Light Vector Mesons Research Articles

Polarization study of the P-wave charmonium radiative decay into a light vector meson at e+e- collider experiment

Abstract In this work, a formalism is presented for the helicity amplitude analysis of the decays ψ(2S) →γ1χcJ, χcJ→γ2V (V=ρ0, Φ, ω) (the subscript 1,2 is used to distinguish the two radiative photons), and the polarization expressions of the P-wave charmonia χcJ and the vector mesons ρ0, Φ, ω for experimental measurements at Electron-Positron Collider. In addition, we derive the formulae of the angular distributions of the χc1,2→γV to extract the degree of transverse polarization PT of e+e- pairs with symmetric beam energy as well as the ratios of two helicity amplitudes x (in χc1 decays) and x, y (in χc2 decays) representing the relative magnitudes of transverse to longitudinal polarization amplitude, and validate it by performing the Monte Carlo simulation. Finally, the statistical sensitivity of PT, x and y are estimated based on the large ψ(2S) data samples collected at the current and proposed future e+e- collider experiment.Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must main tain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd

Evolution and fluctuations of chiral chemical potential in heavy ion collisions

The possible appearance of the effects of local parity breaking in the QCD medium formed in heavy ion collisions due to violation of chiral symmetry can be quantified by corresponding chiral chemical potential [Formula: see text]. The experimental observables sensitive to the effects of local parity violation in strong interaction include search for polarization splitting of the [Formula: see text] and [Formula: see text] mesons via angular dependence of spectral functions in their decay to leptons. In this paper, we study the space-time evolution and fluctuations of [Formula: see text] using relativistic hydrodynamics and estimate their effect on the light vector meson polarization splitting in Pb–Pb collisions at LHC energy.

Dark matter relic density in strongly interacting dark sectors with light vector mesons

Stable dark matter particles may arise as pseudo-Goldstone bosons from the confinement of dark quarks interacting via a non-Abelian gauge force. Their relic abundance is determined not by annihilations into visible particles but by dark pion number-changing processes within the dark sector, such as 3πD→2πD. However, if the dark vector mesons ρD are light enough for 3πD→πDρD annihilations to be kinematically allowed, this process dominates and significantly delays freeze-out. As a result, the preferred dark matter mass scale increases and bounds from the Bullet Cluster can be evaded. Published by the American Physical Society 2024

Symmetries of spatial correlators of light and heavy mesons in high temperature lattice QCD

The spatial z correlators of meson operators in Nf=2+1+1 lattice QCD with optimal domain-wall quarks at the physical point are studied for seven temperatures in the range of 190–1540 MeV. The meson operators include a complete set of Dirac bilinears (scalar, pseudoscalar, vector, axial vector, tensor vector, and axial-tensor vector), and each for six flavor combinations (u¯d, u¯s, s¯s, u¯c, s¯c, and c¯c). In a recent paper [], I focused on the meson correlators of u and d quarks, and discussed their implications for the effective restoration of SU(2)L×SU(2)R and U(1)A chiral symmetries, as well as the emergence of approximate SU(2)CS chiral spin symmetry. In this work, we extend our study to meson correlators of six flavor contents, and first observe the hierarchical restoration of chiral symmetries in QCD, from SU(2)L×SU(2)R×U(1)A to SU(3)L×SU(3)R×U(1)A, and to SU(4)L×SU(4)R×U(1)A, as the temperature is increased from 190 to 1540 MeV. Moreover, we compare the temperature windows for the emergence of the approximate SU(2)CS symmetry in light and heavy vector mesons, and find that the temperature windows are dominated by the (u¯c,s¯c,c¯c) sectors. Published by the American Physical Society 2024

An improved calculation of the D(s)∗D(s)V\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{(s)}^*D_{(s)}V$$\\end{document} and B(s)∗B(s)V\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)}^*B_{(s)}V$$\\end{document} couplings from light-cone sum rules

We present an improved calculation of the D(s)∗D(s)V\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D_{(s)}^*D_{(s)}V$$\\end{document} and B(s)∗B(s)V\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{(s)}^*B_{(s)}V$$\\end{document} coupling constants, where V denotes ρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho $$\\end{document}, K∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$K^*$$\\end{document}, ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\omega $$\\end{document}, and ϕ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\phi $$\\end{document} mesons. These couplings govern the long-distance quantum chromodynamics (QCD) in interactions between heavy pseudo-scalar/vector mesons and light vector mesons. Our analysis is conducted within the framework of QCD light-cone sum rules (LCSRs) by utilizing the light-cone distribution amplitudes (LCDAs) of light vector mesons. By systematically incorporating the subleading power corrections and higher-twist contributions at the leading order (LO) and including the next-to-leading order (NLO) corrections at leading power, we achieve enhanced accuracy in the light-cone operator product expansion (OPE) for the underlying correlation function. In assessing the reliability of the established LCSRs, we consider uncertainties arising from the choice of the quark–hadron duality region in the double dispersion relation. Building upon these improvements, we accomplish an optimized computation and analysis for the strong coupling constants gH∗HV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g_{H^*HV}$$\\end{document} which are used to extract the effective coupling λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda $$\\end{document} in the heavy meson chiral perturbation theory (HMχ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi $$\\end{document}PT). Furthermore, we investigate the SU(3) flavor symmetry-breaking effects in detail and compare our sum rule calculations with previous studies in an exploratory way.

Exclusive production of double light neutral mesons at the e+e− colliders

In this work we investigate the exclusive production of a pair of light neutral mesons in e+e− annihilation, where the final state bears an even C-parity. The production processes can be initiated via the photon fragmentation or the nonfragmentation mechanism. While the fragmentation contribution can be rigorously accounted, the nonfragmentation contributions are calculated within the framework of collinear factorization, where only the leading-twist light-cone distribution amplitudes (LCDAs) of mesons are considered. Mediately solely by the nonfragmentation mechanism, the production rates of double light neutral pseudoscalar mesons are too small to be observed at the commissioning e+e− facilities. In contrast, the production rates of a pair of light neutral vector mesons are greatly amplified owing to the significant kinematic enhancement brought by the fragmentation mechanism. It is found that, at s=3.77 GeV, after including the destructive interference between the nonfragmentation and fragmentation contributions, the production rates for e+e−→ρ0ρ0 and ρ0ω can be lowered by about 10% and 30% relative to the fragmentation predictions. Future precise measurement of these exclusive double neutral vector meson production channels at BESIII experiment may provide useful constraints on the LCDAs of light vector mesons. Published by the American Physical Society 2024

Hadronic structure on the light front. VIII. Light scalar and vector mesons

We use the QCD instanton vacuum model to discuss the emergence of the light scalar and vector mesons on the light front. We take into account both the instanton and anti-instanton single and molecular interactions on the light quarks, in the form of nonlocal effective interactions. Although the molecular induced interactions are suppressed by a power of the packing fraction, they are still sufficient to bind the vector mesons, while keeping most of the scalar spectrum relatively unchanged. We explicitly derive the light front distribution amplitudes and partonic functions for the scalar and vector mesons, and compare them after pertinent QCD evolution, to the available empirical and lattice measured counterparts. The Dirac electric form factors for both the pion and ρ meson are derived, and shown to compare well with current data. Published by the American Physical Society 2024

Searching for minicharged particles at the energy frontier with the MoEDAL-MAPP experiment at the LHC

The MoEDAL’s Apparatus for Penetrating Particles (MAPP) Experiment is designed to expand the search for new physics at the LHC, significantly extending the physics program of the baseline MoEDAL Experiment. The Phase-1 MAPP detector (MAPP-1) is currently undergoing installation at the LHC’s UA83 gallery adjacent to the LHCb/MoEDAL region at Interaction Point 8 and will begin data-taking in early 2024. The focus of the MAPP experiment is on the quest for new feebly interacting particles — avatars of new physics with extremely small Standard Model couplings, such as minicharged particles (mCPs). In this study, we present the results of a comprehensive analysis of MAPP-1’s sensitivity to mCPs arising in the canonical model involving the kinetic mixing of a massless dark U(1) gauge field with the Standard Model hypercharge gauge field. We focus on several dominant production mechanisms of mCPs at the LHC across the mass-mixing parameter space of interest to MAPP: Drell-Yan pair production, direct decays of heavy quarkonia and light vector mesons, and single Dalitz decays of pseudoscalar mesons. The 95% confidence level background-free sensitivity of MAPP-1 for mCPs produced at the LHC’s Run 3 and the HL-LHC through these mechanisms, along with projected constraints on the minicharged strongly interacting dark matter window, are reported. Our results indicate that MAPP-1 exhibits sensitivity to sizable regions of unconstrained parameter space and can probe effective charges as low as 8 × 10−4e and 6 × 10−4e for Run 3 and the HL-LHC, respectively.

Masses of magnetized pseudoscalar and vector mesons in an extended NJL model: The role of axial vector mesons

We study the mass spectrum of light pseudoscalar and vector mesons in the presence of an external uniform magnetic field B→, considering the effects of the mixing with the axial-vector meson sector. The analysis is performed within a two-flavor NJL-like model which includes isoscalar and isovector couplings together with a flavor mixing ’t Hooft-like term. The effect of the magnetic field on charged particles is taken into account by retaining the Schwinger phases carried by quark propagators, and expanding the corresponding meson fields in proper Ritus-like bases. The spin-isospin and spin-flavor decomposition of meson mass states is also analyzed. For neutral pion masses it is shown that the mixing with axial vector mesons improves previous theoretical results, leading to a monotonic decreasing behavior with B that is in good qualitative agreement with lattice QCD (LQCD) calculations, both for the case of constant or B-dependent couplings. Regarding charged pions, it is seen that the mixing softens the enhancement of their mass with B. As a consequence, the energy becomes lower than the one corresponding to a pointlike pion, improving the agreement with LQCD results. The agreement is also improved for the magnetic behavior of the lowest ρ+ energy state, which does not vanish for the considered range of values of B—a fact that can be relevant in connection with the occurrence of meson condensation for strong magnetic fields. Published by the American Physical Society 2024

Correlation function for the Tbb state: Determination of the binding, scattering lengths, effective ranges, and molecular probabilities

We perform a study of the B*+B0,B*0B+ correlation functions using an extension of the local hidden gauge approach which provides the interaction from the exchange of light vector mesons and gives rise to a bound state of these components in I=0 with a binding energy of about 21 MeV. After that, we face the inverse problem of determining the low energy observables, scattering length and effective range for each channel, the possible existence of a bound state, and, if found, the couplings of such a state to each B*+B0,B*0B+ component as well as the molecular probabilities of each of the channels. We use the bootstrap method to determine these magnitudes and find that, with errors in the correlation function typical of present experiments, we can determine all these magnitudes with acceptable precision. In addition, the size of the source function of the experiment from where the correlation functions are measured can be also determined with a high precision. Published by the American Physical Society 2024

Light vector mesons photoproduction and nuclear shadowing

AbstractIn this work, we study the photoproduction of mesons considering the proton and the nucleus as the target. Utilizing the dipole picture and the wave functions obtained via AdS/QCD, we were able to describe the HERA data and extend the formalism to the nuclear case considering the Glauber–Gribov model. The preliminary results obtained in the nuclear regime are compared to the recent LHC data and suggest the presence of a nuclear effect called shadowing.

Exclusive production of ground and excited light vector mesons with a holographic wave function model

AbstractThe exclusive photo‐ and electroproduction of light vector mesons like and is studied in collisions within the color dipole formalism with vector meson wave functions obtained using the AdS/QCD holographic approach. This setup provides a good description of the existing data for the ground vector mesons and permits us to make predictions for the corresponding excited states. The results show significant theoretical uncertainties related to modeling the partial dipole amplitude, which can be constrained with upcoming measurements in future hadron colliders.

Exclusive photo- and electroproduction of excited light vector mesons via holographic model

In this paper, we study total and differential observables of electro- and photoproduction of light rho , omega and phi mesons as functions of the center-of-mass energy of the gamma p collision and momentum transfer squared |t|. The corresponding vector mesons wave functions have been computed in the framework of relativistic AdS/QCD holographic approach. A satisfactory description of all available data on ground-state rho (1S), omega (1S) and phi (1S) mesons production cross sections has been achieved in the color dipole picture. Finally, the key observables of excited rho (2S), omega (2S) and phi (2S) states production in gamma ^{(*)} p collisions have been presented here using a common wave function formalism. This study reveals a large theoretical uncertainty coming from the modeling of the partial dipole amplitude in the nonperturbative kinematical domain. Hence, the latter could benefit from future measurements of photoproduction of the excited states.

Unpolarized generalized parton distributions of light and heavy vector mesons

We study the leading-twist unpolarized generalized parton distributions (GPDs) of light and heavy vector mesons, i.e., the $\ensuremath{\rho}$, $J/\ensuremath{\psi}$, and $\mathrm{\ensuremath{\Upsilon}}$, at zero skewness. An ansatz incorporating the zero-mode contribution is introduced to modify the light front overlap representation of GPDs. The leading Fock-state light front wave functions of vector mesons from Dyson-Schwinger and Bethe-Salpeter equations approach are then employed to study the meson GPDs. The light front spatial distribution of valence quarks within vector mesons is then studied with the impact parameter dependent GPD. We also investigate the electromagnetic and gravitational form factors, which are the first and second Mellin moments of the GPDs. The light-cone mass radius of $\ensuremath{\rho}$ is determined to be 0.30 fm, close to a recent Nambu-Jona-Lasinio model prediction of 0.32 fm. For $J/\ensuremath{\psi}$ and $\mathrm{\ensuremath{\Upsilon}}$, they are predicted to be 0.151 fm and 0.089 fm respectively.

Investigations on the light hadron decays of Zb(10610) and Zb(10650)

The light hadron decay processes of $Z_b(10610)/Z_b(10650)$ provide us a way to study their nature and decay mechanism. In this work, we evaluate the branching ratios of $Z_b(10610)/Z_b(10650) \to VP$ ($V$ and $P$ stand for light vector and pseudoscalar mesons, respectively) using an effective Lagrangian approach, in which the contributions of intermediate bottomed meson triangle loops are considered. In our calculations, the $Z_b(10610)$ and $Z_b(10650)$ are regarded as $B\bar{B}^*+c.c.$ and $B^*\bar{B}^*$ molecular states, respectively. The predicted branching ratios of $Z_b(10610)\rightarrow VP$ are about in the order of $10^{-2}$, while the branching ratios of $Z_b(10650)\rightarrow VP$ are in the order of $10^{-3}$. Furthermore, the dependence of these ratios between different decay modes of $Z_b(10610)/Z_b(10650)$ on the mixing $\eta-\eta^\prime$ angle $\theta_P$ is investigated, which may be a good quantity for the experiments. It is hoped that the calculations here could be tested by future experiments.

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.

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.

Light vector meson photoproduction in ultraperipheral heavy‐ion collisions at the LHC within the Reggeometric Pomeron approach

AbstractBy using the Reggeometric Pomeron model for vector meson production which successfully describes the high energy lepton‐nucleon data, we analyze the light meson production in ultra‐peripheral heavy‐ion collisions at the Large Hadron Collider (LHC). The rapidity distributions for ρ and ϕ photoproduction in lead–lead, xenon–xenon and oxygen– oxygen collisions are investigated.

Investigations of charmless decays of X(3872) via intermediate meson loops

The charmless decay processes of $X(3872)$ provide us a good platform to study the nature and the decay mechanism of $X(3872)$. Based on a molecular nature of $X(3872)$ as a $\overline{D}{D}^{*}$ bound state, we have investigated the charmless decays $X(3872)\ensuremath{\rightarrow}VV$ and $VP$ via intermediate ${D}^{*}\overline{D}+\mathrm{c}.\mathrm{c}.$ meson loops, where $V$ and $P$ stand for light vector and pseudoscalar mesons, respectively. We discuss three cases, i.e., pure neutral components ($\ensuremath{\theta}=0$), isospin singlet ($\ensuremath{\theta}=\ensuremath{\pi}/4$) and neutral components dominant ($\ensuremath{\theta}=\ensuremath{\pi}/6$), where $\ensuremath{\theta}$ is a phase angle describing the proportion of neutral and charged constituents. The proportion of neutral and charged constituent has an influence on the decay widths of $X(3872)\ensuremath{\rightarrow}VV$ and $VP$. With the coupling constant of $X(3872)$ to the $\overline{D}{D}^{*}$ channel obtained under the molecule ansatz of $X(3872)$ resonance, the predicted decay widths of $X(3872)\ensuremath{\rightarrow}VV$ are about tens of keVs, while the decay width can reach a few hundreds of keVs for $X(3872)\ensuremath{\rightarrow}VP$. The dependence of these ratios between different decay modes of $X(3872)\ensuremath{\rightarrow}VV$ and $X(3872)\ensuremath{\rightarrow}VP$ to the mixing angle $\ensuremath{\theta}$ is also investigated. It is expected that the theoretical calculations here can be tested by future experiments.

Neutral pseudoscalar and vector meson masses under strong magnetic fields in an extended NJL model: Mixing effects

Mixing effects on the mass spectrum of light neutral pseudoscalar and vector mesons in the presence of an external uniform magnetic field $\vec B$ are studied in the framework of a two-flavor NJL-like model. The model includes isoscalar and isovector couplings both in the scalar-pseudoscalar and vector sectors, and also incorporates flavor mixing through a 't Hooft-like term. Numerical results for the $B$ dependence of meson masses are compared with present lattice QCD results. In particular, it is shown that the mixing between pseudoscalar and vector meson states leads to a significant reduction of the mass of the lightest state. The role of chiral symmetry and the effect of the alignment of quark magnetic moments in the presence of the magnetic field are discussed.