Search

A reaction model for γ + p → J / ψ + p photoproduction, which exposes the c c ¯ content of the photon in making the transition γ → c c ¯ + P → J / ψ and couples the intermediate c c ¯ system to the proton's valence quarks via Pomeron (P) exchange, is used to deliver a description of available data, viz. both differential and total cross sections from near threshold, where data has newly been acquired, to invariant mass W ≈ 300 GeV. The study suggests that it is premature to link existing γ + p → J / ψ + p data with, for instance, in-proton gluon distributions, the quantum chromodynamics trace anomaly, or pentaquark production. Further developments in reaction theory and higher precision data are necessary before the validity of any such connections can be assessed. [ABSTRACT FROM AUTHOR]

In this brief note, we confront our results on diffractive photoproduction of J / ψ mesons with the putative gluon shadowing ratio defined as R g = σ (γ A → J / ψ A) / σ IA. , where σ IA is the result in impulse approximation. Building on our earlier description of the process in the color-dipole approach, where we took into account the rescattering of c c ¯ states only, we demonstrate that the inclusion of c c ¯ g -Fock states improves the description at small x commonly associated with gluon shadowing. [ABSTRACT FROM AUTHOR]

The mass and width of the tensor tetraquark T = b b c ‾ c ‾ with spin-parity J P = 2 + are calculated in the context of the QCD sum rule method. The tetraquark T is modeled as a diquark-antidiquark state built of components b T C γ μ b and c ‾ γ ν C c ‾ T with C being the charge conjugation matrix. The mass m = (12.795 ± 0.095) GeV of the exotic tensor meson T is found by means of the two-point sum rule approach. Its full width Γ is evaluated by considering processes T → B c − B c − , B c − B c ⁎ − , and B c ⁎ − B c ⁎ −. Partial widths of these decays are computed by means of the three-point sum rule approach which is used to determine the strong couplings at relevant tetraquark-meson-meson vertices. Predictions obtained for the width Γ T = 55.5 − 9.9 + 10.6 MeV , as well as the mass of the tetraquark T can be useful in investigations of fully heavy four-quark mesons. [ABSTRACT FROM AUTHOR]

The global spin alignment of the vector meson has been observed in relativistic heavy ion collisions, but its theoretical origin is still on hot debates. Here we propose to apply the light front framework to explain this phenomenon since the light front form explicitly describes the hadron spin including both the quark spin and the orbital angular momentum. After applying the light front spinor, we find that the spin alignment in the polarization of vector mesons with ρ 00 > 1 / 3 can be naturally manifested and in particular, the obtained spin alignment for ϕ meson is in good agreement with the experimental data. This implies that to explain the spin alignment it is important to properly include the contribution from the gluon interactions that are presented in terms of the orbital angular momentum of the hadron bound state. [ABSTRACT FROM AUTHOR]

Using a symmetry-preserving truncation of the quantum field equations describing hadron properties, parameter-free predictions are delivered for pion and kaon elastic electromagnetic form factors, F P = π , K , thereby unifying them with kindred results for nucleon elastic electromagnetic form factors. Regarding positive-charge states, the analysis stresses that the presence of scaling violations in QCD entails that Q 2 F P (Q 2) should exhibit a single maximum on Q 2 > 0. Locating such a maximum is both necessary and sufficient to establish the existence of scaling violations. The study predicts that, for charged π , K mesons, the Q 2 F P (Q 2) maximum lies in the neighbourhood Q 2 ≃ 5 GeV2. Foreseeable experiments will test these predictions and, providing their Q 2 reach meets expectations, potentially also provide details on the momentum dependence of meson form factor scaling violation. [ABSTRACT FROM AUTHOR]

We present the light-quark mass dependence of the Λ (1405) resonance at leading order in a renormalizable framework of covariant chiral effective field theory. The meson-baryon scattering amplitudes, which are obtained by solving the scattering equation within time-ordered perturbation theory, follow the quark mass trajectory of the Coordinated Lattice Simulations consortium. At M π ≈ 200 MeV and M K ≈ 487 MeV, our parameter-free prediction of Λ (1405) poles is consistent with the recent lattice results of BaSc Collaboration [Phys. Rev. Lett. 132, 051901 (2024)]. Varying the pion mass from 135 MeV to 400 MeV, we present the evolution of double-pole positions of Λ (1405) : the higher pole remains a resonance around the K ¯ N threshold; whereas the lower pole undergoes a transition from resonance to a virtual state, and ultimately to a bound state of the π Σ system, which could be verified by the forthcoming lattice QCD simulations. [ABSTRACT FROM AUTHOR]

We report on the results of the first search for the production of axion-like particles (ALPs) via Primakoff production on nuclear targets, γ A → a A , in the "SRC-CT" experiment using the GlueX detector at Jefferson Lab. This search uses an integrated luminosity of 100 pb ⋅ − 1 nucleon on a 12C target with a real photon beam of energies 6 < E γ < 10.8 GeV, and explores the mass region of 200 < m a < 450 MeV via the decay a → γ γ. This mass range is between the π 0 and η meson masses, which enables the use of the measured η meson production rate to obtain absolute bounds on the ALP production with reduced sensitivity to experimental luminosity and detection efficiency. We find no evidence for an ALP, consistent with previous searches in the quoted mass range, and present limits on the effective photon coupling scale of O (1 TeV − 1). We further find that the ALP production limit we obtain is hindered by the peaking structure of the non-target-related dominant background the in GlueX spectrometer, which we treat by using data on 4He to estimate and subtract it. We comment on how this search can be improved in a future higher-statistics dedicated measurement. [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]

We analyze the modifications that a dense nuclear medium induces in the D s 0 ⁎ (2317) ± and D s 1 (2460) ±. In the vacuum, we consider them as isoscalar D (⁎) K and ▪ S -wave bound states, which are dynamically generated from effective interactions that lead to different Weinberg compositeness scenarios. Matter effects are incorporated through the two-meson loop functions, taking into account the self energies that the D (⁎) , ▪, K , and ▪ develop when embedded in a nuclear medium. Although particle-antiparticle [ D s 0 , s 1 (⁎) (2317 , 2460) + versus D s 0 , s 1 (⁎) (2317 , 2460) − ] lineshapes are the same in vacuum, we find extremely different density patterns in matter. This charge-conjugation asymmetry mainly stems from the very different kaon and antikaon interaction with the nucleons of the dense medium. We show that the in-medium lineshapes found for these resonances strongly depend on their D (⁎) K /▪ molecular content, and discuss how this novel feature can be used to better determine/constrain the inner structure of these exotic states. [ABSTRACT FROM AUTHOR]

In this article, we analyze the electromagnetic form factors of the vector heavy-light mesons to the pseudoscalar heavy-light mesons in the framework of three-point QCD sum rules, where the contributions of vacuum condensate terms 〈 q ‾ q 〉 , 〈 q ‾ g s σ G q 〉 , 〈 g s 2 G 2 〉 , 〈 f 3 G 3 〉 and 〈 q ‾ q 〉 〈 g s 2 G 2 〉 are considered. With these results, we also obtain the radiative decay widths of the vector heavy-light mesons and then compare our results with those of other collaboration's. The final results about the radiative decay widths are Γ (D ⁎ 0 → D 0 γ) = 1.74 − 0.37 + 0.40 keV, Γ (D ⁎ + → D + γ) = 0.17 − 0.07 + 0.08 keV, Γ (D s ⁎ → D s γ) = 0.029 − 0.008 + 0.009 keV, Γ (B ⁎ 0 → B 0 γ) = 0.018 − 0.005 + 0.006 keV, Γ (B ⁎ + → B + γ) = 0.015 − 0.007 + 0.007 keV and Γ (B s ⁎ → B s γ) = 0.016 − 0.005 + 0.003 keV. [ABSTRACT FROM AUTHOR]

We solve for the ρ -meson's wave functions from a light-front QCD Hamiltonian determined for its constituent quark-antiquark and quark-antiquark-gluon Fock components, with a three-dimensional confinement using basis light-front quantization. From this, we obtain the leading-twist valence quark's parton distribution functions and transverse momentum-dependent parton distributions inside the ρ -meson. These results are qualitatively consistent with those of other models. We also demonstrate the important effects of a dynamical gluon on the ρ -meson's gluon densities, helicity, transversity, and tensor polarized distributions. [ABSTRACT FROM AUTHOR]

The azimuthal anisotropy of ▪ mesons in high-multiplicity proton-lead collisions is studied using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 8.16 TeV. The ▪ mesons are reconstructed using their dimuon decay channel. The anisotropy is characterized by the second Fourier harmonic coefficients, found using a two-particle correlation technique, in which the ▪ mesons are correlated with charged hadrons. A large pseudorapidity gap is used to suppress short-range correlations. Nonflow contamination from the dijet background is removed using a low-multiplicity subtraction method, and the results are presented as a function of ▪ transverse momentum. The azimuthal anisotropies are smaller than those found for charmonia in proton-lead collisions at the same collision energy, but are consistent with values found for ▪ mesons in lead-lead interactions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. [ABSTRACT FROM AUTHOR]

We point out a new mechanism giving rise to anomalous tau neutrino appearance at the near detectors of beam-focused neutrino experiments, without extending the neutrino sector. The charged mesons (π ± , K ±) produced and focused in the target-horn system can decay to a (neutrino-philic) light mediator via the helicity-unsuppressed three-body decays. If such a mediator carries non-vanishing hadronic couplings, it can also be produced via the bremsstrahlung of the incident proton beam. The subsequent decay of the mediator to a tau neutrino pair results in tau neutrino detection at the near detectors, which is unexpected under the standard three-flavor neutrino oscillation paradigm. We argue that the signal flux from the charged meson decays can be significant enough to discover the light mediator signal at the on-axis liquid-argon near detector of the DUNE experiment, due to the focusing of charged mesons. In addition, we show that ICARUS-NuMI, an off-axis near detector of the NuMI beam, as well as DUNE, can observe a handful of tau neutrino events induced by beam-proton bremsstrahlung. [ABSTRACT FROM AUTHOR]

Measurements of the elliptic (v 2) and triangular (v 3) azimuthal anisotropy coefficients are presented for ▪ mesons produced in ▪ hadron decays (nonprompt ▪ mesons) in lead-lead collisions at s NN = 5.02 TeV. The results are compared with previously published charm meson anisotropies measured using prompt ▪ mesons. The data were collected with the CMS detector in 2018 with an integrated luminosity of 0.58 nb − 1. Azimuthal anisotropy is sensitive to the interactions of quarks with the hot and dense medium created in heavy ion collisions. Comparing results for prompt and nonprompt ▪ mesons can assist in understanding the mass dependence of these interactions. The nonprompt results show lower magnitudes of v 2 and v 3 and weaker dependences on the meson transverse momentum and collision centrality than those found for prompt ▪ mesons. The results are in agreement with theoretical predictions that include a mass dependence in the interactions of quarks with the medium. [ABSTRACT FROM AUTHOR]

In the last decade a Quasi-Particle Model (QPM) has been developed to study charm quark dynamics in ultra-relativistic heavy-ion collisions supplying a satisfactory description of the main observables for D meson and providing an estimate of the space-diffusion coefficient D s (T) from the phenomenology. In this paper, we extend the approach to bottom quarks describing their propagation in the quark-gluon plasma within an event-by-event full Boltzmann transport approach followed by a coalescence plus fragmentation hadronization. We find that QPM approach is able to correctly predict the first available data on R A A (p T) and v 2 (p T) of single-electron from B decays without any parameter modification w.r.t. the charm. We show also predictions for centralities where data are not yet available for both v 2 (p T) and v 3 (p T). Moreover, we discuss the significant breaking of the expected scaling of the thermalization time τ t h with M Q / T , discussing the evolution with mass of D s (T) to better assess the comparison to lQCD calculations. We find that at T = T c charm quark D s (T) is about a factor of 2 larger than the asymptotic value for M → ∞ , while bottom D s (T) is only a 20% higher. This implies a D s (T) which is consistent within the current uncertainty to the most recent lattice QCD calculations with dynamical quarks for M → ∞. [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]

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]

We study the Z c s (3985) and Z c s (4000) exotic states in the decays of Λ b baryons through a molecular scenario. In the final state interaction, the Λ b → Λ c + D s (⁎) − decays are followed by the Λ c + D s (⁎) − to Z c s − p rescatterings via exchange of a D (⁎) meson. We predict a branching fraction of (3.1 − 2.6 + 1.4) × 10 − 4 for Λ b → Z c s − p , which can be measured in the Λ b → J / ψ K (⁎) − p decay. This study proposes a new approach to test the molecular model, and guides future experimental searches for the Z c s (3985) and Z c s (4000). [ABSTRACT FROM AUTHOR]

In a quasi-particle model of QCD matter at finite temperature with thermal masses for quarks and gluons from hard thermal loops, the equation of state (EOS) can be described by an effective temperature dependence of the strong coupling g (T). Assuming the same effective coupling between the exchanged gluon and thermal partons, the EOS can also be related to parton energy loss. Based on the quasi-particle linear Boltzmann transport (QLBT) model coupled to a (3+1)-dimensional viscous hydrodynamic model of the quark-gluon plasma (QGP) evolution and a hybrid fragmentation-coalescence model for heavy quark hadronization, we perform a Bayesian analysis of the experimental data on D meson suppression R AA and anisotropy v 2 at RHIC and the LHC. We achieve a simultaneous constraint on the QGP EOS and the heavy quark transport coefficient, both consistent with the lattice QCD results. [ABSTRACT FROM AUTHOR]

Photoproduction of π 0 π ± -pairs from quasifree nucleons bound in the deuteron has been investigated to study the helicity dependence of this reaction. Measurements with a liquid deuterium target were used to extract the unpolarized cross sections for reactions on protons and neutrons. A deuterated, longitudinally polarized solid-butanol target, together with a circularly polarized photon beam, determined the double polarization observable E. From these results the spin-dependent cross sections σ 1 / 2 and σ 3 / 2 , corresponding to the anti-parallel and parallel spin configurations of the beam photon and target nucleon, have been derived. The measurements were performed at the Mainz MAMI accelerator with tagged, circularly-polarized photon beams produced via bremsstrahlung from longitudinally polarized electron beams. The reaction products were detected with an almost 4 π solid-angle covering calorimeter composed of the Crystal Ball and TAPS detectors, supplemented by plastic scintillation detectors for charged particle identification. The results are sensitive to sequential decays of nucleon resonances via intermediate states and also to the decay of nucleon resonances by emission of charged ρ mesons, and are compared to recent model results. [ABSTRACT FROM AUTHOR]

The spin and parity of the charmed mesons D s ⁎ + , D ⁎ 0 and D ⁎ + are determined for the first time to be J P = 1 − with significances greater than 10 σ over other hypotheses of 2 + and 3 − , using an e + e − collision data sample with an integrated luminosity of 3.19 fb−1 collected by the BESIII detector at a center-of-mass energy of 4.178 GeV. Different spin-parity hypotheses are tested via a helicity amplitude analysis of the processes e + e − → D s ⁎ + D s − , D ⁎ 0 D 0 and D ⁎ + D − , with D s ⁎ + → D s + γ , D ⁎ 0 → D 0 π 0 , and D ⁎ + → D + π 0. The results confirm the quark model predictions. [ABSTRACT FROM AUTHOR]

We study the CP-odd and CP-even observables of the B mesons decaying into a baryon and antibaryon. We estimate these observables through the P 0 3 model and chiral selection rule. The decay branching ratio of B + → p Λ ‾ is calculated to be (2.31 ± 0.69) × 10 − 7 , which is consistent with the current experiments. The effects of the B − B ‾ oscillations are considered, which largely suppress the direct CP asymmetries in the B s 0 decays. We suggest the experiments to visit B s 0 → Λ (→ p π −) Λ ‾ (→ p ‾ π +) , where the time-averaged CP-odd observables are estimated to be large. The direct CP asymmetries of B + → p Λ ‾ and B 0 → p p ‾ are found to be (26.2 ± 7.9) % and (− 3.1 ± 0.9) % for a positive strong phase and (− 36.9 ± 11.1) % and (4.2 ± 1.3) % for a negative strong phase, respectively. [ABSTRACT FROM AUTHOR]

It has been a challenge to understand the experimental data on both the nuclear modification factor and elliptic flow of D 0 mesons in p −Pb collisions at LHC energies. In this work, we study these collisions with an improved multi-phase transport model. By including the independent fragmentation and a significant Cronin effect (i.e., transverse momentum broadening) for charm quarks, we provide the first simultaneous description of the D 0 meson R pA and v 2 data at p T ≤ 8 GeV/ c. The model also reasonably describes the D 0 meson p T spectra and the low- p T charged hadron spectra, R pA and v 2. Our results show that both parton interactions and the Cronin effect are important for the D 0 meson R pA , while parton interactions are mostly responsible for the D 0 meson v 2. It is thus essential to include the Cronin effect for the simultaneous description of the D 0 meson R pA and v 2. This work implies that the Cronin effect could also be important for heavy hadrons in large systems. [ABSTRACT FROM AUTHOR]

The measurement of the production of f 0 (980) in inelastic pp collisions at s = 5.02 TeV is presented. This is the first reported measurement of inclusive f 0 (980) yield at LHC energies. The production is measured at midrapidity, | y | < 0.5 , in a wide transverse momentum range, 0 < p T < 16 GeV/ c , by reconstructing the resonance in the f 0 (980) → π + π − hadronic decay channel using the ALICE detector. The p T -differential yields are compared to those of pions, protons and ϕ mesons as well as to predictions from the HERWIG 7.2 QCD-inspired Monte Carlo event generator and calculations from a coalescence model that uses the AMPT model as an input. The ratio of the p T -integrated yield of f 0 (980) relative to pions is compared to measurements in e + e − and pp collisions at lower energies and predictions from statistical hadronisation models and HERWIG 7.2. A mild collision energy dependence of the f 0 (980) to pion production is observed in pp collisions from SPS to LHC energies. All considered models underpredict the p T -integrated 2 f 0 (980) /(π + + π −) ratio. The prediction from the canonical statistical hadronisation model assuming a zero total strangeness content of f 0 (980) is consistent with the data within 1.9 σ and is the closest to the data. The results provide an essential reference for future measurements of the particle yield and nuclear modification in p–Pb and Pb–Pb collisions, which have been proposed to be instrumental to probe the elusive nature and quark composition of the f 0 (980) scalar meson. [ABSTRACT FROM AUTHOR]

Meson and anti-meson mixing processes constitute an important source of constraints on models that give tree level contributions to flavor violating neutral processes. In electroweak SU (3) L × U (1) N models, where anomaly cancellation requires that one family of quarks transforms differently from the other ones, processes involving flavor changing neutral currents gain tree level contributions mediated by gauge and scalar fields. Here, we firstly investigate the contributions of the neutral scalar that mimics the standard Higgs to the K 0 − K ¯ 0 , B 0 − B ¯ 0 , and D 0 − D ¯ 0 mixing processes and confront our predictions with experiments. The results will determine the quark mixing matrices V L u , d. In possession of this information we, next, evaluate the contributions of the neutral gauge bosons Z ′ and Z to the K 0 − K ¯ 0 , B 0 − B ¯ 0 , and D 0 − D ¯ 0 processes. This realistic approach to meson transitions will provide severe bounds on M Z ′ and Z − Z ′ mixing angle. [ABSTRACT FROM AUTHOR]

The production yields of non-prompt D s + mesons, namely D s + mesons from beauty-hadron decays, were measured for the first time as a function of the transverse momentum (p T) at midrapidity (| y | < 0.5) in central and semi-central Pb–Pb collisions at a centre-of-mass energy per nucleon pair s NN = 5.02 TeV with the ALICE experiment at the LHC. The D s + mesons and their charge conjugates were reconstructed from the hadronic decay channel D s + → ϕ π + , with ϕ → K − K + , in the 4 < p T < 36 GeV / c and 2 < p T < 24 GeV / c intervals for the 0–10% and 30–50% centrality classes, respectively. The measured yields of non-prompt D s + mesons are compared to those of prompt D s + and non-prompt D 0 mesons by calculating the ratios of the production yields in Pb–Pb collisions and the nuclear modification factor R AA. The ratio between the R AA of non-prompt D s + and prompt D s + mesons, and that between the R AA of non-prompt D s + and non-prompt D 0 mesons in central Pb–Pb collisions are found to be on average higher than unity in the 4 < p T < 12 GeV / c interval with a statistical significance of about 1.6 σ and 1.7 σ , respectively. The measured R AA ratios are compared with the predictions of theoretical models of heavy-quark transport in a hydrodynamically expanding QGP that incorporate hadronisation via quark recombination. [ABSTRACT FROM AUTHOR]

We address the issue of the compositeness of hadronic states and demonstrate that starting with a genuine state of nonmolecular nature, but which couples to some meson-meson component to be observable in that channel, if that state is blamed for a bound state appearing below the meson-meson threshold it gets dressed with a meson cloud and it becomes pure molecular in the limit case of zero binding. We discuss the issue of the scales, and see that if the genuine state has a mass very close to threshold, the theorem holds, but the molecular probability goes to unity in a very narrow range of energies close to threshold. The conclusion is that the value of the binding does not determine the compositeness of a state. However, in such extreme cases we see that the scattering length gets progressively smaller and the effective range grows indefinitely. In other words, the binding energy does not determine the compositeness of a state, but the additional information of the scattering length and effective range can provide an answer. We also show that the consideration of a direct attractive interaction between the mesons in addition to having a genuine component, increases the compositeness of the state. Explicit calculations are done for the T c c (3875) state, but are easily generalized to any hadronic system. [ABSTRACT FROM AUTHOR]

Strange axial-vector kaons, K 1 , and f 1 meson resonances are investigated in the 4-flavor AdS/QCD model. Their underlying differential configurational entropy is computed and the mass spectra of higher-excited resonances, in both these mesonic families, are achieved and discussed. This technique merges the 4-flavor AdS/QCD and experimental data regarding the mass spectrum of K 1 and f 1 meson resonances that have been already detected and reported in the Particle Data Group, also bringing forth a route to explore physical features of the next generation of resonances in the K 1 and f 1 meson families. [ABSTRACT FROM AUTHOR]

This letter reports the first measurement of spin alignment, with respect to the helicity axis, for D ⁎ + vector mesons and their charge conjugates from charm-quark hadronisation (prompt) and from beauty-meson decays (non-prompt) in hadron collisions. The measurements were performed at midrapidity (| y | < 0.8) as a function of transverse momentum (p T) in proton–proton (pp) collisions collected by ALICE at the centre-of-mass energy s = 13 TeV. The diagonal spin density matrix element ρ 00 of D ⁎ + mesons was measured from the angular distribution of the D ⁎ + → D 0 (→ K − π +) π + decay products, in the D ⁎ + rest frame, with respect to the D ⁎ + momentum direction in the pp centre of mass frame. The ρ 00 value for prompt D ⁎ + mesons is consistent with 1/3, which implies no spin alignment. However, for non-prompt D ⁎ + mesons an evidence of ρ 00 larger than 1/3 is found. The measured value of the spin density element is ρ 00 = 0.455 ± 0.022 (stat.) ± 0.035 (syst.) in the 5 < p T < 20 GeV / c interval, which is consistent with a Pythia 8 Monte Carlo simulation coupled with the EvtGen package, which implements the helicity conservation in the decay of D ⁎ + meson from beauty mesons. In non-central heavy-ion collisions, the spin of the D ⁎ + mesons may be globally aligned with the direction of the initial angular momentum and magnetic field. Based on the results for pp collisions reported in this letter it is shown that alignment of non-prompt D ⁎ + mesons due to the helicity conservation coupled to the collective anisotropic expansion may mimic the signal of global spin alignment in heavy-ion collisions. [ABSTRACT FROM AUTHOR]

Tests of the T, CP and CPT symmetries in the neutral kaon system are performed by the direct comparison of the probabilities of a kaon transition process to its symmetry-conjugate. The exchange of in and out states required for a genuine test involving an antiunitary transformation implied by time-reversal is implemented exploiting the entanglement of K 0 K ‾ 0 pairs produced at a ϕ -factory. A data sample collected by the KLOE experiment at DAΦNE corresponding to an integrated luminosity of about 1.7 fb−1 is analysed to study the Δ t distributions of the ϕ → K S K L → π + π − π ± e ∓ ν and ϕ → K S K L → π ± e ∓ ν 3 π 0 processes, with Δ t the difference of the kaon decay times. A comparison of the measured Δ t distributions in the asymptotic region Δ t ≫ τ S allows to test for the first time T and CPT symmetries in kaon transitions with a precision of few percent, and to observe CP violation with this novel method. [ABSTRACT FROM AUTHOR]

The screening masses of mesons provide a gauge invariant and definite order parameter of chiral symmetry restoration. Different mesonic correlation lengths for flavor non-singlets, at least up to NLO, are well-defined gauge invariant physical quantities calculated earlier using the perturbative resummation techniques. The NLO perturbative results match the available non-perturbative lattice QCD results at the high-temperature regime. We have studied the spatial correlation lengths of various mesonic observables using the non-perturbative Gribov resummation, both for quenched QCD and (2 + 1) flavor QCD. The study follows the analogies with the NRQCD effective theory, a well-known theory for studying heavy quarkonia at zero temperature. [ABSTRACT FROM AUTHOR]

The production cross sections of B s 0 mesons and charge conjugates are measured in proton-proton (pp) and PbPb collisions via the exclusive decay channel B s 0 → J / ψ ϕ → μ + μ − K + K − at a center-of-mass energy of 5.02 TeV per nucleon pair and within the rapidity range | y | < 2.4 using the CMS detector at the LHC. The pp measurement is performed as a function of transverse momentum (p T) of the B s 0 mesons in the range of 7 to 50 GeV/ c and is compared to the predictions of perturbative QCD calculations. The B s 0 production yield in PbPb collisions is measured in two p T intervals, 7 to 15 and 15 to 50 GeV/ c , and compared to the yield in pp collisions in the same kinematic region. The nuclear modification factor (R AA) is found to be 1.5 ± 0.6 (stat) ± 0.5 (syst) for 7–15 GeV/ c , and 0.87 ± 0.30 (stat) ± 0.17 (syst) for 15–50 GeV/ c , respectively. Within current uncertainties, the B s 0 results are consistent with models of strangeness enhancement, and suppression by parton energy loss, as observed for the B + mesons. [ABSTRACT FROM AUTHOR]

In the present letter we use holographic methods to show that a very intense magnetic field lowers the temperature at which the mesons melt and decreases the mass gap of the spectrum along with their masses. Consequently, there is a range of temperatures for which mesons can be melted by applying a magnetic field instead of increasing the temperature. We term this effect Magnetic Meson Melting (MMM), and we are able to observe it by constructing a configuration that makes it possible to apply gauge/gravity methods to study fundamental degrees of freedom in a quark-gluon plasma subject to a magnetic field as intense as that expected in high energy collisions. This is achieved by the confection of a ten-dimensional background that is dual to the magnetized plasma and nonetheless permits the embedding of D7-branes in it. For such a background to exist, a scalar field has to be present and hence a scalar operator of dimension 2 appears in the gauge theory. We present here the details of the background and of the embedding of flavor D7-branes in it. Since our results are obtained from the gravity dual of the gauge theory, the analysis is also interesting from the gravitational perspective. [ABSTRACT FROM AUTHOR]

Recent measurements of charm-hadron production in proton-proton collisions at the LHC have found a surprisingly large baryon to meson ratio. We propose that this observation can be explained by the statistical hadronization model (SHM), by employing a largely augmented set of charm-baryon states beyond the current listings of the particle data group. We estimate the additional states using guidance from the relativistic quark model and from lattice QCD. Using charm- and strange-quark fugacity factors to account for the well-known suppression of heavy flavor in elementary collisions, we compute the yields and spectra of D , D s and Λ c hadrons in proton-proton collisions at s = 5 TeV. Our main finding is that the enhanced feeddown from excited charm baryons can account for the Λ c / D 0 ratio measured by ALICE at midrapidity, with some caveat for the forward-rapidity LHCb data. Furthermore, assuming independent fragmentation of charm quarks but with the hadronic ratios fixed by the SHM, the measured transverse-momentum (p T) spectra of D -mesons and Λ c can also be described; in particular, the low- p T enhancement in the observed Λ c / D 0 ratio is attributed to the enhanced feeddown from "missing" charm-baryon states. We comment on the implications of these findings for measurements of D s and Λ c in heavy-ion collisions. [ABSTRACT FROM AUTHOR]

The description of the heavy meson production at large energies and forward rapidities at the LHC is fundamental to derive realistic predictions of the prompt atmospheric neutrino flux at the IceCube Observatory. In particular, the prompt tau neutrino flux is determined by the decay of D s mesons produced in cosmic ray–air interactions at high energies and large values of the Feynman- x F variable. Recent data of the LHCb Collaboration indicate a production asymmetry for D s + and D s − mesons, which cannot be explained in terms of the standard modeling of the hadronization process. In this paper we demonstrate that this asymmetry can be described assuming an asymmetric strange sea (s (x) ≠ s ¯ (x)) in the proton wave function and taking into account the dominant charm and subdominant strange fragmentation into D s mesons. Moreover, we show that the strange quark fragmentation contribution is dominant at large- x F (≥0.3). The prompt ν τ flux is calculated and the enhancement associated with the strange quark fragmentation contribution, disregarded in previous calculations, is estimated. The considered scenario leads to quite sizable enhancement of the high-energy τ -neutrino flux. [ABSTRACT FROM AUTHOR]

We analyze the decay processes of B c → B n M with the S U (3) F flavor symmetry and spin-dependent amplitudes, where B c (B n) and M are the anti-triplet charmed (octet) baryon and nonet meson states, respectively. In the S U (3) F approach, it is the first time that the decay rates and up-down asymmetries are fully and systematically studied without neglecting the O (15 ‾) contributions of the color anti-symmetric parts in the effective Hamiltonian. Our results of the up-down asymmetries based on S U (3) F are quite different from the previous theoretical values in the literature. In particular, we find that the up-down symmetry of α (Λ c + → Ξ 0 K +) S U (3) = 0.94 − 0.11 + 0.06 , which is consistent with the recent experimental data of 0.77 ± 0.78 by the BESIII Collaboration, but predicted to be zero in the literature. We also examine the K S 0 − K L 0 asymmetries between the decays of B c → B n K S 0 and B c → B n K L 0 with both Cabibbo-allowed and doubly Cabibbo-suppressed transitions. [ABSTRACT FROM AUTHOR]

It is argued that heavy-quarks traversing a Quark Gluon Plasma, undergo a multi-stage modification process, similar to the case of light flavors. Such an approach is applied to heavy-quark energy loss, which includes a rare-scattering, multiple emission formalism at momenta large compared to the mass (sensitive only to the transverse diffusion coefficient q ˆ), and a single scattering induced emission formalism (Gunion-Bertsch) at momenta comparable to the mass of the quark [sensitive to q ˆ , and the longitudinal drag (e ˆ) and diffusion ( e ˆ 2) coefficients]. The application of such a multi-stage approach within a 2+1D viscous fluid-dynamical simulation leads to simultaneous agreement with experimental data for the nuclear modification factor of both B and D mesons, as measured by the CMS collaboration at the LHC. The extracted transport coefficients are found to be consistent with those for light flavors. [ABSTRACT FROM AUTHOR]

The energy spectrum of a system containing a static quark anti-quark pair is computed for a wide range of source separations using lattice QCD with N f = 2 + 1 dynamical flavours. By employing a variational method with a basis including operators resembling both the gluon string and systems of two separated static mesons, the first three energy levels are determined up to and beyond the distance where it is energetically favourable for the vacuum to screen the static sources through light- or strange-quark pair creation, enabling both these screening phenomena to be observed. The separation dependence of the energy spectrum is reliably parameterised over this saturation region with a simple model which can be used as input for subsequent investigations of quarkonia above threshold and heavy-light and heavy-strange coupled-channel meson scattering. [ABSTRACT FROM AUTHOR]

We present first data on sub-threshold production of K s 0 mesons and Λ hyperons in Au+Au collisions at s NN = 2.4 GeV. We observe an universal 〈 A p a r t 〉 scaling of hadrons containing strangeness, independent of their corresponding production thresholds. Comparing the yields, their 〈 A p a r t 〉 scaling, and the shapes of the rapidity and the p t spectra to state-of-the-art transport model (UrQMD, HSD, IQMD) predictions, we find that none of them can simultaneously describe these observables with reasonable χ 2 values. [ABSTRACT FROM AUTHOR]

The empirical identification of bound states of gluons has remained a central goal of hadron spectroscopy. We suggest an experimentally challenging, but model–independent way to assess which zero charge, isospin-zero mesons have a large gluonium light-front wavefunction component in the quark and gluon Fock space of QCD. Our method exploits QCD counting rules which relate the power-law fall-off of production amplitudes at high momentum transfer to the meson's twist (dimension minus spin of its minimum interpolating operators). Scalar 0 + glueballs composed of two valence gluons with zero internal orbital angular momentum have twist τ = 2. In contrast, quark-antiquark | q q ¯ 〉 scalar mesons have twist τ ≥ 3 since they have nonzero orbital angular momentum, and multi-quark states such as | q q q ¯ q ¯ 〉 tetraquarks yield twist τ ≥ 4. Thus, the production cross section for both | q q ¯ 〉 and | q q q ¯ q ¯ 〉 mesons will be suppressed by at least one power of momentum transfer relative to glueball production. For example, in single inclusive particle hadroproduction A B → C X , the cross section for glueball production at high transverse momentum p T and fixed x T = 2 p T s will dominate higher twist mesons by at least two powers of p T. Similarly, in exclusive production processes at large CM energy and fixed CM angle, the glueball rate dominates by a power of s : we illustrate the method with a simple reaction, e − e + → ϕ f 0 where the f 0 can be tested to be a glueball versus another type of scalar meson. [ABSTRACT FROM AUTHOR]

At leading-twist accuracy the form factors for the transitions from a virtual photon to the η or η ′ can be expanded into a power series of the variable ω , being related to the difference of the two photon virtualities. The series possess the remarkable feature that only the Gegenbauer coefficients of the meson distribution amplitudes of order l ≤ m contribute to the term ∼ ω m. Thus, for ω → 0 only the asymptotic meson distribution amplitude contributes, allowing for a test of the mixing of the η and η ′ decay constants. Employing the Gegenbauer coefficients determined in an analysis of the form factors in the real photon limit, we present predictions for the γ ⁎ η and γ ⁎ η ′ form factors and compare them to the BaBar data. [ABSTRACT FROM AUTHOR]

A measurement of the production of prompt Λ c + baryons in Pb–Pb collisions at s NN = 5.02 TeV with the ALICE detector at the LHC is reported. The Λ c + and Λ ‾ c − were reconstructed at midrapidity (| y | < 0.5) via the hadronic decay channel Λ c + → p K S 0 (and charge conjugate) in the transverse momentum and centrality intervals 6 < p T < 12 GeV/ c and 0–80%. The Λ c + / D 0 ratio, which is sensitive to the charm quark hadronisation mechanisms in the medium, is measured and found to be larger than the ratio measured in minimum-bias pp collisions at s = 7 TeV and in p–Pb collisions at s NN = 5.02 TeV. In particular, the values in p–Pb and Pb–Pb collisions differ by about two standard deviations of the combined statistical and systematic uncertainties in the common p T interval covered by the measurements in the two collision systems. The Λ c + / D 0 ratio is also compared with model calculations including different implementations of charm quark hadronisation. The measured ratio is reproduced by models implementing a pure coalescence scenario, while adding a fragmentation contribution leads to an underestimation. The Λ c + nuclear modification factor, R AA , is also presented. The measured values of the R AA of Λ c + , D s + and non-strange D mesons are compatible within the combined statistical and systematic uncertainties. They show, however, a hint of a hierarchy (R AA D 0 < R AA D s + < R AA Λ c + ) , conceivable with a contribution from coalescence mechanisms to charm hadron formation in the medium. [ABSTRACT FROM AUTHOR]

We estimate the branching ratio for the inclusive decays Ξ b b q → B ¯ c (⁎) + X c , s , q to be approximately 1%. Our estimate is performed using non-relativistic potential quark model methods that are appropriate if the bottom and charm quarks are heavy compared to the strong interaction scale. Here the superscript (⁎) denotes that we are summing over spin zero B ¯ c and spin one B ¯ c ⁎ mesons and the subscript q denotes a light quark. Our approach treats the two bottom quarks in the baryon Ξ b b q as a small color anti-triplet. This estimate for the inclusive branching ratio to B ¯ c and B ¯ c ⁎ mesons also holds for decays of the lowest lying T b b q ¯ q ¯ tetraquark states, provided they are stable against strong and electromagnetic decay. [ABSTRACT FROM AUTHOR]

The properties of open strange meson K 1 ± in nuclear matter are estimated in the QCD sum rule approach. We obtain a relation between the in-medium mass and width of K 1 − (K 1 +) in nuclear matter, and show that the upper limit of the mass shift is as large as −249 (−35) MeV. The spectral modification of the K 1 meson is possible to be probed by using kaon beams at J-PARC. Such measurement together with that of K ⁎ will shed light on how chiral symmetry is partially restored in nuclear matter. [ABSTRACT FROM AUTHOR]

Abstract Coupling constants of η and η ′ mesons with nucleons have been calculated using the method of QCD sum rules. Starting from vacuum-to-meson correlation function of interpolating fields of two nucleons, its matrix element with respect to nucleon spinors has been considered. Coupling constants at the physical points have been estimated from extrapolation of results obtained at two other points. Anomalous glue has been found to give substantial contribution to the coupling constants and also accounts for a significant OZI-rule violation. [ABSTRACT FROM AUTHOR]

Abstract A measurement of the elliptic flow (v 2) of prompt J / ψ mesons in high-multiplicity p Pb collisions is reported using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy s NN = 8.16 TeV. Prompt J / ψ mesons decaying into two muons are reconstructed in the rapidity region in the nucleon-nucleon center-of-mass frame (y cm), corresponding to either − 2.86 < y cm < − 1.86 or 0.94 < y cm < 1.94. The average v 2 result from the two rapidity ranges is reported over the transverse momentum (p T ) range from 0.2 to 10 GeV. Positive v 2 values are observed for the prompt J / ψ meson, as extracted from long-range two-particle correlations with charged hadrons, for 2 < p T < 8 GeV. The prompt J / ψ results are compared with previous CMS measurements of elliptic flow for open charm mesons (D 0) and strange hadrons. From these measurements, constraints can be obtained on the collective dynamics of charm quarks produced in high-multiplicity events arising from small systems. [ABSTRACT FROM AUTHOR]

Abstract We consider the flavour sextet of charmed meson resonances with J P = 1 + quantum numbers that is predicted by the leading order chiral Lagrangian with up, down and strange quarks. The effect of chiral correction terms as determined previously from QCD lattice data is worked out. Pole masses in the complex energy plane are derived. The most promising signal from such states accessible in experiments like Belle, LHCb and PANDA is foreseen in the s-wave π D ⁎ phase shift and the η D ⁎ invariant mass distribution. For physical quark masses a rapid variation of the phase shift in-between the η D ⁎ and the K ¯ D s ⁎ thresholds is predicted. [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]

Abstract A symmetry-preserving approach to the continuum bound-state problem in quantum field theory is used to calculate the masses, leptonic decay constants and light-front distribution amplitudes of empirically accessible heavy-light mesons. The inverse moment of the B -meson distribution is particularly important in treatments of exclusive B -decays using effective field theory and the factorisation formalism; and its value is therefore computed: λ B (ζ = 2 GeV) = 0.54 (3) GeV. As an example and in anticipation of precision measurements at new-generation B -factories, the branching fraction for the rare B → γ (E γ) ℓ ν ℓ radiative decay is also calculated, retaining 1 / m B 2 and 1 / E γ 2 corrections to the differential decay width, with the result Γ B → γ ℓ ν ℓ / Γ B = 0.47 (15) on E γ > 1.5 GeV. [ABSTRACT FROM AUTHOR]

Abstract The cross sections for ϒ(1S), ϒ(2S), and ϒ(3S) production in lead–lead (PbPb) and proton–proton (pp) collisions at s NN = 5.02 TeV have been measured using the CMS detector at the LHC. The nuclear modification factors, R AA , derived from the PbPb-to- p p ratio of yields for each state, are studied as functions of meson rapidity and transverse momentum, as well as PbPb collision centrality. The yields of all three states are found to be significantly suppressed, and compatible with a sequential ordering of the suppression, R AA (ϒ (1S)) > R AA (ϒ (2S)) > R AA (ϒ (3S)). The suppression of ϒ(1S) is larger than that seen at s NN = 2.76 TeV , although the two are compatible within uncertainties. The upper limit on the R AA of ϒ (3 S) integrated over p T , rapidity and centrality is 0.096 at 95% confidence level, which is the strongest suppression observed for a quarkonium state in heavy ion collisions to date. [ABSTRACT FROM AUTHOR]