Search

We have investigated the internal structure of the open- and hidden-charmed ( DD ∗ / D ¯ D ∗ ) molecules in the unified framework. We first fit the experimental lineshape of the T cc + state and extract the DD ∗ interaction, from which the T cc + is assumed to arise solely. Then we obtain the D D ¯ ∗ interaction by charge conjugation. Our results show that the D D ¯ ∗ interaction is attractive but insufficient to form X (3872) as a bound state. Instead, its formation requires the crucial involvement of the coupled channel effect between the D D ¯ ∗ and c c ¯ components, although the c c ¯ accounts for approximately 1 % only. Besides X (3872) , we have obtained a higher-energy state around 3957.9 MeV with a width of 16.7 MeV, which may be a potential candidate for the X (3940). In J PC = 1 + - sector, we have found two states related to the iso-scalar X ̃ (3872) and h c (2 P) , respectively. Our combined study provides valuable insights into the nature of these DD ∗ / D D ¯ ∗ exotic states. [ABSTRACT FROM AUTHOR]

[Display omitted] We perform a lattice QCD calculation of the η c → 2 γ decay width using a model-independent method that requires no momentum extrapolation of the off-shell form factors. This method also provides a straightforward and simple way to examine the finite-volume effects. The calculation is accomplished using N f = 2 twisted mass fermion ensembles. The statistically significant excited-state effects are observed and eliminated using a multi-state fit. The impact of fine-tuning the charm quark mass is also examined and confirmed to be well-controlled. Finally, using three lattice spacings for the continuum extrapolation, we obtain the decay width Γ η c γ γ = 6.67 (16) stat (6) syst keV, which differs significantly from the Particle Data Group's reported value of Γ η c γ γ = 5.4 (4) keV (2.9 σ tension). We provide insight into the comparison between our findings, previous theoretical predictions, and experimental measurements. [ABSTRACT FROM AUTHOR]

[Display omitted] We propose that the X (3915) observed in the J / ψ ω channel is the same state as the χ c 2 (3930) , and the X (3960) , observed in the D s + D s - channel, is an S -wave D s + D s - hadronic molecule. In addition, the J PC = 0 + + component in the B + → D + D - K + assigned to the X (3915) in the current Review of Particle Physics has the same origin as the X (3960) , which has a mass around 3.94 GeV. To check the proposal, the available data in the D D ¯ and D s + D s - channels from both B decays and γ γ fusion reaction are analyzed considering both the D D ¯ - D s D ¯ s - D * D ¯ * - D s * D ¯ s * coupled channels with 0 + + and a 2 + + state introduced additionally. It is found that all the data in different processes can be simultaneously well reproduced, and the coupled-channel dynamics produce four hidden-charm scalar molecular states with masses around 3.73, 3.94, 3.99 and 4.23 GeV, respectively. The results may deepen our understanding of the spectrum of charmonia as well as of the interactions between charmed hadrons. [ABSTRACT FROM AUTHOR]

We study the processes, e − e + → γ ⁎ γ ⁎ → J / ψ + J / ψ , and e − e + → γ ⁎ γ ⁎ → η c + η c at s = 10.6 GeV in the framework of 4 × 4 Bethe-Salpeter equation. For J / ψ + J / ψ production, the dominant contribution is through fragmentation process, while for η c + η c production, the quark rearrangement diagrams contribute. Our results of cross section for J / ψ + J / ψ and ψ (2 S) + ψ (2 S) are compatible with the experimental upper limits set by Belle Collaboration, while in the absence of experimental data for η c (1 S) + η c (1 S) , and η c (2 S) + η c (2 S) production, we have given theoretical prediction of their cross sections, and compared with NRQCD prediction. [ABSTRACT FROM AUTHOR]

The polarizations of prompt and non-prompt ▪ and ψ (2S) mesons are measured in proton-proton collisions at s = 13 TeV, using data samples collected by the CMS experiment in 2017 and 2018, corresponding to a total integrated luminosity of 103.3 fb − 1. Based on the analysis of the dimuon decay angular distributions in the helicity frame, the polar anisotropy, λ ϑ , is measured as a function of the transverse momentum, p T , of the charmonium states, in the 25–120 and 20–100 GeV ranges for the ▪ and ψ (2S) , respectively. The non-prompt polarizations agree with predictions based on the hypothesis that, for p T ≳ 25 GeV , the non-prompt ▪ and ψ (2S) are predominantly produced in two-body B meson decays. The prompt results clearly exclude strong transverse polarizations, even for p T exceeding 30 times the ▪ mass, where λ ϑ tends to an asymptotic value around 0.3. Taken together with previous measurements, by CMS and LHCb at s = 7 TeV, the prompt polarizations show a significant variation with p T , at low p T. [ABSTRACT FROM AUTHOR]

We report the p + p and p + d differential cross sections measured in the SeaQuest experiment for J / ψ and ψ (2 S) production at ▪ beam energy covering the forward x -Feynman (x F) range of 0.5 < x F < 0.9. The measured cross sections are in good agreement with theoretical calculations based on the nonrelativistic QCD (NRQCD) using the long-distance matrix elements deduced from a recent global analysis of proton- and pion-induced charmonium production data. The σ ψ (2 S) / σ J / ψ cross section ratios are found to increase as x F increases, indicating that the q q ¯ annihilation process has larger contributions in the ψ (2 S) production than the J / ψ production. The σ p d / 2 σ p p cross section ratios are observed to be significantly different for the Drell-Yan process and J / ψ production, reflecting their different production mechanisms. We find that the σ p d / 2 σ p p ratios for J / ψ production at the forward x F region are sensitive to the d ¯ / u ¯ flavor asymmetry of the proton sea, analogous to the Drell-Yan process. The transverse momentum (p T) distributions for J / ψ and ψ (2 S) production are also presented and compared with data collected at higher center-of-mass energies. [ABSTRACT FROM AUTHOR]

We study the potential of X (3872) at finite temperature in the Born-Oppenheimer approximation under the assumption that it is a tetraquark. We argue that, at large number of colors, it is a good approximation to assume that the potential consists in a real part plus a constant imaginary term. The real part is then computed adapting an approach by Rothkopf and Lafferty and using as input lattice QCD determinations of the potential for hybrids. This model allows us to qualitatively estimate at which temperature range the formation of a heavy tetraquark is possible, and to propose a qualitative picture for the dissociation of the state in a medium. Our approach can be applied to other suggested internal structures for the X (3872) and to other exotic states. [ABSTRACT FROM AUTHOR]

Masses and current couplings of the charmonium and bottomonium hybrids c ‾ g c and b ‾ g b with spin-parities J PC = 0 + + , 0 + − , 0 − + , 0 − − and 1 + + , 1 + − , 1 − + , 1 − − are calculated using QCD two-point sum rule method. Computations are performed by taking into account gluon condensates up to dimension 12 including terms ∼ 〈 g s 3 G 3 〉 2. The parameters of the bottom-charm hybrids b ‾ g c with quantum numbers J PC = 0 + , 0 − , 1 + , and 1 − are calculated as well. In computations the dominance of the pole contribution to sum rule results is ensured. It is demonstrated that all charmonia hybrids decay strongly to two-meson final states. The bottomonium hybrids 0 − + and 1 − + as well as the bottom-charm hybrid mesons 0 − (+) and 1 − (+) may be stable against strong two-meson decay modes. Results of the present work are compared with ones obtained using the sum rule and alternative approaches. Our predictions for parameters of the heavy hybrid mesons may be useful to study their various decay channels which are important for interpretation of ongoing and future experiments. [ABSTRACT FROM AUTHOR]

[Display omitted] First evidence of a structure in the J / ψ Λ invariant mass distribution is obtained from an amplitude analysis of Ξ b - → J / ψ Λ K - decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of 3.1 σ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be 4458.8 ± 2.9 - 1.1 + 4.7 MeV and 17.3 ± 6.5 - 5.7 + 8.0 MeV , respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited Ξ - states, Ξ 1690 - and Ξ 1820 - , are seen for the first time in a Ξ b - decay, and their masses and widths are measured with improved precision. The analysis is performed using pp collision data corresponding to a total integrated luminosity of 9 fb - 1 , collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV. [ABSTRACT FROM AUTHOR]

Within the nonrelativistic QCD (NRQCD) factorization framework, we compute the long-awaited O (α s 2) corrections for the exclusive double charmonium production process at B factories, i.e. , e + e − → J / ψ + η c at s = 10.58 GeV. We confirm that NRQCD factorization does hold at next-to-next-to-leading-order (NNLO) for exclusive double charmonium production. It is found that including the NNLO QCD correction considerably reduces the renormalization scale dependence, and also implies the reasonable perturbative convergence behavior for this process. We also include both O (v 2) and O (α s v 2) corrections for this process. With all the available corrections lumped together, our most comprehensive prediction is consistent with both the BaBar and Belle measurement within errors. [ABSTRACT FROM AUTHOR]

The possibility of the existence of mesons with two or more quark-antiquark pairs is investigated with a new application of the Thomas-Fermi (TF) statistical quark model. Quark color couplings are treated in a mean field manner similar to a previous application to baryons, and short and concise expressions for energies are derived. We find that, on average, quarks only interact with antiquarks in such systems. The TF differential equation is constructed and systems with heavy-light quark content are examined. Three types of mesonic systems are defined. In the case of charm quarks, multi-charmonium, multi- Z meson and multi- D meson family types are examined. System analogs for bottom quarks are also constructed. Quantitative trends for system energies of mesonic quark matter are extracted as a function of the number of quark pairs. We find indications from energy plots that multi- Z type mesons (and their bottom quark analogs) are actually stable for a range of quark number pairs. At this initial stage we have not yet included explicit spin interaction couplings between quarks, but we can take one level of degeneracy into account in our two-inequivalent TF function construction. [ABSTRACT FROM AUTHOR]

Heavy vector mesons detected after a heavy ion collision are important sources of information about the quark gluon plasma. The fraction of such particles that survive the plasma phase and reach the detectors is related to the dissociation degree inside the thermal medium. A consistent picture for the thermal behaviour of charmonium and bottomonium quasi-states in a thermal medium was obtained recently using a holographic bottom up model. This model captures the heavy flavour spectroscopy of masses and decay constants in the vacuum (zero temperature) and is consistently extended to finite temperature. The spectral functions that emerge provide a description of the dissociation process in terms of the broadening of the quasi-state peaks with temperature. The holographic approach makes it possible to determine also the quasinormal modes. They are gravity solutions representing the quasi-particle states in the thermal medium, with complex frequencies related to the thermal mass and width. The quasinormal modes for charmonium and bottomonium have been studied very recently and a consistent description of the dissociation process was found. An additional factor can affect the dissociation process: strong magnetic fields are expected to be present when the plasma is formed by non-central heavy ion collisions. So, it is important to understand the effect of such fields on the heavy meson dissociation scenario. Here we extend the holographic determination of quasinormal modes for the case when magnetic fields are present. The real and imaginary parts of the mode frequencies are determined for different values of background eB field. The associated dispersion relations for heavy quarks moving inside the plasma are also investigated for both c c ¯ and b b ¯. [ABSTRACT FROM AUTHOR]

Abstract Measurements of prompt ψ (2S) meson production cross sections in proton–lead (pPb) and proton–proton (pp) collisions at a nucleon–nucleon center-of-mass energy of s NN = 5.02 TeV are reported. The results are based on pPb and pp data collected by the CMS experiment at the LHC, corresponding to integrated luminosities of 34.6 nb − 1 and 28.0 pb − 1 , respectively. The nuclear modification factor R pPb is measured for prompt ψ (2S) in the transverse momentum range 4 < p T < 30 GeV / c and the center-of-mass rapidity range − 2.4 < y CM < 1.93. The results on ψ (2S) R pPb are compared to the corresponding modification factor for prompt J / ψ mesons. The results point to different nuclear effects at play in the production of the excited charmonium state compared to the ground state, in the region of backward rapidity and for p T < 10 GeV / c. [ABSTRACT FROM AUTHOR]

Recent progresses on charmoniumlike state have significantly enriched the discovery of new hadronic states, providing exciting opportunities for further investigations into the fascinating realm of charmonium physics. In this letter, we focus on the vector charmonium family and perform a detailed analysis of the recently observed e + e − → π + D 0 D ⁎ − process. Our findings demonstrate a agreement between the observed peak structures and the predicted characterized energy level structure of higher vector charmonia including the ψ (4220) , ψ (4380) , ψ (4415) , and ψ (4500) , which are derived from an unquenched potential model. This discovery challenges conventional understanding of higher charmonia above 4 GeV and offers fresh insights into the dynamics of charm and anti-charm quarks in the formation of these states. Furthermore, the identification of these higher charmonia in the precisely measured π + D 0 D ⁎ − open-charm decay channel would serve as compelling evidence supporting the unquenched scenario and contribute to a deeper understanding of the nonperturbative aspects of the strong interaction. [ABSTRACT FROM AUTHOR]

The measurements of the inclusive J / ψ yield at midrapidity (| y | < 0.9) and forward rapidity (2.5 < y < 4) in Pb–Pb collisions at s NN = 5.02 TeV with the ALICE detector at the LHC are reported. The inclusive J / ψ production yields and nuclear modification factors, R AA , are measured as a function of the collision centrality, J / ψ transverse momentum (p T), and rapidity. The J / ψ average transverse momentum and squared transverse momentum (〈 p T 〉 and 〈 p T 2 〉) are evaluated as a function of the centrality at midrapidity. Compared to the previous ALICE publications, here the entire Pb–Pb collisions dataset collected during the LHC Run 2 is used, which improves the precision of the measurements and extends the p T coverage. The p T -integrated R AA shows a hint of an increasing trend towards unity from semicentral to central collisions at midrapidity, while it is flat at forward rapidity. The p T -differential R AA shows a strong suppression at high p T with less suppression at low p T where it reaches a larger value at midrapidity compared to forward rapidity. The ratio of the p T -integrated yields of J / ψ to those of D0 mesons is reported for the first time for the central and semicentral event classes at midrapidity. Model calculations implementing charmonium production via the coalescence of charm quarks and antiquarks during the fireball evolution (transport models) or in a statistical approach with thermal weights are in good agreement with the data at low p T. At higher p T , the data are well described by transport models and a model based on energy loss in the strongly-interacting medium produced in nuclear collisions at the LHC. [ABSTRACT FROM AUTHOR]

In present work we study the production of ground and excited charmonium states in e − e + → γ χ c J (n P) (J = 0 , 1) , and e − e + → γ η c (n S) , through leading order (LO) diagrams, which proceed through exchange of a virtual photon that couples to γ and η c / χ c J through the triangular quark loop diagram, in the framework of 4 × 4 Bethe-Salpeter equation (BSE), at center of mass energies s = 10.6 GeV (Belle energy), and 4.6 GeV (BESIII energy). The amplitude simplifies to a general form required by Lorentz-covariance, in terms of its form factors. The cross sections for these processes with leading order diagrams alone at s = 10.6 GeV provide a sizable contribution, which might be mainly due to the BSE being a fully relativistic approach that incorporates the relativistic effect of quark spins and can also describe internal motion of constituent quarks within the hadron in a relativistically covariant manner. Our results are compared with recent Belle data at 10.6 GeV, and BESIII data at 4.6 GeV, as well as other models. Plots of cross sections versus the center-of mass energy, s reveal mild fluctuations in their behaviour for all the three processes in the low energy (s = 4 – 6 GeV) region, and are analyzed in terms of the form factors. [ABSTRACT FROM AUTHOR]

We study the radiative decay of X (3872) based on the assumption that X (3872) is regarded as a c c ‾ charmonium with quantum number J P C = 1 + + (J , P , C represent the spin, parity and charge conjugation, respectively). The form factors of X (3872) transitions to J / ψ γ and ψ ′ γ (ψ ′ denotes ψ (2 S) throughout the paper) are calculated in the framework of the covariant light-front quark model. The phenomenological wave function of a meson depends on the parameter β , whose inverse essentially describes the confinement scale. In the present work, the parameters β for the vector J / ψ and ψ ′ mesons will be determined through their decay constants, which are obtained from the experimental values of their partial decay widths to the electron-positron pair. For X (3872) , we determined the value of β by the decay width of X (3872) → ψ ′ γ. Then, we examined the width of X (3872) → J / ψ γ in a manner of parameter-free prediction and compared it with the experimental value. As a result, an inconsistency or contradiction occurs between the widths of X (3872) → J / ψ γ and X (3872) → ψ ′ γ. We thus conclude that X (3872) cannot be a pure c c ‾ resonance and that other components are necessary in its wave function. [ABSTRACT FROM AUTHOR]

In a research article appeared in this journal [1], the LHCb Collaboration has presented an extraordinary result on the mass spectrum of J/ -pairs produced in proton-proton high energy collisions. The term good diquark was coined in Ref. [14], to contrast the bad diquark, spin S=1 and flavour symmetric, which would give rise to really exotic mesons. The same valence quarks present in Jaffe's tetraquark, are rearranged into two color singlet hadrons bound by the same force that causes nuclear binding. Assuming the diquark cc in colour 3, the total spin of each diquark is S=1: colour antisymmetry and Fermi statistics imply a bad diquark. [Extracted from the article]

Abstract In this paper we report our results on quarkonium spectral functions in the vector channel obtained from quenched lattice QCD simulations at T ∈ [0.75,2.25] T c. The calculations have been performed on very large and fine isotropic lattices where both charm and bottom quarks can be treated relativistically. The spectral functions are reconstructed using the Maximum Entropy Method. We study the dissociation of quarkonium states from the temperature dependence of the spectral functions and estimate heavy quark diffusion coefficients using the low-frequency behavior of the vector spectral functions. [ABSTRACT FROM AUTHOR]

Abstract Quarkonia, i.e. bound states of b b ‾ and c c ‾ quarks, are powerful observables to study the properties of nuclear matter under extreme conditions. The formation of a Quark-Gluon Plasma (QGP), which is predicted by lattice QCD calculations at high temperatures as reached at the LHC energies, has a strong influence on the production and behavior of quarkonia. The latest ALICE results on bottomonium and charmonium production in nucleus−nucleus collisions are presented. This includes measurements of the ϒ (1 S) and ϒ (2 S) nuclear modification factor (R AA) at forward rapidity and the J / ψ R AA and ν 2 as a function of centrality, p T and rapidity in Pb–Pb collisions at s NN = 5.02 TeV. Also, first results from J / ψ measurements in Xe–Xe collisions at s NN = 5.44 TeV are presented. Further on, the experimental results are compared to various calculations from theoretical models. [ABSTRACT FROM AUTHOR]

Abstract A wealth of data on charmonium production in Pb-Pb collisions from the LHC experiments has provided strong evidence for (re-)generation as a dominant production mechanism at low transverse momentum. We present an important extension of the statistical hadronisation model to describe J/ ψ transverse momentum distributions based on input parameters from hydrodynamical simulations. Comparison to the data allows the testing of the degree of thermalisation of charm quarks in the quark-gluon plasma. To this end we will report analyses of the J/ ψ transverse momentum spectra in Pb-Pb collisions at s N N = 2.76 and 5.02 TeV. [ABSTRACT FROM AUTHOR]

Abstract The present work continues a series of the KEDR measurements of the R value that started in 2010 at the VEPP-4M e + e − collider. By combining new data with our previous results in this energy range we measured the values of R uds and R at nine center-of-mass energies between 3.08 and 3.72 GeV. The total accuracy is about or better than 2.6% at most of energy points with a systematic uncertainty of about 1.9%. Together with the previous precise R measurement at KEDR in the energy range 1.84–3.05 GeV, it constitutes the most detailed high-precision R measurement near the charmonium production threshold. [ABSTRACT FROM AUTHOR]

Abstract We study the dissociation of heavy vector mesons in a thermal medium from the point of view of the configurational entropy. Bottomonium and charmonium vector mesons in a plasma are represented using a holographic AdS/QCD model. The quasinormal modes, describing the quasiparticle states, are determined for a representative range of temperature and their corresponding CE is then computed. The main result indicates that the CE is an important contrivance to investigate the stability of the heavy mesons against dissociation in the thermal medium. [ABSTRACT FROM AUTHOR]

Abstract We study the J / ψ photoproduction from nuclei at near-threshold incident photon energies of 5–11 GeV within the nuclear spectral function approach by considering incoherent direct (γ N → J / ψ N) and two-step (γ p → P c + (4450) , P c + (4450) → J / ψ p) photon–nucleon charmonium creation processes. We calculate the absolute and relative excitation functions within the different scenarios for in-medium modification of the directly photoproduced J / ψ mesons. We show that the overall subthreshold J / ψ production in γA reactions reveals some sensitivity to adopted in-medium modification scenarios for J / ψ mesons only if branching ratio B r [ P c + (4450) → J / ψ p ] ∼ 1% and less. Our studies also demonstrate that the presence of the P c + (4450) resonance in J / ψ photoproduction produces above threshold additional enhancements in the behavior of the total J / ψ creation cross section on nuclei, which could be also studied in the future JLab experiments at the upgraded up to 12 GeV CEBAF facility to provide further evidence for its existence. [ABSTRACT FROM AUTHOR]

Using a data sample of 448.1 × 10 6 ψ ( 3686 ) events collected with the BESIII detector at the BEPCII collider, we report the first observation of the electromagnetic Dalitz decay ψ ( 3686 ) → η ′ e + e − , with significances of 7.0 σ and 6.3 σ when reconstructing the η ′ meson via its decay modes η ′ → γ π + π − and η ′ → π + π − η ( η → γ γ ), respectively. The weighted average branching fraction is determined to be B ( ψ ( 3686 ) → η ′ e + e − ) = ( 1.90 ± 0.25 ± 0.11 ) × 10 − 6 , where the first uncertainty is statistical and the second systematic. [ABSTRACT FROM AUTHOR]

We have searched for exclusive production of exotic charmonia in the reaction μ + N → μ + ( J / ψ π + π − ) π ± N ′ using COMPASS data collected with incoming muons of 160 GeV/ c and 200 GeV/ c momentum. In the J / ψ π + π − mass distribution we observe a signal with a statistical significance of 4.1 σ . Its mass and width are consistent with those of the X ( 3872 ) . The shape of the π + π − mass distribution from the observed decay into J / ψ π + π − shows disagreement with previous observations for X ( 3872 ) . The observed signal may be interpreted as a possible evidence of a new charmonium state. It could be associated with a neutral partner of X ( 3872 ) with C = − 1 predicted by a tetraquark model. The product of cross section and branching fraction of the decay of the observed state into J / ψ π + π − is determined to be 71±28(stat)±39(syst) pb. [ABSTRACT FROM AUTHOR]

We study η c - and J / ψ -isoscalar meson bound states in the hadro-charmonium picture. In the hadro-charmonium, the four q q ¯ c c ¯ quarks are arranged in terms of a compact charm-anticharm pair, c c ¯ , embedded in light hadronic matter, q q ¯ , with q = u , d or s . The interaction between the charmonium core and the light matter can be written in terms of the multipole expansion in QCD, with the leading term being the E 1 interaction with chromo-electric field E a . The spectrum of η c - and J / ψ -isoscalar meson bound states is calculated and the results compared with the existing experimental data. [ABSTRACT FROM AUTHOR]

Charmonium spectral functions in vector and pseudoscalar channels at finite temperature are investigated through the complex Borel sum rules and the maximum entropy method. Our approach enables us to extract the peaks corresponding to the excited charmonia, ψ ′ and η c ′ , as well as those of the ground states, J / ψ and η c , which has never been achieved in usual QCD sum rule analyses. We show the spectral functions in vacuum and their thermal modification around the critical temperature, which leads to the almost simultaneous melting (or peak disappearance) of the ground and excited states. [ABSTRACT FROM AUTHOR]

The masses of the low lying charmonium states, namely, the J / Ψ , Ψ ( 3686 ) , and Ψ ( 3770 ) are shifted downwards due to the second order Stark effect. In p ¯ + Au collisions at 6–10 GeV we study their in-medium propagation. The time evolution of the spectral functions of these charmonium states is studied with a Boltzmann–Uehling–Uhlenbeck (BUU) type transport model. We show that their in-medium mass shift can be observed in the dilepton spectrum. Therefore, by observing the dileptonic decay channel of these low lying charmonium states, especially for Ψ ( 3686 ) , we can gain information about the magnitude of the gluon condensate in nuclear matter. This measurement could be performed at the upcoming PANDA experiment at FAIR. [ABSTRACT FROM AUTHOR]

Whether the Y ( 4260 ) can couple to open charm channels has been a crucial issue for understanding its nature. The available experimental data suggest that the cross section line shapes of exclusive processes in e + e − annihilations have nontrivial structures around the mass region of the Y ( 4260 ) . As part of a series of studies of the Y ( 4260 ) as mainly a D ¯ D 1 ( 2420 ) + c . c . molecular state, we show that the partial widths of the Y ( 4260 ) to the two-body open charm channels of e + e − → D ⁎ D ¯ ⁎ and D s ⁎ D ¯ s ⁎ are much smaller than that to D ¯ D ⁎ π + c . c . . The line shapes measured by the Belle Collaboration for these two channels can be well described by the vector charmonium states ψ ( 4040 ) , ψ ( 4160 ) and ψ ( 4415 ) together with the Y ( 4260 ) . It turns out that the interference of the Y ( 4260 ) with the other charmonia produces a dip around 4.22 GeV in the e + e − → D ⁎ D ¯ ⁎ cross section line shape. The data also show an evidence for the strong coupling of the Y ( 4260 ) to the D D ¯ 1 ( 2420 ) , in line with the expectation in the hadronic molecular scenario for the Y ( 4260 ) . [ABSTRACT FROM AUTHOR]

An interesting controversy has emerged challenging the widely accepted nature of the X ( 3915 ) and the X ( 3930 ) resonances, which had initially been assigned to the χ c 0 ( 2 P ) and χ c 2 ( 2 P ) c c ¯ states, respectively. To unveil their inner structure, the properties of the J P C = 0 + + and J P C = 2 + + charmonium states in the energy region of these resonances are analyzed in the framework of a constituent quark model. Together with the bare q q ¯ states, threshold effects due to the opening of nearby meson–meson channels are included in a coupled-channels scheme calculation. We find that the structure of both states is dominantly molecular with a probability of bare q q ¯ states lower than 45%. Our results favor the hypothesis that X ( 3915 ) and X ( 3930 ) resonances arise as different decay mechanisms of the same J P C = 2 + + state. Moreover we find an explanation for the recently discovered M = 3860 MeV / c 2 as a J P C = 0 + + 2 P state and rediscover the lost Y ( 3940 ) as an additional state in the J P C = 0 + + family. [ABSTRACT FROM AUTHOR]

We present new results for the suppression of high transverse momentum charmonium [ J / ψ , ψ ( 2 S ) ] and bottomonium [ ϒ ( 1 S ) , ϒ ( 2 S ) , ϒ ( 3 S ) ] states in Pb+Pb collisions at the Large Hadron Collider. Our theoretical formalism combines the collisional dissociation of quarkonia, as they propagate in the quark–gluon plasma, with the thermal wavefunction effects due to the screening of the Q Q ¯ attractive potential in the medium. We find that a good description of the relative suppression of the ground and higher excited quarkonium states, transverse momentum and centrality distributions is achieved, when comparison to measurements at a center-of-mass energy of 2.76 TeV is performed. Theoretical predictions for the highest Pb+Pb center-of-mass energy of 5.02 TeV at the LHC, where new experimental results are being finalized, are also presented. [ABSTRACT FROM AUTHOR]

We make use of published yields for D -mesons and J / ψ in Pb+Pb collisions at ALICE and a schematic description of the expansion of the hadron gas to study D -meson collisions during the hadronic break-up phase as a production mechanism for charmonium in relativistic heavy ion collisions at the Large Hadron Collider. Our calculation is based on chemical reaction rates with thermal cross sections for an effective meson interaction among pseudoscalar and vector mesons. We find that due to regeneration, the newly measured J / ψ yields are consistent with anywhere from roughly 25% to 110% of the total yield present at hadronization time. This allows us to bound the fractional abundance of J / ψ immediately after hadronization: 0.28 ≤ d N 0 J / ψ / d y d N eq J / ψ / d y ≤ 1.13. Our results are robust under the relaxation of the particulars of our schematic description and imply that it will be difficult to distinguish regeneration during hadronization from regeneration by final-state hadronic interactions. Therefore, regeneration must be taken into account when modeling. [ABSTRACT FROM AUTHOR]

Inspired by the recent precise data, we perform model-independently an isospin decomposition of the timelike octet baryons electromagnetic form factors. As noted in our previous work, the relative magnitude of isoscalar and isovector component is determined with the input of data on various isospin channels. Herein we further assert that their relative phase can be constraint by the phase difference of oscillatory modulation of effective form factors between isospin channels. The framework is extended to analyze the data of differential cross sections and applied to the form factors of nucleon and hyperons with detail and isospin non-conservation of charmonium decay into baryon-anti-baryon as well. We address that isospin analysis is meaningful when the isospin broken scale is compared to or smaller than the uncertainties of data. [ABSTRACT FROM AUTHOR]

Accounting for the LHCb observation that the reported hidden-charm strange pentaquark P c s (4459) 0 can split into two substructures, P c s (4455) 0 and P c s (4468) 0 , with a mass difference of 13 MeV as well as the newly observed hidden-charm pentaquark resonance P c s (4338) 0 with strangeness, we study within the double-peak scenario for the P c s (4459) 0 state the near-threshold J / ψ meson production from protons and nuclei by considering incoherent direct non-resonant (K − p → J / ψ Λ) and two-step resonant (K − p → P c s i 0 → J / ψ Λ , i = 1 , 2, 3; P c s 1 0 = P c s (4338) 0 , P c s 2 0 = P c s (4455) 0 , P c s 3 0 = P c s (4468) 0) charmonium production processes with the main goal of clarifying the possibility to observe within this scenario both above two substructures contributing to the P c s (4459) 0 state and the P c s (4338) 0 resonance in this production. We calculate the absolute excitation functions, energy and momentum distributions for the non-resonant, resonant and for the combined (non-resonant plus resonant) production of J / ψ mesons on protons as well as on carbon and tungsten target nuclei at near-threshold incident antikaon beam momenta by assuming the spin-parity assignments of the hidden-charm resonances P c s (4338) 0 , P c s (4455) 0 and P c s (4468) 0 as J P = (1 / 2) − , J P = (1 / 2) − and J P = (3 / 2) − within four different realistic choices for the branching ratios of their decays to the J / ψ Λ mode (0.125, 0.25, 0.5 and 1%) as well as for two options for the branching fraction of their decays to the K − p channel (0.01 and 0.001%). We show that these combined observables reveal clear sensitivity to these scenarios. Hence, they may be an important tool to provide further evidence for the existence of the above strange hidden-charm pentaquark resonances. [ABSTRACT FROM AUTHOR]

We study the production of the light J P C = 1 − + hybrid isoscalars η 1 ′ (1855) and the yet undiscovered η 1 (1660) as intermediate states in the radiative decays of the charmonium (J / ψ) to two conventional mesons using a flavor symmetric Lagrangian. For this purpose, we use the J / ψ → γ η 1 ′ (1855) → γ η η ′ process as the reference. We find that some of the decay channels have branching ratios similar to or larger than that of the γ η η ′ channel and are sensitive to the mixing between the hybrid isoscalars. We propose that relatively stable γ η f 1 (1285) channel be explored for the presence of the light hybrid isoscalar η 1 h y b (1660). We also exploit the strong decay channels containing at least one vector meson to study the radiative decays of the whole hybrid nonet { π 1 (1600) , K 1 h y b (1750) , η 1 h y b (1660) , η 1 ′ (1855) }. We find that the hybrids cannot radiatively decay into the I = 0 pseudoscalars. Furthermore, the vector decay channels ((ρ / ω / ϕ) γ) of the hybrid isoscalars are sensitive to the strangeness content of the hybrids. We also provide estimates for the branching fractions for the radiative production and partial widths for the radiative decays of the hybrids. [ABSTRACT FROM AUTHOR]

We study the charmonium coherent photoproduction and hadroproduction consistently with modifications from both cold and hot nuclear matters. The strong electromagnetic fields from fast moving nucleus interact with the other target nucleus, producing abundant charmonium in the extremely low transverse momentum region p T < 0.1 GeV/c. This results in significative enhancement of J / ψ nuclear modification factor in semi-central and peripheral collisions. In the middle p T region such as p T < 3 ∼ 5 GeV/c, J / ψ final yield is dominated by the combination process of single charm and anti-charm quarks moving in the deconfined matter, c + c ¯ → J / ψ + g . In the higher p T region, J / ψ production are mainly from parton initial hard scatterings at the beginning of nucleus–nucleus collisions and decay of B hadrons. We include all of these production mechanisms and explain the experimental data well in different colliding centralities and transverse momentum regions. [ABSTRACT FROM AUTHOR]

Bottomonium and charmonium, representing quarkonia states, are scrutinized under the point of view of the information theory, in the AdS/QCD holographic setup. A logarithmic measure of information, comprised by the configurational entropy, is here employed to quantitatively study quarkonia radially excited S -wave states. The configurational entropy provides data regarding the relative dominance and the abundance of the bottomonium and charmonium states, whose underlying information is more compressed, in the Shannon's theory meaning. The derived configurational entropy, therefore, identifies the lower phenomenological prevalence of higher S -wave resonances and higher masses quarkonia in Nature. [ABSTRACT FROM AUTHOR]

We calculate the Wilson coefficients of dimension 6 gluon operators with spin indices in the two point correlation function of the heavy scalar, pseudoscalar, and axialvector currents. Our result completes the list of all Wilson coefficients of gluon operators up to dimension 6 for the correlation functions between heavy quark currents without derivatives. We then use the result to investigate the stability of the QCD sum rule results for the η c , J / Ψ , χ c 0 , and χ c 1 mesons near T c . While the inclusion of the dimension 6 operators increases the stability of the sum rules for all currents, all of them break down slightly above T c with that for the J / ψ persisting to relatively highest temperature. [ABSTRACT FROM AUTHOR]

It is shown that standard constituent quark models produce ( c ¯ c q q q ) hidden-charm pentaquarks, where c denotes the charmed quark and q a light quark, which lie below the lowest threshold for spontaneous dissociation and thus are stable in the limit where the internal c ¯ c annihilation is neglected. The binding is a cooperative effect of the chromoelectric and chromomagnetic components of the interaction, and it disappears in the static limit with a pure chromoelectric potential. Their wave function contains color sextet and color octet configurations for the subsystems and can hardly be reduced to a molecular state made of two interacting hadrons. These pentaquark states could be searched for in the experiments having discovered or confirmed the hidden-charm meson and baryon resonances. [ABSTRACT FROM AUTHOR]

We present a holographic bottom up model for the thermal behavior of c c ¯ vector mesons in a finite temperature and density plasma. There is a clear physical interpretation for the three input energy parameters of the model. Two of them are related to the mass spectrum of the heavy meson. Namely the quark mass and the string tension of the quark–anti-quark interaction. The third parameter is a large energy scale associated with the non-hadronic meson decay. In such a process the heavy meson is transformed into a much lighter state by electroweak processes. The corresponding transition amplitude is assumed to depend on the energy scale associated with this large mass variation. With this three parameter model one can fit the masses and decay constants of J / Ψ and three radial excitations with an rms error of 20.7%. Using the geometry of a charged black hole, one finds the spectral function for charmonium states inside a plasma at finite temperature and density. The charmonium dissociation in the medium is represented by the decrease in the height of the spectral function peaks. [ABSTRACT FROM AUTHOR]

Ultra-peripheral Pb-Pb collisions, in which the two nuclei pass close to each other, but at an impact parameter greater than the sum of their radii, provide information about the initial state of nuclei. In particular, heavy vector meson production, where the particle mass sets a hard scale, proceeds in such collisions by photon-gluon interactions, and gives access to nuclear PDFs. The ALICE collaboration has published measurements of J / ψ and ψ ( 2 S ) photoproduction in ultra-peripheral collisions in LHC Run 1 at forward ( J / ψ ) and mid-rapidity, and has obtained a substantially larger data set in 2015 from LHC Run 2, allowing much more detailed studies of the production mechanism to be performed. In particular, the increased energy and more detailed measurements in the forward region in Run 2 give access to significantly lower values of Bjorken- x than in previous studies. In this talk, the latest available results from Run 2 will be given. [ABSTRACT FROM AUTHOR]

The suppression of charmonium states in heavy-ion collisions is a phenomenon understood as a consequence of quark gluon plasma formation in the hot, dense system formed in heavy ion collisions at the LHC. In addition to hot matter effects in heavy-ion collisions, so-called cold nuclear effects that modify charmonium production are also present. Therefore, a full assessment requires detailed studies in both A+A and p +A collisions. Based on p +Pb data collected in 2013 and pp and Pb+Pb data collected in 2015 at the LHC, the ATLAS experiment has studied prompt and non-prompt J / ψ and ψ (2S) production via the dimuon decay final states. The production yields and excited-to-ground state yield ratios, measured in p +Pb and Pb+Pb with respect to that measured in pp collision data, are presented in intervals of transverse momentum, rapidity and centrality. [ABSTRACT FROM AUTHOR]

The availability at the LHC of the largest collision energy in pp collisions allows a significant advance in the measurement of J / ψ production as function of event multiplicity. The interesting relative increase observed with data at the LHC at s = 7 TeV and at RHIC at s = 0.2 TeV is studied now at unprecedented multiplicities at s = 13 TeV . The measurement at mid-rapidity in the dielectron channel with ALICE is presented and discussed in comparison to predictions from available theoretical models and to data at lower energies. [ABSTRACT FROM AUTHOR]

ALICE at the LHC provides unique capabilities to study charmonium production at low transverse momenta ( p T ). At central rapidity, ( | y | < 0.8 ), ALICE can reconstruct J/ ψ via their decay into two electrons down to zero p T . Results at mid-rapidity on the inclusive J/ ψ nuclear modification factor R A A as a function of centrality in Pb-Pb collisions at s NN = 5.02 TeV and comparisons to lower energies and models are shown. In addition, the yield of the J/ ψ produced with very low p T in the most peripheral collisions and the J/ ψ elliptic flow ( v 2 ) are also presented. [ABSTRACT FROM AUTHOR]

We present the first results from the STAR MTD of mid-rapidity charmonium measurements via the di-muon decay channel in p+p, p+Au, and Au+Au collisions at s NN = 200 GeV at RHIC. The inclusive J / ψ production cross section in p+p collisions can be described by the Non-Relativistic QCD (NRQCD) formalism coupled with the color glass condensate effective theory (CGC) at low transverse momentum ( p T ) and next-to-leading order NRQCD at high p T . The nuclear modification factor in p+Au collisions for inclusive J / ψ is below unity at low p T and consistent with unity at high p T , which can be described by calculations including both nuclear PDF and nuclear absorption effects. The double ratio of inclusive J / ψ and ψ ( 2 S ) production rates for 0 < p T < 10 GeV/ c at mid-rapidity between p+p and p+Au collisions is measured to be 1.37 ± 0.42 ± 0.19. The nuclear modification factor in Au+Au collisions for inclusive J / ψ shows significant J / ψ suppression at high p T in central collisions and can be qualitatively described by transport models including dissociation and regeneration contributions. [ABSTRACT FROM AUTHOR]

The ALICE collaboration has measured the inclusive charmonium production at forward rapidity in Pb–Pb and p–Pb collisions at s NN = 5.02 TeV and s NN = 8.16 TeV , respectively. In Pb–Pb collisions, the J/ ψ and ψ (2S) nuclear modification factors ( R AA ), as well as the J/ ψ elliptic flow ( v 2 ) and averaged squared transverse momentum ( 〈 p T 2 〉 ), are presented. In p–Pb collisions, the J/ ψ nuclear modification factor ( R pPb ) as a function of p t and rapidity is presented. In both systems, our measurements are compared to theoretical calculations and to the results at lower energies. [ABSTRACT FROM AUTHOR]