Exotic Hadrons Research Articles

Detailed derivation of the $\mathbf{^3P_0}$ strong decay model applied to baryons

Abstract We provide an in-detail derivation, through the $^3P_0$ pair creation model, of the transition matrix for a baryon decaying into a meson baryon system. The meson's analysis was successfully conducted in Ref.~\cite{Segovia:2012cd} and we extend the same formalism to the baryon sector, focusing on the $\Delta(1232)\to \pi N$ strong decay width because all hadrons involved in the reaction are very well established, the two hadrons in the final state are stable avoiding further analysis, all quarks are light and so equivalent, and the decay width of the process is relatively well measured. Taking advantage of a very common Rayleigh-Ritz variational method for solving the 2- and 3-body Sch"odinger bound-state equation in which the hadron's radial wave functions are expanded in terms of a Gaussian basis, the expression of the invariant matrix element can be related with the mean-square radii of hadrons involved in the decay. We use their experimental measures in such a way that only the strength of the quark-antiquark pair creation from the vacuum is a free parameter. This is then taken from our previous study of strong decay widths in the meson sector~\cite{Segovia:2012cd}, obtaining a quite compatible result with experiment for the calculated $\Delta(1232)\to \pi N$ decay width and indicating a possible path towards a unified and global description of the baryon and meson strong decay widths within the same constituent quark model framework. Finally, this research work has been developed in setting the stage for a novel raft of applications to exotic hadrons, \emph{i.e.} the description of baryon's coupling to meson-baryon thresholds, one of the mechanism that is thought to be responsible of providing either a large renormalization to naive states or genuine dynamically-generated meson-baryon molecules.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

Analysis of DD* and D¯(*)Ξcc(*) molecule by one boson exchange model based on heavy quark symmetry

Numerous exotic hadrons with heavy quarks have been reported in the experiments. In such states, symmetries of heavy quarks are considered to play a significant role. In particular, the superflavor symmetry, or also called the heavy quark antidiquark symmetry is one of the interesting symmetries, which links a quark Q to an antidiquark Q¯Q¯ having the same color representation as Q. In this paper, we study a D¯Ξcc molecular state as a superflavor partner of the doubly charmed tetraquark Tcc reported by LHCb recently. Tcc locating slightly below the DD* threshold is a candidate of the hadronic molecule. Thus by replacing the singly charmed meson D(*) with the doubly charmed baryon Ξcc(*), superflavor symmetry predicts the existence of the D¯(*)Ξcc(*) bound state. We employ the one boson exchange model respecting with the heavy quark spin symmetry where the parameter is obtained to reproduce the Tcc binding energy. We apply this model with superflavor symmetry to the D¯(*)Ξcc(*) molecule and predict a bound state with I(JP)=0(12−). If the pentaquark state corresponding to D¯(*)Ξcc(*) molecular state is observed in future experiments as predicted in this work, it is more likely that Tcc is a DD* molecular state. Published by the American Physical Society 2024

Experimental Road to a Charming Family of Tetraquarks...and Beyond

Abstract Discovery of the X(3872) meson in 2003 ignited intense interest in exotic (neither $q\bar{q}$ nor $qqq$) hadrons, but a $c\bar{c}$ interpretation of this state was difficult to exclude. An unequivocal exotic was discovered in the $Z_c(3900)^+$ meson—a charged charmonium-like state. A variety of models of exotic structure have been advanced but consensus is elusive. The grand lesson from heavy quarkonia was that heavy quarks bring clarity. Thus, the recently reported triplet of all-charm tetraquark candidates—$X(6600)$, $X(6900)$, and $X(7100)$—decaying to $J/\psi\,J/\psi$ is a great boon, promising important insights. We review some history of exotics, chronicle the road to prospective all-charm tetraquarks, discuss in some detail the divergent modeling of $J/\psi\,J/\psi$ structures, and offer some inferences about them. These states form a Regge trajectory and appear to be a family of radial excitations. A reported, but unexplained, threshold excess could hint at a fourth family member. We close with a brief look at a step beyond: all-bottom tetraquarks.

Heavy exotic hadrons near thresholds: [formula omitted] and its partners

Recent accelerator experiments have reported unexpected states known as exotic hadrons, whose properties cannot be explained by the conventional picture. In 2022, the LHCb collaboration reported the doubly charmed tetraquark Tcc+ which is a genuine exotic states whose minimal quark content is ccūd̄. We consider the Tcc state as a DD∗ hadronic molecule. The one meson exchange potentials are employed as for the hadron interactions, and a bound state properties is investigated. Furthermore, the superflavor symmetry predicts a new pentaquark state D̄Ξcc from Tcc, which is obtained by replacing a D(∗) meson with a Ξcc(∗) baryon. We also study a possible existence of the D̄Ξcc bound state, and its properties.

Maximum entropy method for valence quark distributions in exotic hadrons: a study of the Zc(3900)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(3900)$$\\end{document} case

In this study we demonstrate the application of the maximum entropy method (MEM) to determine the valence quark distribution of exotic hadrons. Our investigation yields three key findings. Firstly, we observe a significant shift towards smaller Bjorken scale x in the peak position of the valence quark distribution for hadrons with an increasing number of valence quarks, consistent with previous results by Kawamura and Kumano. Secondly, assuming that the Zc(3900)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(3900)$$\\end{document} initially consists of four valence quarks, we employ MEM to determine its initial valence quark distribution, estimating a radius of rc=1.276\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$r_c=1.276$$\\end{document} fm at an extremely low resolution scale Q2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q^2$$\\end{document}. Furthermore, we identify a notable discrepancy between our computed charge form factor Gc(q)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$G_c(q)$$\\end{document} at leading order and the outcomes of hadron molecular state calculations. We propose that this form factor can be extracted from the QCD counting rule cross-section, which is grounded in generalized distribution amplitudes (GDA) linked to the multi-quark states.

Isospin sum rules in charmed baryon weak decays

Isospin symmetry is the most precise flavor symmetry. The effective Hamiltonian of charm quark weak decay is zero under the isospin lowering operators I-n\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I_-^n$$\\end{document}, which permits us to generate isospin sum rules through several master formulas. In this work, we derive the master formulas of isospin sum rules for the two- and three-body non-leptonic decays of singly and doubly charmed baryons. Hundreds of isospin sum rules are derived to test of isospin symmetry and provide hints for the new decay modes. The isospin sum rules for multi-body decays are not broken by the intermediate resonances and hence can be used to study the isospin partners of exotic hadrons.

Exotic Hadrons at LHCb

It has been 5 years since the data sample from the LHCb detector, the first experiment optimized for heavy-flavor physics studies at a hadronic collider, was completed. These data led to many major discoveries in exotic hadron spectroscopy, which we review in this article. We supplement the experimental results with a selection of phenomenological interpretations. As the upgraded LHCb detector is expected to collect a larger data sample starting in 2024, we also discuss the potential of the LHCb program in exotic hadron physics for the near future and beyond.

Isospin sum rules for the nonleptonic B decays

Isospin symmetry, as the most precise flavor symmetry, can be used to extract information about hadronic dynamics. The effective Hamiltonian for bottom quark weak decay is zero under the isospin lowering operators I-n\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I_-^n$$\\end{document}, which allows us to generate isospin sum rules through several master formulas. In this work, we derive the master formulas of isospin sum rules for the two- and three-body non-leptonic decays of B mesons. Numerous new isospin sum rules, especially those involving three or more decay channels, are proposed. The isospin sum rules can be used to test isospin symmetry and provide hints the isospin partners of exotic hadrons in B decays. It is found ten percent isospin breaking only in decay modes involving two vector mesons, indicating the complex dynamics of vector mesons. Besides, the isospin analysis suggests the charm tetraquark resonances might be observed in the B-→J/Ψπ-K¯0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ B^- \\rightarrow J/\\Psi \\pi ^-\\overline{K}^0$$\\end{document}, B¯0→J/ΨK¯0ϕ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline{B}^0 \\rightarrow J/\\Psi \\overline{K}^0\\phi $$\\end{document}, and B¯0→D0D¯0K¯0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline{B}^0\\rightarrow D^0\\overline{D}^0\\overline{K}^0$$\\end{document} modes.

Photoproduction of the X(3872) beyond vector meson dominance: the open-charm coupled-channel mechanism

Hidden-charm exotic hadrons will be searched for and investigated at future electron–ion colliders. For instance, the X(3872) can be produced through the exclusive process γ p → X(3872)p. The vector meson dominance model has been commonly employed in estimating the cross sections of such processes. However, the coupled-channel production mechanism through open-charm meson-baryon intermediate states may play a crucial role. To assess the significance of such contributions, we estimate the cross section of the γ p → X(3872)p reaction assuming the coupled-channel mechanism. For energies near the threshold, the total cross section is predicted to be of tens of nanobarns for γ p → X(3872)p, which can be measured at future experimental facilities. Furthermore, the open-charm coupled-channel mechanism leads to a distinct line shape of the total cross section that can be utilized to reveal the production dynamics.

Study of singly anti-charmed pentaquark production in b-factory* *Supported in part by the Youth Foundation of China University of Mining and Technology (JN210003)

The b-factories, such as BelleII, BarBar, and LHCb, emphasize the increasing importance of exotic hadron research. In this paper, we discuss the possible production of singly anti-charmed pentaquark states from B mesons in a b-factory under (3) symmetry analysis. Discussions of both possibilities have been driven by the hypothesis that the pentaquark state considered in this work, known as the lowest lying state , could be bound or unbound. We find the golden channels for the production of the pentaquark ground states, such as . We further estimate the branching ratios for the production of the ground states from B meson decays. Thus, multiple channels are available for experiments, which may remove certain obstacles to the discovery of new pentaquark states.

Quark core-gluon model for heavy hybrid baryons

Besides the ordinary hadrons, quantum chromodynamics (QCD) allows the existence of states in which excitations of the gluonic field can play the role of valence particles, either alone in a glueball, or coupled to quarks in a hybrid. So, hybrid baryons, made of three quarks and a gluon, can exist. Till now, there is no experimental evidence for such exotic hadrons but experimental efforts are being made to search for them at CEBAF Large Acceptance Spectrometer. In this work, a hybrid baryon is considered as a two-body system composed of a color octet three-quark core and a gluon, interacting via a QCD-inspired interaction. A semirelativistic potential model is built in which the dominant interaction is a potential simulating the flux tube confinement, and the Casimir scaling is assumed to link interactions between triplet and octet color sources. This picture is similar to the quark-diquark description for baryons. It is chosen in order to take properly into account the helicity of the gluon. Only cccg and bbbg states are considered because the strong mass asymmetry between the quark core and the gluon is expected to favor the formation of the core. As the results for heavy hybrid baryons seem relevant, we consider this paper as a proof of concept which can be extended for the study of light hybrid baryons. Published by the American Physical Society 2024

Medium-assisted enhancement of χc1(3872) production from small to large colliding systems

Studies of exotic hadrons such as the χc1(3872) state provide crucial insights into the fundamental force governing the strong interaction dynamics, with an emerging frontier to investigate their production in high energy collisions where a partonic medium is present. The latest experimental measurements from the Large Hadron Collider show an intriguing evolution pattern of the χc1(3872)-to-ψ(2S) yield ratio from proton-proton collisions with increasing multiplicities toward proton-lead and lead-lead collisions. Here we propose a mechanism of medium-assisted enhancement for the χc1(3872) production, which competes with the more conventional absorption-induced suppression and results in a nonmonotonic trend from small to large colliding systems. Realistic simulations from this model offer a quantitative description of all available data. Predictions are made for the centrality dependence of this observable in PbPb collisions as well as for its system-size dependence from OO and ArAr to XeXe and PbPb collisions. In both cases, a nonmonotonic behavior emerges as the imprint of the competition between enhancement and suppression and can be readily tested by future data. Published by the American Physical Society 2024

Revealing the mystery of the double charm tetraquark in pp collision

A novel approach is proposed to probe the nature of the double charm tetraquark through the prompt production asymmetry between Tc¯c¯-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{\\bar{c}\\bar{c}}^-$$\\end{document} and Tcc+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{cc}^+$$\\end{document} in pp collisions. When comparing two theoretical pictures, i.e. the compact tetraquark and hadronic molecular pictures, we find that the former one exhibits a significantly larger production asymmetry, enabling the unambiguous determination of the tetraquark’s internal structure. Additionally, distinctive differences in the transverse momentum and rapidity distributions of Tc¯c¯-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{\\bar{c}\\bar{c}}^-$$\\end{document} and Tcc+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T_{cc}^+$$\\end{document} cross sections emerge, particularly at pT≈2GeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p_\ extrm{T}\\approx 2~\ extrm{GeV}$$\\end{document} and y≈±6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$y\\approx \\pm 6$$\\end{document} at a center-of-mass energy of 14TeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$~\ extrm{TeV}$$\\end{document}. The insignificant asymmetry in hadronic molecular picture is because that hadronic molecules are produced in hadronic phase, where the phase space of their constituents needs to be taken into account rigorously. Our work can be extended to the exploration of other double heavy tetraquark candidates, offering a versatile approach to advance our understanding of exotic hadrons.

Identifying an X(3872) tetraquark state versus a molecular state by formation time, velocity, and temperature in relativistic nuclear collisions

The production of exotic hadron X(3872) in pp collisions at s=2.76TeV is investigated by the parton and hadron cascade model PACIAE in this work. In the simulation the final partonic state (quark matter, QM) and the final hadronic state (hadron matter, HM) are continuously processed and recorded. The X(3872) compact tetraquark state and loose molecular state are, respectively, coalesced and recombined in the QM and HM with the quantum statistical mechanics inspired dynamically constrained phase-space coalescence model. The formation time, velocity, and temperature of QM (tetraquark state) and HM (molecular state) are proposed as identifying criteria between the two states. Our results in transverse momentum spectrum and rapidity distribution, etc. show a significant discrepancy between the two states and confirm that they are also valuable criteria identifying the X(3872) compact tetraquark state or molecular state. Published by the American Physical Society 2024

Production of hidden-heavy and double-heavy hadronic molecules at the Z factory of CEPC

With a clean environment and high collision energy, the Circular Electron Positron Collider (CEPC) would be an excellent facility for heavy flavor physics. Using the Monte Carlo event generator ythia, we simulate the production of the charmed (bottom) hadron pairs in the electron-positron collisions at the Z factory of CEPC, and the inclusive production rates for typical candidates of the hidden/double-charm and hidden/double-bottom S-wave hadronic molecules are estimated at an order-of-magnitude level with the final state interactions after the hadron pair production. The predicted cross sections for the hidden-charm meson-meson molecules X(3872) and Zc(3900) are at pb level, which are about two to three orders of magnitude larger than the production cross sections for the double-charm meson-meson molecules Tcc and Tcc*, as the double-charmed ones require the production of two pairs of cc¯ from the Z boson decay. The production cross sections for the hidden-charm pentaquark states Pc and Pcs as meson-baryon molecules are a few to tens of fb, which are about one magnitude larger than those of the possible hidden-charm baryon-antibaryon and double-charm meson-baryon molecules. In the bottom sector, the production cross sections for the Zb states as B(*)B¯* molecules are about tens to hundreds of fb, indicating 106–107 events from a two-year operation of CEPC, and the expected events from the double-bottom molecules are about 2–5 orders of magnitude smaller than the Zb states. Our results shows great prospects of probing heavy exotic hadrons at CEPC. Published by the American Physical Society 2024

Modification of χc1(3872) and ψ(2S) Production in pPb Collisions at sNN=8.16 TeV

The LHCb Collaboration measures production of the exotic hadron χc1(3872) in proton-nucleus collisions for the first time. Comparison with the charmonium state ψ(2S) suggests that the exotic χc1(3872) experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify χc1(3872) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Compositeness of Tcc and X(3872) by considering decay and coupled-channels effects

The compositeness of weakly bound states is discussed using the effective field theory from the viewpoint of the low-energy universality. We introduce a model with coupling of the single-channel scattering to the bare state, and study the compositeness of the bound state by varying the bare state energy. In contrast to the naive expectation that the near-threshold states are dominated by the molecular structure, we demonstrate that a noncomposite state can always be realized even with a small binding energy. At the same time, however, it is shown that a fine tuning is necessary to obtain the noncomposite weakly bound state. In other words, the probability of finding a model with the composite dominant state becomes larger with the decrease of the binding energy, in accordance with the low-energy universality. For the application to exotic hadrons, we then discuss the modification of the compositeness due to decay and coupled-channels effects. We quantitatively show that these contributions suppress the compositeness, because of the increase of the fraction of other components. Finally, as examples of near-threshold exotic hadrons, the structures of Tcc and X(3872) are studied by evaluating the compositeness. We find the importance of the coupled-channels and decay contributions for the structures of Tcc and X(3872), respectively. Published by the American Physical Society 2024

Productions of X(3872), Zc(3900)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(3900)$$\\end{document}, X2(4013)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$X_2(4013)$$\\end{document}, and Zc(4020)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(4020)$$\\end{document} in B(s)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)}$$\\end{document} decays offer strong clues on their molecular nature

The exotic states X(3872) and Zc(3900)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(3900)$$\\end{document} have long been conjectured as isoscalar and isovector D¯∗D\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\bar{D}}^*D$$\\end{document} molecules. In this work, we first propose the triangle diagram mechanism to investigate their productions in B decays as well as their heavy quark spin symmetry partners, X2(4013)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$X_2(4013)$$\\end{document} and Zc(4020)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(4020)$$\\end{document}. We show that the large isospin breaking of the ratio B[B+→X(3872)K+]/B[B0→X(3872)K0]\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathcal {B}}[B^+ \\rightarrow X(3872) K^+]/{\\mathcal {B}}[B^0 \\rightarrow X(3872) K^0] $$\\end{document} can be attributed to the isospin breaking of the neutral and charged D¯∗D\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\bar{D}}^*D$$\\end{document} components in their wave functions. For the same reason, the branching fractions of Zc(3900)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(3900)$$\\end{document} in B decays are smaller than the corresponding ones of X(3872) by at least one order of magnitude, which naturally explains its non-observation. A hierarchy for the production fractions of X(3872), Zc(3900)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(3900)$$\\end{document}, X2(4013)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$X_2(4013)$$\\end{document}, and Zc(4020)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(4020)$$\\end{document} in B decays, consistent with all existing data, is predicted. Furthermore, with the factorization ansatz we extract the decay constants of X(3872), Zc(3900)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(3900)$$\\end{document}, and Zc(4020)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_c(4020)$$\\end{document} as D¯∗D(∗)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\bar{D}}^*D^{(*)}$$\\end{document} molecules via the B decays, and then calculate their branching fractions in the relevant B(s)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)}$$\\end{document} decays, which turn out to agree with all existing experimental data. The mechanism we proposed is useful to elucidate the internal structure of the many exotic hadrons discovered so far and to extract the decay constants of hadronic molecules, which can be used to predict their production in related processes.

Double-gluon charmonium hybrid states with various exotic quantum numbers

We study the double-gluon charmonium hybrid states with various quantum numbers, each of which is composed of one valence charm quark and one valence charm antiquark as well as two valence gluons. We concentrate on the exotic quantum numbers JPC=0−−/0+−/1−+/2+−/3−+ that the conventional q¯q mesons cannot reach. We apply the QCD sum rule method to calculate their masses to be 7.28−0.43+0.38, 5.19−0.46+0.36, 5.46−0.62+0.41, 4.48−0.31+0.25, and 5.54−0.43+0.35 GeV, respectively. We study their possible decay patterns and propose to search for the JPC=2+−/3−+ states in the D*D¯(*)/Ds*D¯s(*)/Σc*Σ¯c(*)/Ξc*Ξ¯c(′,*) channels. Experimental investigations on these states and decay channels can be useful in classifying the nature of the hybrid state, thus serving as a direct test of QCD in the low energy sector. Published by the American Physical Society 2024

Overview of hadron photoproduction experiments in SPring-8 LEPS2 project

An experimental project to study hadron properties through photoproduction reactions is carried out in SPring-8 LEPS2 beamline. As an overview of this project, recent physics achievements and prospects on light baryon spectroscopy, exotic hadrons / bound states, and the origin of hadron mass are discussed with the description of experimental setups.