arXiv subjects

L. Tolos

Publications and source records attributed to L. Tolos.

At least 19 recordsLinked to original sources

arXiv2025

Hadron Physics Opportunities at FAIR

This White Paper outlines a coordinated, decade-spanning programme of hadron and QCD studies anchored at the GSI/FAIR accelerator complex. Profiting from intense deuteron, proton and pion beams coupled with high-rate capable detectors and an international theory effort, the initiative addresses fundamental questions related to the strong interaction featuring confinement and dynamical mass generation. This includes our understanding of hadron-hadron interactions and the composition of hadrons through mapping the baryon and meson spectra, including exotic states, and quantifying hadron structure. This interdisciplinary research connects topics in the fields of nuclear, heavy-ion, and (nuclear) astro (particle) physics, linking, for example, terrestrial data to constraints on neutron star structure. A phased roadmap with SIS100 accelerator start-up and envisaged detector upgrades will yield precision cross sections, transition form factors, in-medium spectral functions, and validated theory inputs. Synergies with external programmes at international accelerator facilities worldwide are anticipated. The programme is expected to deliver decisive advances in our understanding of non-perturbative (strong) QCD and astrophysics, and high-rate detector and data-science technology.

hep-ex↗

arXiv2022

CompOSE Reference Manual

CompOSE (CompStar Online Supernovae Equations of State) is an online repository of equations of state (EoS) for use in nuclear physics and astrophysics, e.g., in the description of compact stars or the simulation of core-collapse supernovae and neutron-star mergers, see http://compose.obspm.fr. The main services, offered via the website, are: a collection of data tables in a flexible and easily extendable data format for different EoS types and related physical quantities with extensive documentation and referencing; software for download to extract and to interpolate these data and to calculate additional quantities; webtools to generate EoS tables that are customized to the needs of the users and to illustrate dependencies of various EoS quantities in graphical form. This manual is an update of previous versions that are available on the CompOSE website, at arXiv:1307.5715 [astro-ph.SR], and that was originally published in the journal "Physics of Particles and Nuclei" with doi:10.1134/S1063779615040061. It contains a detailed description of the service, containing a general introduction as well as instructions for potential contributors and for users. Short versions of the manual for EoS users and providers will also be available as separate publications.

astro-ph.HE↗

arXiv2021

$D\bar{D}^*$ scattering and $χ_{c1}(3872)$ in nuclear matter

We study the behaviour of the $χ_{c1}(3872)$, also known as $X(3872)$, in dense nuclear matter. We begin from a picture in vacuum of the $X(3872)$ as a purely molecular $(D \bar D^*-c.c.)$ state, generated as a bound state from a heavy-quark symmetry leading-order interaction between the charmed mesons, and analyze the $D \bar D^*$ scattering $T-$matrix ($T_{D \bar D^*}$) inside of the medium. Next, we consider also mixed-molecular scenarios and, in all cases, we determine the corresponding $X(3872)$ spectral function and the $D \bar D^*$ amplitude, with the mesons embedded in the dense environment. We find important nuclear corrections for $T_{D \bar D^*}$ and the pole position of the resonance, and discuss the dependence of these results on the $D \bar D^*$ molecular component in the $X(3872)$ wave-function. These predictions could be tested in the finite-density regime that can be accessed in the future CBM and PANDA experiments at FAIR.

hep-ph↗

arXiv2019

Charmed excited baryons with heavy-quark spin symmetry

Recently five $Ω_c$ excited states have been reported by the LHCb Collaboration, four of them corroborated by Belle. The Belle Collaboration has also discovered in 2017 one excited $Ξ_c$ with mass of 2930 MeV. In view of these recent detections, we analyze the possible molecular description of these states, using a unitarized baryon-meson model that incorporates both chiral and heavy-quark spin symmetries in a consistent manner. We pay a special attention to the renormalization procedure, so as to determine the robustness of our predictions. Within our model, we generate dynamically several $Ω_c$ and $Ξ_c$ states. We find that, at least, three of our $Ω_c$ states can be identified with the experimental ones and have spin-parity $J=1/2^-$ or $J=3/2^-$. Moreover, we find a plausible molecular description of not only the $Ξ_c(2930)$ state, but also $Ξ_c(2790)$, $Ξ_c(2815)$ and $Ξ_c(2970)$, reported in the PDG. Interestingly, we determine that $Ξ_c(2930)$ and $Ξ_c(2970)$ are heavy-quark spin partners with $J=1/2^-$ and $J=3/2^-$, respectively, while obtaining that $Ξ_c(2930)$, $Ω_c(3090)$ or the $Ω_c(3119)$, and $Σ_c(2800)$ would belong to the same SU(3) multiplet.

hep-ph↗

arXiv2019

$Ξ_c$ and $Ξ_b$ excited states within a ${\rm SU(6)}_{\rm lsf}\times$HQSS model

We study odd parity $J=1/2$ and $J=3/2$ $Ξ_c$ resonances using a unitarized coupled-channel framework based on a ${\rm SU(6)}_{\rm lsf}\times$HQSS-extended Weinberg-Tomozawa baryon-meson interaction, while paying a special attention to the renormalization procedure. We predict a large molecular $Λ_c \bar K$ component for the $Ξ_c(2790)$ with a dominant $0^-$ light-degree-of-freedom spin configuration. We discuss the differences between the $3/2^-$ $Λ_c(2625)$ and $Ξ_c(2815)$ states, and conclude that they cannot be SU(3) siblings, whereas we predict the existence of other $Ξ_c-$states, two of them related to the two-pole structure of the $Λ_c(2595)$. It is of particular interest a pair of $J=1/2$ and $J=3/2$ poles, which form a HQSS doublet and that we tentatively assign to the $Ξ_c(2930)$ and $Ξ_c(2970)$, respectively. Within this picture, the $Ξ_c(2930)$ would be part of a SU(3) sextet, containing either the $Ω_c(3090)$ or the $Ω_c(3119)$, and that would be completed by the $Σ_c(2800)$. Moreover, we identify a $J=1/2$ sextet with the $Ξ_b(6227)$ state and the recently discovered $Σ_b(6097)$. Assuming the equal spacing rule and to complete this multiplet, we predict the existence of a $J=1/2$ $Ω_b$ odd parity state, with a mass of 6360 MeV and that should be seen in the $Ξ_b \bar K$ channel.

hep-ph↗

arXiv2018

$Ω_c$ excited states within a ${\rm SU(6)}_{\rm lsf}\times$HQSS model

We have reviewed the renormalization procedure used in the unitarized coupled-channel model of Phys. Rev. D85 114032 (2012), and its impact in the $C=1$, $S=-2$, and $I=0$ sector, where five $Ω_c^{(*)}$ states have been recently observed by the LHCb Collaboration. The meson-baryon interactions used in the model are consistent with both chiral and heavy-quark spin symmetries and lead to a successful description of the observed lowest-lying odd parity resonances $Λ_c(2595)$ and $Λ_c(2625)$, and $Λ_b(5912)$ and $Λ_b(5920)$ resonances. We show that some (probably at least three) of the states observed by LHCb will also have odd parity and spins $J=1/2$ and $J=3/2$, belonging two of them to the same ${\rm SU(6)}_{\rm light-spin-flavor}\times$HQSS multiplets that the latter strangenessless heavy$-Λ$ baryons.

hep-ph↗

arXiv2017

Heavy-flavor production and medium properties in high-energy nuclear collisions - What next?

Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice Quantum Chromo-dynamics (QCD). Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop "Tomography of the quark-gluon plasma with heavy quarks}, which was held in October 2016 in Leiden, the Netherlands. In this contribution, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma.

nucl-th↗

arXiv2015

Formation spectra of charmed meson--nucleus systems using an antiproton beam

We investigate the structure and formation of charmed meson--nucleus systems, with the aim of understanding the charmed meson--nucleon interactions and the properties of the charmed mesons in the nuclear medium. The $\bar{D}$ mesic nuclei are of special interest, since they have tiny decay widths due to the absence of strong decays for the $\bar{D} N$ pair. Employing an effective model for the $\bar{D} N$ and $D N$ interactions and solving the Klein--Gordon equation for $\bar{D}$ and $D$ in finite nuclei, we find that the $D^{-}$-${}^{11}\rm{B}$ system has $1 s$ and $2p$ mesic nuclear states and that the $D^{0}$-${}^{11}\rm{B}$ system binds in a $1s$ state. In view of the forthcoming experiments by the PANDA and CBM Collaborations at the future FAIR facility and the J-PARC upgrade, we calculate the formation spectra of the $[D^{-}$-${}^{11}\rm{B}]$ and $[D^{0}$-${}^{11}\rm{B}]$ mesic nuclei for an antiproton beam on a ${}^{12} \rm{C}$ target. Our results suggest that it is possible to observe the $2 p$ $D^{-}$ mesic nuclear state with an appropriate experimental setup.

nucl-th↗

arXiv2015

A study of the $KN$-$K^*N$ coupled systems

We study the strangeness $+1$ meson-baryon systems to obtain improved $KN$ and $K^*N$ amplitudes and to look for a possible resonance formation by the $KN$-$K^*N$ coupled interaction. We obtain amplitudes for light vector meson-baryon systems by implementing the $s$-, $t$-, $u$- channel diagrams and a contact interaction. The pseudoscalar meson-baryon interactions are obtained by relying on the Weinberg-Tomozawa theorem. The transition amplitudes between the systems consisting of pseudoscalars and vector mesons are calculated by extending the Kroll-Ruderman term for pion photoproduction replacing the photon by a vector meson. We fix the subtraction constants required to calculate the loops by fitting our $KN$ amplitudes to the data available for the isospin 0 and 1 $s$-wave phase shifts. We provide the scattering lengths and the total cross sections for the $KN$ and $K^* N$ systems obtained in our model, which can be useful in future in-medium calculations. Our amplitudes do not correspond to formation of any resonance in none of the isospin and spin configurations.

nucl-th↗

arXiv2015

Heavy flavor in relativistic heavy-ion collisions

We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the PYTHIA event generator tuned to fit the transverse momentum spectrum and rapidity distribution of charm quarks from Fixed-Order Next-to-Leading Logarithm (FONLL) calculations. The produced charm quarks scatter in the quark-gluon plasma (QGP) with the off-shell partons whose masses and widths are given by the Dynamical Quasi-Particle Model (DQPM), which reproduces the lattice QCD equation-of-state in thermal equilibrium. The relevant cross sections are calculated in a consistent way by employing the effective propagators and couplings from the DQPM. Close to the critical energy density of the phase transition, the charm quarks are hadronized into $D$ mesons through coalescence and/or fragmentation. The hadronized $D$ mesons then interact with the various hadrons in the hadronic phase with cross sections calculated in an effective lagrangian approach with heavy-quark spin symmetry. The nuclear modification factor $R_{AA}$ and the elliptic flow $v_2$ of $D^0$ mesons from PHSD are compared with the experimental data from the STAR Collaboration for Au+Au collisions at $\sqrt{s_{NN}}$ =200 GeV and to the ALICE data for Pb+Pb collisions at $\sqrt{s_{NN}}$ =2.76 TeV. We find that in the PHSD the energy loss of $D$ mesons at high $p_T$ can be dominantly attributed to partonic scattering while the actual shape of $R_{AA}$ versus $p_T$ reflects the heavy-quark hadronization scenario, i.e. coalescence versus fragmentation. Also the hadronic rescattering is important for the $R_{AA}$ at low $p_T$ and enhances the $D$-meson elliptic flow $v_2$.

nucl-th↗

arXiv2015

Compositeness of the strange, charm and beauty odd parity $Λ$ states

We study the dependence on the quark mass of the compositeness of the lowest-lying odd parity hyperon states. Thus, we pay attention to $Λ-$like states in the strange, charm and beauty, sectors which are dynamically generated using a unitarized meson-baryon model. In the strange sector we use an SU(6) extension of the Weinberg-Tomozawa meson-baryon interaction, and we further implement the heavy-quark spin symmetry to construct the meson-baryon interaction when charmed or beauty hadrons are involved. In the three examined flavor sectors, we obtain two $J^P=1/2^-$ and one $J^P=3/2^-$ $Λ$ states. We find that the $Λ$ states which are bound states (the three $Λ_b$) or narrow resonances (one $Λ(1405)$ and one $Λ_c(2595)$) are well described as molecular states composed of $s$-wave meson-baryon pairs. The $\frac{1}{2}^-$ wide $Λ(1405)$ and $Λ_c(2595)$ as well as the $\frac{3}{2}^-$ $Λ(1520)$ and $Λ_c(2625)$ states display smaller compositeness and so they would require new mechanisms, such as $d$-wave interactions.

hep-ph↗

arXiv2013

The width of the omega meson in the nuclear medium

We evaluate the width of the $ω$ meson in nuclear matter. We consider the free decay mode of the $ω$ into three pions, which is dominated by $ρπ$ decay, and replace the $ρ$ and $π$ propagators by their medium modified ones. We also take into account the quasielastic and inelastic processes induced by a vector-baryon interaction dominated by vector meson exchange, as well as the contributions coming from the $ω\to K \bar K$ mechanism with medium modified $K$, $\bar K$ propagators. We obtain a substantial increase of the $ω$ width in the medium, reaching a value of $129 \pm 10$ MeV at normal nuclear matter density for an $ω$ at rest, which comes mainly from $ωN \to ππN, ωN N \to πNN$ processes associated to the dominant $ω\to ρπ$ decay mode. The value of the width increases moderately with momentum, reaching values of around 200 MeV at 600 MeV/c.

nucl-th↗

arXiv2013

Charming Baryons

We study odd-parity baryonic resonances with one heavy and three light flavors, dynamically generated by meson-baryon interactions. Special attention is paid to Heavy Quark Spin Symmetry (HQSS), hence pseudoscalar and vector mesons and baryons with J^P = 1/2+ and 3/2+ are considered as constituent hadrons. For the hidden-charm sector (N-c-quarks = N-c-antiquarks = 1), the meson-baryon Lagrangian with Heavy Flavor Symmetry is constructed by a minimal extension of the SU(3) Weinberg-Tomozawa (WT) Lagrangian to fulfill HQSS, such that not new parameters are needed. This interaction can be presented in different formal ways: as a Field Lagrangian, as Hadron creation-annihilation operators, as SU(6)xHQSS group projectors and as multichannel matrices. The multichannel Bethe-Salpeter equation is solved for odd-parity light baryons, hidden-charm N and Delta and Beauty Baryons (Lambda-b). Results of calculations with this model are shown in comparison with other models and experimental values for baryonic resonances.

hep-ph↗

arXiv2013

Odd-parity dynamically generated baryon resonances with beauty flavor

We study baryon resonances with heavy flavor in a molecular approach, thus as dynamically generated by baryon-meson scattering. This is accomplished by using a unitary coupled-channel model taking, as bare interaction, the extension of the Weinberg-Tomozawa SU(3) Lagrangian. A special attention is payed to the inclusion of heavy-quark spin symmetry and to the study of the generated baryon resonances that complete the heavy-quark spin multiplets. Our model reproduces the Λ_b(5912) and Λ_b(5920) baryons, which were recently observed by the LHCb collaboration. According to our analysis, these two states are heavy-quark spin symmetric partners. We also make predictions for few Ξ_b baryon resonances, which belong to the same SU(3)xHQSS multiplets as the Λ_b particles.

hep-ph↗

arXiv2013

Hidden charm N and Delta resonances with heavy-quark symmetry

We develop a model to describe odd parity baryon resonances generated dynamically through a unitary baryon-meson coupled-channels approach. The scheme applies to channels with light and/or heavy quark content. Distinct features of the model are that, i) the interaction is an S-wave contact one, ii) it reduces to the SU(3) Weinberg-Tomozawa Hamiltonian when light pseudoscalar mesons are involved, thus, respecting chiral symmetry, iii) spin-flavor in preserved in the light quark sector, and iv) heavy quark spin symmetry is fulfilled in the heavy quark sector. In particular, baryon-meson states with different content in c or in c-bar do not mix. The model is a minimal one and it contains no free parameters. In this work, we focus on baryon resonances with hidden-charm (at least one c-bar and one c quarks). We analyze several possible sectors and, for the sector with zero net charm, we write down the most general Lagrangian consistent with SU(3) and heavy quark spin symmetry. We explicitly study the N and Delta states, which are produced from the S-wave interaction of pseudoscalar and vector mesons with 1/2+ and 3/2+ baryons within the charmless and strangeless hidden charm sector. We predict seven odd parity N-like and five Delta-like states with masses around 4 GeV, most of them as bound states. These states form heavy-quark spin multiplets, which are almost degenerate in mass. The predicted new resonances definitely cannot be accommodated by quark models with three constituent quarks and they might be looked for in the forthcoming PANDA experiment at the future FAIR facility.

hep-ph↗

arXiv2013

Odd parity bottom-flavored baryon resonances

The LHCb Collaboration has recently observed two narrow baryon resonances with beauty. Their masses and decay modes look consistent with the quark model orbitally excited states Lambda_b(5912) and Lambda*_b(5920), with quantum numbers J^P=1/2^- and 3/2^-, respectively. We predict the existence of these states within a unitarized meson-baryon coupled-channel dynamical model, which implements heavy-quark spin symmetry. Masses, quantum numbers and couplings of these resonances to the different meson-baryon channels are obtained. We find that the resonances Lambda^0_b(5912) and Lambda^0_b(5920) are heavy-quark spin symmetry partners, which naturally explains their approximate mass degeneracy. Corresponding bottom-strange baryon resonances are predicted at Xi_b(6035.4) (J^P=1/2^-) and Xi_b(6043.3) (J^P=3/2^-). The two Lambda_b and two Xi_b resonances complete a multiplet of SU(3)-flavor times heavy-quark spin symmetry.

hep-ph↗

arXiv2012

Implications for compact stars of a soft nuclear equation of state from heavy-ion data

We study the implications on compact star properties of a soft nuclear equation of state determined from kaon production at subthreshold energies in heavy-ion collisions. On one hand, we apply these results to study radii and moments of inertia of light neutron stars. Heavy-ion data provides constraints on nuclear matter at densities relevant for those stars and, in particular, to the density dependence of the symmetry energy of nuclear matter. On the other hand, we derive a limit for the highest allowed neutron star mass of three solar masses. For that purpose, we use the information on the nucleon potential obtained from the analysis of the heavy-ion data combined with causality on the nuclear equation of state.

astro-ph.HE↗

arXiv2012

Interaction of vector mesons with baryons and nuclei

After some short introductory remarks on particular issues on the vector mesons in nuclei, in this paper we present a short review of recent developments concerning the interaction of vector mesons with baryons and with nuclei from a modern perspective using the local hidden gauge formalism for the interaction of vector mesons. We present results for the vector baryon interaction and in particular for the resonances which appear as composite states, dynamically generated from the interaction of vector mesons with baryons, taking also the mixing of these states with pseudoscalars and baryons into account. We then venture into the charm sector, reporting on hidden charm baryon states around 4400 MeV, generated from the interaction of vector mesons and baryons with charm, which have a strong repercussion on the properties of the $J/ΨN$ interaction. We also address the interaction of $K^*$ with nuclei and make suggestions to measure the predicted huge width in the medium by means of the transparency ratio. The formalism is extended to study the phenomenon of $J/ψ$ suppression in nuclei via $J/ψ$ photoproduction reactions.

nucl-th↗