Meson States Research Articles

Radiative hadronization: Photon emission at hadronization from quark-gluon plasma

We investigate photon emission at the hadronization stage from a quark-gluon plasma created in relativistic heavy-ion collisions. A recombination-model picture suggests that a quark and an antiquark bind into a meson state in hadronization, which would apparently violate the energy conservation if there is nothing else involved. We consider here a hadronization process where the recombination accompanies a photon emission. This is an analog of the "{\it radiative recombination}" known in plasma physics, such as $e^- + p^+ \to {\rm H}^0 +\gamma$, which occurs when an electromagnetic plasma goes back to a neutral atomic gas. The "radiative hadronization" picture will bring about (i) an enhancement of the photon yield, (ii) significant flow of photons similar to that of hadrons, and (iii) the photon transverse momentum ($p_T$) distribution with a thermal profile whose effective temperature is given by blue-shifted temperature of quarks. Here as a simplest and phenomenological realization of the radiative hadronization, we modify the recombination model to involve a photon emission and evaluate the photon yield with this modified model. Adding this contribution to the direct photon yield along with thermal photon contribution calculated with a hydrodynamic model and a parametrized contribution of prompt photons, we study the $p_T$ spectrum and elliptic flow of the photons produced in heavy-ion collisions at RHIC and LHC energies.

Direct CP violation of three body decay processes from the resonance effect* *Supported by National Natural Science Foundation of China (11605041)

The physical state of mesons can be mixed using the unitary matrix. The decay processes and originate from isospin symmetry breaking. The , , and interferences lead to a resonance contribution to produce strong phases. violation is considered from isospin symmetry breaking due to the new strong phase of the first order. violation can be enhanced greatly for the decay process when the invariant masses of pairs are in the area around the resonance range and resonance range in perturbative QCD. We also discuss the possibility of searching for the predicted violation at the LHC.

Exclusive semileptonic B_c-meson decays to radially excited charmonium and charm meson states

In the wake of recent measurements of ratios of semileptonic branching fractions: {mathscr {R}}_{J/psi }, {mathscr {R}}_D and {mathscr {R}}_{D^{*}} reported by the LHCb, BELLE and HFLAV Collaborations, we calculate invariant form factors for the exclusive semileptonic B_c-meson decays to radially excited charmonium and charm meson states in the full kinematical region within the framework of relativistic independent quark (RIQ) model. We evaluate the lepton mass effect in the decay processes induced by brightarrow c,u transition at the quark level. Our predictions on branching fractions for B_crightarrow eta _c/psi (nS) are found sim 10^{-2}-10^{-4} and that for B_crightarrow D^{*}(nS) are sim 10^{-4} in their e^{-} decay modes, which lie within the detection accuracy of current experiment. Our predictions on branching fractions, forward backward asymmetry and asymmetry parameter are found in reasonable agreement with other model predictions; which can hopefully be tested in future experiments at LHC and Tevatron. Our predicted observable {mathscr {R}} in this sector are found comparable to other standard model (SM) predictions that violate the lepton flavor universality hinting at new physics beyond SM.

Symmetry breaking radiative corrections to B to tensor meson form factors at large recoil

In heavy-to-light B decays, the heavy-quark/large-energy symmetry reduces the number of QCD form factors. At large final state meson energy, these form factors receive sizeable perturbative corrections. The hard-gluon vertex corrections are absorbed in the coefficients of soft-form factors, while the hard-spectator interactions generate symmetry-breaking corrections and end-point singularities. At an order of 1/m b, using the heavy-quark/large-energy symmetry, the end-point singularities can also be absorbed in the soft form factors, whereas the symmetry breaking corrections add separately to the form factors. In this work, we calculate these perturbative corrections for B → Tμ + μ − decays, with T representing the tensor mesons all having J P = 2+. We find that the values of the branching ratio (Br) and the zero-position of the forward–backward asymmetry of decay receive nearly 5% and 14% contributions, respectively, from these radiative corrections. Compared to these observables, the radiative corrections change the averaged longitudinal lepton polarization asymmetry (⟨P L⟩) by 13%. Therefore, prior to attributing any deviation from the SM predictions of these asymmetries as a hint of NP, one has to take into account the contributions of vertex and hard-spectator corrections.

Mixing effects on 1S and 2S state heavy mesons in the light-front quark model

The mass spectra and wave functions of both $1S$ and $2S$ state heavy pseudoscalar ($P$) and vector ($V$) mesons are analyzed within the light-front quark model. Important empirical constraints employed in our analysis of the mass spectra and wave functions are the experimental mass-gap relation, $\mathrm{\ensuremath{\Delta}}{M}_{P}>\mathrm{\ensuremath{\Delta}}{M}_{V}$, where $\mathrm{\ensuremath{\Delta}}{M}_{P(V)}={M}_{P(V)}^{2S}\ensuremath{-}{M}_{P(V)}^{1S}$ and the hierarchy of the decay constants, ${f}_{1S}>{f}_{2S}$, between $1S$ and $2S$ meson states. We maintain the orthogonality of the trial wave functions of the $1S$ and $2S$ states in our variational calculation of the Hamiltonian with the Coulomb plus confining potentials and treat the hyperfine interaction perturbatively for the heavy-heavy and heavy-light $P$ and $V$ mesons due to the nature of the heavy quark symmetry. Realizing that the empirical constraints cannot be satisfied without mixing of the $1S$ and $2S$ states, we find the lower bound of the mixing angle $\ensuremath{\theta}$ between $1S$ and $2S$ states as ${\ensuremath{\theta}}_{c}={\mathrm{cot}}^{\ensuremath{-}1}(2\sqrt{6})/2\ensuremath{\simeq}6\ifmmode^\circ\else\textdegree\fi{}$ and obtain the optimum value of the mixing angle around 12\ifmmode^\circ\else\textdegree\fi{} to cover both the charm and bottom flavors of the heavy quark. The mixing effects are found to be more significant to the $2S$ state mesons than to the $1S$ state mesons. The properties of $1S$ and $2S$ state mesons including the mass spectra, decay constants, twist-2 distribution amplitudes, and electromagnetic form factors are computed. Our results are found to be in a good agreement with the available data and lattice simulations. In particular, the $2S$ state pseudoscalar ${D}_{s}$ meson is predicted to have a mass of 2600 MeV, which is very close to the mass of the newly discovered ${D}_{s0}(2590{)}^{+}$ meson by the LHCb Collaboration. This supports the interpretation of the observed state as a radial excitation of the ${D}_{s}^{+}$ meson.

Properties of B and Bs meson states in a nonrelativistic quark model with the inclusion of coupled channel effects

The mass spectra and decay properties of [Formula: see text] and [Formula: see text] mesons are obtained using the nonrelativistic potential model by applying the variational approach. The quark–anti-quark potential used in our model consists of a Hulthen potential and a confining linear potential. The hyper-fine interaction is introduced to obtain the splittings of the spin-singlet and triplet states, while the spin–orbit and tensor interactions provide the fine structure splittings. The model parameters and the wave functions that reproduce the mass spectra are used to investigate the decay properties of [Formula: see text] and [Formula: see text] mesons. The mass spectra of [Formula: see text] and [Formula: see text] mesons have been enhanced using coupled channel effects.

Configuration entropy and stability of bottomonium radial excitations in a plasma with magnetic fields

Heavy vector mesons produced in a heavy ion collision are important sources of information about the quark gluon plasma. For instance, the fraction of bottomonium states observed in a such a collision is altered by the dissociation effect caused by the plasma. So, it is very important to understand how the properties of the plasma, like temperature ($T$), density, and the presence of background magnetic fields $(eB)$, affect the dissociation of bottomonium in the thermal medium. Anti--de Sitter/QCD holographic models provide a tool for investigating the properties of heavy mesons inside a thermal medium. The meson states are represented by quasinormal modes in a black hole geometry. In this work we calculate the quasinormal modes and the associated complex frequencies for the four lowest levels of radial excitation of bottomonium inside a plasma with a magnetic field background. We also calculate the differential configuration entropy (DCE) for all these states and investigate how the dissociation effect produced by the magnetic field is translated into a dependence of the DCE on the field. An interesting result obtained in this study is that the DCE increases with the radial excitation level $n$. Also, a nontrivial finding of this work is that the energy density associated with the bottomonium quasinormal modes presents a singularity near the black hole horizon for some combination of values of $T$, $eB$, and $n$. As we show here, it is possible to separate the singular factor and define a square integrable quantity that provides a DCE that is always finite. In addition, we discovered that, working with the potentially singular energy density, one finds a very interesting way to use the DCE as a tool for determining the dissociation temperature of the meson quasistates.

Contributions of S-, P-, and D-wave resonances to the quasi-two-body decays B^{0}_{s} rightarrow psi (3686,3770)K pi in the perturbative QCD approach

Based on the perturbative quantum chromodynamics (pQCD) approach and the quasi-two-body approximation, we have studied the three-body decays B^{0}_{s}rightarrow psi (3686,3770)K pi , which include the contributions of the intermediate resonances overline{K }^{*}_{0}(1430)^{0}, overline{K }^{*}(892)^{0}, overline{K }^{*}(1410)^{0}, overline{K }^{*}(1680)^{0}, and overline{K }^{*}_{2}(1430)^{0}. The time-like form factors corresponding to the distribution amplitudes of the S-, P-, and D-wave of the kaon–pion pair were adopted in parameterized form, and describe the interactions between K and pi in the resonance region. First, the decays B^{0}_{s}rightarrow psi (2S,1D)K ^{-}pi ^{+} were calculated, followed by the calculation of the branching ratios of the decays B^{0}_{s}rightarrow psi (3686,3770)K ^{-}pi ^{+} using the 2S–1D mixing scheme. In addition, the pQCD predictions for the decays B^{0}_{s}rightarrow psi (2S,1D)K pi and B^{0}_{s}rightarrow psi (3686,3770)K pi were obtained using the narrow-width approximation relation given by the Clebsch–Gordan coefficients. Our work shows that the overline{K }^{*}(892)^{0} resonance is the main contributor to the total decay, and the branching ratio and the longitudinal polarization fraction of the psi (2S)overline{K }^{*}(892)^{0} decay mode agree well with the currently available data within errors. Furthermore, the theoretical predictions of the psi (2S) and psi (3686) decay modes are very close, indicating that they can be regarded as the same meson state. Finally, the pQCD predictions for branching ratios of decays B^{0}_{s}rightarrow psi (3686,3770)K pi are of the order of 10^{-5} and 10^{-6}, respectively, which can be verified using the ongoing LHCb and Belle II experiments.

Kaon and nucleon states with hidden charm

In this talk we discuss the formation of exotic hadrons with hidden charm arising from three-body interactions. To be more specific, in the strangeness sector, we predict the existence of a mesonic state, $K^*(4307)$, which is dynamically generated from the three-body interactions of the $KD\bar D^*$ system, has a mass around 4307 MeV and quantum numbers $I(J^P) = 1/2 (1^-)$. In the baryonic sector, we predict the existence of $N^*$ states, which are generated from the three-body interactions of the $ND\bar D^*$ system, with masses around 4400∼4600 MeV, widths of 2 ∼20 MeV and positive parity.

Identifying the contribution of higher ρ mesons around 2 GeV in the e+e−→ωπ0 and e+e−→ρη′ processes

The properties of the light vector meson states around 2.0 GeV have been poorly understood for a long time, which has become a barrier to the expansion to higher light vector meson spectrum. Recently, the BESIII collaboration released the measurements of the $e^+ e^- \to \omega\pi^0$ and $e^+ e^- \to \rho\eta^{\prime}$ reactions above 2.0 GeV, both of which are ideal processes to study the isovector $\rho$ meson family. In this work, through carrying out a combined analysis of the Born cross section data for the above two processes with the theoretical support on mass spectrum, and production and strong decay behaviors of the $\rho$ meson family around 2.0 GeV, we identify the enhancement structure near 2034 MeV observed in $e^+e^-\to\omega\pi^0$ to be the interference contribution from two resonances $\rho(1900)$ and $\rho(2150)$, and another enhancement structure at 2111 MeV reported in $e^+e^-\to\rho\eta^{\prime}$ to be the contributions from $\rho(2000)$ and $\rho(2150)$. This conclusion means that the $e^+e^-\to\omega\pi^0$ and $e^+e^-\to\rho \eta^{\prime}$ are the excellent golden channels to establish $\rho(1900)$ and $\rho(2000)$, especially for a $D$-wave state $\rho(2000)$, whose experimental search in the $e^+e^-$ collision should be quite challenging. The relevant cross section measurements with higher precision are expected in the future BESIII and Belle II experiments.

Collisions of False-Vacuum Bubble Walls in a Quantum Spin Chain

We study the real-time dynamics of a small bubble of "false vacuum" in a quantum spin chain near criticality, where the low-energy physics is described by a relativistic (1+1)-dimensional quantum field theory. Such a bubble can be thought of as a confined kink-antikink pair (a meson). We carefully construct bubbles so that particle production does not occur until the walls collide. To achieve this in the presence of strong correlations, we extend a Matrix Product State (MPS) ansatz for quasiparticle wavepackets [Van Damme et al., arXiv:1907.02474 (2019)] to the case of confined, topological quasiparticles. By choosing the wavepacket width and the bubble size appropriately, we avoid strong lattice effects and observe relativistic kink-antikink collisions. We use the MPS quasiparticle ansatz to detect scattering outcomes: In the Ising model, with transverse and longitudinal fields, we do not observe particle production despite nonintegrability (supporting recent observations of nonthermalizing mesonic states). With additional interactions, we see production of confined and unconfined particle pairs. Although we simulated these low-energy, few-particle events with moderate resources, we observe significant growth of entanglement with energy and with the number of collisions, suggesting that increasing either will ultimately exhaust our methods. Quantum devices, in contrast, are not limited by entanglement production, and promise to allow us to go far beyond classical methods. We anticipate that kink-antikink scattering in 1+1 dimensions will be an instructive benchmark problem for relatively near-term quantum devices.

Mass spectra and strong decays of charmed and charmed-strange mesons

A semi-relativistic potential model is adopted to calculate the mass spectra of charmed and charmed-strange meson states up to the $2D$ excitations.The strong decay properties are further analyzed with a chiral quark model by using the numerical wave functions obtained from the potential model. By using the strong decay amplitudes extracted from the chiral quark model, we also systematically study the coupled-channel effects on the bare masses of the $1P$-wave states, since the masses of $D^*_{s0}(2317)$ and $D_{s1}(2460)$ cannot be explained with bare $1P$-wave states within the potential model. Based on our good descriptions of the mass and decay properties for the low-lying well-established states, we give a quark model classification for the high mass resonances observed in recent years. In the $D$-meson family, $D_0(2550)$ can be classified as the radially excited state $D(2^1S_0)$; $D_3^*(2750)$ and $D_2(2740)$ can be classified as the second orbital excitations $D(1^3D_3)$ and $D(1D'_2)$, respectively; $D_J^*(3000)$ may be a candidate of $D(1^3F_4)$ or $D(2^3P_2)$; while $D_J(3000)$ may favor the high mass mixed state $D(2P'_1)$; however, there still exist puzzles for understanding the natures of $D_1^*(2600)$ and $D_1^*(2760)$, whose decay properties cannot be well explained with either pure $D(2^3S_1)$ and $D(1^3D_1)$ states or their mixing. In the $D_s$-meson family, $D_{s3}^*(2860)$ favors the $D_s(1^3D_3)$ assignment; $D_{s1}^*(2700)$ and $D_{s1}^*(2860)$ may favor the mixed states $|(SD)_1\rangle_L$ and $|(SD)_1\rangle_H$ via the $2^3S_1$-$1^3D_1$ mixing, respectively; $D_{sJ}(3040)$ may favor $D_s(2P_1)$ or $D_s(2P_1')$, or corresponds to a structure contributed by both $D_s(2P_1)$ and $D_s(2P_1')$.

Soft gluon fields and anomalous magnetic moment of muon

An impact of nonperturbatively treated soft gluon modes on the value of anomalous magnetic moment of muon a μ is studied within the mean-field approach to QCD vacuum and hadronization. It is shown that radial excitations of vector mesons strongly enhance contribution of hadronic vacuum polarization to a μ , doubling the contribution of one-meson processes compared to the result for ground state mesons. The mean field also strongly influences the hadronic light-by-light scattering contribution due to the Wilson line in quark propagators.

Study of light tetraquark spectroscopy

We calculate the masses of the $qq\overline{q}\overline{q}$ tetraquark ground state and first radial excited state in a constituent quark model where the Cornell-like potential and one-gluon exchange spin-spin coupling are employed. The three coupling parameters for the Cornell-like potential and one-gluon exchange spin-spin coupling are proposed mass-dependent in accordance with lattice QCD data, and all model parameters are predetermined by studying light, charmed, and bottom mesons. The theoretical predictions for light tetraquarks are compared with the observed exotic meson states in the light-unflavored meson sector, and tentative assignments are suggested. The work suggests that ${f}_{0}(1500)$ and ${f}_{0}(1710)$ might be ground light tetraquark states with $J=0$.

Thermal modification of open heavy-flavor mesons from an effective hadronic theory

We have developed a self-consistent theoretical approach to study the modification of the properties of heavy mesons in hot mesonic matter which takes into account chiral and heavy-quark spin-flavor symmetries. The heavylight meson-meson unitarized scattering amplitudes in coupled channels incorporate thermal corrections by using the imaginary-time formalism, as well as the dressing of the heavy mesons with the self-energies. We report our results for the ground-state thermal spectral functions and the implications for the excited mesonic states generated dynamically in the heavy-light molecular model. We have applied these to the calculation of meson Euclidean correlators and transport coefficients for D mesons and summarize here our findings.

Decay processes of a pseudoscalar D(2900)

We study the decay properties of a $D(2900)$ state, with spin parity ${0}^{\ensuremath{-}}$, whose existence was proposed in an earlier study of the $DK\overline{K}$ and coupled-channel system. It was found in the former work that a $D$ meson appears with a mass of about 2900 MeV from the three-body dynamics while the charmless subsystem of the pseudoscalar mesons forms the ${f}_{0}(980)$ resonance. Motivated by the recent experimental investigations of $D$ mesons around 3000 MeV, we now study the two-body decays of $D(2900)$. We find that the nature of the said state sets the main decay channels to be ${D}^{*}\ensuremath{\pi}$, ${D}_{s}^{*}\overline{K}$ and ${D}_{s0}^{*}(2317)\overline{K}$. It turns out that decay width to the last one is the largest, making the ${D}_{s0}^{*}(2317)\overline{K}$ system to be the most favorable one to look for a signal of $D(2900)$. We compare the decay properties of our state with those of the $D$-meson states, proposed within quark models, near 3000 MeV. We hope that our findings and discussions can be useful for the future experimental investigations of charm mesons around 3000 MeV.

Chiral non-Abelian vortices and their confinement in three flavor dense QCD

We find chiral non-Abelian vortices having windings only in one of the diquark condensations of left-handed and right-handed quarks in the color-flavor locked phase of dense QCD. They are the minimum vortices carrying half color magnetic fluxes of those of non-Abelian semi-superfluid vortices (color magnetic flux tubes) and 1/6 quantized superfluid circulations of Abelian superfluid vortices. These vortices carry ${\mathbb C}P^2$ orientational moduli in the internal space corresponding to their fluxes. The ${\mathbb C}P^2$ moduli of two chiral non-Abelian vortices with chiralities opposite to each other are energetically favored to be aligned while those of a vortex and anti-vortex to be orthogonal, and then these vortices attract each other. They are attached by chiral domain walls in the presence of the mass and axial anomaly terms explicitly breaking axial and chiral symmetries. We numerically show that two chiral non-Abelian vortices with chiralities opposite to each other are connected by a chiral domain wall, consisting a mesonic bound state which is nothing but a non-Abelian semi-superfluid vortex. We also show that Abelian and non-Abelian axial vortices attached by chiral domain walls are all unstable to decay into a set of chiral non-Abelian vortices. Furthermore, we find that chiral non-Abelian vortices exhibit unique features: one is the so-called topological obstruction implying that unbroken symmetry generators in the bulk are not defined globally around the vortices, and the other is color non-singlet Aharonov-Bohm (AB) phases implying that quarks encircling these vortices can detect the colors of magnetic fluxes of them at infinite distances.

SU(2) hadrons on a quantum computer via a variational approach

Quantum computers have the potential to create important new opportunities for ongoing essential research on gauge theories. They can provide simulations that are unattainable on classical computers such as sign-problem afflicted models or time evolutions. In this work, we variationally prepare the low-lying eigenstates of a non-Abelian gauge theory with dynamically coupled matter on a quantum computer. This enables the observation of hadrons and the calculation of their associated masses. The SU(2) gauge group considered here represents an important first step towards ultimately studying quantum chromodynamics, the theory that describes the properties of protons, neutrons and other hadrons. Our calculations on an IBM superconducting platform utilize a variational quantum eigensolver to study both meson and baryon states, hadrons which have never been seen in a non-Abelian simulation on a quantum computer. We develop a hybrid resource-efficient approach by combining classical and quantum computing, that not only allows the study of an SU(2) gauge theory with dynamical matter fields on present-day quantum hardware, but further lays out the premises for future quantum simulations that will address currently unanswered questions in particle and nuclear physics.

Correlation of the hidden-charm molecular tetraquarks and the charmoniumlike structures existing in the B→XYZ+K process

The molecular assignments to the three ${P}_{c}$ states and the similar production mechanism between the ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{P}_{c}+K$ and $B\ensuremath{\rightarrow}XYZ+K$ convince us the $B$ decaying to a charmonium state plus light mesons could be the appropriate production process to search for the charmoniumlike molecular tetraquarks. In this work, we systematically study the interactions between a charmed (charmed-strange) meson and an anticharmed (anticharm-strange) meson, which include the ${D}^{(*)}{\overline{D}}^{(*)}$, ${\overline{D}}^{(*)}{\overline{D}}_{1}$, ${D}^{(*)}{\overline{D}}_{2}^{*}$, ${D}_{s}^{(*)}{\overline{D}}_{s}^{(*)}$, ${D}_{s}^{(*)}{\overline{D}}_{s0}^{*}$, ${D}_{s}^{(*)}{\overline{D}}_{s1}^{\ensuremath{'}}$, ${D}_{s}^{(*)}{\overline{D}}_{s1}$, ${D}_{s}^{(*)}{\overline{D}}_{s2}^{*}$ systems. After adopting the one-boson-exchange effective potentials, our numerical results indicate that, on one hand, there can exist a serial of isoscalar charmoniumlike $\mathcal{D}\overline{\mathcal{D}}$ and ${\mathcal{D}}_{s}{\overline{\mathcal{D}}}_{s}$ molecular states, on the other hand, we can fully exclude the charged charmoniumlike states as the isovector charmoniumlike molecules. Meanwhile, we discuss the two-body hidden-charm decay channels for the obtained $\mathcal{D}\overline{\mathcal{D}}$ and ${\mathcal{D}}_{s}{\overline{\mathcal{D}}}_{s}$ molecules, especially the ${D}^{*}{\overline{D}}^{*}$ molecular tetraquarks. By analyzing the experimental data collected from the $B\ensuremath{\rightarrow}XYZ+K$ and the mass spectrum and two-body hidden-charm decay channels for the obtained $\mathcal{D}\overline{\mathcal{D}}$ and ${\mathcal{D}}_{s}{\overline{\mathcal{D}}}_{s}$ molecules, we find several possible hints of the existence of the charmoniumlike molecular tetraquarks, i.e., a peculiar characteristic mass spectrum of the isoscalar ${D}^{*}{\overline{D}}^{*}$ molecular systems can be applied to identify the charmoniumlike molecule. We look forward to the future experiments like the LHCb, Belle II, and BESIII Collaborations can test our results with more precise experimental data.

DIGITAL GENERATORS OF A PSEUDORANDOM PULSES SEQUENCE AND THEIR MODELING WITH USE OF FPGA INTHE ENVIRONMENT CAD QUARTUS II

From the results obtained in publication [1] as well percentage between decay modes of exitated states of mesons, cited in reference book “Particle Data Group” became possible to evaluate the number of hadron final states on which the meson with hidden charm decay. In the paper is shown a rough estimate of final states number for hadron decays of mesons with hidden charm. The most statistically secured are the final states for ηс (1 S), 2 (π+π-) and π+π- K+K- for χс0 (1P) mesons.