Pseudoscalar Meson States Research Articles

Mass Spectrum of Noncharmed and Charmed Meson States in Extended Linear-Sigma Model

The mass spectrum of different meson particles is generated using an effective Lagrangian of the extended linear-sigma model (eLSM) for scalar and pseudoscalar meson fields and quark flavors, up, down, strange, and charm. Analytical formulas for the masses of scalar, pseudoscalar, vector, and axialvector meson states are derived assuming global chiral symmetry. The various eLSM parameters are analytically deduced and numerically computed. This enables accurate estimations of the masses of sixteen noncharmed and thirteen charmed meson states at vanishing temperature. The comparison of these results to a recent compilation of the particle data group (PDG) allows us to draw the conclusion that the masses of sixteen noncharmed and thirteen charmed meson states calculated in the eLSM are in good agreement with the PDG. This shows that the eLSM, with its configurations and parameters, is an effective theoretical framework for determining the mass spectra of various noncharmed and charmed meson states, particularly at vanishing temperature.

Test of the Classicality Concept in Entangled States of Neutral Pseudoscalar Mesons with the Aid of Three-Time Wigner Inequalities

Test of the Classicality Concept in Entangled States of Neutral Pseudoscalar Mesons with the Aid of Three-Time Wigner Inequalities

Nonleptonic three-body charmed baryon weak decays with H(15)

We study the nonleptonic three-body charmed baryon weak decays of Bc→BnPP′ under the SU(3)F flavor symmetry, where Bc denotes the antitriplet charmed baryon, comprising (Ξc0,−Ξc+,Λc+), and Bn and P(P′) represent octet baryon and pseudoscalar meson states, respectively. In addition to 12 parameters from the contributions of the color-antisymmetric part of the effective Hamiltonian, denoted as H(6¯), there are 4 parameters from the color-symmetric one, H(15), which were not included in the previous study. With 16 parameters in total and 28 experimental data points, we obtain the minimal χ2 over degree of freedom of χ2/d.o.f=1.5, which is a great improvement comparing to that without H(15). With the better fitting values, we evaluate the branching ratios and up-down asymmetries of Bc→BnPP′, which present some interesting results such as B(Λc+→(Ξ(1690)0→Σ+K−)K+)≡(1.5±0.4)×10−3 and potential SU(3) breaking effects in Ξc+→pπ+K− and Λc+→Σ+π−K+ to be verified by the experiments at BESIII, Belle-II, and LHCb. Published by the American Physical Society 2024

Neutral pseudoscalar and vector meson masses under strong magnetic fields in an extended NJL model: Mixing effects

Mixing effects on the mass spectrum of light neutral pseudoscalar and vector mesons in the presence of an external uniform magnetic field $\vec B$ are studied in the framework of a two-flavor NJL-like model. The model includes isoscalar and isovector couplings both in the scalar-pseudoscalar and vector sectors, and also incorporates flavor mixing through a 't Hooft-like term. Numerical results for the $B$ dependence of meson masses are compared with present lattice QCD results. In particular, it is shown that the mixing between pseudoscalar and vector meson states leads to a significant reduction of the mass of the lightest state. The role of chiral symmetry and the effect of the alignment of quark magnetic moments in the presence of the magnetic field are discussed.

Ground state pseudoscalar mesons on the light front: From the light to heavy sector

We extract the leading Fock-state light front wave functions (LF-LFWFs) of both the light and heavy pseudoscalar mesons, e.g., the pion (at masses of 130 MeV, 310 MeV and 690 MeV), $\eta_c$ and $\eta_b$, from their covariant Bethe-Salpeter wave functions within the rainbow-ladder (RL) truncation. It is shown that the LF-LFWFs get narrower in $x$ (the longitudinal momentum fraction of meson carried by the quark) with the increasing current quark mass, and the leading twist parton distribution amplitudes (PDAs) inherit this feature. Meanwhile, we find in the pion the LF-LFWFs only contribute around 30\% to the total Fock-state normalization, indicating the presence of significant higher Fock-states within. In contrast, in the $\eta_c$ and $\eta_b$ the LF-LFWFs contribute more than $90$\%, suggesting the $Q\bar{Q}$ valence Fock-state truncation as a good approximation for heavy mesons. We thus study the 3-dimensional parton distributions of the $\eta_c$ and $\eta_b$ with the unpolarized generalized parton distribution function (GPD) and the transverse momentum dependent parton distribution function (TMD). Through the gravitational form factors in connection with the GPD, the mass radii of the $\eta_c$ and $\eta_b$ in the light-cone frame are determined to be $r_{E,{\rm LC}}^{\eta_c} =0.150$ fm and $r_{E,{\rm LC}}^{\eta_b} =0.089$ fm respectively.

Properties of excited Bc states in QCD

The mass and leptonic decay constants of recently observed two new excited Bc states at LHC are studied within the QCD sum rules. Considering the contributions of the ground and radially excited states, the mass and residues of the excited states of pseudoscalar and vector mesons are calculated in the framework of two different approaches of the QCD sum rules, namely, linear combinations of the corresponding sum rules and its derivatives as well as QCD sum rules with the incorporation of the least square fitting method. The obtained results on mass mBc+(2S)=6.88±0.03GeV and mBc⁎+(2S)=6.94±0.03GeV are in good agreement with the experimental data. Our predictions for the decay constants of these states are: fBc+(2S)=0.42±0.02GeV and fBc⁎+(2S)=0.46±0.01GeV, which can be checked at future experiments to be conducted at the LHC. Comparison of our results with the predictions of the other approaches on mass and residues is also presented.

Charmed baryon weak decays with decuplet baryon and SU(3) flavor symmetry

We study the branching ratios and up-down asymmetries in the charmed baryon weak decays of ${\bf B}_c\to {\bf B}_DM$ with ${\bf B}_{c(D)}$ anti-triplet charmed (decuplet) baryon and $M$ pseudo-scalar meson states based on the flavor symmetry of $SU(3)_F$. We propose equal and physical-mass schemes for the hadronic states to deal with the large variations of the decuplet baryon momenta in the decays in order to fit with the current experimental data. We find that our fitting results of ${\cal B}({\bf B}_c\to {\bf B}_DM) $ are consistent with the current experimental data in both schemes, while the up-down asymmetries in all decays are found to be sizable, consistent with the current experimental data, but different from zero predicted in the literature. We also examine the processes of $\Xi_c^0 \to \Sigma^{\prime 0}K_S/K_L$ and derive the asymmetry between the $K_L/K_S$ modes being a constant.

Chiral phase structure of the sixteen meson states in the SU(3) Polyakov linear-sigma model for finite temperature and chemical potential in a strong magnetic field

In characterizing the chiral phase-structure of pseudoscalar ( ), scalar ( ), vector ( ) and axial-vector ( t) meson states and their dependence on temperature, chemical potential, and magnetic field, we utilize the SU(3) Polyakov linear-sigma model (PLSM) in the mean-field approximation. We first determine the chiral (non)strange quark condensates, and , and the corresponding deconfinement order parameters, and , in thermal and dense (finite chemical potential) medium and finite magnetic field. The temperature and the chemical potential characteristics of nonet meson states normalized to the lowest bosonic Matsubara frequency are analyzed. We note that all normalized meson masses become temperature independent at different critical temperatures. We observe that the chiral and deconfinement phase transitions are shifted to lower quasicritical temperatures with increasing chemical potential and magnetic field. Thus, we conclude that the magnetic field seems to have almost the same effect as the chemical potential, especially on accelerating the phase transition, i.e. inverse magnetic catalysis. We also find that increasing the chemical potential enhances the mass degeneracy of the various meson masses, while increasing the magnetic field seems to reduce the critical chemical potential, at which the chiral phase transition takes place. Our mass spectrum calculations agree well with the recent PDG compilations and PNJL, lattice QCD calculations, and QMD/UrQMD simulations.

Covariant Spectator Theory of heavy–light and heavy mesons and the predictive power of covariant interaction kernels

The Covariant Spectator Theory (CST) is used to calculate the mass spectrum and vertex functions of heavy-light and heavy mesons in Minkowski space. The covariant kernel contains Lorentz scalar, pseudoscalar, and vector contributions. The numerical calculations are performed in momentum space, where special care is taken to treat the strong singularities present in the confining kernel. The observed meson spectrum is very well reproduced after fitting a small number of model parameters. Remarkably, a fit to a few pseudoscalar meson states only, which are insensitive to spin-orbit and tensor forces and do not allow to separate the spin-spin from the central interaction, leads to essentially the same model parameters as a more general fit. This demonstrates that the covariance of the chosen interaction kernel is responsible for the very accurate prediction of the spin-dependent quark-antiquark interactions.

Mass spectrum and leptonic decay constants of ground and radially excited states of ηc and ηb in a Bethe–Salpeter equation framework

In this paper, we study the mass spectrum and decay constants of ground state (1S) and radially excited states (2S and 3S) of heavy equal mass pseudoscalar mesons, ηc and ηb. We have employed the framework of Bethe–Salpeter equation (BSE) under Covariant Instantaneous Ansatz (CIA). Our predictions are in reasonable agreement with the data on available states and results of other models.

SU(3) Polyakovlinear−σmodel in magnetic fields: Thermodynamics, higher-order moments, chiral phase structure, and meson masses

Effects of external magnetic field on various properties of the quantum chromodynamics under extreme conditions of temperature and density have been analysed. To this end, we use SU(3) Polyakov linear sigma-model and assume that the external magnetic field eB adds some restrictions to the quarks energy due to the existence of free charges in the plasma phase. In doing this, we apply the Landau theory of quantization. This requires an additional temperature to drive the system through the chiral phase-transition. Accordingly, the dependence of the critical temperature of chiral and confinement phase-transitions on the magnetic field is characterized. Based on this, we have studied the thermal evolution of thermodynamic quantities and the first four higher-order moment of particle multiplicity. Having all these calculations, we have studied the effects of magnetic field on chiral phase-transition. We found that both critical temperature T_c and critical chemical potential increase with increasing the magnetic field eB. Last but not least, the magnetic effects of the thermal evolution of four scalar and four pseudoscalar meson states are studied. We concluded that the meson masses decrease as the temperature increases till T_c. Then, the vacuum effect becomes dominant and rapidly increases with the temperature T. At low T, the scalar meson masses normalized to the lowest Matsubara frequency rapidly decreases as T increases. Then, starting from T_c, we find that the thermal dependence almost vanishes. Furthermore, the meson masses increase with increasing magnetic field. This gives characteristic phase diagram of T vs. external magnetic field $B. At high T, we find that the masses of almost all meson states become temperature independent. It is concluded that the various meson states likely have different T_c's.

PROBING SCALAR MESON STRUCTURES IN χc1 DECAYS INTO PSEUDOSCALAR AND SCALAR

We evaluate the decay branching ratios of χc1 → PS, in a quark model parametrization scheme, where P and S stand for pseudoscalar and scalar meson, respectively. An interesting feature of this decay process is that the [Formula: see text] annihilate via the pQCD hair-pin diagram is supposed to be dominant. Hence, this decay process should be sensitive to the quark components of the final-state light mesons, and would provide a great opportunity for testing the mixing relations among the scalar mesons, i.e. f0(1370), f0(1500) and f0(1710), by tagging the final state pseudoscalar mesons.

Extracting rephase-invariant CP and CPT violating parameters from asymmetries of time-ordered integrated rates of correlated decays of entangled mesons

We present a general model-independent formalism of measuring CP and CPT violating parameters through time-ordered integrated rates of correlated decays of $C=\pm 1$ entangled states of neutral pseudoscalar mesons. We give the general formulae of CP and CPT violating parameters in terms of four measurable asymmetries defined for the time-ordered integrated rates, applicable to all kinds of decay product. Two special cases which are often realized in experiments are discussed specifically.

Predictive AdS/QCD model for mass spectra of mesons with three flavors

The predictive soft-wall AdS/QCD model with a modified 5D metric at the infrared region is constructed to obtain a nontrivial dilaton solution for three flavor quarks $u$, $d$ and $s$. Such a model is shown to incorporate both the chiral symmetry breaking and linear confinement. After considering some high-order terms including the $\mathrm{U}(1{)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1{)}_{R}$ chiral symmetry breaking term, we find that the resulting predictions for the SU(3) octet and singlet resonance states of pseudoscalar, scalar, vector and axial-vector mesons agree well with the experimentally confirmed resonance states. Contributions from the instanton effects given by the determinant term are also discussed. It is observed that the chiral symmetry breaking phenomena of $\mathrm{SU}(3{)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(3{)}_{R}$ and $\mathrm{U}(1{)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1{)}_{R}$ can be well described in this model, while the SU(3) flavor symmetry breaking effect due to quark mass difference in the source term is not enough to explain all of the current experimental data.

Quantum algebra in mixed light pseudoscalar meson states

In this paper, we investigate the entanglement degrees of pseudoscalar meson states via Yangian algebra Y(SU(3)). By making use of the transition effect of generators J of Y(SU(3)), we construct various transition operators, and act with them on the η–π 0–η′ mixing meson state. The entanglement degrees of both the initial state and final state are calculated with the help of entropy theory. The diagrams of entanglement degrees are presented. Our result shows that a state with the desired entanglement degree can be achieved by acting with a properly chosen transition operator on an initial state. Some combinations of generators of Y(SU(3)) make the constitutions of the initial state change, and lead to superpositions of particles with different electrical charges. This sheds new light on the connections among quantum information, particle physics and Yangian algebra.

Prediction for the mass spectra of resonance mesons in the soft-wall AdS/QCD model with a modified 5D metric

A soft-wall anti-de Sitter/QCD model with a modified five-dimensional metric at the infrared region is constructed to obtain a nontrivial dilaton solution, which incorporates the chiral symmetry breaking and linear confinement. By taking the pion mass and decay constant as two input mass scales, the resulting predictions for the resonance states of pseudoscalar, scalar, vector and axial-vector mesons agree remarkably with the experimentally confirmed resonance states. The effects of the quartic interaction term are investigated by taking an appropriate sign and magnitude for maintaining the stability of the bulk scalar potential. It is shown that such a simply modified soft-wall anti-de Sitter/QCD model can lead to a consistent prediction for the mass spectra of resonance states in the pseudoscalar, scalar, vector and axial-vector mesons; the agreement with the experimental data is found to be better than 10% for the excited meson states. The resulting pion form factor also agrees well with the experimental data.

Formula omitted] Decays

The nonet symmetry scheme seems to describe rather well the masses and η–η′ mixing angle of the ground state pseudo-scalar mesons and is thus expected to be also a good approximation for the matrix elements of the pseudo-scalar density operators which play an important role in charmless two-body B decays with η or η′ in the final state. In this talk, I would like to report on a recent work on the B−→K−η,K−η′ decay using nonet symmetry for the matrix elements of pseudo-scalar density operators. We find that the branching ratio B→PP, with an η meson in the final state agrees well with data, while those with an η′ meson are underestimated by 20–30%. This could be considered as a more or less successful prediction for QCDF, considering the theoretical uncertainties involved. This could also indicate that an additional power-suppressed terms could bring the branching ratio close to experiment, as with the B→K∗π and B→K∗η decay for which the measured branching ratios are much bigger than the QCDF predictions.

On the distances between entangled pseudoscalar mesons states

Entangled states of pseudoscalar mesons represent a very interesting tool for studying foundations of quantum mechanics, e.g. for testing Bell inequalities. Recently, they also emerged as a test bench for quantum information protocols. On the other hand, from a quantum information point of view, the characterization of the distance between two quantum states is a topic of the utmost importance. In this letter, with the purpose of providing a useful tool for further investigations, we address the problem of which distance allows a better discrimination between density matrices appearing in pseudoscalar phenomenology.

Nonet symmetry inη,η′andB→Kη,Kη′decays

The nonet symmetry scheme seems to describe rather well the masses and {eta}-{eta}{sup '} mixing angle of the ground state pseudoscalar mesons. It is expected that nonet symmetry should also be valid for the matrix elements of the pseudoscalar density operators which play an important role in charmless two-body B decays with {eta} or {eta}{sup '} in the final state. Starting from the divergences of the SU(3) octet and singlet axial vector currents, we show that nonet symmetry for the pseudoscalar mass term implies nonet symmetry for the pseudoscalar density operators. In this nonet symmetry scheme, we find that the branching ratio B{yields}PP, PV with {eta} in the final state agrees well with data, while those with {eta}{sup '} are underestimated, but by increasing the B{yields}{eta}{sup '} form factor by 40%-50%, one could explain the tree-dominated B{sup -}{yields}{pi}{sup -}{eta}{sup '} and B{sup -}{yields}{rho}{sup -}{eta}{sup '} measured branching ratios. With this increased form factor and with only a moderate annihilation contribution, we are able to obtain 62x10{sup -6} for the penguin-dominated B{sup -}{yields}K{sup -}{eta}{sup '} branching ratios, quite close to the measured value. This supports the predicted value for the B{yields}{eta}{sup '} form factor in PQCD and light-cone sum rules approach.more » A possible increase by 15% of for {eta}{sub 0} would bring the predicted B{sup -}{yields}K{sup -}{eta}{sup '} branching ratio to 69.375x10{sup -6}, very close to experiment.« less

Quenched lattice calculation of semileptonic heavy-light meson form factors

We calculate, in the continuum limit of quenched lattice QCD, the matrix elements of the heavy-heavy vector current between heavy-light pseudoscalar meson states. We present the form factors for different values of the initial and final meson masses at finite momentum transfer. In particular, we calculate the non-perturbative correction to the differential decay rate of the process B → Dlν including the case of a non-vanishing lepton mass.