Meson States Research Articles

Production mechanism of the hidden charm pentaquark states Pcc¯

We investigate hidden charm pentaquark states using an off-shell coupled-channel formalism involving heavy meson and singly heavy baryon scattering. Our approach utilizes an effective Lagrangian to construct the kernel amplitudes, which respect both heavy quark symmetry and hidden local symmetry. After solving the coupled integral equations, we obtain the transition amplitudes for J/ψN scattering and various heavy meson and singly heavy baryon scattering processes. We identify seven distinct peaks related to molecular states of heavy mesons D¯ (D¯*) and singly heavy baryons Σc (Σc*). Four of these peaks can be associated with the known Pcc¯ states: Pcc¯(4312), Pcc¯(4380), Pcc¯(4440), and Pcc¯(4457). We predict two additional resonances with masses around 4.5 GeV, which we interpret as D¯*Σc* molecular states, and identify one cusp structure. Additionally, we predict two P-wave pentaquark states with positive parity, which may be candidates for genuine pentaquark configurations. Notably, these pentaquark states undergo significant modifications in the J/ψN elastic channel, with some even disappearing due to interference from the positive parity channel. The present investigation may provide insight into the absence of pentaquark states in J/ψ photoproduction observed by the GlueX Collaboration. Published by the American Physical Society 2024

Spectroscopy of excited quarkonium states in the light-front quark model

Abstract We have investigated the ground state ($1S$), radially excited states ($2S$) and ($3S$) along with the orbitally excited state ($1P$) for the heavy charmonia ($c \bar c$) and bottomonia ($b \bar b$) mesons in the light-front quark model (LFQM). The light-front wave functions have been successful in explaining various physical properties of meson states in the past, especially for the $1S$ and $2S$ states. However, studies regarding the radially excited state $3S$ and orbitally excited state $1P$ have hardly been pursued before. In this study, we take up these two excited states and investigate the electromagnetic form factors (EMFFs), charge radii, decay constants, parton distribution functions (PDFs) and the distribution amplitudes (DAs) for the quarkonia system. For the sake of completeness, we have also included the study of the ground and the first excited states of quarkonia mesons. We have also illustrated the 3D wave functions for the radially excited states in order to study their nodal structures. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

Anomalous and linear holographic hard wall models for light unflavored mesons

In this work we consider anomalous and linear holographic hard wall (HW) models for light unflavored mesons inspired by the AdS/CFT correspondence. The anomalous dimensions depend on the logarithm of the spin S of the meson state and come from a semiclassical analysis of gauge/string duality. The anomalous HW model produces very good masses and good Regge trajectories for mesons compared with PDG data. Inspired by this anomalous HW model we also propose a phenomenological modification of the dimension of the boundary operators such that the model produces asymptotic linear Regge trajectories. Both anomalous HW models considered here present mass percentage deviations of less than 3%, when compared with PDG data. Published by the American Physical Society 2024

Likelihood analysis of the newly observed f0(2020) , f0(2330) , and f0(2470) in J/ψ→γη′η′ as high-lying unflavored scalar mesons

Inspired by the newly observed three scalar states f0(2020), f0(2330), and f0(2470) by the BESIII collaboration in J/ψ→γη′η′, we carried out the study of spectroscopic behavior of these high-lying unflavored scalar mesonic states. In this work, using the phenomenological description of radial (n,M2) trajectory and the quark pair creation model, we discussed the assignments of the f0(2020), f0(2330), and f0(2470) associated with the f0(2200) as the isoscalar high-lying scalar mesonic states and predicted the spectroscopic properties of their high-lying partners. The present study may provide valuable information for the construction of the scalar meson family. Published by the American Physical Society 2024

Imprinting New Physics by Using Angular Profiles of the Flavor-Changing-Neutral-Current Process Bc → Ds* (→ Dsπ) ℓ+ℓ-

Abstract The decays governed by the flavor-changing-neutral-current (FCNC) transitions, such as $b\rightarrow s\ell ^{+}\ell ^{-}$, provide an important tool to test the physics in and beyond the Standard Model (SM). This work focuses on investigating the FCNC process $B_{c}\rightarrow D_{s}^{*} \left(\rightarrow D_{s}\pi \right)\ell ^{+}\ell ^{-}(\ell =e,\mu ,\tau )$. Being an exclusive process, the initial and final state meson matrix elements involve the form factors, which are nonperturbative quantities and need to be calculated using specific models. By using the form factors calculated in the covariant light-front quark model, we analyze the branching fractions and angular observables such as the forward-backward asymmetry $A_{\mathrm{ FB}}$, polarization fractions (longitudinal and transverse) $F_{L(T)}$, CP asymmetry coefficients $A_{i}$, and CP-averaged angular coefficients $S_{i}$, both in the SM and in some new physics (NP) scenarios. Some of these physical observables are a potential source of finding the physics beyond the SM and help us to distinguish various NP scenarios.

Lepton flavor violation in exclusive b→dℓiℓj and b→sℓiℓj decay modes

We discuss the exclusive lepton flavor violating (LFV) decays modes based on b→dℓiℓj and b→sℓiℓj by considering the ground state mesons and baryons. After spelling out the expressions for such decay rates in a low energy effective theory which includes generic contributions arising from physics beyond the Standard Model, we show that the experimental bounds on meson decays can be used to bound the corresponding modes involving baryons. We find, for example, B(Λb→Λμτ)≲4×10−5. We also consider two specific models and constrain the relevant LFV couplings by using the low energy observables. In the first model, we assume the Higgs mediated LFV and find the resulting decay rates to be too small to be experimentally detectable. We also emphasize that the regions favored by the bounds B(h→μτ)Atlas and B(h→eτ)Atlas are not compatible with B(μ→eγ)MEG to 1σ. In the second model, we assume LFV mediated by a heavy Z′ boson and find that the corresponding b-hadron branching fractions can be O(10−6), thus possibly within experimental reach at LHCb and Belle II. Published by the American Physical Society 2024

Chiral symmetry breaking, chiral partners, and the [formula omitted] and [formula omitted] in medium

We clarify the concept of chiral partners. For a vector meson, the isospin-zero and hypercharge-zero state in the flavor octet mixes with the flavor singlet state. Since the flavor singlet vector meson does not have a chiral partner, the mixed ω and ϕ mesons will not have chiral partners. This means that even when chiral symmetry is restored, these mesons will not become degenerate with their corresponding parity partners. On the other hand, the K1 and K∗ mesons are chiral partners, and both have widths smaller than 100 MeV. Therefore, we emphasize that studying these mesons in environments where chiral symmetry is restored is particularly important for understanding the effect of chiral symmetry restoration on chiral partners and their masses.

Spectra and decay properties of higher lying BC meson states

In this work, the spectra and decay properties of [Formula: see text] mesons [Formula: see text]) have been investigated using a nonrelativistic potential model incorporating corrections from LQCD. The nonrelativistic Schrödinger wave equation is solved numerically using the Matrix Numerov Method. Using the obtained masses and wave functions, decay widths, lifetime, branching ratios and radiative decay widths are computed for the [Formula: see text] system. Influence of the bound state effect on decay width of [Formula: see text] mesons is also analyzed. We compare the obtained results with the experimental data and with other theoretical models.

Bootstrapping pions at large N. Part II. Background gauge fields and the chiral anomaly

We continue the program [1] of carving out the space of large N confining gauge theories by modern S-matrix bootstrap methods, with the ultimate goal of cornering large N QCD. In this paper, we focus on the effective field theory of massless pions coupled to background electromagnetic fields. We derive the full set of positivity constraints encoded in the system of 2 → 2 scattering amplitudes of pions and photons. This system probes a larger set of intermediate meson states, and is thus sensitive to intricate large N selection rules, especially when supplemented with expectations from Regge theory. It also has access to the coefficient of the chiral anomaly. We find novel numerical bounds on several ratios of Wilson coefficients, in units of the rho mass. By matching the chiral anomaly with the microscopic theory, we also derive bounds that contain an explicit N dependence.

Puzzle of the cornell potential on the heavy and heavy-light meson spectra

We computed the eigenvalues and eigenfunctions via the Cornell potential, approximately, using Numerov approach. The experimental data for the quantum states 3 S 1 were utilized to fit the mass spectra. Results were compared with observed data and the results obtained from other potential functions in the existing literature for the heavy ( cc¯, bb¯ and bc¯ ) as well as heavy-light (B, Bs, D and Ds) meson states. The yielded meson spectra based on this potential are matching well with the available experimental data.

Charmonium production in hot magnetized hyperonic matter: Effects of the baryonic Dirac sea and pseudoscalar-vector mixing

We investigate the medium modifications of the masses of pseudoscalar open charm (D and D¯) mesons and the charmonium state [ψ(3770)] in hot isospin asymmetric strange hadronic medium in the presence of an external magnetic field within a chiral effective model. The in-medium partial decay widths of ψ(3770) to charged and neutral DD¯ mesons are computed from the medium modifications of the masses of the initial and final state mesons. These are computed using two light quark pair creation models—(I) the P03 model and (II) a field theoretical (FT) model of composite hadrons with quark (and antiquark) constituents. The production cross sections of ψ(3770), arising from scattering of the D and D¯ mesons, are computed from the relativistic Breit-Wigner spectral function expressed in terms of the in-medium masses and the decay widths of the charmonium state. The effects of the magnetic field are considered due to the Dirac sea (DS) of the baryons, the mixing of the pseudoscalar (S=0) and vector (S=1) meson (PV mixing), the Landau level contributions for the charged hadrons. The anomalous magnetic moments (AMMs) of the baryons are also taken into account in the present study. For magnetized nuclear matter, at ρB=ρ0, the effect of Dirac sea leads to inverse magnetic catalysis (IMC), which is drop of the magnitude of the light quark condensates (proportional to the scalar fields) with increase in the magnetic field, contrary to the opposite effect of magnetic catalysis (MC) at ρB=0. The inclusion of hyperons to the nuclear medium is observed to lead to magnetic catalysis. There are observed to be significant effects from the DS and PV mixing on the properties of the charm mesons. The production cross sections of ψ(3770) arising due to scattering of D+D−(D0D¯0) mesons in the hot magnetized strange hadronic matter are observed to have distinct peak positions, when the magnetic field is large. This is because the production cross sections have contributions from the transverse as well as longitudinal components of ψ(3770), which have nondegenerate masses due to PV [ψ(3770)−ηc′] mixing. These can have observable consequences on the dilepton spectra as well as on the production of the charm mesons in ultrarelativistic peripheral heavy ion collision experiments, where the produced magnetic field is huge. Published by the American Physical Society 2024

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.

χc2 tensor meson transition form factors in the light front approach

We continue our work on the light-front formulation of quarkonium γ∗γ transition form factors, extending the formalism to JPC = 2++ tensor meson states. We present an analysis of γ∗γ → χc2 transition amplitude and the pertinent helicity form factors. Our relativistic formalism is based on the light-front quark-antiquark wave function of the quarkonium. We calculate the two-photon decay width as well as three independent γ∗γ transition form factors for Jz = 0, 1, 2 as a function of photon virtuality Q2. We compare our results for the two-photon decay width to the recently measured ones by the Belle and BES III collaborations. Even when including relativistic corrections, a very small Γ(λ = 0)/Γ(λ = 2) ~ 10−3 ratio is found which is beyond present experimental precision. We also present the form factors as a function of photon virtuality and compare them to the sparse experimental data on the so-called off-shell width. The formalism presented here can be used for other 2++ mesons, excited charmonia or bottomonia or even light qq¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ q\\overline{q} $$\\end{document}-mesons.

First radial excitations of mesons and diquarks in a contact interaction

We present a calculation for the masses of the first radially excited states of 40 mesons and diquarks made up of u, d, s, c, and b quarks, including states that contain one or both heavy quarks. To this end, we employ a combined analysis of the Bethe-Salpeter and Schwinger-Dyson equations within a self-consistent and symmetry-preserving vector-vector contact interaction. The same set of parameters describes ground and excited states of mesons and their diquark partners. The wave function of the first radial excitation contains a zero whose location is correlated with an additional parameter dF which is a function of dressed quark masses. Our results satisfy the equal spacing rules given by the Gell-Mann Okubo mass relations. Wherever possible, we make comparisons of our findings with known experimental observations as well as theoretical predictions of several other models and approaches including lattice quantum chromodynamics, finding a very good agreement. We report predictions for a multitude of radial excitations not yet observed in experiments. Published by the American Physical Society 2024

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

Color symmetry and confinement as an underlying superconformal structure in holographic QCD

Dedicated to the memory of our colleague, Harald Fritzsch, who, together with Murray Gell-Mann, introduced the color quantum number as the exact symmetry responsible for the strong interaction, thus establishing quantum chromodynamics (QCD) as a fundamental non-Abelian gauge theory. A basic understanding of hadron properties, however, such as confinement and the emergence of a mass scale, from first principles QCD has remained elusive: Hadronic characteristics are not explicit properties of the QCD Lagrangian and perturbative QCD, so successful in the large transverse momentum domain, is not applicable at large distances. In this article, we shall examine how this daunting obstacle is overcome in holographic QCD with the introduction of a superconformal symmetry in anti de Sitter (AdS) space which is responsible for confinement and the introduction of a mass scale within the superconformal group. When mapped to light-front coordinates in physical spacetime, this approach incorporates supersymmetric relations between the Regge trajectories of meson, baryon and tetraquark states which can be visualized in terms of specific [Formula: see text] color representations of quarks. We will also briefly discuss here the implications of holographic models for QCD color transparency in view of the present experimental interest.

High-Energy Collision of Quarks and Mesons in the Schwinger Model: From Tensor Networks to Circuit QED.

With the aim of studying nonperturbative out-of-equilibrium dynamics of high-energy particle collisions on quantum simulators, we investigate the scattering dynamics of lattice quantum electrodynamics in 1+1 dimensions. Working in the bosonized formulation of the model and in the thermodynamic limit, we use uniform-matrix-product-state tensor networks to construct multiparticle wave-packet states, evolve them in time, and detect outgoing particles post collision. This facilitates the numerical simulation of scattering experiments in both confined and deconfined regimes of the model at different energies, giving rise to rich phenomenology, including inelastic production of quark and meson states, meson disintegration, and dynamical string formation and breaking. We obtain elastic and inelastic scattering cross sections, together with time-resolved momentum and position distributions of the outgoing particles. Furthermore, we propose an analog circuit-QED implementation of the scattering process that is native to the platform, requires minimal ingredients and approximations, and enables practical schemes for particle wave-packet preparation and evolution. This study highlights the role of classical and quantum simulation in enhancing our understanding of scattering processes in quantum field theories in real time.

New approach to the 3-momentum regularization of the in-medium one- and two-fermion line integrals with applications to cross sections in the Nambu–Jona-Lasinio model

We propose the 3-momentum sphere intersection regularization applied to the one- and two-fermion line integrals at finite temperature and chemical potential. The quark-antiquark polarization function in this new regularization approach is equivalent to the usual 3-momentum regularization, when the absolute value of the external 3-momentum of the polarization is zero. Additionally, it respects the particle-antiparticle symmetry of meson states in the Nambu–Jona-Lasinio (NJL) model for all values of temperature and chemical potential. Without this symmetry, in-medium cross sections calculated in the 3-momentum regularized NJL model are not consistent. To demonstrate the difference between the usual 3-momentum regularization with the one proposed in this work, we study the quark-quark and quark-antiquark cross sections in both regularization schemes. To this end we use the standard SU(3) NJL model, with four- and six-quark interactions. We observe major quantitative and qualitative differences when comparing quark-quark cross sections in both schemes. The quark-antiquark cross sections, on the other hand, are very similar in both regularizations, owning to the equivalence between the regularizations when the absolute value of the external 3-momentum is zero. Published by the American Physical Society 2024

Soliton confinement in the double sine-Gordon model

The double sine-Gordon field theory in the weak confinement regime is studied. It represents the small non-integrable deformation of the standard sine-Gordon model caused by the cosine perturbation with the frequency reduced by the factor of 2. This perturbation leads to the confinement of the sine-Gordon solitons, which become coupled into the ‘meson’ bound states. We classify the meson states in the weak confinement regime, and obtain three asymptotic expansions for their masses, which can be used in different regions of the model parameters. It is shown, that the sine-Gordon breathers, slightly deformed by the perturbation term, transform into the mesons upon increase of the sine-Gordon coupling constant.