Dibaryon Mass Research Articles

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.

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.

Experimental and theoretical backgrounds for generation of dibaryons inNNand3Ninteractions

Numerous experimental and theoretical arguments in favor of the intermediate dibaryon generation in NN and 3N interactions are presented. Using some specific mechanism for the scalar field production when the 2ħω -excited multi-quark system deexcites to the ground state one formulates a concept for σ-dressed dibaryon as a carrier of intermediate-range attraction and a reason for short-range repulsion in NN -interaction. It is argued that the basic mechanisms responsible for large lowering of the Roper-resonance and the dressed dibaryon masses should be very similar. The modern experimental data of a few groups seem to confirm strongly the dibaryon picture in NN and 3N -interactions. Some important common features of the dibaryon and pomeron in highenergy NN scattering are discussed.

Chiral Invariant Phase Space model

The masses of the SU(3)×SU(6) hadrons are calculated in the chiral-invariant phase space (CHIPS) model as a sum of the mean energies of the quarks at a constant temperature Tc with the color-magnetic splitting and the color-electric shift. The masses of hadrons are parametrized by four constants: Tc, ms, ECE and ACM. With the same number of parameters the CHIPS model fits the masses of hadrons better than the classic bag model. The small mass of the d-quark ( md = 2.7MeV) is used to prove that the isotopic shifts of hadrons can be explained by the mass difference between the d- and u-quarks. The dibaryon mass is estimated in CHIPS to be 200MeV higher than in the bag model. The prediction for the mass of the α* cluster is about the same in both models. It is close to 4 . mΔ.

Study ofe+e−→ΛΛ¯,ΛΣ¯0,Σ0Σ¯0using initial state radiation withBABAR

We study the e+e- --> Lambda anti-Lambda gamma, Lambda anti-Sigma0 gamma, Sigma0 anti-Sigma0 gamma processes using 230 fb-1 of integrated luminosity collected by the BABAR detector at e+e- center-of-mass energy of 10.58 GeV. From the analysis of the baryon-antibaryon mass spectra the cross sections for e+e- --> Lambda anti-Lambda, Lambda anti-Sigma0, Sigma0 anti-Sigma0 are measured in the dibaryon mass range from threshold up to 3 GeV/c^2. The ratio of electric and magnetic form factors, |G_E/G_M|, is measured for e+e- --> Lambda anti-Lambda, and limits on the relative phase between Lambda form factors are obtained. We also measure the J/psi --> Lambda anti-Lambda, Sigma0 anti-Sigma0 and psi(2S) --> Lambda anti-Lambda branching fractions.

Hadron spectroscopy from canonical partition functions

A spectroscopic method for staggered fermions based on thermodynamical considerations is proposed. The canonical partition functions corresponding to the different quark number sectors are expressed in the low temperature limit as polynomials of the eigenvalues of the reduced fermion matrix. Taking the zero temperature limit yields the masses of the lowest states. The method is successfully applied to the Goldstone pion and both dynamical and quenched results are presented showing good agreement with that of standard spectroscopy. Though in principle the method can be used to obtain the baryon and dibaryon masses, due to their high computational costs such calculations are practically unreachable.

Penguin-induced radiative baryonic B decays revisited

Weak radiative baryonic B decays B¯→B1B¯2γ mediated by the electromagnetic penguin process b→sγ are re-examined within the framework of the pole model. The meson pole contribution that has been neglected before is taken into account in this work. It is found that the intermediate K∗ contribution dominates in the Σp¯γ mode and is comparable to the baryon pole effect in Λp¯γ and ΞΛ¯γ modes. The branching ratios for B−→Λp¯γ and B−→Ξ0Σ¯−γ are of order 2.6×10−6 and 6×10−7, respectively. The threshold enhancement effect in the dibaryon mass spectrum is responsible by the meson pole diagram. We also study the angular distribution of the baryon in the dibaryon rest frame. The baryon pole diagrams imply that the antibaryon tends to emerge in the direction of the photon in the baryon-pair rest frame. The predicted angular asymmetry agrees with experiment for B−→Λp¯γ. Measurements of the correlation of the photon with the baryon allow us to discriminate between different models for describing the radiative baryonic B decays. For decays B→ΞΣ¯γ, a large correlation of the photon to the Σ¯ and a broad bump in the dibaryon mass spectrum are predicted.

Tensor Interaction Effect in Dibaryon

The gluon and Goldstone boson induced tensor interaction effect onthe dibaryon mass and the D-wave decay width has been studied inthe quark delocalization, color screening model. The effective S-Dwave transition interactions induced by gluon and Goldstone bosonexchanges decrease quickly as the increasing of the channelstrangeness. The K and η meson tensor contribution isnegligible in this model. No six-quark state in the lightflavor world can become a bound one by the help of these tensorinteractions except the deuteron. The partial D-wave decay widthof IJp = ½2+ NΩ state to spin 0, 1 ΛΞfinal state is 20.7 keV and 63.1 keV respectively. It is a very narrowdibaryon resonance and might be detected in therelativistic heavy ion reaction by the existing RHICdetectors through the reconstruction of the ΛΞ vertexmass and the future COMPAS detector at CERN and FAIR projectin Germany.

Diquarks, pentaquarks, and dibaryons

We explore the connection between pentaquarks and dibaryons composed of three diquarks in the framework of the diquark model. With the available experimental data on H dibaryon, we estimate the Pauli blocking and annihilation effects and constrain the $P=-$ pentaquark $SU(3)_F$ singlet mass. Using the $\Theta^+$ pentaquark mass, we estimate $P=-$ dibaryon mass.

Influence of tensor interactions on masses and decay widths of dibaryons

The influence of gluon and Goldstone boson induced tensor interactions on the dibaryon masses and D-wave decay widths has been studied in the quark delocalization, color screening model. The effective S-D wave transition interactions induced by gluon and Goldstone boson exchanges decrease rapidly with increasing strangeness of the channel. The tensor contribution of K and eta mesons is negligible in this model. There is no six-quark state in the light flavor world studied so far that can become bound by means of these tensor interactions besides the deuteron. The partial D-wave decay widths of the IJ(p)=(1/2)2(+)NOmega state to spin 0 and 1 LambdaXi final states are 12.0 and 21.9 keV, respectively. This is a very narrow dibaryon resonance that might be detectable in those production reactions with rich high strangeness particles through the reconstruction of the vertex mass of the decay product LambdaXi by existing detectors at RHIC and COMPASS at CERN or at JHF in Japan and FAIR in Germany in the future.

Dibaryon Mass and Width Calculation with Tensor Interaction

The effect of tensor interaction due to gluon and Goldstone bosonexchange on the dibaryon mass and decay width has been studied inthe framework of the quark delocalization and colour screening model.The effective S–D wave transition interactions induced by gluon andGoldstone boson exchanges decrease quickly with the increasing channelstrangeness, and there is no six-quark state in the light flavour world,which can become a bound one by the help of these tensor interactions,except for the deuteron. The K and η meson exchange effect has beenshown to be negligible after a short-range truncation in this modelapproach. The partial D-wave decay widths, from the NΩ state tothe ΛΞ final states of spins 0 and 1, are 20.7 keV and63.1 keV respectively. This is a very narrow dibaryon resonance, that mightbe detected in the relativistic heavy ion reaction by the existing RHICdetectors through the reconstruction of the ΛΞ vertexmass and by the future COMPAS detector at CERN and the FAIR project in Germany.

Electroproduction of thed*dibaryon

The unpolarized cross section for the electroproduction of the isoscalar $J^\pi = 3^+$ di-delta dibaryon $d^*$ is calculated for deuteron target using a simple picture of elastic electron-baryon scattering from the $\Delta \Delta (^7D_1)$ and the $NN (^3S_1)$ components of the deuteron. The calculated differential cross section at the electron lab energy of 1 GeV has the value of about 0.24 (0.05) nb/sr at the lab angle of 10$^\circ$ (30$^\circ$) for the Bonn B potential when the dibaryon mass is taken to be 2.1 GeV. The cross section decreases rapidly with increasing dibaryon mass. A large calculated width of 40 MeV for $d^*(\Delta\Delta ^7S_3)$ combined with a small experimental upper bound of 0.08 MeV for the $d^*$ decay width appears to have excluded any low-mass $d^*$ model containing a significant admixture of the $\Delta\Delta (^7S_3)$ configuration.

ΔΔdibaryon structure in chiral SU(3) quark model

The structure of the $\ensuremath{\Delta}\ensuremath{\Delta}$ dibaryon is studied in terms of the chiral SU(3) quark model. The ground state energy of $\ensuremath{\Delta}\ensuremath{\Delta}$ dibaryon is evaluated by considering both the $\ensuremath{\Delta}\ensuremath{\Delta}$ and $\mathrm{CC}$ (hidden color) channels. The parameter-dependence of the $\ensuremath{\Delta}\ensuremath{\Delta}$ dibaryon mass is also investigated. It is shown that the resultant mass of the $\ensuremath{\Delta}\ensuremath{\Delta}$ dibaryon is lower than the threshold of the $\ensuremath{\Delta}\ensuremath{\Delta}$ channel but still higher than that of the $\ensuremath{\Delta}N\ensuremath{\pi}$ channel.

Equation of state of hadronic matter with dibaryons in an effective quark model

The equation of state of symmetric nuclear matter with the inclusion of non-strange dibaryons is studied. We pay special attention to the existence of a dibaryon condensate at zero temperature. These calculations have been performed in an extended quark-meson coupling model with density-dependent parameters, which takes into account the finite size of nucleons and dibaryons. A first-order phase-transition to pure dibaryon matter has been found. The corresponding critical density is strongly dependent on the value of the dibaryon mass. The density behavior of the nucleon and dibaryon effective masses and confining volumes have been discussed.

D' Dibaryon in a colored cluster model and dibaryon condensation

d' dibaryon masses and radii are calculated in a colored quark cluster model. The complications due to the Pauli principle are properly taken into account within the Resonating Group Method (RGM). The effect of Bose-Einstein condensation of dibaryons on the equation of state and possible astrophysical consequences are discussed.

Hdibaryon in the chiral color dielectric model

The mass of the $H$ dibaryon with spin, parity ${J}^{\ensuremath{\pi}}{=0}^{+}$, and isospin $I=0$ is calculated in the framework of the chiral color dielectric model. The wave function of the $H$ dibaryon is expressed as a product of two color-singlet baryon clusters. Thus the quark wave functions within the cluster are antisymmetric. Appropriate operators are then used to antisymmetrize intercluster quark wave functions. The radial part of the quark wave functions are obtained by solving the quark and dielectric field equations of motion obtained in the color dielectric model. The mass of the $H$ dibaryon is computed by including the color magnetic energy as well as the energy due to meson interaction. The recoil correction to the $H$ dibaryon mass is incorporated by Peierls-Yoccoz technique. We find that the mass of the $H$ dibaryon is smaller than the $\ensuremath{\Lambda}\ensuremath{-}\ensuremath{\Lambda}$ threshold by over 100 MeV. The implications of our results on the present day relativistic heavy ion experiments are discussed.

Pionic decay of a possibled′dibaryon and the short-rangeNNinteraction

We study the pionic decay of a possible dibaryon d' --> N N \pi in the microscopic quark shell model. The initial d' dibaryon wave function (J^P=0^-, T=0) consists of one 1\hbar\omega six-quark shell-model s^5p[51]_X configuration. The most important final six-quark configurations s^6[6]_X, s^4p^2[42]_X and (s^4p^2-s^52s)[6]_X are properly projected onto the NN channel. The final state NN interaction is investigated by means of two phase-equivalent - but off-shell different - potential models. We demonstrate that the decay width \Gamma_d' depends strongly on the short-range behavior of the NN wave function. In addition, the width \Gamma_d' is very sensitive to the mass and size of the d' dibaryon. For dibaryon masses slightly above the experimentally suggested value M_d'=2.065 GeV, we obtain a pionic decay width of \Gamma_d' = 0.18 - 0.32 MeV close to the experimental value \Gamma_d' = 0.5 MeV.

Dibaryon Condensate in Nuclear Matter: Exact Analysis in One-Dimensional Models

Phase transitions of nuclear matter to the quark–gluon plasma with subsequent restoration of chiral symmetry have been widely discussed in the literature. We investigate the possibility for occurrence of dense nuclear matter with a dibaryon Bose–Einstein condensate as an intermediate state below the quark–gluon phase transition. An exact analysis of this state of matter is presented in a one-dimensional model. The analysis is based on a reduction of the quantization rules for theN-body problem toNcoupled algebraic transcendental equations. We observe that when the Fermi momentum approaches the resonance momentum, the one-particle distribution function increases near the Fermi surface. When the Fermi momen- tum is increased beyond the resonance momentum, the equation of state becomes softer. The observed behavior can be interpreted in terms of formation of a Bose–Einstein condensate of two-fermion resonances (e.g., dibaryons). In cold nuclear matter, it should occur at 2(mN+εF)⩾mDwheremNandmDare the nucleon and dibaryon masses andεFis the nucleon Fermi energy.

Simple description of strange dibaryons in the Skyrme model.

We study strange dibaryons based on the SU(2)-embedded B=2 toroidal soliton. Treating the excursions of the soliton into strange directions as small rigid oscillations, we obtain a good approximation to the bound state approach. We calculate the dibaryon mass formula to order 1/N and find that the doubly strange I=J=0 dibaryon is bound by about 90 MeV.

Dibaryons in nuclei

Nuclear matter with an admixture of dibaryons at zero temperature is studied. The short-range nuclear forces are represented by a delta-like pseudopotential. The concentration of dibaryons as a function of the dibaryon mass is found.