A
bstract
In two recent papers, we used the hadro-quarkonium model to study the properties of hidden-charm and bottom tetraquarks and pentaquarks. Here, we extend the previous results and calculate ...the masses of heavy-quarkonium-kaon/hyperon systems. We also compute the spectrum of hidden-charm and bottom tetraquarks with strangeness in the compact tetraquark (diquark-antidiquark) model. If heavy-light exotic systems with non-null strangeness content were to be observed experimentally, it might be possible to distinguish among the large variety of available theoretical pictures for tetra- and pentaquark states and, possibly, rule out those which are not compatible with the data.
We calculate the masses of χc(2P) and χb(3P) states with threshold corrections in a coupled-channel model. Here, the meson quarkonium core is augmented by higher Fock components due to pair-creation ...effects. According to our results, we interpret the resonances characterized by very small threshold corrections, like χb(3P)'s, as almost pure quarkonia, and those states characterized by non-negligible threshold corrections, like the X(3872), as quarkonium cores plus meson–meson components. We also study the J/ψρ and J/ψω hidden-flavor strong decays of the X(3872). The decays are calculated as the dissociation of one of these components (D0D¯0⁎) into a cc¯ state (J/ψ) plus a light meson (ρ or ω) in a potential model. In particular, our result for the ratio between the X(3872)→J/ψω and J/ψρ widths (0.6) is compatible with the present experimental data (0.8±0.3) within the experimental error.
We compute masses of positive-parity spin-1/2 and -3/2 baryons composed of u, d, s, c and b quarks in a quark-diquark picture. The mathematical foundation for this analysis is implemented through a ...symmetry-preserving Schwinger-Dyson equations treatment of a vector-vector contact interaction, which preserves key features of quantum chromodynamics, such as confinement, chiral symmetry breaking and low-energy Goldberger-Treiman relations. This study requires a computation of diquark correlations containing these quarks which in turn are readily inferred from solving the Bethe-Salpeter equations of the corresponding mesons. Therefore, it serves as a unified formalism for a multitude of mesons and baryons. It builds on our previous works on the study of masses, decay constants and form factors of quarkonia and light mesons, employing the same model. We use two sets of parameters, one which remains exactly the same for both the light and heavy sector hadrons, and another where the coupling strength is allowed to evolve according to the available mass scales of quarks. Our results are in very good agreement with the existing experimental data as well as predictions of other theoretical approaches whenever comparison is possible.
We study baryo-charmonium ηc- and J/ψ-N⁎, ηc(2S)-, ψ(2S)- and χc(1P)-N and baryo-bottomonium ηb(2S)-, ϒ(2S)- and χb(1P)-N bound states, where N is the nucleon and N⁎ a nucleon resonance. In the ...baryo-quarkonium model, the five qqqQQ¯ quarks are arranged in terms of a heavy quarkonium core, QQ¯, embedded in light baryonic matter, qqq, with q=u or d. The interaction between the QQ¯ core and the light baryon can be written in terms of the QCD multipole expansion. The spectrum of baryo-charmonium states is calculated and the results compared with the existing experimental data. In particular, we can interpret the recently discovered Pc(4380) and Pc(4450) pentaquarks as ψ(2S)-N and χc2(1P)-N bound states, respectively. We observe that in the baryo-bottomonium sector the binding energies are, on average, slightly larger than those of baryo-charmonia. Because of this, the hidden-bottom pentaquarks are more likely to form than their hidden-charm counterparts. We thus suggest the experimentalists to look for five-quark states in the hidden-bottom sector in the 10.4–10.9 GeV energy region.
We calculate the masses of
χ
c
(
3
P
)
states with threshold corrections in a coupled-channel model. The model was recently applied to the description of the properties of
χ
c
(
2
P
)
and
χ
b
(
3
P
)
...multiplets (Ferretti and Santopinto in Phys Lett B 789:550, 2019. We also compute the open-charm strong decay widths of the
χ
c
(
3
P
)
states and their radiative transitions. According to our predictions, the
χ
c
(
3
P
)
states should be dominated by the charmonium core, but they may also show small meson-meson components. The
X
(4274) is interpreted as a
c
c
¯
χ
c
1
(
3
P
)
state. More information on the other members of the
χ
c
(
3
P
)
multiplet, as well as a more rigorous analysis of the
X
(4274)’s decay modes, are needed to provide further indications on the quark structure of the previous resonance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The last decade has seen a marked shift in how the internal structure of hadrons is understood. Modern experimental facilities, new theoretical techniques for the continuum bound-state problem and ...progress with lattice-regularised QCD have provided strong indications that soft quark+quark (diquark) correlations play a crucial role in hadron physics. For example, theory indicates that the appearance of such correlations is a necessary consequence of dynamical chiral symmetry breaking, viz. a corollary of emergent hadronic mass that is responsible for almost all visible mass in the universe; experiment has uncovered signals for such correlations in the flavour-separation of the proton’s electromagnetic form factors; and phenomenology suggests that diquark correlations might be critical to the formation of exotic tetra- and penta-quark hadrons. A broad spectrum of such information is evaluated herein, with a view to consolidating the facts and therefrom moving toward a coherent, unified picture of hadron structure and the role that diquark correlations might play.
We provide results for the open-flavor strong decays of strange and nonstrange baryons into a baryon-vector/pseudoscalar meson pair. The decay amplitudes are computed in the P30 pair-creation model, ...where ss¯ pair-creation suppression is included for the first time in the baryon sector, in combination with the U(7) and hypercentral models. The effects of this ss¯ suppression mechanism cannot be reabsorbed in a redefinition of the model parameters or in a different choice of the P30 model vertex factor. Our results for the decay amplitudes are compared with the existing experimental data and previous P30 and elementary meson emission model calculations. In this respect, we show that distinct quark models differ in the number of missing resonances they predict and also in the quantum numbers of states. Therefore, future experimental results will be important in order to disentangle different models of baryon structure. Finally, in the appendixes, we provide some details of our calculations, including the derivation of all relevant flavor couplings with strangeness suppression. This derivation may be helpful to calculate the open-flavor decay amplitudes starting from other models of baryons.
The observation of five
Ω
c
= ssc states by LHCb Aaij et al. Phys. Rev. Lett.
118
, 182001 (
2017
) and the confirmation of four of them by Belle Yelton et al. Phys. Rev. D
97
, 051102 (
2018
), may ...represent an important milestone in our understanding of the quark organization inside hadrons. By providing results for the spectrum of
Ω
c
baryons and predictions for their
Ξ
c
+
K
-
and
Ξ
c
′
+
K
-
decay amplitudes within an harmonic oscillator based model, we suggest a possible solution to the
Ω
c
quantum number puzzle and we extend our mass and decay width predictions to the
Ω
b
states. Finally, we discuss why the set of
Ω
c
(
b
)
baryons is the most suitable environment to test the validity of three-quark and quark–diquark effective degrees of freedom.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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