\ensuremath{\psi},{\ensuremath{\eta}}_{c})$ from one lattice set, although we note that the nonrelativistic approximation is not expected to be very good in this case.

Universal description ofS-wave meson spectra in a renormalized light-cone QCD-inspired model

A light-cone QCD-inspired model, with the mass squared operator consisting of a harmonic oscillator potential as confinement and a Dirac-delta interaction, is used to study the S-wave meson spectra. The two parameters of the harmonic potential and quark masses are fixed by masses of rho(770), rho(1450), J/psi, psi(2S), K*(892) and B*. We apply a renormalization method to define the model, in which the pseudo-scalar ground state mass fixes the renormalized strength of the Dirac-delta interaction. The model presents an universal and satisfactory description of both singlet and triplet states of S-wave mesons and the corresponding radial excitations.

Toy model for pion production in nucleon-nucleon collisions. II. The role of three-particle singularities

The influence of three-particle breakup singularities on s-wave meson production in nucleon-nucleon collisions is studied within the distorted wave Born approximation. This study is based on a simple scalar model for the two-nucleon interaction and the production mechanism. An algorithm for the exact numerical treatment of the inherent three-body cuts, together with its straightforward implementation is presented. It is also shown that two often-used approximations to avoid the calculation of the three-body breakup are not justified. The possible impact on pion production observables is discussed.