Heavy Quark Symmetry Research Articles

Masses and radiative decay widths of Ds0*(2317) and Ds1′(2460) and their bottom analogs

We study the mass spectra and radiative decays of Ds0*(2317) and Ds1′(2460) in an unquenched framework. In addition to coupled channel effects between the cs¯ cores and D(*)K channels, D(*)K−D(*)K self-interactions are also considered in this work and we succeed to reproduce their mass spectra. Furthermore, we study the radiative decays of the Ds0*(2317) and Ds1′(2460) by simultaneously including the compound structures of conventional cs¯ cores and D(*)K components. We also calculate their bottom analogs with heavy quark symmetry. Our study offers useful insights into the important unquenched effects in the formation of Ds0*(2317), Ds1′(2460), and the bottom counterparts. Published by the American Physical Society 2024

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

Investigation on the bottom analogs Tbb− of Tcc+

We investigate the doubly bottom state Tbb− composed of two bottom mesons with JP=1+. The potentials are obtained using the one-boson exchange model. With the heavy quark flavor symmetry, all the parameters in the model are determined by fitting the experimental data of doubly charmed state Tcc+ from our previous work. Our analysis indicates that the isospin symmetry is well preserved. We identify a deeply bound Tbb− state with quantum numbers I(JP)=0(1+), in contrast to the loosely bound Tcc+. Additionally, we discover a resonant Tbb− state with I(JP)=1(1+). Furthermore, our investigation into the B¯B¯*−B¯*B¯* coupled channel effect reveals its important impact. The binding energy of the bound I(JP)=0(1+) states becomes deeper, while the resonant Tbb− state with I(JP)=1(1+) remains nearly unchanged. Published by the American Physical Society 2024

Mass and decay width of Tccs from symmetries

We analyze the mass and width of the doubly heavy tetraquark Tccs composed of a heavy diquark and a light-quark cloud with strangeness with assuming that a color antitriplet heavy diquark is a dominant component of the doubly charmed tetraquarks Tcc and Tccs. We construct an effective Lagrangian for masses of heavy hadrons based on the superflavor symmetry between the doubly heavy tetraquarks and the singly heavy baryons by including the terms that simultaneously break the heavy-quark and light-flavor symmetries, and predict the mass of Tccs as M(Tccs)=4047±11 MeV. The comparison of this prediction with future experimental observation will give a clue to understand the color structure of the heavy diquark. We also predict the mass of Ωcc as M(Ωcc)=3706−15+14 MeV. We next calculate the decay width of Tccs, based solely on the light-flavor symmetry, as Γ(Tccs)=42±24 MeV. Published by the American Physical Society 2024

Entanglement suppression and low-energy scattering of heavy mesons

Recently entanglement suppression was proposed to be one possible origin of emergent symmetries. Here we test this conjecture in the context of heavy meson scatterings. The low-energy interactions of D(*)D¯(*) and D(*)D(*) are closely related to the hadronic molecular candidates X(3872) and Tcc(3875)+, respectively, and can be described by a nonrelativistic effective Lagrangian manifesting heavy-quark spin symmetry, which includes only constant contact potentials at leading order. We explore entanglement suppression in a tensor-product framework to treat both the isospin and spin degrees of freedom. Using the X(3872) and Tcc(3875)+ as inputs, we find that entanglement suppression indeed leads to an emergent symmetry, namely, a light-quark spin symmetry, and as such the D(*)D¯(*) or D(*)D(*) interaction strengths for a given total isospin do not depend on the total angular momentum of light (anti)quarks. The X(3872) and Tcc(3875)+ are predicted to have five isoscalar partners and one isoscalar partner, respectively, while the corresponding partner numbers derived solely from heavy-quark spin symmetry are three and one, respectively. The predictions need to be confronted with experimental data and lattice quantum chromodynamics results to further test the entanglement suppression conjecture. Published by the American Physical Society 2024

D * s0(2317) and B*s0 as Molecular States

Abstract We investigate the dynamical generation of the $D_{s0}^{*}(2317)$ and $B_{s0}^{*}$ mesons using a meson-exchange model with a coupled-channel formalism. Our primary focus is on the $D_s^+\pi ^0$ channel below the $DK$ threshold. First, we construct the invariant kernel amplitudes, incorporating effective Lagrangians based on heavy-quark symmetry, flavor SU(3) symmetry, and hidden local symmetry. Since the $D_{s0}^{*}(2317)$ state implies isospin symmetry breaking, we introduce $\pi ^0\!-\!\eta$ isospin mixing. We subsequently solve the coupled-channel integral equations, which include four different channels, i.e. $D_s^+\pi ^0$, $D^0 K^+$, $D^+ K^0$, and $D_s^+\eta$. We carefully analyze how the pole corresponding to the $D_{s0}^{*}(2317)$ state emerges from the coupled channels. Our findings reveal that the pole positions of the $D_{s0}^{*}(2317)$ meson are at $\sqrt{s_R}=(2317.9 - i 0.0593)$ MeV and those of the $\bar{B}_{s0}^{*}$ meson are at $(5756.43-i0.0215)$ MeV, respectively. We also discuss their decay widths and destructive interference of the two sources. In conclusion, our current results provide a clear indication supporting the interpretation of the $D_{s0}^{*}(2317)$ meson as a $DK$ molecular state within the present coupled-channel formalism. In addition, we discuss the possible existence of $\bar{B}_{s0}^{*}$.

Signature decay modes of the compact doubly-heavy tetraquarks [formula omitted] and [formula omitted]

Based on the expectations that the lowest-lying doubly-bottom tetraquark Tbbu¯d¯ (JP=1+) and the bottom-charm tetraquark Tbcu¯d¯ (JP=0+) are stable against strong and electromagnetic decays, we work out a number of semileptonic and non-leptonic weak decays of these hadrons, making use of the heavy quark symmetry. In doing this, we concentrate on the exclusive decays involving also tetraquarks in the final states, i.e., transitions such as Tbbu¯d¯→Tbcu¯d¯(ℓ−νℓ,h−) and Tbcu¯d¯→Tccu¯d¯(ℓ−νℓ,h−), where h−=π−,ρ−,a1−,Ds−,Ds⁎−. So far, only the JP=1+ tetraquark Tccu¯d¯ has been discovered, which we identify with the I=0Tcc+ object, compatible with JP=1+ and having the pole mass relative to the D⁎+D0 mass threshold and decay widths δm=M(Tcc+)−(M(D⁎+)+M(D0))=−360±40−0+4 keV and Γ(Tcc+)=48−14+2 keV. Experimental discoveries of the transitions worked out here, and related ones involving doubly-heavy baryons, will quantify the diquark-antidiquark component of these tetraquarks.

Production of Xb via radiative transition of ϒ(10753)

We studied the radiative transitions between the ϒ(10753), the S−D mixed state of the ϒ(4S) and ϒ1(3D13), and the Xb, the heavy quark flavor symmetry counterpart of the X(3782) in the bottomonium sector. The radiative transition was assumed to occur through the intermediate bottom mesons, including P-wave B1(′) mesons as well as the S-wave B(*) ones. The consideration of the B1(′) mesons leads to the couplings to be in S-wave, and hence enhances the contributions of the intermediate meson loops. The radiative decay width for the ϒ(10753)→γXb is predicted to be order of 10 keV, corresponding to a branching fraction of 10−4. Based on the theoretical results, we strongly suggest to search for the Xb in the e+e−→γXb with Xb→ππχb1 near s=10.754 GeV, and it is hoped that the calculations here could be tested by the future Belle II experiments. Published by the American Physical Society 2024

Coupled-channel description of charmed heavy hadronic molecules within the meson-exchange model and its implication

Motivated by the first observation of the double-charm tetraquark Tcc+(3875) by the LHCb Collaboration, we investigate the nature of Tcc+ as an isoscalar DD* hadronic molecule in a meson-exchange potential model incorporated by the coupled-channel effects and three-body unitarity. The D0D0π+ invariant mass spectrum can be well-described and the Tcc+ pole structure can be precisely extracted. Under the hypothesis that the interactions between the heavy flavor hadrons can be saturated by the light meson-exchange potentials, the near-threshold dynamics of Tcc+ can shed light on the binding of its heavy-quark spin symmetry (HQSS) partner D*D* (I=0) and on the nature of other heavy hadronic molecule candidates such as X(3872) and Zc(3900) in the charmed-anticharmed systems. The latter states can be related to Tcc+ in the meson-exchange potential model with limited assumptions based on the SU(3) flavor symmetry relations. The combined analysis, on the one hand, indicates the HQSS breaking effects among those HQSS partners, and on the other hand, highlights the role played by the short and long-distance dynamics for the near threshold D(*)D(*) and D(*)D¯(*)+c.c. systems. Published by the American Physical Society 2024

Improved method to determine the Ξc−Ξc′ mixing

We develop an improved method to explore the Ξc−Ξc′ mixing, which arises from the flavor SU(3) and heavy quark symmetry breaking. In this method, the flavor eigenstates under the SU(3) symmetry are at first constructed, and the corresponding masses can be nonperturbatively determined. Matrix elements of the mass operators, which break the flavor SU(3) symmetry sandwiched by the flavor eigenstates, are then calculated. Diagonalizing the corresponding matrix of Hamiltonian gives the mass eigenstates of the full Hamiltonian and determines the mixing. Following the previous lattice QCD calculation of Ξc and Ξc′, and estimating an off diagonal matrix element, we extract the mixing angle between the Ξc and Ξc′. Preliminary numerical results for the mixing angle confirm the previous observation that such mixing is incapable to explain the large SU(3) symmetry breaking in semileptonic decays of charmed baryons. Published by the American Physical Society 2024

Heavy flavor conserved semi-leptonic decay of Bs in the covariant light-front approach

We study the heavy flavor conserved semi-leptonic decay Bs→Bℓν in the covariant light front approach. The covariant light front quark model is used to calculate the transition form factors of Bs→B(⁎) as well as Ds→D, which are consistent with the leading power predictions from the heavy quark symmetry. The angular distribution analysis on the Bs→B(⁎)lν¯ decay is performed by investigating the forward-backward asymmetry of the lepton. We also study the angular distribution of Bs→B⁎(→Bγ)lν¯ decay both through the lepton forward-backward asymmetry and the azimuth angle. The branching fractions of Bs→Blν¯ and Bs→B⁎lν¯ are at the order 10−8 and 10−9, respectively. The number of Bs→Blν¯ events is estimated to be 1.76. The branching fraction of Bs→B⁎(→Bγ)lν¯ is at the order 10−11, which is calculated by introducing Breit-Wigner distribution for the intermediate B⁎.

Hunting for Xb via hidden bottomonium decays Xb→ππχbJ

In this work, we investigate the isospin breaking decay Xb→π0χbJ and the isospin conserved decay Xb→ππχbJ, where Xb is taken to be the heavy quark flavor symmetry counterpart of X(3872) in the bottomonium sector as a B*B¯ molecule candidate. Since the mass of this state may be far below the BB¯* threshold and the mass difference between the neutral and charged bottom meson is small compared to the binding energy of the Xb, the isospin-violating decay channel Xb→π0χbJ would be highly suppressed. The calculated partial width of Xb→ππχb1 is found to be about tens of keVs, 1–2 order(s) of magnitude larger than those of Xb→ππχb2 and Xb→ππχb0. Taking into account the fact that the total width of Xb may be smaller than a few MeV like X(3872), the calculated branching ratios Xb→ππχb1 may reach to orders of 10−2, which makes it a possible channel for the experimental searching of the Xb. Published by the American Physical Society 2024

QED contributions to Ξc+−Ξc′+ mixing

We explore the quantum electrodynamic (QED) corrections to the Ξc+−Ξc′+ mixing within the framework of light-front quark model (LFQM) in the three-quark picture. After explicitly investigating the relation between the Ξc−Ξc′ mixing and the flavor SU(3) and heavy quark symmetry breaking, we derive the QED contributions to the Ξc+−Ξc′+ mixing angle. Numerical results indicate the QED contribution is smaller than the one from the mass difference between the strange and up/down quark provided by a recent lattice quantum chromodynamics analysis. Adding these contributions together we find that at this stage the Ξc+−Ξc′+ mixing is small and still incapable to account for the large SU(3) symmetry breaking in the semileptonic Ξc decays. Published by the American Physical Society 2024

Bottom-charmed baryons in a nonrelativistic quark model

In this work, we study the low-lying mass spectra for bottom-charmed baryons in a nonrelativistic quark model by solving the three-body Schrödinger equation. The lowest Ξbc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Xi _{bc}$$\\end{document}, Ξbc′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Xi _{bc}^\\prime $$\\end{document}, Ωbc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega _{bc}$$\\end{document}, and Ωbc′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega _{bc}^\\prime $$\\end{document} states are predicted to be about 6979, 6953, 7109, and 7092 MeV, respectively. Also, the strong decays for the low-lying excited states are investigated. Our results indicate that some of λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda $$\\end{document}-mode P-wave bottom-charmed baryons are relatively narrow, which can be searched for in future experiments. For the low-lying ρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho $$\\end{document}-mode and ρ-λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho -\\lambda $$\\end{document} hybrid states, their strong decays are highly suppressed and they can survive as extremely narrow states. Moreover, the mass spectra and strong decays for bottom-charmed baryons preserve the heavy quark symmetry well. We hope our calculations can provide helpful information for further experimental and theoretical researches.

The properties of radially excited charmonia in the light front quark model

Investigating the properties of excited charmonia is important to clarify its internal structure. In this paper, we present the mass spectra (MS) and decay constants (DC) for charmonia up to 3S states calculated by means of the light-front quark model based on a variational approach. In particular, we consider the QCD-motivated effective Hamiltonian, which includes both confinement (linear and screened) and Coulomb-like potentials. Furthermore, since the existence of the nature of heavy quark symmetry, we treat hyperfine interactions perturbatively. We developed the harmonic oscillator expansion method to approximate the wave function (WF) for excited states. We found that the results of our theoretical calculations, using screened potentials rather than linear ones, are in good agreement with experimental data. By looking at the mass and decay constant result, we found that our result on the ψ(3S) state matched the properties of the ψ(4040) resonance.

Heavy-quark spin symmetry breaking in the Born-Oppenheimer approximation

Heavy-quark spin symmetry is explicitly broken by the mass splitting between a heavy-light pseudoscalar meson and its vector partner. This fact plays a pivotal role in the physics of states whose mass lies close to the threshold of an open-flavor meson pair, like X(3872). We show that this source of heavy-quark spin symmetry breaking can be systematically included within the diabatic representation of the Born-Oppenheimer approximation. We verify that including all the appropriate coupled channels guarantees conservation of total angular momentum, parity, and charge-conjugation parity. This marks a fundamental step towards a unified, first-principles study of quarkonia and meson molecules with hidden flavor.

Masses and magnetic moments of exotic fully heavy pentaquarks

Inspired by the observation of a resonant state X(6600) of fully charm tetraquark by the CMS experiment of LHCb Collaboration in double J/psi decay channel, we perform a systematical study of all configurations of fully heavy pentaquarks P_{Q_{1}Q_{2}Q_{3}Q_{{4}}bar{Q_{5}}} (Q_{i}=c,b, i=1,2,3,4,5) in their ground states in unified framework of MIT bag model. The color-spin wavefunctions of pentaquarks, classified via Young tableau and presented in terms of the Young–Yamanouchi bases, are used to compute masses and magnetic moments of fully heavy pentaquarks via numerical variational method, predicting a set of masses ranging from 8.229 GeV for the P_{ccccbar{c}} to 24.770 GeV for the P_{bbbbbar{b}}. Combining with computed masses of fully heavy mesons and baryons, we find that masses of fully heavy hadrons(mesons, baryons, tetraquarks and pentaquarks) with identical flavor rise almost linearly with the number of valence quarks in hadrons, being consistent with the heavy quark symmetry in the heavy-quark limit.

Possible molecular dibaryons with csssqq quarks and their baryon–antibaryon partners

In this work, we systematically investigate the charmed–strange dibaryon systems with csssqq quarks and their baryon–antibaryon partners from the interactions varXi ^{(',*)}_{c}varXi ^{(*)}, varOmega ^{(*)}_cvarLambda , varOmega ^{(*)}_cvarSigma ^{(*)}, varLambda _cvarOmega and varSigma ^{(*)}_cvarOmega and their baryon–antibaryon partners from interactions varXi ^{(',*)}_{c}bar{varXi }^{(*)}, varOmega ^{(*)}_cbar{varLambda }, varOmega ^{(*)}_cbar{varSigma }^{(*)}, varLambda _cbar{varOmega } and varSigma ^{(*)}_cbar{varOmega }. The potential kernels are constructed with the help of effective Lagrangians under SU(3), heavy quark, and chiral symmetries to describe these interactions. To search for possible molecular states, the kernels are inserted into the quasipotential Bethe–Salpeter equation, which is solved to find poles from scattering amplitude. The results suggest that 36 and 24 bound states can be found in the baryon–baryon and baryon–antibaryon interactions, respectively. However, much large values of parameter alpha are required to produce the bound states from the baryon–antibaryon interactions, which questions the existence of these bound states. Possible coupled-channel effect are considered in the current work to estimate the couplings of the molecular states to the channels considered.

Resolution of the LHCb ηc anomaly

Due to the heavy-quark symmetry of Non-Relativistic Quantum Chromodynamics (NRQCD), the cross-section for the production of ηc can be predicted. This NRQCD prediction when confronted with data from the LHCb is seen to fail miserably. We address this LHCb ηc anomaly in this paper using a new approach called modified NRQCD, an approach that has been shown to work extremely well for studying J/ψ, ψ′ and χc production at the LHC. We show, in the present paper, that the predictions for ηc production agrees very well with LHCb measurements at the three different values of energy that the experiment has presented data for. Modified NRQCD also explains the intriguing agreement of the LHCb ηc data with the colour-singlet prediction. The remarkable agreement of the theoretical predictions with the LHCb data suggests that modified NRQCD is closer to apprehending the true dynamics of quarkonium production.

X(3872) , X(4014) , and their bottom partners at finite temperature

The properties of the $X(3872)$ and its spin partner, the $X(4014)$, are studied both in vacuum and at finite temperature. Using an effective hadron theory based on the hidden-gauge Lagrangian, the $X(3872)$ is dynamically generated from the $s$-wave rescattering of a pair of pseudoscalar and vector charm mesons. By incorporating the thermal spectral functions of open charm mesons, the calculation is extended to finite temperature. Similarly, the properties of the $X(4014)$ are obtained out of the scattering of charm vector mesons. By applying heavy-quark flavor symmetry, the properties of their bottom counterparts in the axial-vector and tensor channels are also predicted. All the dynamically generated states show a decreasing mass and acquire an increasing decay width with temperature, following the trend observed in their meson constituents. These results are relevant in relativistic heavy-ion collisions at high energies, in analyses of the collective medium formed after hadronization or in femtoscopic studies, and can be tested in lattice-QCD calculations exploring the melting of heavy mesons at finite temperature.