Meson Interactions Research Articles

Hadronic Molecules with Four Charm or Beauty Quarks

We apply extended local hidden-gauge formalism to study meson–meson interactions with the quark constituents ccc¯c¯, ccc¯b¯/c¯c¯cb, ccb¯b¯/c¯c¯bb, bbc¯b¯/b¯b¯cb, and bbb¯b¯, in which the exchanged mesons are the fully heavy vector mesons J/ψ, Bc* and Υ. We solve the coupled-channel Bethe–Salpeter equation to derive two poles in the bbc¯b¯ system and two poles in the ccc¯b¯ system. There are also four charge-conjugated poles in the b¯b¯cb and c¯c¯cb systems. In the bbc¯b¯ system, one pole corresponds to a sub-threshold bound state when the cutoff momentum is set to Λ>850MeV. The other pole in this system corresponds to a sub-threshold bound state when Λ>1100MeV. In the ccc¯b¯ system, the two poles correspond to sub-threshold bound states only when Λ>1550MeV and Λ>2650MeV. This makes them difficult to identify as deeply bound hadronic molecules. We propose investigating the two poles of the bbc¯b¯ system in the μ+μ−Bc−channel at the LHC.

Roles of the scalar f0(500) and f0(980) in the process D0→π0π0K¯0

Motivated by the near-threshold enhancement and the dip structure around 1 GeV in the π0π0 invariant mass distribution of the process D0→π0π0K¯0 observed by the CLEO Collaboration, we have investigated this process by taking into account the contribution from the S-wave pseudoscalar meson–pseudoscalar meson interactions within the chiral unitary approach, and also the one from the intermediate resonance K¯*(892). Our results are in good agreement with the CLEO measurements, which implies that the near-threshold enhancement near the π0π0 threshold is mainly due to the contributions from the scalar meson f0(500) and the intermediate K¯*, and the cusp structure around 1 GeV in the π0π0 invariant mass distribution should be associated with the scalar meson f0(980). Published by the American Physical Society 2024

Octet baryon and heavy meson interactions in chiral effective field theory

We calculate the effective potentials of the octet baryon and heavy meson systems using the chiral effective field theory up to the next-to-leading order. We consider the contact terms, one-pseudoscalar-meson and two-pseudoscalar-meson exchange contributions, facilitating a comprehensive analysis of the short-, mid-, and long-range interactions in these systems. The low energy constants are correlated with those of the N¯N interaction using a quark-level Lagrangian approach. We also incorporate the decuplet baryon contributions in the loop diagrams. Our research provides new insights into several near-threshold charmed baryons [e.g., Λc(2940), Ξc(3055), and Ωc(3188), etc.] around 3 GeV from the hadronic molecular perspective. We also observe several molecular states, referred to as Ξc, within the mass range of 3100–3500 MeV. Further measurements of their resonance parameters and decay patterns in experiments may help to discriminate the conventional baryon and hadronic molecule explanations for these near-threshold states. Published by the American Physical Society 2024

Description of the processes e+e− → π+π− and τ− → π−π0ντ in the NJL model with value of the vector coupling constant gρ = 6

It is shown that the processes e+e−→π+π− and τ−→π−π0ντ can be described in a unified approach in satisfactory agreement with experiment using the vector coupling constant gρ=6. In this case, in addition to quark loops, it is also necessary to take into account meson loops corresponding to the next order in 1/Nc. These loops must be taken into account when describing the γ(W)→ρ transition, as well as in interaction of mesons in the final state.

Worldvolume fermions as baryons in holographic quantum chromodynamics with instantons

In this study, we investigated worldvolume fermions on the flavor brane in the D0–D4/D8 model, which is holographically equivalent to four-dimensional quantum chromodynamics with instantons or equivalently with a theta angle. The action involving the worldvolume fermions was obtained by the T-duality rules in string theory, and we accordingly derived their effective five-dimensional and canonical four-dimensional forms by using the systematic dimensional reduction and decomposition of the spinor. Subsequently, we used the AdS/CFT dictionary to evaluate the two-point correlation function as the spectral function for the worldvolume fermions and interpreted the fermions as baryons by analyzing their quantum number with the baryon vertex in holography. In this sense, the interacted action involving the worldvolume fermions and gauge field on the flavor brane was finally derived in holography, which describes the various interactions of mesons and baryons with instantons in the large-N limit. Therefore, this study provides a holographic picture to describe baryons and their interactions based on string theory, particularly in the presence of instantons or a theta angle.

Two states for the Ξ(1820) resonance

We recall that the chiral unitary approach for the interaction of pseudoscalar mesons with the baryons of the decuplet predicts two states for the Ξ(1820) resonance, one with a narrow width and the other one with a large width. We contrast this fact with the recent BESIII measurement of the K−Λ mass distribution in the ψ(3686) decay to K−ΛΞ¯+, which demands a width much larger than the average of the PDG, and show how the consideration of the two Ξ(1820) states provides a natural explanation to the experimental data.

Study of the B−→K−ηηc decay due to the DD¯ bound state

We study the B−→K−ηηc decay by taking into account the S-wave contributions from the pseudoscalar meson-pseudoscalar meson interactions within the unitary coupled-channel approach, where the DD¯ bound state is dynamically generated. In addition, the contribution from the intermediate resonance K0*(1430)−, with K0*(1430)−→K−η, is also considered. Our results show that there is a clear peak around 3720 MeV in the ηηc invariant mass distribution, which could be associated with the DD¯ bound state. The future precise measurements of the B−→K−ηηc process at the Belle II and LHCb experiments could be, therefore, used to check the existence of the DD¯ bound state, and to deepen our understanding of the hadron-hadron interactions. Published by the American Physical Society 2024

Analysis of Tcc and Tbb based on the hadronic molecular model and their spin multiplets

Tcc(ccu¯d¯)+ has been reported by the LHCb experiment in 2022. The analysis using the Breit-Wigner parametrization found the small binding energy, 0.273 MeV, which is measured from the threshold of D*+D0. In this paper, we consider Tcc as a DD* hadronic molecule as a deuteronlike state. The one-boson exchange model is employed as for the heavy meson interactions, where we determine the cutoff parameter Λ to reproduce the reported binding energy of Tcc with I(JP)=0(1+). We discuss the properties of the bound state and also search for Tcc with quantum numbers other than 0(1+). Furthermore, we analyze Tbb as a bottom counterpart of Tcc, which involves two bottom quarks, and obtain several bound states. Finally, we consider the light-cloud basis for wave functions of the doubly heavy tetraquarks in the heavy quark limit. Using the basis, we find the spin multiplets of their bound states, indicating the spin structures of diquarks in Tcc and Tbb with the finite quark masses. Published by the American Physical Society 2024

Dynamical generation of the scalar f0(500) , f0(980) , and K0*(700) resonances in the Ds+→K+π+π− reaction

We develop a model aimed at understanding the three mass distributions of pairs of mesons in the Cabibbo-suppressed Ds+→K+π+π− decay recently measured with high statistics by the BESIII collaboration. The largest contributions to the process come from the Ds+→K+ρ0 and Ds+→K*0π+ decay modes, but the Ds+→K0*(1430)π+ and Ds+→K+f0(1370) modes also play a moderate role and all of them are introduced empirically. Instead, the contribution of the f0(500), f0(980), and K0*(700) resonances is introduced dynamically by looking at the decay modes at the quark level, hadronizing qq¯ pairs to give two mesons, and allowing these mesons to interact, for which we follow the chiral unitary approach, to finally produce the K+π+π− final state. While the general features of the mass distributions are fairly obtained, we pay special attention to the specific effects created by the light scalar resonances, which are visible in the low mass region of the π+π−(f0(500)) and K+π−(K0*(700)) mass distributions and a narrow peak for π+π− distribution corresponding to f0(980) excitation. The contribution of these three resonances is generated by only one parameter. We see the agreement found in these regions as further support for the nature of the light scalar states as dynamically generated from the interaction of pseudoscalar mesons. Published by the American Physical Society 2024

Impact of vector meson polarization on its interaction with matter

The production of unstable particles on different nuclei provides the possibility to determine the total cross section of the interaction of vector mesons V=rho ,omega ,varphi , K^{*0}(892),J/psi etc. with nucleons. This interaction is defined by a set of amplitudes that correspond to the transverse (helicity lambda =pm 1) or longitudinal (lambda =0) polarization of the vector meson. The total cross section for the interaction of transversely polarized vector mesons with nucleon sigma _T=sigma (V_T N) has been extracted from the coherent photoproduction of vector mesons off nuclei, while the vector meson production in charge exchange reactions as pi ^pm (K^pm )+Arightarrow V^0(K^{*0})+A' provides the unique opportunity to obtain the not yet measured total cross section for longitudinally polarized vector meson interacting with nucleon sigma _L=sigma (V_L N). We shortly discuss the importance of the knowledge of sigma _L and possibility to extract its value from experiments on nuclear target.

Model independent analysis of femtoscopic correlation functions: An application to the [formula omitted

We face the inverse problem of obtaining the interaction between coupled channels from the correlation functions of these channels. We apply the method to the interaction of the D0K+, D+K0, and Ds+η channels, from where the Ds0⁎(2317) state emerges. We use synthetic data extracted from an interaction model based on the local hidden gauge approach and find that the inverse problem can determine the existence of a bound state of the system with a precision of about 20 MeV. At the same time, we can determine the isospin nature of the bound state and its compositeness in terms of the channels. Furthermore, we evaluate the scattering length and effective range of all three channels, as well as the couplings of the bound state found to all the components. Lastly, the size parameter of the source function, R, which in principle should be a magnitude provided by the experimental teams, can be obtained from a fit to the data with relatively high accuracy. These findings show the value of the correlation function to learn about the meson–meson interaction for systems which are difficult to access in other present facilities.

Non-universality of leptons as a source of new physics from tree level interactions of pseudoscalar mesons

This article is based on the study of pure leptonic decays of charged pseudoscalar mesons taking non-universality into account. We calculate the branching ratios of the processes π±,K±,D±,Ds±,B±. For the search for new physics (NP), we examine the discrepancies between theoretical and experimental results. The discrepancies are possibly due to massive neutrinos, processed massless in the Standard Model (SM), and universal coupling of leptons. We focus on the non-universality of leptons in order to find the bounds on Non-Standard Interaction (NSI) parameters ɛ. We use charge current like NSI and conclude that these decays could provide strong constraints on the NSI parameter.

Hadronic J/ψ regeneration in Pb+Pb collisions

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≤dN0J/ψ/dydNeqJ/ψ/dy≤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.

Interactions of omega mesons in nuclear matter and with nuclei

In-medium interactions of omega -mesons in infinite nuclear matter and finite nuclei are investigated in a microscopic approach, focused on the particle-hole excitations of the medium involving nucleonic NN^{-1} and N^*N^{-1} modes, where N^* denotes a nucleon resonance. The nuclear polarization tensors include relativistic mean-field dynamics by self–consistent scalar and vector fields. The resulting self-energies are transmitted to finite nuclei in local density approximation. Real and imaginary parts of longitudinal and transversal self-energies are discussed. The relation of the present approach to meson cloud models is addressed and an ambiguity is pointed out. Applications to recent data on the in–medium width of omega mesons scattered on a Niobium target serve to determine unknown N^*Nomega in-medium coupling constants. The data are well described by N^*N^{-1} self–energies containing S–wave and P-wave N^* resonances. Exploratory investigations, however, show that the spectroscopic composition of self-energies depends crucially on the near-threshold properties of the width which at present is known only within large error bars. The calculations predict the prevalence of transversal self–energies, implying that vector current conservation is still maintained in the nuclear medium by slightly more than 90%. Schrödinger-equivalent potentials are derived and scattering lengths and effective range parameters are extracted for the longitudinal and transversal channel. Longitudinal and transversal spectral distributions are discussed and the dependencies on momentum and nuclear density are investigated. Schrödinger-type omega +{}^{93}Nb optical potentials are constructed. Low-energy parameters are determined, are used to study the pole structure of the S-matrix at threshold. The effective range expansion of the omega-nucleus K-matrix led to a omega +{}^{93}Nb bound states with binding energy Re(varepsilon _B)=-448 keV but of width Gamma _B=4445 keV.

Non universality of leptons as a source of new physics from non standard interactions of pseudoscalar mesons

The rare decays, K+→π+νν¯, B+→π+νν¯ and D+→π+νν¯, are investigated in the frame work of nonstandard neutrino interactions (NSI). It is claimed that NSI are arising due to non-universality of the leptons and bounds on NSI parameters ϵll′uL are determined. For this purpose, the branching ratios (Br) of these processes with in the Standard Model (SM) and beyond the SM are calculated by applying the non-universality of the leptons. The NSI in K+→π+νν¯ and B+→π+νν¯ proceed with u quark in the loop while other two with d quark in the loop. Very stringent 1 σ level constrains on non-standard parameters (ϵττuL and ϵτl′uL) are pointed out.

First characterization of the scattering length distribution of the vector meson interaction with the deuteron

First characterization of the scattering length distribution of the vector meson interaction with the deuteron

Exploring fully heavy scalar tetraquarks [formula omitted

The masses, current couplings and widths of the fully heavy scalar tetraquarks X4Q=QQQ‾Q‾, Q=c,b are calculated by modeling them as four-quark systems composed of axial-vector diquark and antidiquark. The masses m(′) and couplings f(′) of these tetraquarks are computed in the context of the QCD sum rule method by taking into account a nonperturbative term proportional to the gluon condensate 〈αsG2/π〉. Results m=(6570±55)MeV and m′=(18540±50)MeV are used to fix kinematically allowed hidden-flavor decay channels of these states. It turns out that, the processes X4c→J/ψJ/ψ, X4c→ηcηc, and X4c→ηcχc1(1P) are possible decay modes of X4c. The partial widths of these channels are evaluated by means of the couplings gi,i=1,2,3 which describe strong interactions of tetraquark X4c and mesons at relevant vertices. The couplings gi are extracted from the QCD three-point sum rules by extrapolating corresponding form factors gi(Q2) to the mass-shell of a final meson. The mass of the scalar tetraquark X4b is below the ηbηb and ϒ(1S)ϒ(1S) thresholds, therefore it does not fall apart to these bottomonia, but transforms to conventional particles through other mechanisms. Comparing m=(6570±55)MeV and Γ4c=(110±21)MeV with parameters of structures observed by the LHCb, ATLAS and CMS collaborations, we interpret X4c as the resonance X(6600) reported by CMS. Comparisons are made with other theoretical predictions.

Vector meson-nucleon scattering length $$|\alpha _{VN}|$$ and trace anomalous energy contribution to the nucleon mass $$T_{A}$$

Low-energy scattering processes of vector meson and nucleon are an important window for studying non-perturbative QCD. The interaction of vector meson with nucleon, vector meson-nucleon scattering length $|\alpha_{VN}|$, is an important component of the study of hadronic interactions. Nowadays many scattering length values $|\alpha_{VN}|$ have been reported using the recent photoproduction experiment data or quasi data. In addition, the study of trace anomalous energy contribution to the proton mass is also a hot topic in non-perturbative QCD and hadron physics. However, it is difficult to measure proton trace anomalous energy experimentally, and the study of the trace anomaly of proton is still inconclusive. In this study, we established the relationship between the scattering length of the vector meson-proton $|\alpha_{Vp}|$ and the trace anomaly contribution of the proton mass $T_{A}$. With the scattering length values extracted by using the Vector Meson Dominance model, we obtained the trace anomaly contribution of the proton mass $T_{A}$ = (22.8$\%$ $\pm$ 1.2$\%$), which is of similar order of magnitude as the 23$\%$ given by Lattice QCD calculation. We conjecture that the trace anomaly contribution of nucleon is independent of the type of vector meson probe. We hope that high precision measurements of vector meson-nucleon scattering length could give us a better chance to explore the origin of the nucleon mass.

Spanning the full range of neutron star properties within a microscopic description

The high-density behavior of nuclear matter is analyzed within a relativistic mean-field description with non-linear meson interactions. To assess the model parameters and their output, a Bayesian inference technique is used. The Bayesian setup is limited only by a few nuclear saturation properties, the neutron star maximum mass larger than 2 M$_\odot$, and the low-density pure neutron matter equation of state (EOS) produced by an accurate N$^3$LO calculation in chiral effective field theory. Depending on the strength of the non-linear scalar vector field contribution, we have found three distinct classes of EOSs, each one correlated to different star properties distributions. If the non-linear vector field contribution is absent, the gravitational maximum mass and the sound velocity at high densities are the greatest. However, it also gives the smallest speed of sound at densities below three times saturation density. On the other hand, models with the strongest non-linear vector field contribution predict the largest radii and tidal deformabilities for 1.4 M$_\odot$ stars, together with the smallest mass for the onset of the nucleonic direct Urca processes and the smallest central baryonic densities for the maximum mass configuration. These models have the largest speed of sound below three times saturation density, but the smallest at high densities, in particular, above four times saturation density the speed of sound decreases approaching approximately $\sqrt{0.4}c$ at the center of the maximum mass star. On the contrary, a weak non-linear vector contribution gives a monotonically increasing speed of sound. A 2.75 M$_\odot$ NS maximum mass was obtained in the tail of the posterior with a weak non-linear vector field interaction. We found that pQCD favors models with a large non-linear vector field contribution or hyperons.

Theoretical study of Ds+→π+π0π0

Inspired by the BESIII Collaboration's recent amplitude analysis on ${D}_{s}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$, we develop a model based on the chiral unitary approach to describe the ${D}_{s}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ decay, where ${D}_{s}^{+}$ decays into ${\ensuremath{\pi}}^{+}$ and a quark-antiquark pair through weak decay of a charm quark. The interaction of pseudoscalar mesons produced by the hadronization of a quark-antiquark pair will lead to dynamically generated ${f}_{0}(980)$. The dominant amplitudes from resonances ${f}_{0}(1370)$ and ${f}_{2}(1270)$ in the BESIII fit are also included in our model. In addition to the above contributions, to obtain a good fit, we also add an amplitude from the resonance ${f}_{2}(1430)$ to our model. Our model provides a good fit for the ${M}_{{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}}$ and ${M}_{{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}}$ invariant mass distributions simultaneously.