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A. Valcarce

Publications and source records attributed to A. Valcarce.

At least 19 recordsLinked to original sources
arXiv2025

Exotic Heavy Hadrons

We review our recent findings on the structure and properties of exotic heavy hadrons, focusing on two main topics. First, we examine the role of correlations driven by the short-range Coulomb-like color interaction in hidden heavy-flavor pentaquarks. We show how this framework consistently accounts for the observed pattern of $P_c$ and $P_{cs}$ states in the hidden-charm sector and enables predictions for the hidden-bottom sector, where experimental data are still lacking. The second topic explores the possibility of forming stable multihadron molecules from deeply bound two-hadron exotic states. In this context, a bound state of three $B$ mesons, denoted as $T_{bbb}$, with quantum numbers $(I)J^P = (1/2)2^-$, is presented. We find that the binding energy generally decreases as the number of hadrons increases, primarily due to effects of the Pauli principle and the appearance of new decay thresholds. Nonetheless, resonances may still arise in specific cases, depending on the internal thresholds of the system. Finally, we discuss how the decay width of an exotic multihadron resonance can offer valuable insights into its internal structure and underlying~dynamics.

hep-ph↗
arXiv2025

Open-Flavor Heavy Hadron Production in Heavy-Ion Collisions

We study the production of open-flavor heavy hadrons in relativistic heavy-ion collisions. The hadronization in the quark-gluon plasma is described in the quark coalescence model. We evaluated yields and transverse momentum distributions. A simultaneous study of conventional and exotic hadrons is carried out. The Wigner functions are evaluated using hadron wave functions obtained from a single realistic quark model. Thus, results are presented in a single framework for the production of open-flavor heavy mesons, baryons, and exotic tetraquarks, in particular: $D^{0}$, $B^{0}$, $\Lambda_{Q}$, $\Sigma_{Q}$, $\Xi_{Q}$, $\Xi_{QQ^\prime}$, and $T_{QQ^\prime}$ ($Q,Q^\prime=c$ or $b$). The consequences of a partial restoration of chiral symmetry at the hadronization temperature are studied in detail.

hep-ph↗
arXiv2025

Pauli principle forbids $\Omega_{QQQ}\Omega_{QQQ}\Omega_{QQQ}$ bound states

Lattice QCD studies have shown the attractive character of the $^1S_0$ $\Omega_{QQQ}\Omega_{QQQ}$, $Q=s,c,b$, interaction, predicting deeply bound states as the mass of the heavy quark increases. This has led to the question of the possible existence of bound states of more than two $\Omega_{QQQ}$ baryons, in particular $\Omega_{QQQ}\Omega_{QQQ}\Omega_{QQQ}$ bound states. We discuss how these states might not exist in nature in any flavor sector. The reason would be due to the simultaneous action of two consequences of the Pauli principle in the different partial waves: one at the baryon level, affecting the $^1S_0$ partial wave, and the other due to the quark substructure, affecting the $^5S_2$ partial wave.

hep-ph↗
arXiv2025

$\Omega_{bbb}\Omega_{bbb}\Omega_{bbb}$ tribaryons

We study the possible existence of bound states of three $\Omega_{bbb}$ baryons. We consider only $S$ wave interactions and we start from recent lattice QCD results which give a strongly attractive potential between two $\Omega_{bbb}$ baryons in the $^1S_0$ channel. We analyze different scenarios. At baryonic level, the $\Omega_{bbb}\Omega_{bbb}$ interaction could be understood to be basically spin-independent, so that the two contributing channels, $^1S_0$ and $^5S_2$, would have a very similar interaction. This baryonic analysis leads to the existence of bound states in the three-body system. At the quark level, repulsive effects would appear in the $^5S_2$ channel, making it more repulsive than the $^1S_0$ channel. We study the effect of such repulsion in terms of its range.

hep-ph↗
arXiv2022

Hidden-flavor pentaquarks

We have recently studied hidden-charm pentaquarks, $c\bar c qqq$, using dynamical correlations between the heavy quarks arising from the Coulomb-like nature of the short-range interaction. A pattern was obtained that compares well with the experimental data. We extend our description to other flavor sectors which can be framed within the same type of structures discussed in the original paper. A detailed comparison is made with other results in the literature and with experimental data. Predictions will be a useful tool to discriminate between different models of multiquark system dynamics.

hep-ph↗
arXiv2022

$(I,J^P)=(1,1/2^+)$ $\Sigma NN$ quasibound state

JLab has recently found indications of the possible existence of a $\Sigma NN$ resonance at $(3.14 \pm 0.84) - i (2.28 \pm 1.2)$ MeV. In the past, using models that exploit symmetries between the two-baryon sector with and without strangeness, hyperon-nucleon interactions have been derived that reproduce the experimental data of the strangeness $-1$ sector. We make use of these interactions to review existing Faddeev studies of the $\Lambda NN$-$\Sigma NN$ system that show theoretical evidences about a $(I,J^P)=(1,1/2^+)$ $\Sigma NN$ quasibound state near threshold. The calculated position of the pole is at 2.92$\,-i\,$2.17 MeV, in reasonable agreement with the experimental findings.

nucl-th↗
arXiv2022

Constituent quark-model hidden-flavor pentaquarks

We study hidden-flavor pentaquarks, $Q\bar Q qqq$, based on a constituent quark-model with a standard quark-quark interaction that reproduces the low-energy meson and baryon spectra. We make use of dynamical correlations between the heavy quarks arising from the Coulomb-like nature of the short-range interaction. A detailed comparison is made with other results in the literature and with experimental data. Our results show a different pattern for open-flavor and hidden-flavor pentaquarks, as suggested by the data. Further implications about the existence of quarkonia bound to nuclei are discussed.

hep-ph↗
arXiv2020

Doubly charmed multibaryon systems

We study two- and three-baryon systems with two units of charm looking for possible bound states or resonances. All two-baryon interactions are consistently derived from a constituent quark model tuned in the light-flavor hadron phenomenology: spectra and interactions. The presence of the heavy quarks makes the two-body interactions simpler than in the light-flavor sector. Our results show a narrow two-body resonance with quantum numbers $(I,J^P)=(0,0^+)$. It is located 6.2 MeV below the $Σ_cΣ_c$ threshold and has a width of 4.7 MeV. The foregoing two-body state contributes to generate a $N Σ_cΣ_c$ resonance with quantum numbers $(I,J^P)=(1/2,1/2^+)$ and a separation energy of 0.2 MeV.

hep-ph↗
arXiv2020

Stable bound states of $N$'s, $\Lambda$'s, and $\Xi$'s

We review our recent work about the stability of strange few-body systems containing $N$'s, $\Lambda$'s, and $\Xi$'s. We make use of local central Yukawa-type Malfliet-Tjon interactions reproducing the low-energy parameters and phase shifts of the nucleon-nucleon system and the latest updates of the hyperon-nucleon and hyperon-hyperon ESC08c Nijmegen potentials. We solve the three- and four-body bound-state problems by means of Faddeev equations and a generalized Gaussian variational method, respectively. The hypertriton, $\Lambda np$ $(I)J^P=(1/2)1/2^+$, is bound by 144 keV; the recently discussed $\Lambda nn$ $(I)J^P=(1/2)1/2^+$ system is unbound, as well as the $\Lambda\Lambda nn$ $(I)J^P=(1)0^+$system, being just above threshold. Our results indicate that the $\Xi NN$, $\Xi\Xi N$ and $\Xi\Xi NN$ systems with maximal isospin might be bound.

nucl-th↗
arXiv2020

Hidden and open heavy-flavor hadronic states

We discuss the stability of hidden and open heavy-flavor hadronic states made of either two or three mesons. References are made in passing to studies regarding two and three-body systems containing baryons. We perform a comparative study analyzing the results in terms of quark and hadron degrees of freedom. Compact and molecular states are found to exist in very specific situations. We estimate the decay width for the different scenarios: weak decays for bound states by the strong interaction, and strong decays for hadronic resonances above a decay threshold. The experimental observation of narrow hadrons lying well above their lowest decay threshold is theoretically justified.

hep-ph↗
arXiv2020

$ΛΛN$-$ΞNN$ $S$ wave resonance

We use an existing model of the $ΛΛN - ΞNN$ three-body system based in two-body separable interactions to study the $(I,J^P)=(1/2,1/2^+)$ three-body channel. For the $ΛΛ$, $ΞN$, and $ΛΛ- ΞN$ amplitudes we have constructed separable potentials based on the most recent results of the HAL QCD Collaboration. They are characterized by the existence of a resonance just below or above the $ΞN$ threshold in the so-called $H$-dibaryon channel, $(i,j^p)=(0,0^+)$. A three-body resonance appears {2.3} MeV above the $Ξd$ threshold. We show that if the $ΛΛ- ΞN$ $H$-dibaryon channel is not considered, the $ΛΛN - ΞNN$ $S$ wave resonance disappears. Thus, the possible existence of a $ΛΛN - ΞNN$ resonance would be sensitive to the $ΛΛ- ΞN$ interaction. The existence or nonexistence of this resonance could be evidenced by measuring, for example, the $Ξd$ cross section.

nucl-th↗
arXiv2020

Neutral baryonic systems with strangeness

We review the status as regards the existence of three- and four-body bound states made of neutrons and $Λ$ hyperons. For interesting cases, the coupling to neutral baryonic systems made of charged particles of different strangeness has been addressed. There are strong arguments showing that the $Λnn$ system has no bound states. $ΛΛnn$ strong stable states are not favored by our current knowledge of the strangeness $-1$ and $-2$ baryon-baryon interactions. However, a possible $Ξ^- t$ quasibound state decaying to $ΛΛnn$ might exist in nature. Similarly, there is a broad agreement about the nonexistence of $ΛΛn$ bound states. However, the coupling to $ΞNN$ states opens the door to a resonance above the $ΛΛn$ threshold.

nucl-th↗
arXiv2019

$Ξ^- t$ quasibound state instead of $ΛΛnn$ bound state

We study the coupled $ΛΛnn-Ξ^- pnn$ system to check whether the inclusion of channel coupling is able to bind the $ΛΛnn$ system. We use a separable potential three-body model of the coupled $ΛΛnn - Ξ^- pnn$ system as well as a variational four-body calculation with realistic interactions. Our results exclude the possibility of a $ΛΛnn$ bound state by a large margin. However, we have found a $Ξ^- t$ quasibound state above the $ΛΛnn$ threshold.

nucl-th↗
arXiv2019

Spectroscopy, lifetime and decay modes of the $T^-_{bb}$ tetraquark

We present the first full-fledged study of the flavor-exotic isoscalar $T_{bb}^-\equiv b b \bar u \bar d$ tetraquark with spin and parity $J^P=1^+$. We report accurate solutions of the four-body problem in a quark model, characterizing the structure of the state as a function of the ratio $M_Q/m_q$ of the heavy to light quark masses. For such a standard constituent model, $T_{bb}^-$ lies approximately 150 MeV below the strong decay threshold $B^-\bar {B^*}^{0}$ and 105 MeV below the electromagnetic decay threshold $B^- \bar B^0 γ$. We evaluate the lifetime of $T_{bb}^-$, identifying the promising decay modes where the tetraquark might be looked for in future experiments. Its total decay width is $Γ\approx 87 \times 10^{-15}$ GeV and therefore its lifetime $τ\approx$ 7.6 ps. The promising final states are ${B^*}^{-}\, {D^*}^{+} \, \ell^- \, \bar ν_\ell$ and $\bar {B^*}^{0} \, {D^*}^{0} \, \ell^- \, \bar ν_\ell $ among the semileptonic decays, and ${B^*}^{-} \, {D^*}^{+} \, {D_s^*}^-$, $\bar {B^*}^{0} \, {D^*}^{0} \, {D_s^*}^- $, and ${B^*}^{-} \, {D^*}^{+} \, ρ^-$ among the nonleptonic ones. The semileptonic decay to the isoscalar $J^P=0^+$ tetraquark $T_{bc}^0$ is also relevant but it is not found to be dominant. There is a broad consensus about the existence of this tetraquark, and its detection will validate our understanding of the low-energy realizations of Quantum Chromodynamics (QCD) in the multiquark sector.

hep-ph↗
arXiv2019

Charmed baryon$-$nucleon interaction

We present a comparative study of the charmed baryon$-$nucleon interaction based on different theoretical approaches. For this purpose, we make use of i) a constituent quark model tuned in the light-flavor baryon$-$baryon interaction and the hadron spectra, ii) existing results in the literature based both on hadronic and quark-level descriptions, iii) (2+1)-flavor lattice QCD results of the HAL QCD Collaboration at unphysical pion masses and their effective field theory extrapolation to the physical pion mass. There is a general qualitative agreement among the different available approaches to the charmed baryon$-$nucleon interaction. Different from hadronic models based on one-boson exchange potentials, quark$-$model based results point to soft interactions without two-body bound states. They also support a negligible channel coupling, due either to tensor forces or to transitions between different physical channels, $Λ_c N - Σ_c N$. Short-range gluon and quark-exchange dynamics generate a slightly larger repulsion in the $^1S_0$ than in the $^3S_1$ $Λ_c N$ partial wave. A similar asymmetry between the attraction in the two $S$ waves of the $Λ_c N$ interaction also appears in hadronic approaches. A comparative detailed study of Pauli suppressed partial waves, as the $^1S_0 (I=1/2)$ and $^3S_1 (I=3/2)$ $Σ_c N$ channels, would help to disentangle the short-range dynamics of two-baryon systems containing heavy flavors. The possible existence of charmed hypernuclei is discussed.

hep-ph↗
arXiv2019

Production of exotic tetraquarks $QQ\bar{q}\bar{q}$ in heavy-ion collisions at the LHC

We investigate the production of exotic tetraquarks, $QQ\bar{q}\bar{q} \equiv T_{QQ}$ ($Q=c$ or $b$ and $q=u$ or $d$), in relativistic heavy-ion collisions using the quark coalescence model. The $T_{QQ}$ yield is given by the overlap of the density matrix of the constituents in the emission source with the Wigner function of the produced tetraquark. The tetraquark wave function is obtained from exact solutions of the four-body problem using realistic constituent models. The production yields are typically one order of magnitude smaller than previous estimations based on simplified wave functions for the tetraquarks. We also evaluate the consequences of the partial restoration of chiral symmetry at the hadronization temperature on the coalescence probability. Such effects, in addition to increasing the stability of the tetraquarks, lead to an enhancement of the production yields, pointing towards an excellent discovery potential in forthcoming experiments. We discuss further consequences of our findings for the search of exotic tetraquarks in central Pb+Pb collisions at the LHC.

hep-ph↗
arXiv2019

$ΩNN$ and $ΩΩN$ states

The lattice QCD analysis of the HAL QCD Collaboration has recently derived $ΩN$ and $ΩΩ$ interacting potentials with nearly physical quark masses ($m_π\simeq $ 146 MeV and $m_K \simeq $ 525 MeV). They found an attractive interaction in the $ΩN$ $^5S_2$ channel which supports a bound state with a central binding energy of 1.54 MeV. The $ΩΩ$ $^1S_0$ channel shows an overall attraction with a bound state with a central binding energy of 1.6 MeV. In this paper we looked closely at the $ΩNN$ and $ΩΩN$ three-body systems making use of the latest HAL QCD Collaboration $ΩN$ and $ΩΩ$ interactions. Our results show that the $Ωd$ system in the state with maximal spin $(I)J^P=(0)5/2^+$ is bound with a binding energy of about 20 MeV. The $(I)J^P=(1)3/2^+$ $Ωnn$ state presents a resonance decaying to $ΛΞn$ and $ΣΞn$, with a separation energy of $\sim$ 1 MeV. The $(I)J^P=(1/2)1/2^+$ $ΩΩN$ state also exhibits a resonance decaying to $ΛΞΩ$ and $ΣΞΩ$, with a separation energy of $\sim$ 4.6 MeV. We have calculated the contribution of the Coulomb potential to differentiate among the different charged states.

hep-ph↗