Search

Motivated by the last experimental and theoretical advances in the analysis of possible baryonium resonances, the $X(1835)$ and their partners, we perform a constituent-quark-model based coupled-channels calculation of the proton-antiproton scattering in order to analyze the possible existence of bound states or near-threshold structures. The used $N\overline N$ potential is derived from a $G$-parity transformation of the quark-model-based $NN$ interaction which has described well deuteron properties, $NN$ phase shifts, and even hadron-hadron phenomenology. The additional $N\overline N$ annihilation is taken into account by a complex phenomenological potential whose real part is generated by one-pion and one-gluon exchange annihilation potentials and its imaginary part is an energy-independent potential of Gaussian form. Then, all the parameters of the interaction are constrained by the $NN$ sector except those determining the imaginary part of the annihilation potential. Our study concludes that the nucleon-antinucleon dynamics is complex and rich in scattering singularities near the proton-antiproton and neutron-antineutron thresholds., Comment: 7 pages, 2 figures, 3 tables

In this work we investigate the possible emergence of Efimov states in the $D^*D^*D^*$ system with $J^P=0^-$ and isospin $I=\tfrac{1}{2}$, assuming the existence of the heavy partner of the $T_{cc}^+$, dubbed $T_{cc}^*$, near the $D^*D^*$ threshold as predicted by Heavy-Quark Spin Symmetry. We find that $(I)J^P=(\frac{1}{2})0^-$ three-body bound states can be formed, with properties that suggest that the Efimov effect can be realised for reasonable values of the molecular probability and binding energy of the $T_{cc}^*$., Comment: 6 pages, 5 figures. Proceedings of the 10th International Conference on Quarks and Nuclear Physics (QNP2024). 8-12 July, 2024. Barcelona, Spain

In this work we analyze the $\bar KN$ interaction in the framework of a constituent quark model. The near-threshold elastic and charge exchange cross sections are evaluated, finding a good agreement with the experimental data. Furthermore, the possible existence of $\bar KN$ bound states are explored, finding two poles in the isoscalar $J^P=\frac{1}{2}^-$ sector that can be interpreted as the experimental $\Lambda(1405)$ state., Comment: 7 pages, 2 figures, 3 tables

Dibaryons are the simplest system in which the baryon-baryon interaction, and hence the underlying quark-quark interaction, can be studied in a clear way. Although the only dibaryon known today is the deuteron (and possibly the $d^*$), fully heavy dibaryons are good candidates for bound states because in such systems the kinetic energy is small and the high symmetry of the wave function favours binding. In this study, the possible existence of $\Omega_{ccc}\Omega_{ccc}$ and $\Omega_{bbb}\Omega_{bbb}$ dibaryons is investigated in the framework of a constituent quark model that satisfactorily describes the deuteron, the $d^*(2380)$ and the $NN$ interaction. $J^P=0^+$ candidates are found in both systems with binding energies of the order of MeV., Comment: 9 pages, 8 figures

The LHCb Collaboration announced in 2021 the discovery of a new tetraquark-like state, named $T_{cc}^+$, with minimum quark content $cc\bar u\bar d$, close to the $D^0D^{*+}$ threshold. This has motivated countless theoretical works trying to identify the dynamics which is responsible of the formation of such state; in particular, the one performed by us in Ref. \cite{Ortega:2022efc}, where a $D^0D^{*+}$ molecular candidate whose mass, width, scattering length and effective ranges are in reasonable agreement with experimental measurements. We explore herein the possibility of having $T_{cc}^+$ partners in all doubly-heavy tetraquark sectors, considering doubly represented light antiquarks $u$, $d$ or $s$, and taking into account all possible spin-parity quantum numbers. The computation is done using a constituent-quark-model based meson-meson coupled-channels framework which has been tested many times in the last fifteen years describing conventional heavy mesons and baryons, their coupling with hadron-hadron thresholds but also in exploring its application to compact multiquark structures. The advantage of using an approach with such a relatively large history is that it allows us to make predictions because all the parameters have already been constrained from our previous works. Then, from this perspective, we present a parameter-free model-dependent prediction of doubly-heavy tetraquarks that may be partners of the discovered $T_{cc}^+$ state., Comment: 8 pages, 1 figure, 6 tables. arXiv admin note: text overlap with arXiv:2211.06118

We provide an in-detail derivation through the $^3P_0$ pair creation model of the transition matrix for a baryon decaying into a meson-baryon system. The meson's analysis was conducted in Ref. [1] and we extend the same formalism to the baryon sector, focusing on the $\Delta(1232)\to \pi N$ strong decay width because all hadrons involved in the reaction are very well established, the two hadrons in the final state are stable, avoiding further analysis, all quarks are light and so equivalent, and the decay width of the process is relatively well measured. Taking advantage of a Gaussian expansion method for the hadron's radial wave functions, the expression of the invariant matrix element can be related with the mean-square radii of hadrons involved in the decay. We use their experimental measures in such a way that only the strength of the quark-antiquark pair creation from the vacuum is a free parameter. This is then taken from our previous study of strong decay widths in the meson sector, obtaining a quite compatible result with experiment for the calculated $\Delta(1232)\to \pi N$ decay width., Comment: 27 pages, 2 figures

The emergence of the Efimov effect in the $D^*D^*D^*$ system is explored under the assumption that the heavy partner of the $T_{cc}^+$ exists as a $D^*D^*$ molecule with $(I)J^P=(0)1^+$. The three-to-three relativistic scattering amplitude is obtained from the ladder amplitude formalism, built from an energy-dependent contact two-body potential where the molecular component of the $T_{cc}^*$ state can be varied. We find that $(I)J^P=(\tfrac{1}{2})0^-$ three-body bound states can be formed, with properties that suggest that the Efimov effect can be realised for reasonable values of the molecular probability and binding energy of the $T_{cc}^*$., Comment: 7 pages, 5 figures, 1 table

The $\Upsilon(10753)$ state has been recently observed by the Belle and Belle~II collaborations with enough global significance to motivate an assessment of the high-energy spectrum usually predicted by any reasonable \emph{na\"ive} quark model. In the framework of a constituent quark model which satisfactorily describes a wide range of properties of conventional hadrons containing heavy quarks, the quark-antiquark and meson-meson degrees of freedom have been incorporated with the goal of elucidating the influence of open-bottom meson-meson thresholds into the $\Upsilon$ states whose masses are within the energy range of the $\Upsilon(10753)$'s mass. It is well known that such effects could be relevant enough as to generate dynamically new states and thus provide a plausible explanation of the nature of the $\Upsilon(10753)$ state. In particular, we have performed a coupled-channels calculation in which the bare states $\Upsilon(4S)$, $\Upsilon(3D)$, $\Upsilon(5S)$ and $\Upsilon(4D)$ are considered together with the threshold channels $B\bar{B}$, $B\bar{B}^\ast$, $B^\ast \bar{B}^\ast$, $B_s\bar{B}_s$, $B_s\bar{B}_s^\ast$ and $B_s^\ast \bar{B}_s^\ast$. Among the results we have described, the following conclusions are of particular interest: (i) a richer complex spectrum is gained when thresholds are present and bare bound states are sufficiently non-relativistic; (ii) those poles obtained in the complex energy plane do not have to appear as simple peaks in the relevant cross sections; and (iii) the $\Upsilon(10750)$ candidate is interpreted as a dressed hadronic resonance whose structure is an equally mixture of a conventional $b\bar b$ state and $B^\ast \bar B^\ast$ molecule., Comment: 11 pages, 2 figures, 6 tables

This brief deals with the satisfaction of the daily cooling demand by a hybrid system that consists of a vapour-compression refrigeration cycle and a thermal energy storage (TES) unit, based on phase change materials. The addition of the TES tank to the original refrigeration plant allows to schedule the cooling production regardless of the instantaneous demand, given that the TES tank can store cold energy and release it whenever deemed appropriate. The scheduling problem is posed as an optimization problem based on mixed-integer non-linear programming (MINLP), since it includes both discrete and continuous variables. The latter corresponds to the references on the main cooling powers involved in the problem (cooling production at the evaporator and TES charging/discharging), whereas the discrete variables define the operating mode scheduling. Therefore, in addition to the hybrid features of the physical plant, a hybrid optimal control strategy is also proposed. A receding horizon approach is applied, similar to model predictive control (MPC) strategies, while economic criteria are imposed in the objective function, as well as feasibility issues. The TES state estimation is also addressed, since its instantaneous charge ratio is not measurable. The proposed strategy is applied in simulation to a challenging cooling demand profile and the main advantages of the MINLP-based strategy over a non-linear MPC-based scheduling strategy previously developed are highlighted, regarding operating cost, ease of tuning, and ability to adapt to cooling demand variations., Comment: 22 pages, 11 figures. Postprint of the final published work

This work addresses the modelling, power control, and optimization of a thermal energy storage (TES) system combined with a vapour-compression refrigeration facility based on phase change materials (PCM). Given a novel design of a PCM-based TES tank and its interconnection with an existing refrigeration system, the joint dynamic modelling is first studied, exploring the different time scales that coexist at the interconnected system. Diverse operating modes are defined, according to the intended use of the TES tank as a cold-energy buffer to decouple cooling demand and production, whereas the static characteristic and power limits are calculated and show the high coupling between the main cooling powers involved (TES charging/discharging power, and direct power production at the evaporator). In this light, a decoupling control strategy is proposed, where the low-level controllers are simply PI regulators and the refrigerant/secondary mass flows are considered as virtual manipulated variables, applying a feedforward-based cascade strategy. The control performance is evaluated through a thorough simulation that includes all operating modes, where the reference tracking is shown to be fast and reliable enough to address high-level scheduling strategies, where the references on the main cooling powers are intended to be imposed considering economic and efficiency criteria., Comment: 37 pages, 20 figures. Postprint of the final published work

This paper proposes a computationally efficient simulation strategy for cold thermal energy storage (TES) systems based on phase change material (PCM). Taking as a starting point the recent design of a TES system based on PCM, designed to complement a vapour-compression refrigeration plant, the new highly efficient modelling strategy is described and its performance is compared against the pre-existing one. The need for a new computationally efficient approach comes from the fact that, in the near future, such a TES model is intended to be used in combination with the model of the own mother refrigeration plant, in order to address efficient, long-term energy management strategies, where computation time will become a major issue. Comparative simulations show that the proposed computationally efficient strategy reduces the simulation time to a small fraction of the original figure (from around 1/30th till around 1/120th, depending on the particular choice of the main sampling interval), at the expense of affordable inaccuracy in terms of the PCM charge ratio., Comment: 36 pages, 14 figures. Postprint of the final published work

This work is focused on optimal control of mechanical compression refrigeration systems. A reduced-order state-space model based on the moving boundary approach is proposed for the canonical cycle, which eases the controller design. The optimal cycle (that satisfying the cooling demand while maximizing efficiency) is defined by three variables, but only two inputs are available, therefore the controllability of the proposed model is studied. It is shown through optimization simulations how optimal cycles for a range of the cooling demand turn out not to be achieved by keeping the degree of superheating to a minimum. The Practical NMPC and a well-known feedback-plus-feedforward strategy from the literature are compared in simulation, both showing trouble in reaching the optimal cycle, which agrees with the controllability study., Comment: 39 pages, 14 figures. Postprint of the final published work

This paper studies the design and dynamic modelling of a novel thermal energy storage (TES) system combined with a refrigeration system based on phase change materials (PCM). Cold-energy production supported by TES systems is a very appealing field of research, since it allows flexible cold-energy management, combining demand fulfilment with cost reduction strategies. The paper proposes and compares two different simulation models for a cold-energy storage system based on PCM. First, a continuous model is developed, the application of which is limited to decoupled charging/discharging operations. Given such conditions, it is a relatively precise model, useful for the tuning of the TES parameters. The second proposed model is a discrete one, which, despite implementing a discrete approximation of the system behaviour, allows to study more general conditions, such as series of partial charging/discharging operations. Simulation results of both models are compared regarding decoupled charging/discharging operations, and the ability of the discrete model to represent more realistic partial operations is analysed., Comment: 48 pages, 14 figures. Postprint of the final published work

This study investigates the properties of the $T_{\psi\psi}$ tetraquark candidates within a coupled-channels calculation of the $c\bar c- c\bar c$ system, specifically focusing on the $J^P=0^\pm$, $1^\pm$, and $2^\pm$ sectors. The analysis includes various channels containing a $J/\psi$, $\psi^\prime$, $\eta_c$, and $\eta_c^\prime$ meson. By searching for poles in the scattering matrix, a total of 29 states in different $J^P$ sectors with masses ranging from 6.1 to 7.6 GeV/c$^2$ are identified. The study further investigates the masses, widths and branching ratios of these states, leading to the identification of two potential candidates for the experimental $T_{\psi\psi}(6200)$ tetraquark, one candidate for $T_{\psi\psi}(6600)$, two for $T_{\psi\psi}(6700)$, four for $T_{\psi\psi}(6900)$, and three for $T_{\psi\psi}(7200)$ tetraquarks. Additionally, the paper discusses strategies to discriminate between different candidates and explores possible detection channels for further $c\bar c- c\bar c$ states., Comment: 9 pages, 3 tables and 1 figure

This document presents the initial scientific case for upgrading the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) to 22 GeV. It is the result of a community effort, incorporating insights from a series of workshops conducted between March 2022 and April 2023. With a track record of over 25 years in delivering the world's most intense and precise multi-GeV electron beams, CEBAF's potential for a higher energy upgrade presents a unique opportunity for an innovative nuclear physics program, which seamlessly integrates a rich historical background with a promising future. The proposed physics program encompass a diverse range of investigations centered around the nonperturbative dynamics inherent in hadron structure and the exploration of strongly interacting systems. It builds upon the exceptional capabilities of CEBAF in high-luminosity operations, the availability of existing or planned Hall equipment, and recent advancements in accelerator technology. The proposed program cover various scientific topics, including Hadron Spectroscopy, Partonic Structure and Spin, Hadronization and Transverse Momentum, Spatial Structure, Mechanical Properties, Form Factors and Emergent Hadron Mass, Hadron-Quark Transition, and Nuclear Dynamics at Extreme Conditions, as well as QCD Confinement and Fundamental Symmetries. Each topic highlights the key measurements achievable at a 22 GeV CEBAF accelerator. Furthermore, this document outlines the significant physics outcomes and unique aspects of these programs that distinguish them from other existing or planned facilities. In summary, this document provides an exciting rationale for the energy upgrade of CEBAF to 22 GeV, outlining the transformative scientific potential that lies within reach, and the remarkable opportunities it offers for advancing our understanding of hadron physics and related fundamental phenomena., Comment: Updates to the list of authors; Preprint number changed from theory to experiment; Updates to sections 4 and 6, including additional figures

Using proton-proton collisions at centre-of-mass energies $7$, $8$, and $13$ TeV, with a total integrated luminosity of $9\,\text{fb}^{-1}$, the LHCb collaboration has performed amplitude analyses of the $B^+\to D^+D^-K^+$, $B^+\to D^- D_s^+ \pi^+$ and $B^0\to \bar{D}^0 D_s^+ \pi^-$ decays, observing that new $T_{cs}$ and $T_{c\bar s}$ resonances are required in order to explain the experimental data. These signals could be the first observation of tetraquark candidates that do not contain a heavy quark-antiquark pair; in fact, they consist of four different flavours of quarks, one of which is a doubly charged open-charm state. We present herein an analysis of the $T_{cs}$ and $T_{c\bar s}$ states, which is an extension of our recently published study of similar $T_{cc}^+$ exotic candidates. Our theoretical framework is a constituent-quark-model-based coupled-channels calculation of $qq^\prime \bar s \bar c$ and $cq\bar s\bar q^{\prime}$ tetraquark sectors for $T_{cs}$ and $T_{c\bar s}$ structures, respectively. We explore the nature, and pole position, of the singularities that appear in the scattering matrix with spin-parity quantum numbers: $J^P=0^\pm$, $1^\mp$, and $2^\pm$. The constituent quark model has been widely used in the heavy quark sector, and thus all model parameters are already constrained from previous works. This makes our predictions robust and parameter-free. We find many singularities in the solution of various scattering-matrix problems which are either virtual states or resonances, but not bound states. Some of them fit well with the experimental observations of the spin-parity, mass and width of $T_{cs}$ and $T_{c\bar s}$ candidates, and thus tentative assignments are made; however, with caution, because the experimental Breit-Wigner parameters are related to the pole characteristics., Comment: 10 pages, 4 tables

The recently discovered $T_{cc}^+$ is evaluated as a $DD^*$ molecular structure in the $J^P=1^+$ sector. A coupled-channels calculation in charged basis, considering the $D^0D^{*\,+}$, $D^+D^{*\,0}$ and $D^{*\,0}D^{*\,+}$ channels, is done in the framework of a constituent quark model that successfully described other molecular candidates in the charmonium spectrum such as the $X(3872)$. The $T_{cc}^+$ is found as a $D^0D^{*\,+}$ molecule ($87\%$) with a binding energy of $387$ keV/c$^2$ and a width of $81$ keV, in agreement with the experimental measurements. The quark content of the state forces the inclusion of exchange diagrams to treat indistinguishable quarks between the $D$ mesons, which are found to be essential to bind the molecule. The $D^0D^0\pi^+$ line shape, scattering lengths and effective ranges of the molecule are also analyzed, which are found to be in agreement with the LHCb analysis. We search for further partners of the $T_{cc}^+$ in other charm and bottom sectors, finding different candidates. In particular, in the charm sector we find a shallow $J^P=1^+$ $D^+D^{*\,0}$ molecule ($83\%$), dubbed $T_{cc}^\prime$, just $1.8$ MeV above the $T_{cc}^+$ state. In the bottom sector, we find an isoscalar and an isovector $J^P=1^+$ bottom partners, as $BB^*$ molecules lying $21.9$ MeV/c$^2$ ($I=0$) and $10.5$ MeV/c$^2$ ($I=1$), respectively, below the $B^0B^{*\,+}$ threshold., Comment: 11 pages, 3 figures, 7 tables

Hidden-charm pentaquark-like $P_{\psi s}^\Lambda(4459)^0$ and $P_{\psi s}^\Lambda(4338)$ resonances are studied in a constituent quark model as molecular meson-baryon structures. Such states are found in the $J^P(I)=\frac{1}{2}^-(0)$ channel with masses and widths compatible with the experimental measurements in a coupled-channels calculation with all the parameters constrained from previous studies. Other candidates are explored in the $J^P=\frac{1}{2}^-$, $\frac{3}{2}^-$ and $\frac{5}{2}^-$ channels in the charm and bottom sectors, with isospins $0$ ($P_{\psi s}^\Lambda$ and $P_{\Upsilon s}^\Lambda$) and $1$ ($P_{\psi s}^\Sigma$ and $P_{\Upsilon s}^\Sigma$). Additionally, the formalism is extended to study the $P_{\psi ss}^N$ ($P_{\Upsilon ss}^N$) pentaquarks, where eight candidates are predicted as $\bar D_s \Xi_c$ molecules in $I=\frac{1}{2}$, with $J^P=\frac{1}{2}^-$, $\frac{3}{2}^-$ and $\frac{5}{2}^-$ for the charm sector and nine candidates as $B_s \Xi_b$ for the bottom one., Comment: 8 pages, 1 figure, 7 tables

The European Organization for Nuclear Research (CERN) has recently approved a world-unique QCD facility in which an updated version of the external M2 beam line of the CERN SPS in conjunction with a universal spectrometer of the COMPASS experiment is used. One of its main goals is to use highly intense and energetic kaon beams to map out the complete spectrum of excited kaons with an unprecedented precision; having a broad impact not only on low-energy QCD phenomenology, but also on many high-energy particle processes where excited kaons appear, such as the study of CP violation in heavy-meson decays studied at LHCb and Belle~II. In support of the experimental effort, the kaon spectrum is computed herein using a constituent quark model which has been successfully applied to a wide range of hadronic observables, from light to heavy quark sectors, and thus the model parameters are completely constrained. The model's prediction can be used as a template against which to compare the already collected data and future experimental findings, in order to distinguish between conventional and exotic kaon states. We also compare our results with those available in the literature in order to provide some general statements, common to all calculations., Comment: 11 pages, 1 figure, 13 tables

The production of single-charmed baryons $\Lambda_c^+ \Lambda_c^-$, $\Lambda_c^+ \Sigma_c^-$+h.c. and $\Sigma_c^+ \Sigma_c^-$ in $p\bar p$ collisions is studied in the framework of a constituent quark model which has satisfactorily described the $N\bar N$ system and the strangeness production $p\bar p\to \Lambda\bar \Lambda$, $\Lambda\bar\Sigma$ and $\Sigma\bar\Sigma$ processes. Predictions on the total cross sections are analyzed for different approaches to the underlying $n\bar n\to c\bar c$ process, mediated by one gluon annihilation diagrams. The results indicate that the cross section is of the order of $1$ nb between $10-14$ GeV for $\Lambda_c^+\Lambda_c^-$ and $\Lambda_c^+ \Sigma_c^-$ channels, and around $0.01-0.1$ nb for $\Sigma_c^+\Sigma_c^-$. This estimations can be relevant for their future search in facilities like $\bar{P}$ANDA., Comment: 7 pages, 6 figures

The properties of the $B_c$-meson family ($c\bar b$) are still not well determined experimentally because the specific mechanisms of formation and decay remain poorly understood. Unlike heavy quarkonia, i.e. the hidden heavy quark-antiquark sectors of charmonium ($c\bar c$) and bottomonium ($b\bar b$), the $B_c$-mesons cannot annihilate into gluons and they are, consequently, more stable. The excited $B_c$ states, lying below the lowest strong-decay $BD$-threshold, can only undergo through radiative decays and hadronic transitions to the $B_c$ ground state, which then decays weakly. As a result of this, a rich spectrum of narrow excited states below the $BD$-threshold appear, whose total widths are two orders of magnitude smaller than those of the excited levels of charmonium and bottomonium. In a different article, we determined bottom-charmed meson masses using a non-relativistic constituent quark model which has been applied to a wide range of hadron physical observables, and thus the model parameters are completely constrained. Herein, continuing to our study of the $B_c$ sector, we calculate the relevant radiative decay widths and hadronic transition rates between $c\bar b$ states which are below $BD$-threshold. This shall provide the most promising signals for discovering excited $B_c$ states that are below the lowest strong-decay $BD$-threshold. Finally, our results are compared with other models to measure the reliability of the predictions and point out differences., Comment: 13 pages, 9 tables. arXiv admin note: text overlap with arXiv:1601.05093

The discovery of the $Z_c(3900)^\pm$ and $Z_b(10610)^\pm$ structures in the heavy quarkonium spectrum showed the need to incorporate hadron structures beyond the naive $qqq$ and $q\bar q$ systems in quark models. The new charged structure called $Z_{cs}(3985)^-$, spotted in the $K^+$ recoil-mass spectrum close to the $D^-_s D^{*0}/D^{*-}_sD^0$ threshold, is a new evidence in this line. In this work, we analyze the $Z_{cs}(3985)^-$ state, following the calculation of the $Z_c$ and $Z_b$ states using a chiral constituent quark model in a coupled-channels calculation, with all the parameters constrained from previous calculations. The pole structure of the S-matrix shows two virtual poles below the $D_s^-D^{*\,0}$ and $D_s^{*\,-}D^{*\,0}$ thresholds compatible with the $Z_{cs}(3985)^\pm$ and a new predicted $Z_{cs}(4110)^\pm$ structure, the SU(3) flavor partner of the $Z_c(4020)^\pm$. The $K^+$ recoil-mass spectrum is calculated in good agreement with LHCb and BESIII experimental data, with no fine tuning of the model parameters. Our results indicate that the $Z_{cs}(3985)^\pm$ and $Z_{cs}(4000)^\pm$ signals originate from the same virtual state., Comment: 5 pages, 2 figures. Conference proceeding. Submitted to Suplemento de la Revista Mexicana de F\'isica, 19th International conference on hadron spectroscopy and structure in memoriam Simon Eidelman

We explore the possible existence of the $J^{PC}=1^{+-}$ counterpart of the $X(3872)$ state in a coupled-channels calculation within a constituent quark model, with the aim of confirming the existence of the so-called $\tilde{X}(3872)$ state observed by the COMPASS Collaboration. Two states are found in the energy region of the $\tilde X(3872)$ signal, both with almost equal mixture of $c\bar c$ $2^1P_1$ state and $D^*\bar D^{(*)}$ channels: One that can be identified as the dressed $c\bar c$ $2^1P_1$ and a bound state below the $D\bar D^*$ threshold. We provide predictions of strong and radiative decays that could help to clarify the existence of such structures., Comment: 6 pages, 4 tables, 2 figures

The recent discovery of the $D_{s0}(2590)^+$ meson by the LHCb Collaboration has stimulated the analysis of meson-meson channels effects in the two-body quark-antiquark meson spectrum. This resonance, assigned to the radial excitation of the pseudoscalar $D_s^+$ meson, has a mass much lower than the predictions of naive quark models, which could indicate a non-negligible $D^{(*)}K^{(*)}$ coupling which reduces its mass. Based on the importance of nearby meson-meson thresholds in the dynamics of P-wave $D_s$ mesons such as the $D_{s0}^*(2317)^+$ and $D_{s1}(2460)^+$, in this work we perform a coupled-channels calculation including the $D^{(*)}K^{(*)}$, $D_s^{(*)}\omega$ and $D_s^*\eta$ channels, and study the impact of incorporating those channels in the mass of the bare $c\bar s$. The coupling between two and four-quark sectors is done by means of the $^3P_0$ mechanism, with all the parameters constrained from previous studies of the heavy meson spectroscopy. The masses, widths and production line shapes of the resulting state are analyzed., Comment: 7 pages, 3 figures, 3 tables

The discovery of the $X(3872)$ meant the revival of the heavy meson spectroscopy beyond naive $q\bar q$ structures. Once that the $SU(3)$ scheme, which was very useful in the dawn of the quark models, does not work for these states, one has to use new symmetries, like Heavy Quark Spin Symmetry (HQSS) and Heavy Flavor Symmetry (HFS), to look for new states. However, at the energy regions where these new states appear, new factors are involved and it is not straightforward to relate the predictions of the symmetries with the data. In this work, we present a critical analysis of this problem and show, in a coupled-channels model, how the relative position of the bare $Q\bar Q$ states with respect to meson-meson thresholds and the coupling with other channels modulate the strength of the interaction and, hence, modify the structure of the predicted states. We found a possible candidate to the $X(3872)$ partner at $10599$ MeV$/c^2$., Comment: 9 pages, 6 figures, 6 tables

The $Z_b(10610)^\pm$ and $Z_b(10650)^\pm$ are two bottomonium-like structures discovered in the $\pi h_b(mP)$, $\pi \Upsilon(nS)$ and $B^\ast\bar B^{(\ast)}+h.c.$ invariant mass spectra, where $m=\{1,2\}$ and $n=\{1,2,3\}$. Their nature is puzzling due to their charge, which forces its minimal quark content to be $b\bar b u\bar d$ ($b\bar b d\bar u$). Thus, it is necessary to explore four-quark systems in order to understand their inner structure. Additionally, their strong coupling to channels such as $\pi \Upsilon$ and the closeness of their mass to $B^\ast\bar B^{(\ast)}$-thresholds stimulates a molecular interpretation. Within the framework of a constituent quark model which satisfactorily describes a wide range of properties of (non-)conventional hadrons containing heavy quarks, we perform a coupled-channels calculation of the $I^G(J^{PC})=1^+(1^{+-})$ hidden-bottom sector including $B^{(\ast)}\bar B^{\ast}+h.c.$, $\pi h_b$, $\pi \Upsilon$ and $\rho\eta_b$ channels. We analyze the line shapes in the different channels, describing the $\Upsilon(5S)\to \pi B^{(*)}\bar B^{(*)}$ by means of the $^3P_0$ model. Since our description of the line shapes promising, we perform the same coupled-channels calculation for the $Z_b$'s with $J^{--}$, where $J=\{0,1,2\}$. This allows us to obtain a fair description of the corresponding line shapes. The study of the analytic structure of the $S$-matrix suggests that the experimental $Z_b$ structures arise as a combination of several poles with $J^{PC}=0^{--}$, $1^{\pm-}$ and $2^{--}$ quantum numbers nearby the $B\bar B^\ast$ and $B^\ast\bar B^\ast$ thresholds., Comment: 10 pages, 5 figures. arXiv admin note: text overlap with arXiv:1808.00914

The discovery of a new charged structure in the $K^+$ recoil-mass spectrum near the $D^-_s D^{*0}/D^{*-}_sD^0$ threshold, dubbed $Z_{cs}(3985)^-$, reinforce the idea that the structure of hadrons goes beyond the naive $qqq$ and the $q\bar q$ structures. The existence of this state, with quark content $c\bar c s\bar u$, can be expected from the well-established $Z_c(3900)^\pm$ and $Z_c(4020)$ states using SU(3) flavor symmetry. The $Z_c$ structures have been explained using the chiral constituent quark model in a coupled-channels calculation and, in this work, we undertake the study of the $Z_{cs}(3985)^-$ using the same model. We are able to reproduce the $K^+$ recoil-mass spectrum without any fine tuning of the model parameters. The study of the analytical structure of the S-matrix allows us to conclude that the structure is due to the presence of one virtual pole. A second state, the SU(3) flavor partner of the $Z_c(4020)$ is predicted at $\sim\!\! 4110$ MeV/$c^2$. New states in the hidden bottom strange sector are also predicted., Comment: 7 pages, 5 figures, 1 table. arXiv admin note: text overlap with arXiv:1808.00914

Heavy hadron spectroscopy was well understood within the naive quark model until the end of the past century. However, in 2003, the $X(3872)$ was discovered, with puzzling properties difficult to understand in the simple naive quark model picture. This state made clear that excited states of heavy mesons should be coupled to two-meson states in order to understand not only the masses but, in some cases, unexpected decay properties. In this work we will review how the naive quark model can be complemented with the coupling to two hadron thresholds. This program has been already applied to the heavy meson spectrum with the chiral quark model and we show some examples where thresholds are of special relevance., Comment: 24 pages, 8 figures, 5 tables

The lineshapes of specific production experiments of the exotic state such as $X(3872)$ with $J^{PC}=1^{++}$ quantum numbers involving triangle singularities have been found to become highly sensitive to the binding energy of weakly bound states, thus offering in principle the opportunity of benchmark determinations. We critically analyze recent proposals to extract accurately and precisely the $X(3872)$ mass, which overlook an important physical effect by regarding their corresponding production lineshapes as a sharp mass distribution and, thus, neglecting the influence of initial nearby continuum states in the $1^{++}$ channel. The inclusion of these states implies an effective cancellation mechanism which operates at the current and finite experimental resolution of the detectors so that one cannot distinguish between the $1^{++}$ bound-state and nearby $D \bar D^*$ continuum states with the same quantum numbers. In particular, we show that the lineshape for resolutions above 1 MeV becomes rather insensitive to the binding energy unless high statistics is considered. The very existence of the observed bumps is a mere consequence of short distance correlated $\bar D D^*$ pairs, bound or unbound. The cancellation also provides a natural explanation for a recent study reporting missing but unknown decay channels in an absolute branching ratio global analysis of the $X(3872)$., Comment: 11 pages, 8 figures

Thunderstorms and lightnings are natural particle accelerator systems. Terrestrial gamma-ray flashes, caused by relativistic runaway electron avalanches, produce bursts of $X$ and $\gamma$ rays, energetic enough to produce photo-nuclear reactions within the atmosphere. Such reactions cause the generation of new isotopes, which modify the air composition locally and produce new ways of detecting and characterizing this high-energy phenomena. In this work we explore, using the general purpose Monte Carlo transport code FLUKA, the production of secondaries after a Terrestrial gamma-ray flash and analyze the generation of new isotopes in detail. Their abundance, time and energy profiles are studied, which can be useful for establishing new measuring strategies., Comment: 31 pages, 6 figures, 2 tables

The bottom-charmed ($B_c$) mesons are more stable than their charmonium ($c\bar c$) and bottomium ($b\bar b$) partners because they cannot annihilate into gluons. However, the low production cross-sections and signal-to-background ratios avoided until now their clear identification. The recent experimental results reported by CMS and LHCb at CERN open the possibility of having a $B_c$ spectrum as complete as the ones of charmonium and bottomonium. Motivated by this expectation, we compute bottom-charmed meson masses in the region energies in which decay meson-meson thresholds are opened, looking for the analogs to the $X(3872)$ in the $B_c$ spectroscopy. We use a constituent quark model in which quark-antiquark degrees of freedom are complemented by four-body Fock states configurations. The model has been applied to a wide range of hadronic observables, in particular to the $X(3872)$, and thus the model parameters are completely constrained. No extra states are found in the $J^P=0^+$ and $J^P=1^+$ sectors. However, in the $J^P=2^+$ sector we found an additional state very close to the $D^*B^*$ threshold which could be experimentally detected., Comment: 7 pages, 4 tables

The nature of the recently discovered $Z_c$ and $Z_b$ structures is intriguing. Their charge forces its minimal quark content to be $Q\bar Q q\bar q$ (where $Q=\{c,b\}$ and $q=\{u,d\}$). In this work we perform a molecular coupled-channels calculation of the $I^G(J^{PC})=1^+(1^{+-})$ charm and bottom sectors in the framework of a constituent quark model which satisfactorily describes a wide range of properties of (non-)conventional hadrons containing heavy quarks. All the relevant channels are included for each sector, i.e.: The $D^{(\ast)}\bar D^{\ast}+h.c.$, $\pi J/\psi$ and $\rho\eta_c$ channels for the $Z_c$ and $B^{(\ast)}B^{\ast}$ and $\Upsilon(nS)\pi$ ($n=1,2,3$) channels for the $Z_b$ analysis. Possible structures of these resonances will be discussed., Comment: 10 pages, 2 tables, 7 figures. Proceedings of the 24th European Conference on Few-Body Problems in Physics

All existing experimental evidence of the bound state nature of the $X(3872)$ relies on considering its decay products with a finite experimental spectral mass resolution which is typically $\Delta m \ge 2 $MeV and much larger than its alleged binding energy, $B_X=0.00(18)$MeV. On the other hand, we have found recently that there is a neat cancellation in the $1^{++}$ channel for the invariant $D \bar D^*$ mass around the threshold between the continuum and bound state contribution. This is very much alike a similar cancellation in the proton-neutron continuum with the deuteron in the $1^{++}$ channel. Based on comparative fits of experimental cross section deuteron and $X(3872)$ prompt production in pp collisions data with a finite $p_T$ to a common Tsallis distribution we find a strong argument questioning the bound state nature of the state but also explaining the large observed production rate likely consistent with a half-bound state., Comment: 6 pages, 4 figures, 1 table

A constituent quark model, which has recently been successfully applied to the study of heavy quarkonium properties such as its spectrum but also a diverse array of observables related with their electromagnetic, strong and weak decays and reactions, is used herein to compute ground- and excited-state masses of $QQQ$-baryons containing either $c$- or $b$-quarks. Considering the lack of experimental information about the spectra of triply-heavy baryons, we believe that our computation could help on finding new states, since it is expected that phenomenological quark models describe triply-heavy baryons to a similar degree of accuracy as heavy quarkonia. The quark model parameters previously used to describe $c\bar c$ and $b\bar b$ properties have not been modified for this analysis. The non-relativistic three-body bound-state problem is solved by means of the Gau\ss ian expansion method which provides enough accuracy and simplifies the subsequent evaluation of the matrix elements. Several low-lying states with quantum numbers $J^P=\frac{1}{2}^{\pm}$, $\frac{3}{2}^{\pm}$, $\frac{5}{2}^{\pm}$ and $\frac{7}{2}^+$ are reported. We compare our results with those predicted by many other theoretical formalisms. There is a general trend of agreement about the mass of the ground state in each sector of triply-heavy baryons; however, the situation is more puzzling for the excited states and thus appropriate comments on the most relevant features of our comparison are given., Comment: 12 pages, 10 tables, 4 figures

In recent years, the discovery in quarkonium spectrum of several states not predicted by the naive quark model has awakened a lot of interest. A possible description of such states requires the enlargement of the quark model by introducing quark-antiquark pair creation or continuum coupling effects. The unquenching of the quark models is a way to take these new components into account. In the spirit of the Cornell Model, this is usually done by coupling perturbatively a quark-antiquark state with definite quantum numbers to the meson-meson channel with closest threshold. In this work we present a method to coupled quark-antiquark states with meson-meson channels, taking into account effectively the non-perturbative coupling to all quark-antiquark states with the same quantum numbers. The method will be applied to the study of the X(3872) resonance and a comparison with the perturbative calculation will be performed., Comment: 6 pages

The typical binding energy of heavy hadron spectroscopy makes the system accessible to perturbative calculations in terms of non-relativistic QCD. Within NRQCD the predictions of heavy quarkonium energy levels rely on the accurate description of the static QCD potential $V_{\rm QCD}(r)$. Historically, heavy quarkonium spectroscopy was studied using phenomenological approaches such as the Cornell model $V_{\rm Cornell}=-\kappa/r+\sigma\, r$, which assumes a short-distance dominant Coulomb potential plus a liner rising potential that emerges at long distances. Such model works reasonably well in describing the charmonium and bottomonium spectroscopy. However, even when there are physically-motivated arguments for the construction of the Cornell model, there is no conection a priori with QCD parameters. Based on a previous work on heavy meson spectroscopy, we calibrate the Cornell model with NRQCD predictions for the lowest lying bottomonium states at N$^3$LO, in which the bottom mass is varied within a wide range. We show that the Cornell model mass parameter can be identified with the low-scale short-distance MSR mass at the scale $R = 1$ GeV. This identification holds for any value of $\alpha_s$ or the bottom mass. For moderate values of $r$, the NRQCD and Cornell static potentials are in head-on agreement when switching the pole mass to the MSR scheme, which allows to simultaneously cancel the renormalon and sum up large logarithms., Comment: 12 pages, 5 figures. XIII Quark Confinement and the Hadron Spectrum. arXiv admin note: text overlap with arXiv:1811.01982

Along the years, the Cornell Model has been extraordinarily successful in describing hadronic phenomenology, in particular in physical situations for which an effective theory of the strong interactions such as NRQCD cannot be applied. As a consequence of its achievements, a relevant question is whether its model parameters can somehow be related to fundamental constants of QCD. We shall give a first answer in this article by comparing the predictions of both approaches. Building on results from a previous study on heavy meson spectroscopy, we calibrate the Cornell model employing NRQCD predictions for the lowest-lying bottomonium states up to N$^3$LO, in which the bottom mass is varied within a wide range. We find that the Cornell model mass parameter can be identified, within perturbative uncertainties, with the MSR mass at the scale $R = 1\,$GeV. This identification holds for any value of $\alpha_s$ or the bottom mass, and for all perturbative orders investigated. Furthermore, we show that: a) the "string tension" parameter is independent of the bottom mass, and b) the Coulomb strength $\kappa$ of the Cornell model can be related to the QCD strong coupling constant $\alpha_s$ at a characteristic non-relativistic scale. We also show how to remove the $u=1/2$ renormalon of the static QCD potential and sum-up large logs related to the renormalon subtraction by switching to the low-scale, short-distance MSR mass, and using R-evolution. Our R-improved expression for the static potential remains independent of the heavy quark mass value and agrees with lattice QCD results for values of the radius as large as $0.8\,$fm, and with the Cornell model potential at long distances. Finally we show that for moderate values of $r$, the R-improved NRQCD and Cornell static potentials are in head-on agreement., Comment: 22 pages, 13 figures, 3 tables

Since the discovery of the $J/\psi$, the quark model was very successful in describing the spectrum and properties of heavy mesons including only $q\bar q$ components. However since 2003, with the discovery of the $X(3872)$, many states that can not be accommodated on the naive quark model have been discovered, and they made unavoidable to include higher Fock components on the heavy meson states. We will give an overview of the success of the quark model for heavy mesons and point some of the states that are likely to be more complicated structures such as meson-meson molecules., Comment: Contribution to the Proceedings of the 15th International Workshop on Meson Physics - MESON2018

The $Z_{c}(3900)^\pm/Z_c(3885)^\pm$ and $Z_{c}(4020)^\pm$ are two charmonium-like structures discovered in the $\pi J/\psi$ and $D^\ast\bar D^{(\ast)}+h.c.$ invariant mass spectra. Their nature is puzzling due to their charge, which forces its minimal quark content to be $c\bar c u\bar d$ ($c\bar c d\bar u$). Thus, it is necessary to explore four-quark systems in order to understand their inner structure. Additionally, their strong coupling to channels such as $\pi J/\psi$ and the closeness of their mass to $D^\ast\bar D^{(\ast)}$-thresholds stimulates both a molecular interpretation or a coupled-channels threshold effect. In this work we perform a coupled-channels calculation of the $I^G(J^{PC})=1^+(1^{+-})$ sector including $D^{(\ast)}\bar D^{\ast}+h.c.$, $\pi J/\psi$ and $\rho\eta_c$ channels in the framework of a constituent quark model which satisfactorily describes a wide range of properties of (non-)conventional hadrons containing heavy quarks. The meson-meson interactions are dominated by the non-diagonal $\pi J/\psi-D^\ast\bar D^{(\ast)}$ and $\rho\eta_c-D^\ast\bar D^{(\ast)}$ couplings which indicates that the $Z_{c}(3900)^\pm/Z_c(3885)^\pm$ and $Z_{c}(4020)^\pm$ are unusual structures. The study of the analytic structure of the $S$-matrix allows us to conclude that the point-wise behavior of the line shapes in the $\pi J/\psi$ and $D\bar D^*$ invariant mass distributions is due to the presence of two virtual states that produce the $Z_c$ peaks., Comment: 10 pages, 5 figures, 2 tables. Accepted for publication in The European Physical Journal C

The masses of the $D^\ast_{s0}(2317)$ and $D_{s1}(2460)$ resonances lie below the $DK$ and $D^\ast K$ thresholds respectively, which contradicts the predictions of naive quark models and points out to non-negligible effects of the $D^{(\ast)}K$ loops in the dynamics of the even-parity scalar ($J^\pi=0^+$) and axial-vector ($J^\pi=1^+$) $c\bar s$ systems. Recent lattice QCD studies, incorporating the effects of the $D^{(\ast)}K$ channels, analyzed these spin-parity sectors and correctly described the $D^\ast_{s0}(2317)-D_{s1}(2460)$ mass splitting. Motivated by such works, we study the structure of the $D_{s0}^\ast(2317)$ and $D_{s1}(2460)$ resonances in the framework of an effective field theory consistent with heavy quark spin symmetry, and that incorporates the interplay between $D^{(\ast)}K$ meson-meson degrees of freedom and bare P-wave $c\bar s$ states predicted by constituent quark models. We extend the scheme to finite volumes and fit the strength of the coupling between both types of degrees of freedom to the available lattice levels, which we successfully describe. We finally estimate the size of the $D^{(\ast)}K$ two-meson components in the $D^\ast_{s0}(2317)$ and $D_{s1}(2460)$ resonances, and we conclude that these states have a predominantly hadronic-molecular structure, and that it should not be tried to accommodate these mesons within $c\bar{s}$ constituent quark model patterns., Comment: 21 pages, 5 figures. Matches the published version. arXiv admin note: text overlap with arXiv:1706.01247 by other authors

The positive parity $\chi_{cJ}(2P)$ charmonium states are expected to lie around the 3.9 GeV/$c^2$ energy region, according to the predictions of quark models. However, a plethora of states with difficult assignment and unconventional properties have been discovered over the years, i.e., the $X(3872)$, $X(3940)$, $Y(3940)$, $X(3915)$, $X(3860)$ and the $X(3930)$ resonances, which complicates the description of this intriguing region. In this work we analyze the $0^{++}$ and $2^{++}$ sectors, employing a coupled-channels formalism successfully applied to the $1^{++}$ sector, where the $X(3872)$ was described as a $D\bar D^\ast+h.c.$ molecule with a sizable $c\bar c$ $(2^3P_1)$ component. This coupled-channels formalism is based on a widely-used Constituent Quark Model, which describes the quark-quark interactions, and the $^3P_0$ quark pair creation mechanism, used to couple the two and four quark sectors. The recent controversy about the quantum numbers of the $X(3915)$ state, the properties of the $X(3930)$ one and the nature of the new $X(3860)$ resonance are analyzed in a unified theoretical framework, being all the parameters completely constrained from previous calculations in the low-lying heavy quarkonium phenomenology., Comment: 6 pages, 2 tables. XVII International Conference on Hadron Spectroscopy and Structure - Hadron2017

The question on whether or not weakly bound states should be effectively incorporated in a hadronic representation of the QCD partition function is addressed by analyzing the example of the $X(3872)$, a resonance close to the $D\bar D^*$ threshold which has been suggested as an example of a loosely bound molecule. This can be decided by studying the $D \bar D^*$ scattering phase-shifts in the $J^{PC}=1^{++}$ channel and their contribution to the level density in the continuum, which also gives information on its abundance in a hot medium. In this work, it is shown that, in a purely molecular picture, the bound state contribution cancels the continuum, resulting in a null occupation number density at finite temperature, which implies the $X(3872)$ does not count below the Quark-Gluon Plasma crossover ($T \sim 150$MeV). However, if a non-zero $c \bar c$ component is present in the $X(3872)$ wave function such cancellation does not occur for temperatures above $T\gtrsim 250$MeV., Comment: 4 pages, 2 figures. XVII International Conference on Hadron Spectroscopy and Structure

The non-perturbative nature of QCD at hadronic scales implied the development of phenomenological approaches such as quark models or, more recently, computer-based calculations using Lattice QCD. However, the unique properties of heavy quarkonium systems allow an entire calculation in terms of non-relativistic perturbative QCD. In this work, the bottomonium spectrum, up to $n = 3$, and the ground state charmonium states, are analyzed in the framework of Non-Relativistic Quantum Chromodynamics at N$^3$LO. For bottomonium, finite charm quark mass effects in the QCD potential and the $\overline{MS}$-pole mass relation are incorporated to the highest known order, $\mathcal{O}(\varepsilon^3)$ in the $\Upsilon$-scheme counting. The bottom quark pole mass is expressed in terms of the MSR mass, a low-scale short-distance mass which cancels the $u = 1/2$ renormalon of the static potential. We study the $n_\ell = 3$ and $n_\ell = 4$ schemes, finding a negligible difference between the two if finite $m_c$ effects are smoothly incorporated in the MSR mass definition. We find that bottomonium $n=3$ states are not well behaved within perturbative NRQCD. Hence, fitting to the $n=1,2$ $b\bar b$ states we obtain $\overline{m}_b(\overline{m}_b) = 4.216\pm 0.039$ GeV. Similarly, from the lowest lying charmonium states we find $\overline{m}_c(\overline{m}_c)=1.273 \pm 0.054$ GeV., Comment: 6 pages, 2 figures. XVII International Conference on Hadron Spectroscopy and Structure