Assuming <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>6900</mn><mo stretchy="false">)</mo></math> is a tetraquark state, the decay width of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>X</mi><mo stretchy="false">(</mo><mn>6900</mn><mo stretchy="false">)</mo><mo stretchy="false">→</mo><mn>2</mn><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> is calculated in a covariant quark model, with the diquark-antidiquark <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">[</mo><mi>c</mi><mi>c</mi><mo stretchy="false">]</mo><mo stretchy="false">[</mo><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">]</mo></math> picture. Two possible structures, vector-vector and axial-vector–axial-vector coupling, are investigated. The result indicates that the axial-vector–axial-vector coupling is consistent with the experiments. Additionally, as another application of the covariant quark model, the decay width of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>X</mi><mo stretchy="false">(</mo><mn>6900</mn><mo stretchy="false">)</mo><mo stretchy="false">→</mo><mn>2</mn><msub><mrow><mi>η</mi></mrow><mrow><mi>c</mi></mrow></msub></mrow></math> is predicted to be 66–88 keV.

China

Duo-Duo Lu

Shao-Zhou Jiang

Investigating the internal structure of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>X</mi><mo stretchy="false">(</mo><mn>6900</mn><mo stretchy="false">)</mo></mrow></math> in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>2</mn><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> decay channel

Using <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>10</mn><mn>087</mn><mo>±</mo><mn>44</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mn>6</mn></msup><mtext> </mtext><mtext> </mtext><mi>J</mi><mo>/</mo><mi>ψ</mi></math> events collected with the BESIII detector, we perform the first amplitude analysis of the process <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math>. The decay is dominated by the intermediate processes <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><msup><mi>π</mi><mn>0</mn></msup><msub><mi>b</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1235</mn><msup><mo stretchy="false">)</mo><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><msup><mi>π</mi><mn>0</mn></msup><mi>ρ</mi><mo stretchy="false">(</mo><mn>1450</mn><msup><mo stretchy="false">)</mo><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>η</mi><msub><mi>h</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1170</mn><mo stretchy="false">)</mo><mo stretchy="false">→</mo><mi>γ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math>. Contributions from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><msub><mi>a</mi><mn>0</mn></msub><mo stretchy="false">(</mo><mn>980</mn><msup><mo stretchy="false">)</mo><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><msub><mi>a</mi><mn>2</mn></msub><mo stretchy="false">(</mo><mn>1320</mn><msup><mo stretchy="false">)</mo><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><msub><mi>a</mi><mn>2</mn></msub><mo stretchy="false">(</mo><mn>1700</mn><msup><mo stretchy="false">)</mo><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math> are observed with a statistical significance exceeding <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>5</mn><mi>σ</mi></math>, constituting the first observation of radiative transitions of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> to isospin-triplet scalar mesons. The total branching fraction of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math> is measured to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>25.7</mn><mo>±</mo><mn>0.3</mn><mo>±</mo><mn>1.5</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>6</mn></mrow></msup></math>, where the first uncertainty is statistical and the second systematic. This result is consistent with the previous measurement, with the precision improved by more than a factor of two.

M. Ablikim

Russia

M.N. Achasov

Sweden

P. Adlarson

X.C. Ai

Italy

C.S. Akondi

Germany

R. Aliberti

A. Amoroso

Q. An

Y.H. An

Y. Bai

JINR

O. Bakina

H.R. Bao

X.L. Bao

M. Barbagiovanni

Poland

V. Batozskaya

Mongolia

K. Begzsuren

N. Berger

M. Berlowski

M.B. Bertani

D. Bettoni

F. Bianchi

E. Bianco

A. Bortone

I. Boyko

United States

R.A. Briere

A. Brueggemann

D. Cabiati

H. Cai

M.H. Cai

X. Cai

A. Calcaterra

G.F. Cao

N. Cao

Türkiye

S.A. Cetin

X.Y. Chai

J.F. Chang

T.T. Chang

G.R. Che

Y.Z. Che

C.H. Chen

Chao Chen

G. Chen

H.S. Chen

H.Y. Chen

M.L. Chen

S.J. Chen

S.M. Chen

T. Chen

W. Chen

X.R. Chen

X.T. Chen

X.Y. Chen

Y.B. Chen

Y.Q. Chen

Z.K. Chen

J. Cheng

L.N. Cheng

South Korea

S.K. Choi

X. Chu

G. Cibinetto

F. Cossio

United Kingdom

J. Cottee-Meldrum

H.L. Dai

J.P. Dai

X.C. Dai

A. Dbeyssi

R.E. de Boer

D. Dedovich

C.Q. Deng

Z.Y. Deng

A. Denig

I. Denisenko

M. Destefanis

F. De Mori

E. Di Fiore

X.X. Ding

Y. Ding

Y.X. Ding

Yi. Ding

J. Dong

L.Y. Dong

M.Y. Dong

X. Dong

M.C. Du

S.X. Du

Shaoxu Du

X.L. Du

Y.Q. Du

Y.Y. Duan

Z.H. Duan

P. Egorov

G.F. Fan

J.J. Fan

Y.H. Fan

J. Fang

Jin Fang

S.S. Fang

W.X. Fang

Y.Q. Fang

L. Fava

Amplitude analysis of the isospin-violating decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><mi>η</mi><msup><mi>π</mi><mn>0</mn></msup></math>

Azimuthal anisotropies in heavy-ion collisions are conventionally interpreted as signatures of hydrodynamic flow. We demonstrate that in peripheral collisions, a significant <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>cos</mi><mn>2</mn><mi>ϕ</mi></math> asymmetry in the decay leptons of coherently photoproduced <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> mesons arises purely from the initial-state geometry of the nuclear electromagnetic field. This modulation originates from the linear polarization of coherent photons, which is radially aligned in impact parameter space and transferred to the vector meson. By employing light-cone perturbation theory within the dipole formalism, we calculate the centrality dependence of this asymmetry for collisions at RHIC and LHC energies. Our predictions quantitatively reproduce STAR data. This observable thus provides a rigorous benchmark for distinguishing electromagnetic initial-state effects from collective medium dynamics.

Ding Yu Shao

Han-Qing Yu

Cheng Zhang

Jian Zhou

Geometry-induced azimuthal anisotropy in coherent <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> photoproduction

We investigate the $$e^+ e^- \rightarrow \eta J/\psi $$ cross section by employing a model that combines relativistic Breit–Wigner amplitudes with a unitarized coupled-channel approach to account for resonant and non-resonant contributions, respectively. By performing a global fit to the BESIII experimental data, we determine the essential free parameters of the transition amplitudes. Furthermore, we analyze the role of a dynamically generated $$D\bar{D}^*$$ pole near 3.88 GeV and demonstrate its critical contribution to shaping the observed cross-section line shape.

Mexico

Sara Rahmani

Analysis of the $$e^+e^- \rightarrow \eta J/\psi $$ cross section within a unitarized coupled-channel approach

The <italic>X</italic>(2370) particle was first discovered in <math altimg='si14.svg'><mrow><mi>J</mi><mo>&#8594;</mo><mi>&#947;</mi><msup><mi>&#960;</mi><mo>+</mo></msup><msup><mi>&#960;</mi><mo>&#8722;</mo></msup><msup><mi>&#951;</mi><mo>&#8242;</mo></msup></mrow></math> process in 2011 with the BESIII experiment at BEPCII Collider. In 2024, the spin-parity quantum numbers of the <italic>X</italic>(2370) was determined to be <math altimg='si7.svg'><msup><mn>0</mn><mrow><mo>&#8722;</mo><mo>+</mo></mrow></msup></math> in <math altimg='si6.svg'><mrow><mi>J</mi><mo>&#8594;</mo><mi>&#947;</mi><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msup><mi>&#951;</mi><mo>&#8242;</mo></msup></mrow></math> process. New decay modes of <math altimg='si15.svg'><mrow><mi>X</mi><mrow><mo>(</mo><mn>2370</mn><mo>)</mo></mrow><mo>&#8594;</mo><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msup><mi>&#960;</mi><mn>0</mn></msup></mrow></math>, <italic>&#960;</italic> 0 <italic>&#960;</italic> 0 <italic>&#951;</italic> and <italic>a</italic> 0 <italic>&#960;</italic> 0 were observed recently. The mass, spin-parity quantum numbers, production and decay properties of the <italic>X</italic>(2370) particle are consistent with the features of the lightest pseudoscalar glueball.

Shan Jin

BESIII discovers a glueball-like particle <italic>X</italic>(2370) in <italic>J</italic> particle decays

Based on a sample of (10087 ± 44) × 10 $\textit{J}$/$\textit{ψ}$ events collected at the center-of-mass energy $$ \sqrt{s}=3.0969 $$ GeV with the BESIII detector, we search for the charmonium rare weak decay $$ J/\psi \to {\overline{D}}^0{\overline{K}}^{\ast 0}+\textrm{c}.\textrm{c}. $$ . No significant signal is observed, and the upper limit on its decay branching fraction at the 90% confidence level is set as 1.4 × 10 , improving the sensitivity of the previous best limit by an order of magnitude.

M. Achasov

X. Ai

Y. Ban

M. Bertani

R. Briere

M. Cai

G. Cao

S. Cetin

X. Chai

J. Chang

G. Che

Y. Che

C. Chen

H. Chen

M. Chen

S. Chen

X. Chen

Y. Chen

Z. Chen

S. Choi

J. Cui

H. Dai

J. Dai

X. Dai

R. Boer

C. Deng

Z. Deng

I. Denysenko

F. Mori

B. Ding

X. Ding

L. Dong

M. Dong

M. Du

S. Du

Y. Duan

Z. Duan

G. Fan

J. Fan

Y. Fan

S. Fang

W. Fang

Y. Fang

F. Feldbauer

G. Felici

C. Feng

J. Feng

L. Feng

Search for the charmonium weak decay $$ J/\psi \to {\overline{D}}^0{\overline{K}}^{\ast 0}+\textrm{c}.\textrm{c}. $$

We present a next-to-next-to-leading-order (NNLO) calculation within the nonrelativistic QCD framework for the process <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><msup><mi>Z</mi><mo>*</mo></msup><mo stretchy="false">→</mo><mi>J</mi><mo>/</mo><mi>ψ</mi><mo>+</mo><mi>J</mi><mo>/</mo><mi>ψ</mi></math>. We find that the NNLO contribution is two to three times larger than the next-to-leading-order contribution, which itself is already three to five times larger than the leading-order result. In the high-energy limit, we provide analytic expressions for the leading-power coefficients in the asymptotic expansion of the two-loop amplitudes. Our results are directly applicable to the bottomonium process <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi><mo stretchy="false">→</mo><mi mathvariant="normal">ϒ</mi><mo>+</mo><mi mathvariant="normal">ϒ</mi></math>. Using the obtained hadronic amplitudes, we predict the decay width of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson into these rare dicharmonium and dibottomonium final states.

Switzerland

Xiang Chen

Xin Guan

Chuan-Qi He

Yan-Qing Ma

Two-loop QCD corrections to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><msup><mi>Z</mi><mo>*</mo></msup><mo stretchy="false">→</mo><mi>J</mi><mo>/</mo><mi>ψ</mi><mo>+</mo><mi>J</mi><mo>/</mo><mi>ψ</mi></math>

We study the dissociative associated production of a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> meson and a dimuon via double parton scattering (DPS) in nucleus-proton ultraperipheral collisions. This new channel, characterized by a rapidity gap, is sensitive to the photon and gluon distributions of the proton. We derive a DPS pocket formula for this process, together with a corresponding expression for the effective cross section. Furthermore, we demonstrate the kinematic dependence of the effective cross section and present predictions for the differential DPS cross section at LHC and FCC energies.

Brazil

Bruna O. Stahlhöfer

Edgar Huayra

Emmanuel G. de Oliveira

Dissociative associated <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">J</mi><mo>/</mo><mi>ψ</mi></math> and dimuon production in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>A</mi><mi>p</mi></math> ultraperipheral collisions via double parton scattering

Motivated by the first LHCb searches for the rare $$ {\overline{B}}_{s,d}^0 $$ → $\textit{J}$/$\textit{ψμ}$ $\textit{μ}$ decays, we perform a detailed study of these processes within the QCD factorization formalism. Since the transverse size of the $\textit{J}$/$\textit{ψ}$ meson is small in the heavy quark mass limit, this formalism is generally expected to hold for these decays. We include both the leading- and next-to-leading-order QCD corrections to the hard-scattering kernels, which are convoluted with the light-cone distribution amplitudes (LCDAs) of the initial- and final-state hadrons. It is numerically found that, depending on the model parameters for the leading-twist $\textit{B}$-meson LCDA, the maximum branching ratios of $$ {\overline{B}}_s^0 $$ → $\textit{J}$/$\textit{ψμ}$ $\textit{μ}$ and $$ {\overline{B}}_d^0 $$ → $\textit{J}$/$\textit{ψμ}$ $\textit{μ}$ , integrated over the dimuon invariant mass squared $\textit{q}$ from 1 GeV to ( $$ {m}_{B_{s,d}} $$ − $\textit{m}$ ) , can reach up to 2.21 × 10 and 7.69 × 10 at the leading order in $\textit{α}$ , respectively. After incorporating the non-factorizable one-loop vertex corrections, these branching ratios are further reduced by about one order of magnitude, with $$ \mathcal{B}{\left.\left({\overline{B}}_s^0\to J/\psi {\mu}^{+}{\mu}^{-}\right)\right|}_{q^2\ge 1{\textrm{GeV}}^2} $$ = 2.88 × 10 and $$ \mathcal{B}{\left.\left({\overline{B}}_d^0\to J/\psi {\mu}^{+}{\mu}^{-}\right)\right|}_{q^2\ge 1{\textrm{GeV}}^2} $$ = 1.07 × 10 . In addition, we have presented the dimuon invariant mass distributions of the individual and total helicity amplitudes squared, as well as the differential and integrated longitudinal polarization fractions of the $\textit{J}$/$\textit{ψ}$ meson, which could be probed by the future LHCb and Belle II experiments with more accumulated data.

Xin-Qiang Li

Yan Shi

Ya-Dong Yang

Xing-Bo Yuan

Chun-Yang Zhao

$$ {\overline{B}}_{s,d}^0 $$ → $\textit{J}$/$\textit{ψμ}$ + $\textit{μ}$ − decays in QCD factorization