Heavy Mesons Research Articles

Approximate mass spectra and root mean square radii of quarkonia using Cornell potential plus spin-spin interactions

We proposed a global spin-dependent potential energy function which fits the description of the non-relativistic quark model. The spin dependencies of our model result from the harmonic approximation of the Gaussian function in the spin-spin component. The approximation enables us to obtain analytical solutions of the bound states for the heavy mesons singlet and triplet states using the conventional Nikiforov-Uvarov method. The obtained mass spectra and expectation values for the low through high-lying quantum states are in agreement with the results obtained for other potential functions in the existing literature. The splitting of the masses occurs at a distance greater than the obtained characteristic radius of the heavy mesons which were found to be within the experimentally observed 1fm. The proposed potential model may be extended to obtain other meson spectroscopic parameters such as the decay constants, wave function at the origin and electromagnetic radiative transitions.

Looking for heavy axial tensor mesons via their strong decays in light cone QCD

In this study, the strong coupling constants of the unobserved heavy axial tensor mesons to the heavy vector and pseudoscalar $\ensuremath{\pi}$ and $K$ mesons, ${D}_{2}{D}^{*}\ensuremath{\pi}$, ${D}_{s2}{D}^{*}K$, ${B}_{2}{B}^{*}\ensuremath{\pi}$, ${B}_{s2}{B}^{*}K$ as well as a heavy axial tensor to axial vector and light pseudoscalar $\ensuremath{\pi}$ and $K$-mesons, ${D}_{2}{D}_{1}\ensuremath{\pi}$, ${D}_{s2}{D}_{1}K$, ${B}_{2}{B}_{1}\ensuremath{\pi}$, ${B}_{s2}{B}_{1}K$ vertices have been investigated within the light cone QCD sum rules method. Having obtained the strong coupling constants, we estimate the corresponding decay widths that will hopefully be verified in future experiments.

Hadronic loop effects to excited scalar charmed mesons revisited

We re-examine the hadronic loop effects on the masses of and calculated in quark models in the framework of heavy meson chiral perturbation theory (HMCHPT). Unlike previous approaches, ours reproduces the observed scalar charm states reported by the Particle Data Group (PDG). We show why previous approaches of using HMCHPT in studying mass shift effects due to chiral loops gave unsatisfactory results.

X(3872) , X(4014) , and their bottom partners at finite temperature

The properties of the $X(3872)$ and its spin partner, the $X(4014)$, are studied both in vacuum and at finite temperature. Using an effective hadron theory based on the hidden-gauge Lagrangian, the $X(3872)$ is dynamically generated from the $s$-wave rescattering of a pair of pseudoscalar and vector charm mesons. By incorporating the thermal spectral functions of open charm mesons, the calculation is extended to finite temperature. Similarly, the properties of the $X(4014)$ are obtained out of the scattering of charm vector mesons. By applying heavy-quark flavor symmetry, the properties of their bottom counterparts in the axial-vector and tensor channels are also predicted. All the dynamically generated states show a decreasing mass and acquire an increasing decay width with temperature, following the trend observed in their meson constituents. These results are relevant in relativistic heavy-ion collisions at high energies, in analyses of the collective medium formed after hadronization or in femtoscopic studies, and can be tested in lattice-QCD calculations exploring the melting of heavy mesons at finite temperature.

Quantum information entropy of heavy mesons in the presence of a point-like defect

Using Schrödinger’s formalism, we investigate the quantum eigenstates of the heavy mesons trapped by a point-like defect and by Cornell’s potential. One implements this defect to the model considering a spherical metric profile coupled to it. Furthermore, the Nikiforov–Uvarov method is applied to theory to study the quantum eigenstates of the heavy mesons. To calculate the quantum information entropy (QIE), one considers the wave functions that describe the charmonium and bottomonium states. To explore the QIE, we use the well-known Shannon’s entropy formulated at the position and reciprocal space. The analysis of the QIE gives us relevant information about how the quantum information change with the variation of the point-like defect. Consequently, considering the Bialynicki-Birula and Mycielski (BBM) relation, we show how this defect influences the quarkonium position and momentum uncertainty measures.

Electromagnetic form factors and charge radii of pseudoscalar and scalar mesons: A comprehensive contact interaction analysis

We carry out a comprehensive survey of electromagnetic form factors of all light, heavy and heavy-light ground-state pseudoscalar and scalar mesons. Our analysis is based upon a Schwinger-Dyson equations treatment of a vector $\times$ vector contact interaction. It incorporates confinement and ensures axial vector and vector Ward-Takahashi identities are satisfied along with the corresponding corollaries such as the Goldberger-Treiman relations. The algebraic simplicity of the model allows us to compute the form factors at arbitrarily large virtualities of the probing photon momentum squared with relative ease. Wherever possible and insightful, we compare our results for the electromagnetic form factors and the charge radii with those obtained earlier through Schwinger-Dyson equations, lattice and with experimental observations available. We also comment on the scope and shortcomings of the model.

Theoretical Investigation of Meson Spectrum via Exact Quantization Rule Technique

The energy eigenvalues with the Extended Cornell potential were obtained by analytically solving the radial Schrödinger equation using the Exact Quantization Rule technique (ECP). It was then used for computing the mass spectra of the heavy mesons like charmonium (cc-) and bottomonium (bb-) as well as heavy-light mesons such as bottom-charm bc- and charm-Strange cs- for various quantum states. Two exceptional cases such as the Coulomb and Cornell potentials, were taken into consideration when some of the potential parameters were set to zero. The current potential offers good outcomes when compared to experimental data and work of other researchers with a maximum error of 0.0065 GeV.

Flavor-changing light bosons with accidental longevity

We consider a model with a complex scalar field that couples to (e, μ) or (μ, τ) within the “longevity” window: left[|{m}_{l_1}-{m}_{l_2}|,{m}_{l_1}+{m}_{l_2}right] in which l1 and l2 are the two different charged leptons. Within such a mass window, even a relatively large coupling (e.g. of the size commensurate with the current accuracy/discrepancy in the muon g − 2 experiment) leads to long lifetimes and macroscopic propagation distance between production and decay points. We propose to exploit several existing neutrino experiments and one future experiment to probe the parameter space of this model. For the μ − e sector, we exploit the muonium decay branching ratio and the production and decay sequence at the LSND experiment, excluding the parametric region suggested by gμ − 2 anomaly. For the τ − μ sector, we analyze three main production mechanisms of scalars at beam dump experiments: the Drell-Yan process, the heavy meson decay, and the muon scattering. We explore the constraints from the past CHARM and NuTeV experiments, and evaluate sensitivity for the proposed beam dump experiment, SHiP. The latter can thoroughly probe the parameter space relevant for the gμ− 2 anomaly.

Exploration of trace anomaly contribution to proton mass based on light vector meson photoproduction

In the quantum chromodynamics, the mass source of the proton is decomposed into four parts by the energy momentum tensor: quark energy term, gluon energy term, quark mass term and trace anomaly term. And the trace anomaly term is the most crucial contribution for studying the internal structure of the proton. In this work, under the definition of the vector meson dominant model, the trace anomaly contribution of the proton is extracted from the experimental data of light vector mesons rho , omega and phi photoproduction at the near-threshold, which are (0.53pm 0.15)%, (1.47pm 0.48)% and (2.73pm 0.54)%, respectively. Further, combined with the results extracted from the heavy vector meson J/psi photoproduction, the distribution of the trace anomaly contribution with the vector meson mass is given for the first time. These results may provide important theoretical information for determining the range of the trace anomaly contribution and for further understanding the origin of the proton mass.

D ∗ jet fragmentation function paradox and combination mechanism

In the framework of the perturbative Quantum Chromodynamics factorization, the production of a hadron includes contributions from fragmentation as well as combination, with the latter being of higher twist. In particular, the heavy meson production can be via the combination of a heavy quark with a light one, and the cross section can be factorized to be the convolution of the combination matrix element, the light quark distribution function, and the hard partonic sub-cross section of the heavy quark production. The partonic distribution and the combination matrix element are functions of a scaling variable, respectively, which is the momentum fraction of the corresponding quark with respect to the heavy meson. We studied the D *± production in jet via combination in pp collision at the LHC. The total result is comparable with the experimental data. The combination matrix elements can be further studied in various hadron production processes.

Perturbative and non-perturbative interactions between heavy quarks and quark-gluon plasma within a unified approach

While perturbative QCD is sufficient for understanding the color, mass and energy dependences of parton energy loss and jet quenching at large transverse momentum in heavy-ion collisions, a simultaneous description of heavy flavor nuclear modification factor RAA and elliptic flow coefficient v2 at low and intermediate pT still remains a challenge due to the effects from non-perturbative interactions. In this work, we extend the linear Boltzmann transport model by implementing a generalized Cornell-type potential that incorporates both short-range Yukawa interaction and long-range color confining interaction between heavy quarks and the QGP medium. Combining our new approach for heavy-quark-QGP interaction with a (3+1)-dimensional hydrodynamic model CLVisc for the QGP evolution and a hybrid fragmentation-coalescence model for heavy quark hadronization, we obtain a satisfactory description of heavy meson RAA and v2 from low to intermediate to high pT observed at both RHIC and the LHC. By model-data-comparison, we obtain for the first time the in-medium heavy quark potential from open heavy flavor measurements; the result is in agreement with the lattice QCD calculation. Our study indicates that while jet quenching at high pT is dominated by perturbative QCD interactions, non-perturbative interactions are indispensible for understanding heavy flavor quenching and flow at low and intermediate pT.

Phase shifts of the light pseudoscalar meson and heavy meson scattering in heavy meson chiral perturbation theory

We calculate the complete T matrices of the elastic light pseudoscalar meson and heavy meson scattering to the third order in heavy meson chiral perturbation theory. We determine the low-energy constants by fitting the phase shifts and scattering lengths from lattice QCD simulations simultaneously and predict the phase shifts at the physical meson masses. The phase shifts in the Dpi (I=1/2), DK(I=0), D{bar{K}}(I=0), D_s{bar{K}}, Deta and D_seta S waves are so strong that bound states or resonances may be generated dynamically in all these channels. The DK(I=0) channel corresponds to the well-known exotic state D_{s0}^{*}(2317). The DK(I=0) channel corresponds to the well-known exotic state D_{s0}^{*}(2317). The coupled-channel Dpi , Deta and D_s{bar{K}} scattering corresponds to D_{0}^{*}(2400). The coupled-channel Dpi , Deta and D_s{bar{K}} scattering corresponds to D_{0}^{*}(2400). We also predict the scattering lengths and scattering volumes and observe good convergence in the scattering volumes. Our calculations provide a possibility to accurately investigate the exotic state in the light pseudoscalar meson and heavy meson interactions.

Can transverse mass scaling shed light on the event-activity dependence of ϒ -meson production at the LHC?

Measurements by the CMS experiment [S. Chatrchyan et al. (CMS Collaboration), J. High Energy Phys. 04 (2014) 103; A. M. Sirunyan et al. (CMS Collaboration), J. High Energy Phys. 11 (2020) 001] reveal a deficit of charged particle tracks in events with higher $\mathrm{\ensuremath{\Upsilon}}(\mathrm{nS})$ states. This observation is suggested to be a manifestation of the excited bottomonia suppression in $pp$ interactions. Transverse mass (${m}_{\mathrm{T}}$) scaling can be implied to check this assumption in an independent way. The scaling has been observed for a wide range of particle species in proton-proton collisions at various energies from the SPS to RHIC and the LHC. The observed scaling is known to be different for baryons and mesons, and this work presents a comprehensive study of the ${m}_{\mathrm{T}}$-scaling of mesons at LHC energies with a focus on heavier mesons. The study demonstrates patterns in the scaling properties of mesons, which are related to the particle quark content. In particular, light species and ground-state quarkonia obey the same scaling, whereas open-flavor particles deviate from it because their spectra are significantly harder. The magnitude of deviation depends on the flavor of the heaviest quark in the meson. By extending the ${m}_{\mathrm{T}}$-scaling assumption to the excited bottomonia states, it is observed that the measured cross sections of $\mathrm{\ensuremath{\Upsilon}}(2\mathrm{S})$ and $\mathrm{\ensuremath{\Upsilon}}(3\mathrm{S})$ are reduced by factors of 1.6 and 2.4 compared to the expectation from the scaling. This observation is consistent with recently observed differences between the event-activity dependence of different $\mathrm{\ensuremath{\Upsilon}}(\mathrm{nS})$ meson states.

Leptophobic dark photon interpretation of the [formula omitted] puzzle

The decays of η and η′ mesons provide unique opportunities for testing the properties of low energy Quantum Chromodynamics and for the search of new physics beyond the Standard Model. However, recent experimental results on the rare decays of η(′)→π0(η)γγ cannot be self-consistently described by the combination of the Vector Meson Dominance and Linear Sigma Model employing the same set of parameters. We show that this tension can be attributed to the presence of a leptophobic dark photon B, and find representative values of the parameters which provide consistent description of these three decays, simultaneously. Unlike existing strategies of Dalitz analysis searching for the bump at mB, we propose the usage of mismatch between these decays to constrain the parameters of the hypothetical dark photon. Additionally, we discuss possible signatures of sub-GeV B boson in heavy meson decays.

Low-lying doubly heavy baryons: Regge relation and mass scaling

In framework of heavy-diquark–light-quark endowed with heavy-pair binding, we explore excited baryons QQ^{prime }q containing two heavy quarks (QQ^{prime }=cc,bb,bc) by combining the method of Regge trajectory with the perturbative correction due to the heavy-pair interaction in baryons. Two Regge relations, one linear and the other nonlinear, are constructed semi-classically in the QCD string picture, and a mass scaling relation based on the heavy diquark–heavy antiquark symmetry are employed between the doubly heavy baryons and heavy mesons. We employ the ground-state mass estimates compatible with the observed doubly charmed baryon Xi _{cc} and spectra of the heavy quarkonia to determine the trajectory parameters and the binding energies of the heavy pair, and thereby compute the low-lying masses of the excited baryons Xi _{QQ^{prime }} and Omega _{QQ^{prime }} up to 2S and 1P excitations of the light quark and heavy diquark. The level spacings of heavy diquark excitations are found to be smaller generally than that of the light-quark excitations, in according with the nature of adiabatic expansion between the heavy and light-quark dynamics.

The Role of Scalar and Mass Interactions in a Relativistic Model of the Charmonium Spectrum

Lorentz scalar and mass interactions are studied in more detail in the framework of a reduced Dirac equation for heavy quark-antiquark mesons. A microscopic model for these interactions is proposed and analyzed. The charmonium mass spectrum is reproduced by means of two free parameters; a third parameter is fixed by means of a phenomenological hypothesis in accordance with the model.

Multiplicity-dependent production of heavy mesons with strangeness in small systems at LHCb

The phenomenon of strangeness enhancement, originally proposed as a signature of quark-gluon plasma formation, has received considerable new interest following recent observations in small collision systems. LHCb is uniquely well suited to study such effects in the heavy quark sector, down to very low transverse momentum. Here we will present new LHCb results on the production rates of B0s relative to B0 mesons versus multiplicity in pp collisions. Potential implications for the hadronization mechanism of heavy quarks and our understanding of the factorization of fragmentation functions will be discussed.

Preparations for a search of the muon EDM at PSI

Electric dipole moments (EDMs) of fundamental particles violate time invariance and the combined symmetry of charge and parity (CP). The existence of a large muon EDM (muEDM) is made plausible by tensions with Standard Model predictions for semileptonic decays of heavy meson measured at LHCb, BaBar, and Belle, as well as the muon’s anomalous magnetic moment (AMM). A discovery of the muEDM would manifest CP and lepton flavor universality (LFU) violation, revealing physics beyond the SM (BSM). The most sensitive muEDM search to date provides an upper limit of 1.8 × 10−19 e cm (CL 95%), extracted from high-precision data collected to measure the muon AMM. At the Paul Scherrer Institute, we are setting up a dedicated search for the muEDM using, for the first time, the frozen-spin technique to target an ultimate sensitivity better than 6 × 10−23 e cm. This novel technique increases the sensitivity to EDM-induced spin precession by cancelling the AMM-induced precession with the application of a precisely tuned electric field perpendicular to the muon momentum and the magnetic field. In this configuration, the dominant source of precession is the EDM coupling to the large relativistic electric field in the muon rest frame, generated by its motion in a strong 3 T uniform magnetic field. In a precursor experiment, we will apply the frozen-spin technique in a compact solenoid demonstrating a sensitivity of better than 3 × 10−21 e cm, probing uncharted and otherwise inaccessible territory in BSM theories.

Chiral symmetry restoration and properties of Goldstone bosons at finite temperature* *Supported in part by the National Natural Science Foundation of China (12075117, 11775112, 11535005, 11690030, 11905104, 11805024, 11947406) and Jiangsu Provincial Natural Science Foundation of China (BK20180323)

We study chiral symmetry restoration by analyzing thermal properties of QCD's(pseudo-) Goldstone bosons, especially the pion. The meson properties are obtained from the spectral densities of mesonic imaginary-time correlation functions. To obtain the correlation functions, we solve the Dyson-Schwinger equations and the inhomogeneous Bethe-Salpeter equations in the leading symmetry-preserving rainbow-ladder approximation. In chiral limit, the pion and its partner sigma degenerate at the critical temperature . At , it was found that the pion rapidly dissociates, which signals deconfinement phase transition. Beyond the chiral limit, the pion dissociation temperature can be used to define the pseudo-critical temperature of the chiral phase crossover, which is consistent with that obtained by the maximum point of chiral susceptibility. A parallel analysis for kaon and pseudoscalar suggests that heavy mesons may survive above .

THE EFFECT OF TOPOLOGICAL DEFECT ON THE MASS SPECTRA OF HEAVY AND HEAVY-LIGHT QUARKONIA

In this present study, the effect of Topological Defect on the mass spectra of heavy and heavy-light mesons such as charmonium, bottomonium, and charm-strange ,bottom-charm respectively are studied with the Hulthen plus Yukawa potential. The Schrödinger equation is solved analytically using the Nikiforov-Uvarov method. The approximate solutions of the energy spectrum and un-normalized wave function were obtained. We applied the present results to predict the mass spectra of heavy and heavy-light mesons in the presence and absence of a topological defect for different quantum states. We noticed that when the topological defect increases the mass spectra are shifted and move closer to the experimental data. However, when compared to the work of other researchers, the results established an improvement.