Vector Meson Dominance Model Research Articles

Hadron-ion collisions in Pythia and the vector-meson dominance model for photoproduction

Hadron-ion collisions in Pythia and the vector-meson dominance model for photoproduction

ρ meson magnetic dipole moment from BaBar e+e−→π+π−π0π0 cross section measurement

We obtain the value of the magnetic dipole moment of the ρ meson, using data from the collaboration for the e+e−→π+π−2π0 process. The considered center of mass energy range is from 0.9 to 1.8 GeV. We describe the γ*→4π vertex using a vector meson dominance model, including the intermediate resonant contributions relevant at these energies. We find μρ=2.7±0.3 in e/2mρ units. We improve on the previous extracted value, where preliminary data from the same collaboration was used, by considering definite data, better grounded values of the parameters involved, and an explicit gauge invariant description of the process. Published by the American Physical Society 2024

Photoproduction of the X(3872) beyond vector meson dominance: the open-charm coupled-channel mechanism

Hidden-charm exotic hadrons will be searched for and investigated at future electron–ion colliders. For instance, the X(3872) can be produced through the exclusive process γ p → X(3872)p. The vector meson dominance model has been commonly employed in estimating the cross sections of such processes. However, the coupled-channel production mechanism through open-charm meson-baryon intermediate states may play a crucial role. To assess the significance of such contributions, we estimate the cross section of the γ p → X(3872)p reaction assuming the coupled-channel mechanism. For energies near the threshold, the total cross section is predicted to be of tens of nanobarns for γ p → X(3872)p, which can be measured at future experimental facilities. Furthermore, the open-charm coupled-channel mechanism leads to a distinct line shape of the total cross section that can be utilized to reveal the production dynamics.

Systematic investigation of trace anomaly contribution in nucleon mass

In this work, under the framework of the vector meson dominance model, the trace anomaly contribution value inside neutrons is extracted for the first time based on vector meson photoproduction data. Furthermore, we systematically compare and analyze the trace anomaly contributions of protons and neutrons. The results show that the trace anomaly contributions of protons and neutrons are close, which indirectly confirms that their internal structures and dynamic properties may have certain similarities. In addition, the main factors affecting the extraction of the trace anomaly contribution of nucleons are discussed in detail. This study not only provides a theoretical basis for us to better understand the source of nucleon mass but also makes a useful exploration and discussion on how to extract the trace anomaly contribution of nucleons more accurately in the future. Published by the American Physical Society 2024

Study of weak radiative decays of D0→Vγ

The weak radiative decay of D0→Vγ with V=K¯0, and ϕ, ρ0, and ω, is systematically studied in the vector meson dominance model. It allows us to distinguish the short-distance mechanisms which can be described by the tree-level transitions in the nonrelativistic constituent quark model, and the long-distance mechanisms which are related to the final-state interactions (FSIs). We find that the FSI effects play a crucial role in D0→Vγ and the SU(3) flavor symmetry can provide a natural constraint on the relative phase between the short and long-distance transition amplitudes. Our analysis suggests that the D-meson weak radiative decays can serve as a good case for investigating the nonperturbative QCD mechanisms at the charm quark mass region. Published by the American Physical Society 2024

Improved measurement of the decays η′→π+π−π+(0)π−(0) and search for the rare decay η′→4π0

Using a sample of 10 billion J/ψ events collected with the BESIII detector, the decays η′→π+π−π+π−, η′→π+π−π0π0 and η′→4π0 are studied via the process J/ψ→γη′. The branching fractions of η′→π+π−π+π− and η′→π+π−π0 π0 are measured to be (8.56±0.25(stat)±0.23(syst))×10−5 and (2.12±0.12(stat)±0.10(syst))×10−4, respectively, which are consistent with previous measurements but with improved precision. No significant η′→4π0 signal is observed, and the upper limit on the branching fraction of this decay is determined to be less than 1.24×10−5 at the 90% confidence level. In addition, an amplitude analysis of η′→π+π−π+π− is performed to extract the doubly virtual isovector form factor α for the first time. The measured value of α=1.22±0.33(stat)±0.04(syst), is in agreement with the prediction of the vector meson dominance model. Published by the American Physical Society 2024

E+e−→Λc+Λ¯c− Cross Sections and the Λc+ Electromagnetic Form Factors within the Extended Vector Meson Dominance Model

Within the extended vector meson dominance model, we investigate the e+e−→Λc+Λ¯c− reaction and the electromagnetic form factors of the charmed baryon Λc+ . The model parameters are determined by fitting them to the cross sections of the process e+e−→Λc+Λ¯c− and the magnetic form factor |G M| of Λc+ . By considering four charmonium-like states, called ψ(4500), ψ(4660), ψ(4790), and ψ(4900), we can well describe the current data on the e+e−→Λc+Λ¯c− reaction from the reaction threshold up to 4.96 GeV. In addition to the total cross sections and |G M|, the ratio |G E/G M| and the effective form factor |G eff| for Λc+ are also calculated, and found that these calculations are consistent with the experimental data. Within the fitted model parameters, we have also estimated the charge radius of the charmed Λc+ baryon.

Dilepton production in proton-proton reaction at 4.5 GeV with the HADES spectrometer

Spectra of dileptons emitted in hadron collisions are important tool to study electromagnetic decays of resonances and the validity of the Vector Meson Dominance model. Furthermore, they provide reference spectra for the hot and dense (heavy-ion A+A collisions) and cold nuclear matter (p+A collisions). In February 2022, proton-proton reactions at 4.5 GeV beam kinetic energy were measured by HADES experiment. The aim of the analysis is to study the specific channels that produced dileptons, such as baryonic resonance Dalitz decays (Δ/N* → Ne+e−) and vector meson decays (ρ/ω/φ→ e+e−). In addition, the investigations of dielectron production above the φ meson mass will be enabled. In this contribution, different steps of the e+e− pair reconstruc tion are discussed.

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.

Role of the ρ(1450) in low-energy observables from an analysis in the meson dominance approach

The $\ensuremath{\rho}(1450)$ vector meson (${\ensuremath{\rho}}^{\ensuremath{'}}$) is becoming increasingly important to properly describe precision observables. We analyze a set of decay modes and cross sections, in the low-energy regime, to determine the role played by this meson. This is done through the extraction of the parameters for its description, in the context of the vector meson dominance model and its effective hadronic interactions, involving the low mass lying hadrons ($\ensuremath{\rho}$, $\ensuremath{\omega}$, and $\ensuremath{\pi}$). In a first step, we determine the parameters of the model from ten decay modes which are insensitive to the ${\ensuremath{\rho}}^{\ensuremath{'}}$. Then, we consider the $\ensuremath{\omega}\ensuremath{\rightarrow}3\ensuremath{\pi}$ decay and exhibit the need to extend the description, by incorporating the ${\ensuremath{\rho}}^{\ensuremath{'}}$ and a contact term as prescribed by the Wess-Zumino-Witten anomaly. In a second step, we incorporate the data from the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}3\ensuremath{\pi}$ cross section (as measured by SND, CMD2, BABAR, and BESIII) and then the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ data (as measured by SND and CDM2) to further restrict the ${\ensuremath{\rho}}^{\ensuremath{'}}$ parameters validity region. As an application of the results, we compute the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}4\ensuremath{\pi}$ cross section for the so-called omega channel, measured by BABAR, and find a good description of the data considering the parameters found. As a byproduct, the coupling between $\ensuremath{\rho}$, $\ensuremath{\omega}$, and $\ensuremath{\pi}$ (${g}_{\ensuremath{\rho}\ensuremath{\omega}\ensuremath{\pi}}=11.314\ifmmode\pm\else\textpm\fi{}0.383\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$) is found to be consistent with all the relevant observables, upon the inclusion of the ${\ensuremath{\rho}}^{\ensuremath{'}}$ and the contact term.

First extraction of the proton mass radius and scattering length $$\vert\alpha_{\rho^{0}p}\vert$$ from ρ0 photoproduction

As it involves the lightest physical states excited from the vacuum by the vector quark current, near-threshold ρ0 photoproduction is considered a possible way to research the proton radius and the absolute value of the scattering lengths of the ρ0-proton interaction. In this study, under the assumption of a scalar form factor of dipole form, the value of the proton mass radius is calculated as (0.85 ± 0.06) fm by fitting the differential cross section of the γp → ρ0p reaction at near-threshold energy. For light vector meson photoproduction, because the exchange of a scalar quark-antiquark pair is not suppressed and should dominate the scalar gluon exchange, the radius we extract from ρ0 photoproduction is likely to represent the quark radius of the proton. This fact may explain why the value obtained in this study is very near the proton charge radius. Moreover, the absolute value of the ρ0-proton scattering length $$\vert\alpha_{\rho^{0}p}\vert=(0.31 \pm 0.06)$$ fm is obtained for the first time within the vector meson dominance model. This result disobeys the rule that the absolute value of the vector meson and proton scattering length $$\vert\alpha_{V_{p}}\vert$$ increases with the meson’s mass, which can be attributed to treating the ρ0 meson as a point in the analysis. These results provide useful theoretical information for an in-depth understanding of proton structure and the proton-vector meson interaction.

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.

Observation of the hindered electromagnetic Dalitz decay ψ(3686)→e+e−ηc

Using a data sample of (448.1±2.9)×106 ψ(3686) decays collected at an e+e− center-of-mass energy of 3.686 GeV by the BESIII detector at Beijing Electron Positron Collider II, we report an observation of the hindered electromagnetic Dalitz decay ψ(3686)→e+e−ηc with a significance of 7.9σ. The branching fraction is determined to be B(ψ(3686)→e+e−ηc)=(3.77±0.40stat±0.18syst)×10−5, agreeing well with the prediction of the vector meson dominance model. This is the first measurement of the electromagnetic Dalitz transition between the ψ(3686) and the ηc, which provides new insight into the electromagnetic properties of this decay, and offers new opportunities to measure the absolute branching fractions of ηc decays.Received 26 August 2022Accepted 9 November 2022DOI:https://doi.org/10.1103/PhysRevD.106.112002Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBranching fractionElectromagnetic transitionsPhysical SystemsQuarkoniaPropertiesForm factorsTechniquesLepton collidersParticles & Fields

Analysis of the contribution of the quantum anomaly energy to the proton mass

Inspired by the recent Hall C and GlueX measurements of $J/\psi$ photoproduction, a systematic analysis of the contribution of quantum anomalous energy (QAE) to the proton mass is carried out under the framework of the vector meson dominance model. The results show that the effective Pomeron model and the parametrized two gluon exchange model can explain the cross section of $J/\psi$ photoproduction well. Based on the predicted cross section values given by the two models, the distribution of the QAE contribution with the energy is extracted for the first time. Finally, the average value of the QAE contribution is estimated to be (3.50$\pm$0.70)$\%$, which suggests that the QAE contribution to the proton mass is small. Accordingly, we compared this result with those of other groups and explored the causes for the differences.

Contribution of exclusive (π0π0,π0η,ηη)γ channels to the leading order HVP of the muon g−2

We evaluate the contributions of $(\pi^0\pi^0, \pi^0\eta, \eta\eta)\gamma$ exclusive channels to the dispersion integral of the leading order HVP of the muon anomalous magnetic moment. These channels are included in some way in previous evaluations of the $\pi^0\omega, \eta\omega$ and $\eta\phi$ contributions to $a_{\mu}^{\rm had, LO}$, where the vector resonances (decaying into $\pi^0/\eta+ \gamma$) are assumed to be on-shell. Since the separation of resonance and background contributions in a given observable is, in general, a model-dependent procedure, here we use pseudoscalar mesons and the photon as the $in$ and $out$ states of the $e^+e^- \to (\pi^0\pi^0, \pi^0\eta, \eta\eta)\gamma$ $S$-matrix, such that the cross section contains the interferences among different contributing to the amplitudes. We find $a^{\rm had, LO}_{\mu}(P^0_1P^0_2\gamma)=(1.13\pm 0.13 ) \times 10^{-10}$, where uncertainties stem mainly from vector meson dominance model parameters. Improved experimental studies of these exclusive channels in the whole range below 2 GeV would reduce model-dependency.

ψ(*)p scattering length based on near-threshold charmonium photoproduction

Under the framework of Vector Meson Dominance model, the value of scattering length can be expressed as a function of the ratio between total cross section $\sigma (W)$ and $R (W)$, where $R(W)$ is the ratio between final momentum $|{\bf p}_3 |$ and initial momentum $|{\bf p}_1|$ and positively correlated with the center-of-mass energy. Based on the theoretical study of charmoniums photoproduction within two gluon exchange model and effective pomeron model, we research the scattering lengths of vector mesons and proton interaction in this work. Results show that the scattering length $\left|\alpha_{J/\psi p}\right|$ obtained from the two models are close and basically in agreement with the theoretical prediction of Strakovsky and co-workers. Additionally, we first calculate the scattering length of $\psi(2S) $-proton interaction in two gluon exchange model and effective pomeron model as $ 1.31\pm 0.92$ am (1 am = $10^{-3}$ fm) and $ 3.24 \pm 0.63$ am, respectively. This is a little bit different from the two models and requires precise measurements from subsequent experiments. In short, our results will provide a theoretical reference for future studies on characterizing the vector meson-proton scattering length.

Rare decays of the B s –meson into four charged leptons in the framework of the Standard Model

In the framework of the Standard Model we present new theoretical predictions for the branching ratios, double and single differential distributions and forward—backward leptonic asymmetries for the decay. In our consideration we take into account the —resonance contribution; the main contributions of four charmonium resonances : and —resonant contribution from and ‘tails’ contributions from and resonances; non—resonant contribution of the - pairs, bremsstrahlung and the contribution of the weak annihilation. We provide the prediction for the branching ratio of decay with and without the —resonance contribution. We use the model of vector meson dominance (VMD) for calculation of resonances contributions and take into account all substantive terms in amplitude that was not considered in the previously papers.

Calculations of differential momentum transfer spectra for J/ψ photoproduction in heavy-ion collisions * *Supported by the National Natural Science Foundation of China (12005220, 12175223) and MOST (2018YFE0104900)

Understanding the gluonic structure in nuclei is one of the most important goals in modern nuclear physics, for which J/ψ photoproduction is suggested as a powerful tool to probe the gluon density distribution. The experimental investigation of the photoproduction process is conventionally studied in ultra-peripheral heavy-ion collisions, and has recently been extended to hadronic collisions. However, theoretical efforts in hadronic heavy-ion collisions are still lacking in the literature. In this paper, we build up a phenomenological framework to calculate the differential momentum transfer spectra for J/ψ photoproduction in hadronic heavy-ion collisions based on a vector meson dominance model. For the first time, we include the effect of internal photon radiation in the calculations, and we find that the results with internal photon radiation could describe the experimental measurements from STAR very well.

QCD analysis of electromagnetic Dalitz decays J/ψ→η(′)ℓ+ℓ−

The electromagnetic Dalitz decays $J/\ensuremath{\psi}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{(\ensuremath{'})}{e}^{+}{e}^{\ensuremath{-}}$ with large recoil momentum are studied in the framework of perturbative QCD. Meanwhile, the soft contributions from the small recoil momentum region are described by the overlap of soft wave functions, and the resonance contributions are estimated by the vector meson dominance model. Based on this dynamical picture, the transition form factors ${f}_{\ensuremath{\psi}{\ensuremath{\eta}}^{(\ensuremath{'})}}({q}^{2})$ in full kinematic region are calculated for the first time, and we find that the transition form factors are insensitive to the shapes of ${\ensuremath{\eta}}^{(\ensuremath{'})}$ distribution amplitudes. Our prediction of the normalized transition form factor ${F}_{\ensuremath{\psi}\ensuremath{\eta}}({q}^{2})\ensuremath{\equiv}{f}_{\ensuremath{\psi}\ensuremath{\eta}}({q}^{2})/{f}_{\ensuremath{\psi}\ensuremath{\eta}}(0)$ agrees well with its experimental data. In addition, we also find that the branching ratios $\mathcal{B}(J/\ensuremath{\psi}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{(\ensuremath{'})}{e}^{+}{e}^{\ensuremath{-}})$ are dominated by the contributions of perturbative QCD, and the resonance contributions are negligibly small as well as the soft contributions due to the suppression of the kinematic factor. With all these contributions, our results of the branching ratios $\mathcal{B}(J/\ensuremath{\psi}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{(\ensuremath{'})}{e}^{+}{e}^{\ensuremath{-}})$ and the ratio ${R}_{J/\ensuremath{\psi}}^{e}=\mathcal{B}(J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\eta}{e}^{+}{e}^{\ensuremath{-}})/\mathcal{B}(J/\ensuremath{\psi}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}{e}^{+}{e}^{\ensuremath{-}})$ are in good agreement with their experimental data. Using the obtained ${F}_{\ensuremath{\psi}{\ensuremath{\eta}}^{(\ensuremath{'})}}({q}^{2})$, we give the predictions of the branching ratios $\mathcal{B}(J/\ensuremath{\psi}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{(\ensuremath{'})}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$ and their ratio ${R}_{J/\ensuremath{\psi}}^{\ensuremath{\mu}}$.

Electromagnetic Dalitz decays of D(s)∗ mesons

Rare electromagnetic (EM) decays of charmed mesons are useful laboratories to explore the structure of hadronic states and the interactions between photons and charmed mesons, to test the chiral perturbation theory in flavor sector and to search for new physics including dark photons. In this paper, we calculate the relative branching ratios of EM Dalitz decays [Formula: see text] to their corresponding radiative decays [Formula: see text] with transition form factor in vector-meson dominance model, where [Formula: see text] represents [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. The corresponding dileptonic invariant mass spectra and the leptonic angular distributions are also presented.