Dibaryon States Research Articles

Mass spectrum of hexaquarks in the Gürsey-Radicati mass formula

It is conventionally claimed that hexaquarks are exotic particles, most of which we know have not yet been experimentally detected. In this work, we attempt to extend a simple phenomenological model based on the Gürsey-Radicati mass model for hadrons, including charm and bottom baryons, and predict the mass of dibaryon states. To illustrate our goal, we perform a numerical tuning of this model, which consists of five sets, each containing six or seven free parameters for baryons and dibaryons. In the long run, other predicted values for the mass of the extra hexaquarks may turn out to be consistent with the forthcoming experimental results. As we have claimed, the results of this work give us a deeper insight into the structural properties of six-quark particles. Finally, we have also included other available data from other works and compared them with ours.

Doubly charmed dibaryon states* *Supported by the China National Funds for Distinguished Young Scientists (11825503), the National Key Research and Development Program of China (2020YFA0406400), the 111 Project (B20063), the National Natural Science Foundation of China (12175091, 11965016, 12247101, 12047501), and the project for top-notch innovative talents of Gansu province

In this work, we study the doubly charmed dibaryon states with the () configuration. The mass spectra of doubly charmed dibaryon states are obtained systematically within the chromomagnetic interaction model. In addition to the mass spectrum analysis, we illustrate their two-body strong decay behaviours. Our results suggest that there may be narrow states or even stable states that cannot decay through the strong interaction. We hope that our results will provide valuable information for further experimental searches for doubly charmed dibaryon states.

Observation of * *Supported in part by National Key R&D Program of China under Contracts Nos. Supported in part by National Key R&D Program of China (2020YFA0406300, 2020YFA0406400); National Natural Science Foundation of China (NSFC) (11975118, 11625523, 11635010, 11735014, 11822506, 11835012, 11935015, 11935016, 11935018, 11961141012, 12022510, 12025502, 12035009, 12035013, 12061131003, 12075252, 12192260, 12192261, 12192262, 12192263, 12192264, 12192265); the Natural Science

Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESIII detector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 , the process is observed for the first time with a statistical significance of . The average Born cross sections in the energy ranges of (4.160, 4.380) GeV, (4.400, 4.600) GeV and (4.610, 4.700) GeV are measured to be fb, fb and fb, respectively, where the first uncertainties are statistical and the second are systematic. The line shapes of the and invariant mass spectra are consistent with phase space distributions, indicating that no hexaquark or di-baryon state is observed.

Possibility of dibaryon formation near the N*(1440)N threshold: Reexamination of isoscalar single-pion production

The isoscalar single-pion production exhibits a broad bump in the energy dependence of the total cross section, which does not correspond to the usual opening of the ${N}^{*}(1440)$ production channel with subsequent pion decay. We reevaluate the current database and investigate whether the observed bump structure with a width of about 150 MeV points to the formation of dibaryon states with $I({J}^{P})=0({1}^{+})$ and $0({1}^{\ensuremath{-}})$ near the ${N}^{*}(1440)N$ threshold. This situation would be similar to the situation at the $\mathrm{\ensuremath{\Delta}}(1232)N$ threshold, where the signature of a number of dibaryonic resonances has been found.

Dibaryon resonances and short-range NN interaction* *The work has been partially supported by RFBR, grants Nos. 19-02-00011 and 19-02-00014. M.N.P. also appreciates support from the Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS”

The dibaryon concept for nuclear force is presented, assuming that the attraction between nucleons at medium distances is mainly due to the s-channel exchange of an intermediate six-quark (dibaryon) state. To construct the respective NN interaction model, a microscopic six-quark description of the NN system is used, in which symmetry aspects play a special role. It is shown that the NN interaction in all important partial waves can be described by the superposition of long-range t-channel one-pion exchange and s-channel exchange by an intermediate dibaryon. The model developed in this study provides a good description of both elastic phase shifts and inelasticities of NN scattering in all S, P, D, and F partial waves at energies from zero to 600–800 MeV and even higher. The parameters of the intermediate six-quark states, corresponding to the best fit of NN scattering data, are found to be consistent with the parameters of the known dibaryon resonances in those NN partial configurations, where their existence has been experimentally confirmed. Predictions for new dibaryon states are given as well.

An estimate of dibaryon production in the process of at anda facility* *Supported by the National Natural Science Foundation of China (11475192), the Sino-German CRC 110 "Symmetries and the Emergence of Structure in QCD" project by NSFC (12070131001), the Key Research Program of Frontier Sciences, CAS (Y7292610K1), and the National Key Research and Development Program of China (2020YFA0406300), IHEP Innovation

Although was first observed by WASA@COSY, its existence has yet to be further confirmed in different types of processes at other facilities. In this work, the possible production of the single dibaryon state in the process of in a future experiment at the anda facility is estimated. Following the method used in our previous study (Chin. Phys. C 46, 023105), a phenomenological Lagrangian approach is employed to study the single production. Based on the conclusions obtained by the non-relativistic constituent quark model, the cross section of the reaction via the intermediate state is estimated, which is in the order of . It is shown that the dominant contribution comes from the diagram with the subprocess. However, it is difficult to measure owing to the large background. Further, although the cross section of the diagram with the subprocess is small, i.e., only approximately of the total cross section or even smaller, the corresponding number of events is still sufficiently large and can be measured at anda because the outgoing and come from the same source .

Investigation of Δ0Δ0 dibaryon in QCD

We study a hypothetical ${\mathrm{\ensuremath{\Delta}}}^{0}{\mathrm{\ensuremath{\Delta}}}^{0}$ dibaryon state by means of the QCD sum rule method. We construct a scalar interpolating current to extract the mass and decay constant of this state taking into account contributions of various quark, gluon, and mixed vacuum condensates. The predictions for the mass and decay constants are ${m}_{D}=232{6}_{\ensuremath{-}126}^{+114}\text{ }\text{ }\mathrm{MeV}$ and ${f}_{D}=2.9{4}_{\ensuremath{-}0.34}^{+0.30}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\text{ }\text{ }{\mathrm{GeV}}^{7}$, respectively. We also made an estimation about binding energy and size of the ${\mathrm{\ensuremath{\Delta}}}^{0}{\mathrm{\ensuremath{\Delta}}}^{0}$ dibaryon. The obtained mass value is below the ${\mathrm{\ensuremath{\Delta}}}^{0}{\mathrm{\ensuremath{\Delta}}}^{0}$ threshold and may be a good dibaryon candidate for being observed experimentally.

Possible dibaryon production at anda with a Lagrangian approach * *Supported by the National Natural Science Foundation of China (11475192, 11975245), the Sino-German CRC 110 "Symmetries and the Emergence of Structure in QCD" Project by NSFC (12070131001), the Key Research Program of Frontier Sciences, CAS (Y7292610K1), and the National Key Research and Development Program of China (2020YFA0406300), the IHEP Innovation

In order to confirm the existence of the dibaryon state observed at WASA@COSY, we estimate the cross section for production of the possible dibaryon and anti-dibaryon pair in the energy region of the upcoming experiments at anda. Based on some qualitative properties of extracted from the analyses in the non-relativistic quark model, the production cross section for this spin-3 particle pair are calculated with the help of a phenomenological effective relativistic and covariant Lagrangian approach.

Phenomenological mass model for exotic hadrons and predictions for masses of non-strange dibaryons as hexaquarks

We investigate the mass spectra of exotic hadrons known as hexaquarks in the form of dibaryons. We use a phenomenological model based on an extended version of the Gürsey–Radicati mass formula for hadrons to include non-charmed baryons, charmed baryons, and non-strange dibaryons to be able to predict masses of potential dibaryon states. We perform six numerical fits of this model to input data for three different sets of masses of baryons and dibaryons. We find that the model can fit some of the data sets well, especially the sets including charmed baryons and non-strange dibaryons, and observe that the predicted mass of one of the dibaryons is close to the measured mass of the observed hexaquark candidate d⁎(2380) reported by the WASA-at-COSY experiment. The predicted mass of the deuteron is slightly larger than its measured mass. Finally, for the data sets including charmed baryon and non-strange dibaryon masses, we find that the predicted masses of potential dibaryon states are all in the range from 1900 MeV to 3700 MeV.

Study of e+e−→2(pp¯) at center-of-mass energies between 4.0 and 4.6 GeV

Using data taken at 23 center-of-mass energies between 4.0 and 4.6 GeV with the BESIII detector at the BEPCII collider and with a total integrated luminosity of approximately $15$ fb$^{-1}$, the process $e^+e^-\to 2(p \bar{p})$ is studied for the first time. The Born cross sections for $e^+e^-\to 2(p \bar{p})$ are measured, and no significant structure is observed in the lineshape. The baryon pair ($pp$ and $\bar{p}\bar{p}$) invariant mass spectra are consistent with phase space, therefore no hexaquark or di-baryon state is found.

Exotic ΩΩ dibaryon states in a molecular picture * *Supported by the National Natural Science Foundation of China (11722540, 12075019), the Fundamental Research Funds for the Central Universities, and the National Key Research and Development Program of China (2020YFA0406400)

We investigate the exotic dibaryon states with and in a molecular picture. We construct a tensor molecular interpolating current and calculate the two-point correlation function within the method of QCD sum rules. Our calculations indicate that the masses of the scalar and tensor dibaryon states are and , respectively, which are below the threshold. Within error, these results do not negate the existence of loosely bound molecular dibaryon states. These exotic strangeness and doubly-charged dibaryons, if they exist, may be identified in heavy-ion collision processes in the future.

Nature of $$\varvec{S}$$-wave $$\varvec{NN}$$ interaction and dibaryon production at nucleonic resonance thresholds

Phase shifts and inelasticity parameters for $NN$ scattering in the partial-wave channels ${}^3S_1$--${}^3D_1$ and ${}^1S_0$ at energies $T_{\rm lab}$ from zero to about 1 GeV are described within a unified $NN$ potential model assuming the formation of isoscalar and isovector dibaryon resonances near the $NN^*(1440)$ threshold. Evidence for these near-threshold resonances is actually found in the recent WASA experiments on single- and double-pion production in $NN$ collisions. There, the excitation of the Roper resonance $N^*(1440)$ exhibits a structure in the energy dependence of the total cross section, which corresponds to the formation of dibaryon states with $I(J^\pi)=0(1^+)$ and $1(0^+)$ at the $NN^*(1440)$ threshold. These two $S$-wave dibaryon resonances may provide a new insight into the nature of the strong $NN$ interaction at low and intermediate energies.

Triply-charmed dibaryon states or two-baryon scattering states from QCD sum rules

In this article, we construct the color-singlet-color-singlet type currents to study the scalar and axialvector $\Xi_{cc}\Sigma_c$ dibaryon states with QCD sum rules in details by taking into account both the dibaryon states and two-baryon scattering sates at the hadron side, and examine the existence of the $\Xi_{cc}\Sigma_c$ dibaryon states. Our calculations indicate that the two-baryon scattering states cannot saturate the QCD sum rules, it is necessary to introduce the dibaryon states, the color-singlet-color-singlet type currents couple potentially to the molecular states, not to the two-particle scattering states, the molecular states begin to receive contributions at the order $\mathcal{O}(\alpha_s^0)$, not at the order $\mathcal{O}(\alpha_s^2)$.

光子ビームで探るクォーク・グルーオン多体系――ダイバリオンの発見から分光へ

光子ビームで探るクォーク・グルーオン多体系――ダイバリオンの発見から分光へ

Towards the decay properties of deuteron-like state dNΩ

Recent lattice QCD calculations showed that a $d_{N\Omega}$ dibaryon state similar to the deuteron with small binding energy may exist. In this work we propose a hadronic molecular approach to study the dynamical properties of this exotic state. We use a phenomenological Lagrangian approach to describe the coupling of the $d_{N\Omega}$ state to its constituents and the decays into conventional hadrons, $d_{N\Omega} \to \Lambda \Xi$ and $d_{N\Omega} \to \Sigma \Xi$. Predictions for the sum of the decay rates are in the range of a few hundred keV. In addition, we find that the $d_{N\Omega} \to \Lambda \Xi$ mode is dominant, preferably searched for in a future RHIC experiment.

Dibaryons cannot be the dark matter

The hypothetical $SU(3)$ flavor-singlet dibaryon state $S$ with strangeness $\ensuremath{-}2$ has been discussed as a dark-matter candidate capable of explaining the curious 5-to-1 ratio of the mass density of dark matter to that of baryons. We study the early-universe production of dibaryons and find that irrespective of the hadron abundances produced by the QCD quark/hadron transition, rapid particle reactions thermalized the $S$ abundance, and it tracked equilibrium until it ``froze out'' at a tiny value. For the plausible range of dibaryon masses (1860--1890 MeV) and generous assumptions about its interaction cross sections, $S$'s account for at most ${10}^{\ensuremath{-}11}$ of the baryon number and, thus, cannot be the dark matter. Although it is not the dark matter, if the $S$ exists, it might be an interesting relic.

Charmed dibaryon resonances in the potential quark model

Charmed dibaryon states with the spin-parity [Formula: see text], and [Formula: see text] are predicted for the two-body [Formula: see text] ([Formula: see text], [Formula: see text], or [Formula: see text]) systems. We employ the complex scaling method for the coupled channel Hamiltonian with the [Formula: see text]-CTNN potentials, which were proposed in our previous study. We find four sharp resonance states near the [Formula: see text] and [Formula: see text] thresholds. From the analysis of the binding energies of partial channel systems, we conclude that these resonance states are Feshbach resonances. We compare the results with the [Formula: see text] resonance states in the heavy quark limit, where the [Formula: see text] and [Formula: see text] thresholds are degenerate, and find that they form two pairs of the heavy-quark doublets in agreement with the heavy quark spin symmetry.

Shedding Light on Hexaquarks

Several new findings in the four, five and six quark systems reheat the interest in the field of multiquark states (beyond the trivial [Formula: see text] and [Formula: see text]). A lot of progress has recently been made in the 6q sector, on both the theoretical and experimental side. A resonance like structure observed in double-pionic fusion to the deuteron, at M = 2.38 GeV with [Formula: see text] = 70 MeV and [Formula: see text] has been consistently observed in a wealth of reaction channels, supporting the existence of a resonant dibaryon state - the [Formula: see text]. These studies include measurement of all the principle strong decay channels in pn collisions in the quasifree mode by the WASA-at-COSY and HADES collaborations. The internal structure of the [Formula: see text] is largely unknown. It can contain various ”hidden color” 6q configurations, [Formula: see text] molecular states with angular momentum L = 0,2,4,6 as well as meson-assisted dressed dibaryon structures. The large set of experimental data obtained to date gives some constraints on the internal structure of the [Formula: see text] dibaryon, but does not settle the issue. The [Formula: see text] is the only multiquark state which can be produced copiously at current facilities, offering unique access to information beyond its basic quantum numbers, particularly its physical size and internal structure.

On the determination of Ω − Ω scattering amplitudes from finite volume spectra

The elastic scattering phase shifts to the two-particle energy levels in a finite cubic box is related by the Lüscher’s formula. In this paper, based on the nonrelativistic quantum mechanics model which is usually assumed to be the low energy scattering case in lattice simulations, we confirmed the generalized Lüscher’s formula for the case of two-particle scattering with arbitrary spin in Ref. 1. In particular, Lüscher’s formula is synthesized for two-spin-3/2-particle scattering, i.e. [Formula: see text] scattering on lattice that may help us study the promising dibaryon states.

Role of scalar dibaryon andf0(500)in the isovector channel of low-energy neutron-proton scattering

We calculate the total and the differential cross section for $np$ scattering at low energies in the isospin $I=1$ channel within the so-called extended Linear Sigma Model. This model contains conventional (pseudo)scalar and (axial--)vector mesons, as well as the nucleon and its chiral partner within the mirror assignment. In order to obtain good agreement with experimental data analysis results we need to consider two additional resonances: the lightest scalar state $f_{0}(500)$ and a dibaryon state with quantum numbers $I=1,$ $J^{P}=0^{+}$ (also known as $^{1}S_{0}$ resonance). The resonance $f_{0}(500)$ is coupled to nucleons in a chirally invariant way through the mirror assignment and is crucial for a qualitatively correct description of the shape of the differential cross section. On the other hand, the dibaryon is exchanged in the $s$--channel and is responsible of the large cross section close to threshold. We compare our results to data analysis results performed by the SAID program of the CNS Data Analysis Center (in the following "SAID results").