Search

In this paper, we adopt an extended relativized quark model to investigate the triply-heavy tetrquarks systematically. The mass spectra are obtained by solving the four-body relativized Hamiltonian including the Coulomb potential, confining potential, spin-spin interactions, and relativistic corrections. We find that all of the triply-heavy tetraquarks lie above the corresponding meson-meson thresholds, and thus no stable one exists. In particular, besides the spin-spin interactions, the Coulomb and confining potentials also contribute to the mass splittings in the $cb\bar c \bar q$ and $cb\bar b \bar q$ systems. Moreover, the whole mass spectra for triply heavy tetraquarks show quite similar patterns, which preserve the light flavor SU(3) symmetry and heavy quark symmetry well. Through the fall-apart mechanism, the triply-heavy tetraquarks may easily decay into the heavy quarkonium plus heavy-light mesons, which are good candidates for investigation in future experiments., Comment: 15 pages, 4 figures. Minor modifications, accepted version

We discuss two complementary strategies to search for light dark matter (LDM) exploiting the positron beam possibly available in the future at Jefferson Laboratory. LDM is a new compelling hypothesis that identifies dark matter with new sub-GeV "hidden sector" states, neutral under standard model interactions and interacting with our world through a new force. Accelerator-based searches at the intensity frontier are uniquely suited to explore it. Thanks to the high intensity and the high energy of the CEBAF (Continuous Electron Beam Accelerator Facility) beam, and relying on a novel LDM production mechanism via positron annihilation on target atomic electrons, the proposed strategies will allow us to explore new regions in the LDM parameters space, thoroughly probing the LDM hypothesis as well as more general hidden sector scenarios., 11 pages, 8 figures. Prepared for submission in EPJA. This work supersedes the corresponding contribution in arXiv:2007.15081. Added aknowledgement to Jefferson Lab

We investigate the hidden-charm pentaquarks as a Λc͞D⁽*⁾ – Σc⁽*⁾͞D⁽*⁾ hadronic molecule coupling to a compact five-quark state. The coupling to the compact state leads to an hadron short-range interaction generating an attraction. In addition, the one pion exchange potential (OPEP) as a long-range interaction is introduced by the Lagrangians satisfying the chiral and heavy quark spin symmetries. The OPEP has been known as a driving force to bind atomic nuclei, where the tensor term leading the coupled-channel effect generates a strong attraction. The mass degeneracy of heavy hadrons due to the heavy quark spin symmetry enhances the OPEP derived by the πD⁽*⁾͞D⁽*⁾ and πΣc⁽*⁾Σc⁽*⁾ couplings. Introducing those interactions, we consistently explain the masses and widths of the Pc states reported by LHCb in 2019. The short range interaction has a dominant role to determine the energy-level structures, while the OPEP tensor term does the decay width., Facultad de Ciencias Exactas

Positron beams, both polarized and unpolarized, are identified as essential ingredients for the experimental programs at the next generation of lepton accelerators. In the context of the hadronic physics program at Jefferson Lab (JLab), positron beams are complementary, even essential, tools for a precise understanding of the electromagnetic structure of nucleons and nuclei, in both the elastic and deep-inelastic regimes. For instance, elastic scattering of polarized and unpolarized electrons and positrons from the nucleon enables a model independent determination of its electromagnetic form factors. Also, the deeply-virtual scattering of polarized and unpolarized electrons and positrons allows unambiguous separation of the different contributions to the cross section of the lepto-production of photons and of lepton-pairs, enabling an accurate determination of the nucleons and nuclei generalized parton distributions, and providing an access to the gravitational form factors. Furthermore, positron beams offer the possibility of alternative tests of the Standard Model of particle physics through the search of a dark photon, the precise measurement of electroweak couplings, and the investigation of charged lepton flavor violation. This document discusses the perspectives of an experimental program with high duty-cycle positron beams at JLab., Comment: 18 pages, 7 figures This version superseeds the previous version which scientific content was decomposed into several more elaborated articles. All of these articles will be collected in the EPJ A Topical Issue about "Positron beam and physics at Jefferson Lab (e+@Jlab)"

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., 113 pages, 41 figures, 8 tables

NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross-section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the fact that the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave functions in the two types of processes and the formal similarity of the transition operators. The main experimental tools for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer at the INFN-LNS laboratory. However, the tiny values of DCE cross-sections and the resolution requirements demand beam intensities much higher than those manageable with the present facility. The on-going upgrade of the INFN-LNS facilities promoted by the POTLNS a project in this perspective is intimately connected to the NUMEN project. This paper describes the solutions proposed as a result of the R&D activity performed during the recent years. The goal is to develop suitable technologies allowing for the measurements of DCE cross-section under extremely high beam intensities. a PIR01_00005 — potenziamento dell’infrastruttura di ricerca Laboratori Nazionali del Sud per la produzione di fasci di ioni ad alta intensitá.

The structure of odd-$A ^{115,117}\mathrm{Rh}$ and $^{115,117}\mathrm{Pd}$ isotopes is studied by means of the neutron-proton interacting boson-fermion model (IBFM-2). ${J}^{P}={\frac{1}{2}}^{+}$ quantum number assignment for the $^{115,117}\mathrm{Pd}$ ground states is critically discussed and the predicted energy levels are compared to the existing experimental data. The resulting nuclear wave functions are used to compute the $\ensuremath{\beta}$-decay $ft$ values of the transitions from $^{115,117}\mathrm{Rh}$ to $^{115,117}\mathrm{Pd}$ in the microscopic IBFM-2 and the results compared with the data.

Using a relativized diquark model Hamiltonian, we calculate the masses of $J^{PC}=0^{++}$ ground-state tetraquarks in the following systems: $b s \bar b \bar s$, $bb \bar n \bar n$ ($n=u, d$), $bb \bar s \bar s$, $cc\bar c \bar c$, $b b \bar b \bar b$, $b c\bar b \bar c$ and $b b \bar c \bar c$. We also compute extensive spectra for the fully-heavy quark flavour combinations. Finally, as a test of the diquark model approach, we compute the masses of fully-heavy baryons in the diquark model. Our results may be compared soon to the forthcoming experimental data for fully-heavy three-quark systems., Comment: Accepted on Eur. Phys. J. C

Background: Heavy-ion induced two-nucleon transfer reactions are powerful tools to reveal peculiar aspects of the atomic nucleus, such as pairing correlations, single-particle and collective degrees of freedom, and more. Also, these processes are in competition with the direct meson exchange in the double charge exchange reactions, which have recently attracted great interest due to their possible connection to neutrinoless double-beta decay. In this framework, the exploration of two-nucleon transfer reactions in the 20Ne+116Cd collision at energies above the Coulomb barrier is particularly relevant since the 116Cd nucleus is a candidate for the double-beta decay. Methods: We measured the excitation energy spectra and absolute cross sections for the two reactions using the MAGNEX large acceptance magnetic spectrometer to detect the ejectiles. We performed direct coupled reaction channels and sequential distorted wave Born approximation calculations using the double folding S\~ao Paulo potential to model the initial and final state interactions. The spectroscopic amplitudes for two- and singleparticle transitions were derived by different nuclear structure approaches: microscopic large-scale shell model, interacting boson model-2 and quasiparticle random phase approximation. Results: The calculations are able to reproduce the experimental cross sections for both two-neutron and twoproton transfer reactions. The role of couplings with the inelastic channels are found to be important in the two-proton transfer case. A competition between the direct and the sequential process is found in the reaction mechanism. For the two-proton transfer case, the inclusion of the 1g7/2 and 2d5/2 orbitals in the model space is crucial.

A constituent gluon model that is informed by recent lattice field theory is developed. The model is then used to compute hybrid strong decay widths that could be useful for the GlueX Collaboration at Jefferson Lab and the PANDA Collaboration at FAIR. Commensurately, forthcoming data from GlueX and PANDA will test the model. Widths tend to be typical of charmonia, except for those of the lightest hybrid S-wave multiplet. Selection rules, extensions, limitations, and applications are discussed., Facultad de Ciencias Exactas

We study the bottomonium spectrum using a relativistic potential model in the momentum space. This model is based on a complete one gluon exchange interaction with a momentum dependent screening factor to account for the effects due to virtual pair creation that appear close to the decay thresholds. The overall model does not make use of nonrelativistic approximations. We fit well established bottomonium states below the open charm threshold and predict the rest of the spectrum up to $\approx 11200$ MeV and $J^{PC}=3^{--}$. Uncertainties are treated rigorously and propagated in full to the parameters of the model using a Monte Carlo to identify if which deviations from experimental data can be absorbed into the statistical uncertainties of the models and which can be related to physics beyond the $b\bar{b}$ picture, guiding future research. We get a good description of the spectrum, in particular the Belle measurement of the $\eta_b(2S)$ state and the $\Upsilon(10860)$ and $\chi_b(3P)$ resonances., Comment: 11 pages, 3 figures, 8 tables

We investigate the hidden-charm pentaquarks as superpositions of $\Lambda_c \bar{D}^{(*)}$ and $\Sigma_c^{(*)} \bar{D}^{(*)}$ (isospin $I = 1/2$) meson-baryon channels coupled to a $uudc\bar{c}$ compact core by employing an interaction satisfying the heavy quark and chiral symmetries. Our model can consistently explain the masses and decay widths of $P_c^+(4312)$, $P_c^+(4440)$ and $P_c^+(4457)$ with the dominant components of $\Sigma_c \bar D$ and $\Sigma_c \bar D^\ast$ with spin parity assignments $J^P = 1/2^{-}, 3/2^{-}$ and $1/2^{-}$, respectively. We analyze basic properties of the $P_c$'s such as masses and decay widths, and find that the mass ordering is dominantly determined by the quark dynamics while the decay widths by the tensor force of the one-pion exchange., Comment: 6 pages, 2 figures

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. peerReviewed

We present the spectrum of ground state heavy-light mesons. Our analysis is provided by a symmetry preserving Schwinger-Dyson Bethe-Salpeter Equation (SDBSE) approach of a vector-vector contact interaction model. This model offers a simple-to-implement alternative to perform exploratory studies of QCD. Despite the simplicity of this model, our results for D are in agreement within 9%, and for B within 2% when we compare them with experimental data.

We investigate the hidden-charm and hidden-bottom pentaquarks as meson-baryon molecules coupled to the five-quark states. As a result of our calculation it emerges that in the charm sector, one needs to add the five-quark potential to the pion exchange potential in order to produce bound and resonant states, whereas, in the bottom sector, the pion exchange interaction alone is strong enough to produce states. Thus, from this investigation, it comes out that the hidden-bottom pentaquarks are more likely to be produced than their hidden-charm counterparts, and, for this reason, we suggest that the experimentalists should look for the hidden-bottom pentaquarks.

The observation of five $$\varOmega _c $$Ωc= 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 $$\varOmega _{ c}$$Ωc baryons and predictions for their $$\varXi _{ c}^{+}K^{-}$$Ξc+K- and $$\varXi _{ c}'^{+}K^{-}$$Ξc′+K- decay amplitudes within an harmonic oscillator based model, we suggest a possible solution to the $$\varOmega _{c}$$Ωc quantum number puzzle and we extend our mass and decay width predictions to the $$\varOmega _b$$Ωb states. Finally, we discuss why the set of $$\varOmega _{ c(b)}$$Ωc(b) baryons is the most suitable environment to test the validity of three-quark and quark–diquark effective degrees of freedom.

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-diaquark 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., 15 pages, 8 figures

An updated overview of recent results on Heavy-Ion induced reactions of interest for neutrinoless double beta decay is reported in the framework of the NUMEN project. The NUMEN idea is to study heavy-ion induced Double Charge Exchange (DCE) reactions with the aim to get information on the nuclear matrix elements for neutrinoless double beta (0νββ) decay. Moreover, to infer the neutrino average masses from the possible measurement of the half- life of 0νββ decay, the knowledge of the nuclear matrix elements is a crucial aspect. Uma visão geral atualizada dos resultados recentes sobre reações induzidas por íons pesados ​​de interesse para o decaimento beta duplo sem neutrinos é relatada na estrutura do projeto NUMEN. A ideia do NUMEN é estudar reações de Double Charge Exchange (DCE) induzidas por íons pesados ​​com o objetivo de obter informações sobre os elementos da matriz nuclear para o decaimento beta duplo sem neutrinos (0νββ). Além disso, para inferir as massas médias dos neutrinos a partir da possível medição da meia-vida do decaimento 0νββ, o conhecimento dos elementos da matriz nuclear é um aspecto crucial. 1308 012002

Using the eikonal approximation and small momentum transfer approximation a simple model for differential cross section for double charge exchange has been derived and under those hypothesis a factorization of the reaction part and the nuclear part holds. Moreover, the explicit form for a double charge exchange effective potential has been derived in the closure approximation and also and explicit expression for the nuclear matrix elements that are of the form of Double Gamow-Teller and Double Fermi in the microscopic IBM-2.Using the eikonal approximation and small momentum transfer approximation a simple model for differential cross section for double charge exchange has been derived and under those hypothesis a factorization of the reaction part and the nuclear part holds. Moreover, the explicit form for a double charge exchange effective potential has been derived in the closure approximation and also and explicit expression for the nuclear matrix elements that are of the form of Double Gamow-Teller and Double Fermi in the microscopic IBM-2.

International audience; NUMEN aims at accessing experimentally driven information on Nuclear Matrix Elements (NME) involved in the half-life of the neutrinoless double beta decay (0νββ), by high-accuracy measurements of the cross sections of Heavy Ion (HI) induced Double Charge Exchange (DCE) reactions. First evidence about the possibility to get quantitative information about NME from experiments is found for the (^18O,^18Ne) and (^20Ne,^20O) reactions. Moreover, to infer the neutrino average masses from the possible measurement of the half-life of 0νββ decay, the knowledge of the NME is a crucial aspect. The key tools for this project are the high resolution Superconducting Cyclotron beams and the MAGNEX magnetic spectrometer at INFN Laboratori Nazionali del Sud in Catania (Italy). The measured cross sections are extremely low, limiting the present exploration to few selected isotopes of interest in the context of typically low-yield experimental runs. A major upgrade of the LNS facility is foreseen in order to increase the experimental yield of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest.

We perform a quantitative analysis of the decays of c c c ¯ c ¯ tetraquarks with J P C = 0 + + , 2 + + into 4 muons and into hidden- and open-charm mesons and estimate, for the first time, the fully charmed tetraquark decay width. The calculated cross section upper limit is ∼ 39 ( 780 ) fb for the 4 muons channel, and ∼ 42 ( 616 ) pb for the D ( ⁎ ) D ¯ ( ⁎ ) → e μ channel, in the 0 + + ( 2 + + ) case. Decay widths depend upon the additional parameter ξ = | Ψ T ( 0 ) | 2 / | Ψ J / ψ ( 0 ) | 2 , which can be computed with a considerable error. We find Γ ( 0 + + ) ∼ Γ ( 2 + + ) = 97 ± 30 . On the basis of our results and with the present sensitivity, LHCb should detect both 0 + + and 2 + + fully-charmed tetraquarks.

We describe the electroproduction ratios of baryon–meson states from nucleon, inferring from the sea quarks in the nucleon using an extension of the quark model that takes into account the sea. As a result we provide, with no adjustable parameters, the predictions of ratios of exclusive meson–baryon final states: ΛK+, Σ⁎K, ΣK, pπ0, and nπ+. These predictions are in agreement with the new JLab experimental data showing that sea quarks play an important role in the electroproduction. We also predicted further ratios of exclusive reactions that can be measured and tested in future experiments. In particular, we suggested new experiments on deuterium and tritium. Such measurements can provide crucial tests of different predictions concerning the structure of nucleon and its sea quarks helping to solve an outstanding problem. Finally, we compute the so called strangeness suppression factor, λs, that is the suppression of strange quark–antiquark pairs compared to nonstrange pairs, and we found that our finding with this simple extension of the quark model is in good agreement with the results of JLab and CERN experiments.

We describe the relativistic interacting quark-diquark model formalism and its application to the calculation of strange and nonstrange baryon spectra. The results are compared to the existing experimental data. We also discuss the application of the model to the calculation of other baryon observables, like baryon magnetic moments, open-flavor strong decays and baryon masses with self-energy corrections.

In this contribution, we present a study of ground- and excited-state Ω c and Ω b baryons consisting of two strange quarks and a heavy charm or bottom quark. An analysis in the quark model shows that the recently observed excited Ω c and Ω b states can be interpreted in terms of λ-mode excitations.

The formalism to describe heavy-ion double charge exchange (DCE) processes in the eikonal and small-momentum transfer approximations introduced in Phys. Rev. C 98, 061601(R) (2018) is briefly discussed. It is also shown that, under the previous approximations, the heavy-ion DCE cross-section can be factorized in terms of a reaction and a nuclear part. A double charge exchange effective potential is explicitly derived in the closure approximation and also for the first time the explicit form of the DCE nuclear matrix elements, that are of the form of double Gamow-Teller and double Fermi. The recent hypothesis of a linear correlation between double Gamow-Teller neutrinoless double beta decay and DCE nuclear matrix elements is confirmed thanks to the first explicit derivation of DCE nuclear matrix elements, and by means of microscopic IBM2 calculations.

We perform a quantitative analysis of the b b b ¯ b ¯ tetraquark decays into hidden- and open-bottom mesons and calculate, for the first time, the b b b ¯ b ¯ tetraquark total decay width. On the basis of our results, we propose the b b b ¯ b ¯ → B + B − ( B 0 B ¯ 0 ) ( B s 0 B ¯ s 0 ) → l + l − + X decays as the most suitable channels to observe the b b b ¯ b ¯ tetraquark states, since the calculated two-lepton cross section upper limit, ≃39 fb, is so large as to be potentially detectable with the 2018 LHCb sensitivity, paving the way to the observation of the b b b ¯ b ¯ tetraquark in the future LHCb upgrade. The 4μ signal for the ground state, J P C = 0 + + , is likely to be too small even for the upgraded LHCb, but it may not be hopeless for the J P C = 2 + + fully-bottom state.

International audience; The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the fact that the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the$^{40}$Ca($^{18}$O,$^{18}$Ne)$^{40}$Ar reaction at 270MeV give an encouraging indication on the capability of the proposed technique to access relevant quantitative information. The main experimental tools for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy-ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than those manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article.

We calculate the spectrum of $q\overline{q}c\overline{c}$ and $s\overline{s}c\overline{c}$ tetraquarks, where $q$, $s$, and $c$ stand for light ($u$, $d$), strange, and charm quarks, respectively, in a relativized diquark model, characterized by one-gluon-exchange plus confining potential. In the diquark model, a $q\overline{q}c\overline{c}$ ($s\overline{s}c\overline{c}$) tetraquark configuration is made up of a heavy-light diquark, $qc$ ($sc$), and anti-diquark, $\overline{q}\overline{c}$ ($\overline{s}\overline{c}$). According to our results, 13 charmonium-like observed states can be accommodated in the tetraquark picture, both in the hidden-charm ($q\overline{q}c\overline{c}$) and hidden-charm hidden-strange ($s\overline{s}c\overline{c}$) sectors.

We investigate the hidden-charm pentaquarks and the hidden bottom pentaquarks as, respectively, $\bar{D}^{(*)}\Lambda_c$, $\bar{D}^{(*)}\Sigma_c^{(*)}$ and $\bar{B}^{(*)}\Lambda_b$, $\bar{B}^{(*)}\Sigma_b^{(*)}$ molecules coupled to the five-quark states. The hidden charmed and bottom pentaquark states have been described by taking into account both the meson-baryon channels, which encodes the dynamics at long distances, and a compact five-quark core, which encodes the short distance part. As a result of our calculation, we find that, unlike the charmed sector, in the bottom sector, the pion exchange interaction is strong enough to produce resonant and bound states. As the hidden-bottom pentaquarks are more likely to form than their hidden-charm counterparts, the bottom sector is the more interesting environment to look for new pentaquark states.

The hidden-charm and hidden-bottom pentaquarks are investigated as meson-baryon molecules coupled to the five-quark states. As a result of our calculation, we find that, in the charm sector, one needs the five-quark potential in addition to the pion exchange potential in order to produce bound and resonant states, whereas, in the bottom sector, the pion exchange interaction is strong enough to produce states. Thus, from this investigation, it emerges that the hidden-bottom pentaquarks are more likely to form than their hidden-charm counterparts; for this reason, we suggest that the experimentalists should look for pentaquark states in the bottom sector.

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.

In this paper, we investigate the hidden-charm pentaquarks as $\bar{D}^{(\ast)}\Lambda_{\rm c}$ and $\bar{D}^{(\ast)}\Sigma^{(\ast)}_{\rm c}$ molecules coupled to the five-quark states. Furthermore, we extend our calculations to the hidden-bottom sector. The coupling to the five-quark states is treated as the short range potential, where the relative strength for the meson-baryon channels is determined by the structure of the five-quark states. We found that resonant and/or bound states appear in both the charm and bottom sectors. The five-quark state potential turned out to be attractive and, for this reason, it plays an important role to produce these states. In the charm sector, we need the five-quark potential in addition to the pion exchange potential in producing bound and resonant states, whereas, in the bottom sector, the pion exchange interaction is strong enough to produce states. Thus, from this investigation, it emerges that the hidden-bottom pentaquarks are more likely to form than their hidden-charm counterparts; for this reason, we suggest that the experimentalists should look for states in the bottom sector., Comment: 58 pages, 13 figures, and 10 tables, published version

Recently, various two-neutron transfer studies using the $(^{18}\mathrm{O},^{16}\mathrm{O})$ reaction were performed with a large success. This was achieved because of a combined use of the microscopic quantum description of the reaction mechanism and of the nuclear structure. In the present work we use this methodology to study the two-neutron transfer reaction of the $^{18}\mathrm{O}+^{64}\mathrm{Ni}$ system at 84 MeV incident energy, to the ground and first ${2}^{+}$ excited state of the residual $^{66}\mathrm{Ni}$ nucleus. All the experimental data were measured by the large acceptance MAGNEX spectrometer at the Instituto Nazionale di Fisica Nucleare --Laboratori Nazionali del Sud (Italy). We have performed exact finite range cross section calculations using the coupled channel Born approximation (CCBA) and coupled reaction channel (CRC) method for the sequential and direct two-neutron transfers, respectively. Moreover, this is the first time that the formalism of the microscopic interaction boson model (IBM-2) was applied to a two-neutron transfer reaction. From our results we conclude that for two-neutron transfer to the ground state of $^{66}\mathrm{Ni}$, the direct transfer is the dominant reaction mechanism, whereas for the transfer to the first excited state of $^{66}\mathrm{Ni}$, the sequential process dominates. A competition between long-range and short-range correlations is discussed, in particular, how the use of two different models (Shell model and IBM's) help to disentangle long- and short-range correlations.

The recent observation of two hidden-charm pentaquark states by LHCb collaborations prompted us to investigate the exotic states close to the $\overline{D}{\mathrm{\ensuremath{\Lambda}}}_{\mathrm{c}}$, ${\overline{D}}^{*}{\mathrm{\ensuremath{\Lambda}}}_{\mathrm{c}}$, $\overline{D}{\mathrm{\ensuremath{\Sigma}}}_{\mathrm{c}}$, $\overline{D}{\mathrm{\ensuremath{\Sigma}}}_{\mathrm{c}}^{*}$, ${\overline{D}}^{*}{\mathrm{\ensuremath{\Sigma}}}_{\mathrm{c}}$ and ${\overline{D}}^{*}{\mathrm{\ensuremath{\Sigma}}}_{\mathrm{c}}^{*}$ thresholds. We therefore studied the hadronic molecules that form the coupled-channel system of ${\overline{D}}^{(*)}{\mathrm{\ensuremath{\Lambda}}}_{\mathrm{c}}$ and ${\overline{D}}^{(*)}{\mathrm{\ensuremath{\Sigma}}}_{\mathrm{c}}^{(*)}$. As the heavy quark spin symmetry manifests the mass degenerations of $\overline{D}$ and ${\overline{D}}^{*}$ mesons, and of ${\mathrm{\ensuremath{\Sigma}}}_{\mathrm{c}}$ and ${\mathrm{\ensuremath{\Sigma}}}_{\mathrm{c}}^{*}$ baryons, the coupled channels of ${\overline{D}}^{(*)}{\mathrm{\ensuremath{\Sigma}}}_{\mathrm{c}}^{(*)}$ are important in these molecules. In addition, we consider the coupling to the ${\overline{D}}^{(*)}{\mathrm{\ensuremath{\Lambda}}}_{\mathrm{c}}$ channel whose thresholds are near the ${\overline{D}}^{(*)}{\mathrm{\ensuremath{\Sigma}}}_{\mathrm{c}}^{(*)}$ thresholds, and the coupling to the state with nonzero orbital angular momentum mixed by the tensor force. This full coupled-channel analysis of ${\overline{D}}^{(*)}{\mathrm{\ensuremath{\Lambda}}}_{\mathrm{c}}\ensuremath{-}{\overline{D}}^{(*)}{\mathrm{\ensuremath{\Sigma}}}_{\mathrm{c}}^{(*)}$ with larger orbital angular momentum has never been performed before. By solving the coupled-channel Schr\"odinger equations with the one meson exchange potentials with respect to the heavy quark spin and chiral symmetries, we studied the hidden-charm hadronic molecules with $I({J}^{P})=1/2(3/{2}^{\ifmmode\pm\else\textpm\fi{}})$ and $1/2(5/{2}^{\ifmmode\pm\else\textpm\fi{}})$. We conclude that the ${J}^{P}$ assignment of the observed pentaquarks is $3/{2}^{+}$ for ${P}_{\mathrm{c}}^{+}(4380)$ and $5/{2}^{\ensuremath{-}}$ for ${P}_{\mathrm{c}}^{+}(4450)$, which is in agreement with the results of the LHCb analysis. In addition, we give predictions for other ${J}^{P}=3/{2}^{\ifmmode\pm\else\textpm\fi{}}$ states at 4136.0, 4307.9 and 4348.7 MeV in ${J}^{P}=3/{2}^{\ensuremath{-}}$, and 4206.7 MeV in ${J}^{P}=3/{2}^{+}$, which can be further investigated by means of experiment.

We present an unquenched quark model calculation of the mass shifts of ground-state octet and decuplet baryons due to the coupling to the meson-baryon continuum. All ground-state baryons and pseudoscalar mesons are included in our calculation as intermediate states. The $q\bar{q}$ pair creation effects are taken explicitly into account through a microscopic, QCD-inspired, quark-antiquark pair creation mechanism.

The NUMEN project aims at accessing experimentally driven information on Nuclear Matrix Elements (NME) involved in the half-life of the neutrinoless double beta decay (0νββ), by high-accuracy measurements of Heavy Ion (HI) induced Double Charge Exchange (DCE) reaction cross sections. In particular, the (18O,18Ne) and (20Ne,20O) reactions are used as tools for β+β+ and β−β− decays, respectively. In the experiments, performed at INFN - Laboratory Nazionali del Sud (LNS) in Catania, the beams are accelerated by the Superconducting Cyclotron (CS) and the reaction ejectiles are detected the MAGNEX magnetic spectrometer. The measured cross sections are challengingly low (a few nb), being the total reaction cross section much larger (a few b), thus a high sensitivity and a large rejection capability are demanded to the experimental set-up. This limits the present exploration to few selected isotopes of interest in the context of typically low-yield experimental runs. A major upgrade of the LNS facility is foreseen in order to increase the experimental yield of at least two orders of magnitude, still keeping the high sensitivity of the present set-up, making it feasible a systematic study of all the cases of interest. Frontiers technologies are going to be developed, to this purpose, for the accelerator and the detection systems. In parallel, advanced theoretical models are being developed in order to extract the nuclear structure information from the measured cross sections.

The aim of the NUMEN project is to access the Nuclear Matrix Elements (NME), involved in the half life of the neutrinoless double beta decay (0νββ), by measuring the cross sections of Heavy Ions (HI) induced Double Charge Exchange (DCE) reactions with high accuracy. First evidence of the possibility to get quantitative information about NME from experiments is shown in the reaction 40Ca(18O,18Ne)40Ar at 270 MeV, performed with MAGNEX spectrometer using Superconducting Cyclotron (CS) beams at INFN - Laboratory Nazionali del Sud (LNS) in Catania. Preliminary tests on 116Sn and 116Cd target are already performed. High beam intensity is the new frontiers for these studies.

We discuss the possible existence of the fully-heavy tetraquarks. We calculate the ground-state energy of the $bb \bar b \bar b$ bound state, where $b$ stands for the bottom quark, in a nonrelativistic effective field theory framework with one-gluon-exchange (OGE) color Coulomb interaction, and in a relativized diquark model characterized by OGE plus a confining potential. Our analysis advocates the existence of uni-flavor heavy four-quark bound states. The ground state $bb\bar b\bar b$ tetraquark mass is predicted to be $(18.72\pm0.02)$~GeV. Mass inequality relations among the lowest $QQ\bar{Q}\bar{Q}$ state, where $Q\in \{c, b\}$, and the corresponding heavy quarkonia are presented, which give the upper limit on the mass of ground state $QQ\bar{Q}\bar{Q}$. The possible decays of the lowest $bb\bar{b}\bar{b}$ are highlighted, which might provide useful references in the search for them in ongoing LHC experiments, and its width is estimated to be a few tens of MeV., Comment: Version accepted for publication in Eur. Phys. J. C

We resume our results on the heavy quarkonium hybrids [19], and on the recently observed pentaquark states [16–18]. The latter have been investigated in three different scenarios: as compact pentaquark states [20], as a quantum superposition of D(*)Λc, D(*)Σc andD(*)Σ(*)c$D^{(\ast )} \Sigma _{c}^{(\ast )}$andmeson-baryon states [30], and as a quantum superposition of meson-baryon molecular states and compact five-quark states [31].

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 ${^{3}P}_{0}$ pair-creation model, where $s\overline{s}$ 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 $s\overline{s}$ suppression mechanism cannot be reabsorbed in a redefinition of the model parameters or in a different choice of the ${^{3}P}_{0}$ model vertex factor. Our results for the decay amplitudes are compared with the existing experimental data and previous ${^{3}P}_{0}$ 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.