Heavy Mesons Research Articles

Masses of doubly heavy tetraquarks with error bars

In the heavy-quark limit, the two heavy quarks in a doubly heavy baryon or a doubly heavy tetraquark are bound by their color-Coulomb potential into a compact diquark. The doubly heavy hadrons are related by the approximate heavy-quark--diquark symmetry of QCD to the heavy hadrons obtained by replacing the heavy diquark by a heavy antiquark. Effective field theories can be used to expand the masses of singly heavy hadrons and doubly heavy hadrons in inverse powers of the heavy quark masses. The coefficients in the expansions for doubly heavy tetraquarks can be determined from those for heavy mesons, heavy baryons, and doubly heavy baryons using heavy-quark--diquark symmetry. We predict the masses of the ground-state doubly heavy tetraquarks with error bars using as inputs the masses of heavy mesons and heavy baryons measured in experiments and the masses of doubly heavy baryons calculated using lattice QCD. The only doubly heavy tetraquarks predicted to be stable with respect to strong decays are $bb$ tetraquarks with light flavor $\bar u \bar d$, $\bar s \bar u$ and $\bar s \bar d$.

On scaling of Schrödinger equation and some results for heavy quarks mesons

We consider the scaling of the Schrödinger equation in order to explicitly compute the energy density levels for a specific class of potentials. The resulting eigenvalues spectrum is compared to the heavy quarks mesons spectroscopy, showing a fair agreement with experimental data for the J/ps and, for the heavier case Y, an excellent agreement with the experimental data.

The elliptic asymmetry of heavy quarkonia in pA collisions from the initial state

We compute the azimuthal angular correlation between a heavy quarkonium (or an open charm meson) and a charged light hadron produced in pA collisions in the color glass condensate framework. The obtained elliptic asymmetries (v2) of J/ψ and D0 mesons agree with the recent experimental data from the LHC quite well. Our calculation demonstrates that an initial state effect due to the interaction between the partons inside the projectile proton and the dense gluons inside the target nucleus can generate a sizable collectivity which can be measured at RHIC and the LHC. In this framework, we find the mass dependence for the heavy quarkonium v2 is quite weak, while that for the open meson v2 is rather strong. It will be very interesting to test our results regarding other heavy mesons in the future experimental measurements.

Analytical Solutions of the Schrödinger Equation with Class of Yukawa Potential for a Quarkonium System Via Series Expansion Method

A class of Yukawa potential is adopted as the quark-antiquark interaction potential for studying the mass spectra of heavy mesons. The potential was made to be temperature-dependent by replacing the screening parameter with Debye mass. We solved the radial Schrödinger equation analytically using the series expansion method and obtained the energy eigenvalues. The present results are applied for calculating the mass spectra of heavy mesons such as charmonium and bottomonium . Two special cases were considered when some of the potential parameters were set to zero, resulting into Hellmann potential, and Coulomb potential, respectively. The present potential provides satisfying results in comparison with experimental data and the work of other researchers.

Light-Cone Distribution Amplitudes of Doubly-Heavy Baryons

Doubly-heavy baryons, whose dynamics is determined by a light quark situated in a color field of a static pair of heavy quarks, are investigated. Non-local interpolation currents are introduced and corresponding matrix elements between the baryon and vacuum state are expressed in terms of light-cone distribution amplitudes. Model functions for baryon distribution amplitudes are suggested and their scale dependence is studied in the perturbative QCD framework. The similarity between the heavy meson and doubly-heavy baryon distribution amplitudes is discussed.

Strong interaction of doubly heavy spin-3/2 baryons with light vector mesons

We calculate the strong coupling constants among the doubly heavy spin- frac{3}{2} baryons Xi ^*_{QQ} and Omega ^*_{QQ}, with Q and Q' being c or b quark, with light vector meson by means of the light-cone QCD sum rules. The matrix elements defining these vertices are described by four coupling constants g_1, g_2, g_3, and g_4 . The unwanted pollution coming from the doubly heavy spin- frac{1}{2} baryons are removed by a special ordering of Dirac matrices and selection of appropriate Lorentz structures. The strong coupling constants are basic parameters that carry information on the nature of the strong interaction among hadronic multiplets. Investigation of these parameters may help physicists in the construction of the strong potentials among the doubly heavy baryons and light vector mesons. The values obtained for the strong coupling constants may also help experimental groups in analyses of the data produced at various hadron colliders.

Nuclear form factor of xenon from photoproduction of vector mesons in Xe-Xe ultraperipheral collisions at the LHC

Using the Gribov-Glauber model for photon-nucleus scattering and a generalization of the vector meson dominance model for the hadronic structure of the photon, we calculate cross sections of light and heavy vector meson photoproduction in ultraperipheral Xe-Xe collisions at 5.44 TeV at the Large Hadron Collider. Analyzing the momentum transfer distribution in this process, we examine the feasibility to extract the nuclear isoscalar form factor of Xe isotopes, which are needed in searches for dark matter with Xenon-based detectors.

A new machine learning approach for predicting the spectra of meson bound states

In this paper, we investigate the benefits of machine learning (ML) approaches in predicting the spectra of meson bound states. A linear model (LM) approach is used to predict the spectra of some heavy mesons. Our proposed method has been successfully reproduced in recent experiments, to validate known outcomes. Our results are compared favorably to those obtained using other techniques. This novel perspective opens up a new future in the use of ML in the field of particle physics.

Heavy Quark Symmetry and Fine Structure of the Spectrum of Hadronic Dark Matter

We analyze the structure of excited states of new heavy hadrons in the scenario with hadronic dark matter. Fine mass-splitting in a doublet of new mesons stipulates the existence of charged metastable heavy mesons. We describe the structure of new meson excited states in the framework of the heavy quark effective theory. Phenomenological consequences of fine and hyperfine splitting are considered in the hadronic dark matter scenario and beyond.

Configuration entropy description of charmonium dissociation under the influence of magnetic fields

Heavy ion collisions, produced in particle accelerators, lead to the formation of a new state of matter, known as the quark gluon plasma. It is not possible to observe directly the plasma, where quarks and gluons are not confined into hadrons. All the available information comes from the particles that reach the detectors after the strongly interacting matter hadronizes. Among those particles, one that plays an important role is the charmonium J/ψ heavy meson, made of a cc¯ quark anti-quark pair. The fraction of such particles produced in a heavy ion collision is related to the dissociation level caused by the plasma. On the other hand, the dissociation of J/Ψ in the plasma is influenced by the temperature and the density of the medium and also by the presence of magnetic fields, that are produced in non central collisions. A very interesting tool to study stability of physical systems is the configuration entropy (CE). In recent years many examples in various kinds of physical systems appeared in the literature, where an increase in the CE is associated with an increase in the instability of the system. In this letter we calculate the CE for charmonium quasistates inside a plasma with a magnetic field background, in order to investigate how the instability, corresponding in this case to the dissociation in the thermal medium, is translated into the dependence of the CE on the field.

Scalar spectrum in a graviton soft wall model

In this study we present a unified phenomenological analysis of the scalar glueball and scalar meson spectra within an AdS/QCD framework in the bottom up approach. For this purpose we generalize the recently developed graviton soft-wall (GSW) model, which has shown an excellent agreement with the lattice QCD glueball spectrum, to a description of glueballs and mesons with a unique energy scale. In this scheme, dilatonic effects, are incorporated in the metric as a deformation of the AdS space. We apply the model also to the heavy meson spectra with success. We obtain quadratic mass equations for all scalar mesons while the glueballs satisfy an almost linear mass equation. Besides their spectra, we also discuss the mixing of scalar glueball and light scalar meson states within a unified framework: the GSW model. To this aim, the light-front (LF) holographic approach, which connects the mode functions of AdS/QCD to the LF wave functions, is applied. This relation provides the probabilistic interpretation required to properly investigate the mixing conditions.

Single diffractive production of open heavy flavor mesons

In this paper we discuss the single diffractive production of open heavy flavor mesons and non-prompt charmonia in $pp$ collisions. Using the color dipole approach, we found that the single diffractive production constitutes 0.5-2 per cent of the inclusive production of the same mesons. In Tevatron kinematics our theoretical results are in reasonable agreement with the available experimental data. In LHC kinematics we found that the cross-section is sufficiently large and could be accessed experimentally. We also analyzed the dependence on multiplicity of co-produced hadrons and found that it is significantly slower than that of inclusive production of the same heavy mesons.

Next-to-leading-logarithm kT resummation for Bc → J/ψ decays

We derive the kT resummation for a transverse-momentum-dependent charmonium wave function, which involves the bottom quark mass mb, the charm quark mass mc, and the charm quark transverse momentum kT, up to the next-to-leading-logarithm (NLL) accuracy under the hierarchy mb≫mc≫kT. The resultant Sudakov factor is employed in the perturbative QCD (PQCD) approach to the Bc→J/ψ transition form factor A0Bc→J/Ψ(0) and the Bc+→J/ψπ+ decay. We compare the NLL resummation effect on these processes with the leading-logarithm one in the literature, and find a (5−10)% enhancement to the form factor A0Bc→J/Ψ(0) and a (10−20)% enhancement to the decay rate BR(Bc+→J/Ψπ+). The improved kT resummation formalism is applicable to the PQCD analysis of heavy meson decays to other charmonia.

Diabatic description of charmoniumlike mesons

We apply the diabatic formalism, first introduced in molecular physics, to the description of heavy-quark mesons. In this formalism the dynamics is completely described by a diabatic potential matrix whose elements can be derived from unquenched lattice QCD studies of string breaking. For energies far below the lowest open flavor meson-meson threshold, the resulting diabatic approach reduces to the well-known Born-Oppenheimer approximation where heavy-quark meson masses correspond to energy levels in an effective quark-antiquark potential. For energies close below or above that threshold, where the Born-Oppenheimer approximation fails, this approach provides a set of coupled Schr\"{o}dinger equations incorporating meson-meson components nonperturbatively, i.e. beyond loop corrections. A spectral study of heavy mesons containing $c\overline{c}$ with masses below $4.1$ GeV is carried out within this framework. From it a unified description of conventional as well as unconventional resonances comes out.

Distribution amplitudes of heavy mesons and quarkonia on the light front

The ladder kernel of the Bethe–Salpeter equation is amended by introducing a different flavor dependence of the dressing functions in the heavy-quark sector. Compared with earlier work this allows for the simultaneous calculation of the mass spectrum and leptonic decay constants of light pseudoscalar mesons, the D_u, D_s, B_u, B_s and B_c mesons and the heavy quarkonia eta _c and eta _b within the same framework at a physical pion mass. The corresponding Bethe–Salpeter amplitudes are projected onto the light front and we reconstruct the distribution amplitudes of the mesons in the full theory. A comparison with the first inverse moment of the heavy meson distribution amplitude in heavy quark effective theory is made.

Relativistic corrections to the vector meson light front wave function

We compute a light front wave function for heavy vector mesons based on long distance matrix elements constrained by decay width analyses in the Non Relativistic QCD framework. Our approach provides a systematic expansion of the wave function in quark velocity. The first relativistic correction included in our calculation is found to be significant, and crucial for a good description of the HERA exclusive $\mathrm{J}/\psi$ production data. When looking at cross section ratios between nuclear and proton targets, the wave function dependence does not cancel out exactly. In particular the fully non-relativistic limit is found not to be a reliable approximation even in this ratio. The important role of the Melosh rotation to express the rest frame wave function on the light front is illustrated.

Strong interaction coupling-constant sum rules for heavy hadrons with broken SU(3) symmetry

Heavy baryons [Formula: see text] and heavy mesons [Formula: see text] for heavy quarks [Formula: see text], [Formula: see text], or [Formula: see text] and light quarks [Formula: see text], [Formula: see text], or [Formula: see text] are considered. Strong interaction coupling-constant sum rules with first-order breaking of SU(3) flavor symmetry are obtained for reaction [Formula: see text] where [Formula: see text] or [Formula: see text], [Formula: see text] or [Formula: see text], and [Formula: see text] is a light meson. Specific results for couplings of doubly charmed baryons and charm and bottom mesons are presented. Also, SU(3) Clebsch-Gordan coefficients for the product of representations [Formula: see text] are explicitly determined.

Heavy flavor quenching and flow: the roles of initial condition, pre-equilibrium evolution, and in-medium interaction * * Supported by the Natural Science Foundation of China (NSFC) (11805082, 11775095, 11890711, 11935007), a Project of Shandong Province Higher Educational Science and Technology Program (J17KB128), the China Scholarship Council (CSC) (201906775042), the U.S. Department of Energy (DOE) (DE-SC0013460), and the National Science Foundation

Within an advanced Langevin-hydrodynamics framework coupled to a hybrid fragmentation-coalescence hadronization model, we study heavy flavor quenching and flow in relativistic heavy-ion collisions. We investigate how the initial heavy quark spectrum, the in-medium energy loss and hadronization mechanisms of heavy quarks, the evolution profile of the pre-equilibrium stage, the medium flow, and the temperature dependence of heavy quark diffusion coefficients influence the suppression and elliptic flow of heavy mesons at the RHIC and the LHC. Our results show that the different modeling of initial conditions, pre-equilibrium evolution, and in-medium interactions can individually yield uncertainties of approximately 10-40% in D meson suppression and flow at a low transverse momentum. We also find that proper combinations of collisional versus radiative energy loss, coalescence versus fragmentation in hadronization, and the inclusion of medium flow are the most important factors for describing the suppression and elliptic flow of heavy mesons.

Sensitivity study with a D and B mesons modular simulation code of heavy flavor RAA and azimuthal anisotropies based on beam energy, initial conditions, hadronization, and suppression mechanisms

Heavy flavor probes provide important information about the in-medium properties of the quark-gluon plasma produced in heavy-ion collisions. In this work, we investigate the effects of 2D+1 event-by-event fluctuating hydrodynamic backgrounds on the nuclear suppression factor and momentum anisotropies of heavy flavor mesons and non-photonic electrons. Using the state-of-the-art D and B mesons modular simulation code (called "DAB-MOD"), we perform a systematic comparison of different transport equations in the same background, including a few energy loss models --- with and without energy loss fluctuations --- and a relativistic Langevin model with different drag parametrizations. We present the resulting D and B mesons $R_{AA}$, $v_2$, $v_3$, and $v_4$ as well as multi-particle cumulants, in AuAu collisions at $\sqrt{s_\text{NN}}=200\, \text{GeV}$ and PbPb collisions at $\sqrt{s_\text{NN}}=2.76 \, \text{TeV}$ and $\sqrt{s_\text{NN}}=5.02 \, \text{TeV}$, and compare them to the available experimental data. The $v_2\{4\}/v_2\{2\}$ ratio, which is known to be a powerful probe of the initial conditions and flow fluctuations in the soft sector, is also studied in the context of heavy flavor. We also investigate the correlations between the transverse anisotropies of heavy mesons and all charged particles to better understand how heavy quarks couple to the hydrodynamically expanding quark-gluon plasma. We study the influence that different initial conditions and the implementation of heavy-light quark coalescence has on our results.

Collectivity of heavy mesons in proton-nucleus collisions

Using a model based on the Color Glass Condensate framework and the dilute-dense factorization, we systematically study the azimuthal angular correlations between a heavy flavor meson and a light reference particle in proton-nucleus collisions. The obtained second harmonic coefficients (also known as the elliptic flows) for $J/\psi$ and $D^0$ agree with recent experimental data from the LHC. We also provide predictions for the elliptic flows of $\Upsilon$ and $B$ meson, which can be measured in the near future at the LHC. This work can shed light on the physics origin of the collectivity phenomenon in the collisions of small systems.