BESIII Collaboration Research Articles

Likelihood analysis of the newly observed f0(2020) , f0(2330) , and f0(2470) in J/ψ→γη′η′ as high-lying unflavored scalar mesons

Inspired by the newly observed three scalar states f0(2020), f0(2330), and f0(2470) by the BESIII collaboration in J/ψ→γη′η′, we carried out the study of spectroscopic behavior of these high-lying unflavored scalar mesonic states. In this work, using the phenomenological description of radial (n,M2) trajectory and the quark pair creation model, we discussed the assignments of the f0(2020), f0(2330), and f0(2470) associated with the f0(2200) as the isoscalar high-lying scalar mesonic states and predicted the spectroscopic properties of their high-lying partners. The present study may provide valuable information for the construction of the scalar meson family. Published by the American Physical Society 2024

Su(3) symmetry analysis in charmed baryon two body decays with penguin diagram contribution

An increasing number of experimental measurements from the BESIII, Belle, and Belle-II collaborations encourage investigations into charmed baryon two-body decay processes. By including contributions from the penguin diagrams that are ignored in previous studies, we perform a global analysis with SU(3) flavor symmetry. Assuming all form factors are real, we achieve a remarkable minimal χ2/d.o.f=0.788\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi ^{2}/d.o.f = 0.788$$\\end{document} and find that the contribution of the amplitude proportional to Vcb∗Vub\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$V_{cb}^*V_{ub}$$\\end{document} is of the order ∼0.01\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim 0.01$$\\end{document}, comparable with the contribution of the tree-level diagram. Additionally, by using the KPW theorem to reduce the number of amplitudes from 13 to 7 in the leading contribution, it becomes possible to consider the complex form factor case for the leading IRA amplitude in the global analysis. However, the analysis of complex form factors significantly conflicts with the experimental data Br(Ξc0→Ξ-π+)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Br(\\Xi _c^0\\rightarrow \\Xi ^-\\pi ^+)$$\\end{document}, and by excluding this data, χ2/d.o.f\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\chi ^2/d.o.f$$\\end{document} is reduced from 5.95 to 1.19. Although the analysis of complex form factors shows a significant central value of the penguin diagram contribution, the large errors from the corresponding form factors make it a challenge to precisely determine its true contribution. Consequently, the direct CP violation in decay processes is predicted to be approximately zero. With more data in future experiments, the penguin diagram contribution with the amplitude proportional to Vcb∗Vub\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$V_{cb}^*V_{ub}$$\\end{document} will be precisely determined, allowing for a more accurate prediction of CP violation. Our analysis necessitates further theoretical investigations and experimental measurements in the future.

Searching for |Vcd| through the exclusive decay [formula omitted] within QCD sum rules

In this paper, we carry out an investigation into the semileptonic decays Ds+→K0ℓ+νℓ with ℓ=(e,μ) by employing the QCD light-cone sum rules approach. The vector transition form factor (TFF) f+Ds+K0(q2) for Ds+→K0 decay is calculated while considering its next-to-leading order contribution. Subsequently, we briefly introduce the twist-2, 3 kaon distribution amplitudes, which are calculated by using QCD sum rules within the framework of the background field theory. At the large recoil point, the TFF has f+Ds+K0(0)=0.692−0.026+0.027. Then, we extrapolate f+Ds+K0(q2) to the whole physical q2-region via the simplified z(q2,t)-series expansion, and the behavior of TFF f+Ds+K0(q2) is exhibited in the numerical results part, including the theoretical and experimental predictions for comparison. In addition, we compute the differential branching fraction B(Ds+→K0ℓ+νℓ) with the electron and muon channels, which are expected to be B(Ds+→K0e+νe)=3.379−0.275+0.301×10−3 and B(Ds+→K0μ+νμ)=3.351−0.273+0.299×10−3 as well as contained other results for comparison. Our results show good agreement with the BESIII measurements and theoretical predictions. Furthermore, we present our prediction with respect to the CKM matrix element |Vcd| by using the B(Ds+→K0e+νe) result from BESIII Collaboration, yielding |Vcd|=0.221−0.010+0.008. Finally, we provide the ratio between Ds+→K0e+νe and Ds+→ηe+νe channels, i.e.RK0/ηe=0.144−0.020+0.028.

Evidence of the hc→KS0K+π−+c.c. decay

Based on (2.712±0.014)×109 ψ(3686) events collected by the BESIII Collaboration, evidence of the hadronic decay hc→KS0K+π−+c.c. is found with a significance of 4.3σ in the ψ(3686)→π0hc process. The branching fraction of hc→KS0K+π−+c.c. is measured to be (7.3±1.8±0.8)×10−4, where the first and second uncertainties are statistical and systematic, respectively. Combining with the exclusive decay width of ηc→KK¯π, our result indicates inconsistencies with both pQCD and NRQCD predictions. Published by the American Physical Society 2024

Axion-like particles in radiative quarkonia decays

Radiative quarkonia decays offer an ideal setting for probing Axion-Like Particle (ALP) interactions. This paper provides a comprehensive review of ALP production mechanisms through the e+e− → γa process at B- and Charm-factories, alongside an analysis of potential ALP decay channels. We derive constraints on ALP couplings to Standard Model (SM) fields, based on recent experimental results on quarkonia decays by the Belle II and BESIII collaborations. The analysis distinguishes between “invisible” and “visible” ALP decay scenarios. The “invisible” scenario, characterised by a mono-γ plus missing-energy signature, enables stringent limits on ALP-photon and ALP-quark (b or c) couplings. Moreover, extensive research at flavour factories has explored various “visible” ALP decays into SM final states, which depend on a larger set of ALP-SM couplings. To streamline the “visible” ALP scenario, we introduce additional theoretical assumptions, such as universal ALP-fermion couplings, or we adopt specific benchmark ALP models, aiming to minimise the number of independent variables in our analysis.

Determination of the number of ψ(3686) events taken at BESIII* *The BESIII Collaboration thanks the staff of BEPCII and the IHEP computing center for their strong support. This work is supported in part by National Key R&D Program of China under Contracts Nos. 2020YFA0406300, 2020YFA0406400; National Natural Science Foundation of China (NSFC) under Contracts Nos. 12150004, 11635010, 11735014, 11835012, 11935015,

The number of ψ(3686) events collected by the BESIII detector during the 2021 run period is determined to be (2259.3±11.1)×106 by counting inclusive ψ(3686) hadronic events. The uncertainty is systematic and the statistical uncertainty is negligible. Meanwhile, the numbers of ψ(3686) events collected during the 2009 and 2012 run periods are updated to be (107.7±0.6)×106 and (345.4±2.6)×106, respectively. Both numbers are consistent with the previous measurements within one standard deviation. The total number of ψ(3686) events in the three data samples is (2712.4±14.3)×106.

How does the X(3872) show up in e+e− collisions: Dip versus peak

We demonstrate that the dip observed near the total energy of 3872 MeV in the recent cross section data from the BESIII Collaboration for e+e−→J/ψπ+π− admits a natural explanation as a coupled-channel effect: it is a consequence of unitarity and a strong S-wave DD¯* attraction that generates the state X(3872). We anticipate the appearance of a similar dip in the e+e−→J/ψπ+π−π0 final state near the D*D¯* threshold driven by the same general mechanism, then to be interpreted as a signature of the predicted spin-2 partner of the X(3872). Published by the American Physical Society 2024

Strong decays of the vector tetraquark states with the masses about 4.5 GeV via the QCD sum rules

We suppose that there exist three vector hidden-charm tetraquark states with the JPC=1−− at the energy about 4.5GeV, and investigate the two-body strong decays systematically. We obtain thirty QCD sum rules for the hadronic coupling constants based on rigorous quark-hadron duality, then obtain the partial decay widths, therefore the total widths approximately, which are compatible with the experimental data of the Y(4500) from the BESIII collaboration. The Y(4500) may be one vector tetraquark state having three main Fock components, or consists of three different vector tetraquark states. We can search for the typical decays Y→D¯10D0−D¯0D102, D¯1−D+−D¯−D1+2, D¯00D⁎0−D¯⁎0D002, D¯0−D⁎+−D¯⁎−D0+2, ηcω, J/ψω to diagnose the nature of the Y(4500).

Poles and poltergeists in e+e−→DD¯ data

A recent report of e+e−→DD¯ events by the BESIII collaboration suggests the presence of a structure R at 3900 MeV. We argue that this structure, called G(3900) in the past, is not in fact due to a new cc¯ resonance but rather naturally emerges due to a combination of interference between nearby resonances and the opening of the D*D¯ channel. We further find that the appearance of this structure does not require suppression because of a radial node in the ψ(4040) wave function, although a node improves fit quality. The measured e+e− coupling of ψ(4040) is found to be substantially smaller than previously estimated. In addition, we report new corrections to the measured cross section σ(e+e−→DD¯) at energies near ψ(3770). Published by the American Physical Society 2024

Complete determination of SU(3)F amplitudes and strong phase in Λc+→Ξ0K+

The BESIII collaboration has recently reported the first time measurement of the decay asymmetry α(Λc+→Ξ0K+)=0.01±0.16(stat)±0.03(syst) and also a sizable phase shift of δP−δS=−1.55±0.25 or 1.59±0.25 between S- and P-wave amplitudes. This implies significant strong phase shifts in the decay amplitudes. The strong phases indicate the existence of rescattering or loop effects, which are challenging to calculate due to nonperturbative effects. By employing the flavor SU(3)F symmetry and applying the Körner-Pati-Woo theorem to reduce the number of parameters, we find that the current data already allow us to obtain, for the first time, model-independent decay amplitudes and their strong phases. The establishment of the existence of sizable strong phases opens a window for future investigations into CP violation. In our fit, a notable discrepancy emerges in the branching ratio of Ξc0→Ξ−π+. The direct relationship between Γ(Λc+→Λe+νe) and Γ(Ξc0→Ξ−e+νe), along with newly discovered SU(3)F relations, collectively suggests an underestimation of B(Ξc0→Ξ−π+) in experimental findings. Published by the American Physical Society 2024

Possible Hexaquark Explanation for the 4406.9 MeV/c2 Resonance in Electron-Positron Collisions at Center-of-Mass Energies from 4.23 to 4.70 GeV

Bevelacqua Resources, 7531 Flint Crossing Circle SE, Owens Cross Roads, AL 35763 USA The BESIII Collaboration observed two resonance structures in the e+ e¯ → π+ π− ψ(3823) reactions at center-of-mass energies from 4.23 to 4.70 GeV. The first resonance (R1) has a mass of 4406.9 MeV/c2 and is based on a π+ π¯ Ψ(3823) structure. A second resonance (R2) is based on a π+ π¯ γ ηc1 structure with a mass of 4647.9 MeV/c2. The spin and parity of these states was not provided in Ref. 1. A first-order hexaquark mass formula is applied to evaluate the possible mass and Jπ value of the candidate R1 hexaquark. The R2 state, with a photon included in the final state, is not consistent with the first-order hexaquark model, and is not evaluated. The first-order hexaquark model yields a R1 resonance mass within 1% of the experimental value. The model also suggests that the R1 has a 2¯ spin assignment. KEYWORDS: First Order Mass Formula, Hexaquark, Weak Coupling Model, π+ π¯ Ψ(3823) structure, and R1 Resonance at 4406.9 MeV/c2.

Non-resonant contributions to three-body D → K (s) π ω decays

Recently, the BESIII collaboration has reported an improved measurement of the branching fraction for D 0 → K − π + ω decay, the first observations and branching fraction measurements for D0→KS0π0ω and D+→KS0π+ω decays with the values of (3.392 ± 0.044 stat ± 0.085 syst )%, (0.848 ± 0.046 stat ± 0.031 syst )%, and (0.707 ± 0.041 stat ± 0.029 syst )%, respectively. In this work, we have obtained the non-resonant amplitudes under the factorization approach. The calculated values for branch ratios are B(D0→K−π+ω)=(3.302±0.195)% , B(D0→KS0π0ω)=(0.782±0.067)% , and B(D+→KS0π+ω)=(0.702±0.111)% which are in good agreement with reported experimental values.

Dark photon and Axion-like particle search at BESIII

Numerous indirect astronomical and cosmological evidences have suggested the existence of dark matter (DM) in the universe. Its existence provides a strong hint that there may be a dark sector, consisting of particles that do not interact with the known strong, weak, or electromagnetic force. Intriguingly, this dark sector might couple to the Standard Model via portals, which include the possibility of axion-like particle, light Higgs boson, dark photon and spin- 1/2 fermions. BESIII experiment has collected the largest data samples at the J/ψ and ψ(3686) on threshold in the world, which provides a clean reaction environment to search for dark sector and new physics. This proceeding summarizes the recent results in the search of dark photon and axion-like particles published by the BESIII Collaboration.

Small Angle Initial State Radiation Analysis of the Pion Form Factor at BESIII

The time-like pion form factor (FF), i.e. the cross section of the process e+e− → π+π−, is presently a matter of intense discussion within the particle physics community. The e+e− → π+π− process is the largest contributor to the hadronic vacuum polarization (HVP) correction in the Standard Model prediction of the muon anomalous magnetic moment (aμ). Recent lattice QCD evaluations of the HVP, as well as a new measurement of the pion FF by the CMD-3 collaboration, have hinted at possible shortcomings in previous measurements, thus preventing an unambiguous interpretation of the latest experimental value of aμ. An intense effort is ongoing to provide new experimental insights into the pion FF, and the BESIII collaboration aims to contribute with a new measurement of world-leading precision. In this work, preliminary studies towards such a measurement are presented.

Radiative decays in covariant confined quark model* *Supported by Ho Chi Minh City University of Technology and Education (T2022-26)

Radiative decays are revisited in light of new experimental data from the BaBar and BESIII Collaborations. The radiative couplings encoding nonperturbative QCD effects are calculated in the framework of the covariant confined quark model developed by us. We compare our results with other theoretical studies and experimental data. The couplings (in ) and calculated in our model agree with the corresponding experimental data and . The most interesting case is the decay , for which a recent prediction based on light-cone sum rules at next-to-leading order deviates from the first (and only to date) lattice QCD result at nearly . Our calculation yields , which falls somehow between the two mentioned results, although it is larger than those predicted in other studies using quark models or QCD sum rules.

Isospin violating decays of vector charmonia

We study the isospin violating decays of vector charmonia to ΛΣ¯0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda \\overline{\\Sigma }^0$$\\end{document} and its charge conjugate. They are dominated by the single photon annihilation and can be evaluated reliably with timelike form factors. We utilize the quark-pair creation model, which is valid for the OZI suppressed decays, to evaluate the form factors. We obtain the branching fractions of B(J/ψ→ΛΣ¯0+c.c.)=(2.4±0.4)×10-5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{B}(J/\\psi \\rightarrow \\Lambda \\overline{\\Sigma }^0+c.c.)=(2.4\\pm 0.4)\ imes 10^{-5}$$\\end{document} and B(ψ(2S)→ΛΣ¯0+c.c.)=(3.0±0.5)×10-6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{B}(\\psi (2\\,S)\\rightarrow \\Lambda \\overline{\\Sigma }^0+c.c.)=(3.0\\pm 0.5)\ imes 10^{-6}$$\\end{document}, which are compatible with the measurements by the BESIII collaborations, respectively. The decay asymmetries are found to be αJ/ψ=0.314\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha _{J/\\psi }=0.314$$\\end{document} and αψ(2S)=0.461\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha _{\\psi (2S)}=0.461$$\\end{document}, which can be examined at BESIII in the foreseeable future.

Can the new states around 2.2 GeV be identified as the ω(3D)?

Recently, the BESIII Collaboration reported that there exist two explicit enhancement structures near 2.25[Formula: see text]GeV, one has the mass of [Formula: see text][Formula: see text]MeV and the width of [Formula: see text][Formula: see text]MeV and another structure has the mass of [Formula: see text][Formula: see text]MeV and the width of [Formula: see text][Formula: see text]MeV when analyzing the cross section of subprocesses. Earlier, the BESIII Collaboration reported the existence of the [Formula: see text], with a mass of [Formula: see text][Formula: see text]MeV and width of [Formula: see text][Formula: see text]MeV. Based on these experimental results, we carried out a study. We present the comparison of the mass spectrum between theoretical and experimental masses and examine the two-body strong decays of these states within two different approaches to the [Formula: see text] model. We find that the newly discovered states are most likely to be an [Formula: see text] state. This discovery could be useful in establishing entire [Formula: see text] mesons.

Revealing the inner structure of the newly observed η 1(1855) via photoproduction

Very recently, a new hadronic exotic state η 1(1855) at the invariant mass spectrum of was observed by the BESIII Collaboration. According to its properties, such as the mass and decay width, the η 1(1855) have been suggested to be a compact multi-quark state, a hadron molecule, or a hybrid meson. In order to distinguish the various interpretations of the η 1(1855), a Reggeized model combined with the vector dominance model for η 1(1855) photoproduction on the proton target is presented. The η 1(1855) photoproduction is dominated by the t-channel vector mesons ρ, ω, and ϕ exchange. If the η 1(1855) is a hybrid meson, the Primakoff effect also should be included. Our calculations show that the total cross section of the η 1(1855) production via γ p reaction can reach up to 0.276 pb for θ = 15° or 0.119 pb for θ = 0°, about 0.0297% or 0.0128% of the total cross section obtained by considering the η 1(1855) as an S-wave molecule. We also find their line shapes are sizably different. If the η 1(1855) is a molecular state, the photoproduction of η 1(1855) near the threshold offers a nice place to test its molecular nature. However, it should be better to take high energy, at least above E γ = 16.97 GeV, to observe the production of η 1(1855) if η 1(1855) is a hybrid meson. These results can be measured in the GlueX experiment or electron-ion collider in China to test the nature of the η 1(1855).

Investigating the [formula omitted] exotic state in the [formula omitted] decays

An analysis of the J/ψ→ηη′γ decay by the BESIII collaboration claims the observation of an exotic state η1(1855) with IGJPC=0+1−+. To establish its C-parity partner η1′(1855) in the picture of the KK¯1(1400) molecular state, we propose that J/ψ→η1′(1855)η(′) receives the main contributions from the final state interaction of KK⁎(K+K⁎−, K−K⁎+, K0K¯⁎0, and K¯0K⁎0). Specifically, K and K⁎ in J/ψ→KK⁎ decays transform as η1′(1855)η(′), by exchanging a K1(1400). We predict B(J/ψ→η1′(1855)η)=(6.3−3.5+12.6)×10−6, and B(J/ψ→η1′(1855)η′)=(6.5−4.6+6.6)×10−6, which can be studied in the J/ψ→K⁎K¯⁎η(′) decays.

A0(980)-meson twist-2 distribution amplitude within the QCD sum rules and investigation of D → a0(980)(→ηπ)e+νe

In this paper, moments of a0(980)-meson twist-2 light-cone distribution amplitudes were deeply researched by using QCD sum rules approach within background field theory. Up to 9th-order accuracy, we present 〈ξ2;a0n〉|μ0 at the initial scale μ0=1GeV, i.e. 〈ξ2;a01〉|μ0=−0.307(43), 〈ξ2;a03〉|μ0=−0.181(34), 〈ξ2;a05〉|μ0=−0.078(28), 〈ξ2;a07〉|μ0=−0.049(26), 〈ξ2;a09〉|μ0=−0.036(24), respectively. An improved light-cone harmonic oscillator model for a0(980)-meson twist-2 light-cone distribution amplitudes is adopted, where its parameters are fixed by using the least squares method based on the 〈ξ2;a0n〉|μ0, and their goodness of fit reach to 95.4%. Then, we calculate the D→a0(980) transition form factors within the light-cone sum rules approach, and at largest recoil point, we obtain f+D→a0(0)=1.058−0.035+0.068 and f−D→a0(0)=0.764−0.036+0.044. As a further application, the branching fractions of the D→a0(980)ℓν¯ℓ semileptonic decays are given. Taking the decay a0(980)→ηπ into consideration, we obtain B(D0→a0(980)−(→ηπ−)e+νe)=(1.330−0.134+0.216)×10−4, B(D+→a0(980)0(→ηπ0)e+νe)=(1.675−0.169+0.272)×10−4, which are consistent with the BESIII collaboration and PDG data within errors. Finally, we present the angle observables of forward-backward asymmetries, q2-differential flat terms and lepton polarization asymmetry of the semileptonic decay D→a0(980)ℓν¯ℓ.