A dark photon is an Abelian gauge boson arising from a new $ U(1)_D $ gauge symmetry, coupled to the Standard Model through kinetic mixing. The mixing parameter $\textit{ϵ}$ induces an effective coupling to the electromagnetic current, while $ g_\chi $ couples the dark photon to a stable dark matter particle $\textit{χ}$. We study $ J/\psi $ two-body and four-body decays mediated by a light dark photon ( $ m_U \lt 3.0 $ GeV) within the non-relativistic QCD (NRQCD) framework, considering both visible decays of the dark photon into SM fermions and invisible decays into dark sector particles. We investigate the detection sensitivity of BESIII and STCF experiments to the dark photon mass $ m_U $ and kinetic mixing parameter $\textit{ϵ}$. Our results show that, for two-body final states with $ m_U \lt 2m_\chi $ , BESIII sets $\textit{ϵ}$ upper limits of $ 9.3\times10^{-4} $ and $ 7.6\times10^{-4} $ for lepton-pair and hadronic signals, respectively, while STCF yields $ 3.7\times10^{-4} $ and $ 3.1\times10^{-4} $ . For invisible decays ( $ m_U\ge 2m_\chi $ ), BESIII achieves an $\textit{ϵ}$ limit of $ 1.4\times10^{-3} $ in the mass range $ 0.3\sim0.8 $ GeV, and STCF reaches $ 2.3\times10^{-4} $ in $ 0.3\sim1.9 $ GeV; no signals are expected in other mass regions, and visible decays are severely suppressed throughout. For four-body decay channels, BESIII yields an $\textit{ϵ}$ upper limit of $ 7.6\times10^{-5} $ for $ m_U \lt 2.2 $ GeV, whereas STCF achieves $ 1.2\times10^{-5} $ over the full mass range. When $ m_U\ge 2m_\chi $ , visible modes are nearly excluded; BESIII and STCF set $\textit{ϵ}$ limits from invisible decays of $ 8.8\times10^{-5} $ for $ m_U \lt 2.4 $ GeV and $ 1.4\times10^{-5} $ for $ m_U \lt 2.8 $ GeV, respectively, with no detectable signals at higher masses. Except for the limit of $ 9.3\times10^{-4} $ , all the above $\textit{ϵ}$ bounds lie in regions that are not currently excluded by collider experiments. Compared with the constraints from two-body final state processes, the limits derived from four-body decay channels lie well below existing experimental bounds, providing supportive references for constraining this parameter in BESIII and STCF experiments. Numerical results for the decay ratios $ \Gamma/\Gamma_{J/\psi} $ , expected event numbers, significance $ S/\sqrt{B} $ , and $ p_T $ distributions are presented where applicable.

China

Xiao Liang

Chun-Yuan Li

Bin-Peng Shang

Zong-Guo Si

Hong-Xin Wang

Xing-Hua Yang

Dai-Xing Zhang

Searching for dark photons in $\textit{J/ψ}$ decays * Supported in part by the National Natural Science Foundation of China (12105162, 12305106, 12235008, 12321005), the Natural Science Foundation of Shandong Province (ZR2021QA058, ZR2021QA040), and the Youth Innovation Technology Project of Higher School in Shandong Province (2023KJ146)

We investigate the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math>-wave <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mi>c</mi></msub><msub><mi>η</mi><mi>c</mi></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo stretchy="false">/</mo><mi>ψ</mi><mi>J</mi><mo stretchy="false">/</mo><mi>ψ</mi></math> scattering in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>J</mi><mrow><mi>P</mi><mi>C</mi></mrow></msup><mo>=</mo><mo stretchy="false">(</mo><mn>0</mn><mo>,</mo><mn>2</mn><msup><mo stretchy="false">)</mo><mrow><mo>+</mo><mo>+</mo></mrow></msup></math> channels up to a center-of-mass energy of 6.6 GeV. The calculations are carried out at two unphysical pion masses, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>π</mi></msub><mo>≈</mo><mn>420</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> and 250 MeV in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>N</mi><mi>f</mi></msub><mo>=</mo><mn>2</mn></math> lattice QCD. For each <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>π</mi></msub></math>, we extract the finite-volume energy levels on two lattices with an identical lattice spacing (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>a</mi><mo>≃</mo><mn>0.136</mn><mtext> </mtext><mtext> </mtext><mi>fm</mi></math>) but different spatial volumes. Since the coupled-channel effects between the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mi>c</mi></msub><msub><mi>η</mi><mi>c</mi></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo stretchy="false">/</mo><mi>ψ</mi><mi>J</mi><mo stretchy="false">/</mo><mi>ψ</mi></math> channels are found to be negligible, we analyze the corresponding scattering properties using the single-channel L"uscher method. We find that the interactions in these dicharmonium systems are dominated by the quark rearrangement effect. In the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>0</mn><mrow><mo>+</mo><mo>+</mo></mrow></msup></math> channel, the near-threshold attraction in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo stretchy="false">/</mo><mi>ψ</mi><mi>J</mi><mo stretchy="false">/</mo><mi>ψ</mi></math> and repulsion in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mi>c</mi></msub><msub><mi>η</mi><mi>c</mi></msub></math> can be explained through the Fierz rearrangement. The attractive interaction in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mo>​</mo><mn>1</mn></msup><msub><mi>S</mi><mn>0</mn></msub></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo stretchy="false">/</mo><mi>ψ</mi><mi>J</mi><mo stretchy="false">/</mo><mi>ψ</mi></math> channel allows for the existence of a near-threshold scalar structure, which may correspond to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>6200</mn><mo stretchy="false">)</mo></math>. In the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>2</mn><mrow><mo>+</mo><mo>+</mo></mrow></msup></math> channel, while the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mo>​</mo><mn>5</mn></msup><msub><mi>S</mi><mn>2</mn></msub></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo stretchy="false">/</mo><mi>ψ</mi><mi>J</mi><mo stretchy="false">/</mo><mi>ψ</mi></math> system exhibits a repulsive interaction near threshold, the scattering amplitude has a Castillejo-Dalitz-Dyson zero at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>6.45</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and a resonance pole at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>R</mi></mrow></msub></mrow></msqrt><mo>=</mo><mrow><mo stretchy="false">[</mo><mn>6.543</mn><mo stretchy="false">(</mo><mn>10</mn><mo stretchy="false">)</mo><mo>−</mo><mi>i</mi><mn>0.548</mn><mo stretchy="false">(</mo><mn>34</mn><mo stretchy="false">)</mo><mo>/</mo><mn>2</mn><mo stretchy="false">]</mo></mrow><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>π</mi></msub><mo>≈</mo><mn>420</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>R</mi></mrow></msub></mrow></msqrt><mo>=</mo><mrow><mo stretchy="false">[</mo><mn>6.538</mn><mo stretchy="false">(</mo><mn>13</mn><mo stretchy="false">)</mo><mo>−</mo><mi>i</mi><mn>0.537</mn><mo stretchy="false">(</mo><mn>56</mn><mo stretchy="false">)</mo><mo>/</mo><mn>2</mn><mo stretchy="false">]</mo></mrow><mtext> </mtext><mi>GeV</mi></mrow></math> for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>π</mi></msub><mo>≈</mo><mn>250</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math>, where the uncertainties are statistical. This resonance may correspond to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>6600</mn><mo stretchy="false">)</mo></math> (or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>6400</mn><mo stretchy="false">)</mo></math>) reported by the ATLAS and CMS Collaborations. Our result supports its <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>2</mn><mrow><mo>+</mo><mo>+</mo></mrow></msup></math> assignment, in agreement with the latest spin-parity determination by CMS. Despite the observed dominance of the quark rearrangement effect, the light-hadron dynamics underlying dicharmonium scattering need to be explored at lighter pion masses. Furthermore, since our lattices are coarse and the lattice volumes are small, the associated systematic uncertainties should be controlled in future studies using more sophisticated lattice setups.

Geng Li

Chunjiang Shi

Ying Chen

Wei Sun

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>η</mi></mrow><mrow><mi>c</mi></mrow></msub><msub><mrow><mi>η</mi></mrow><mrow><mi>c</mi></mrow></msub></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mi>J</mi><mo>/</mo><mi>ψ</mi></math> scattering from lattice QCD

We report the first searches for charged-lepton-flavor violation in decays of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mrow><mi>b</mi><mi>J</mi></mrow></msub><mo stretchy="false">(</mo><mn>1</mn><mi>P</mi><mo stretchy="false">)</mo></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>=</mo><mn>0</mn></math>, 1, and 2) to a pair of charged leptons using 158 million <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">ϒ</mi><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo></math> decays collected with the Belle detector in <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></math> collisions at the KEKB collider. No significant signal is observed, and we set upper limits on the branching fractions for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mrow><mi>b</mi><mi>J</mi></mrow></msub><mo stretchy="false">(</mo><mn>1</mn><mi>P</mi><mo stretchy="false">)</mo></math> decays to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>±</mo></msup><msup><mi>μ</mi><mo>∓</mo></msup></math> at the level of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>6</mn></mrow></msup></math> and to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>±</mo></msup><msup><mi>τ</mi><mo>∓</mo></msup></math> or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>μ</mi><mo>±</mo></msup><msup><mi>τ</mi><mo>∓</mo></msup></math> at the level of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></math>. Limits on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mrow><mi>b</mi><mn>0</mn></mrow></msub><mo stretchy="false">(</mo><mn>1</mn><mi>P</mi><mo stretchy="false">)</mo></math> decays are translated into bounds on the corresponding Wilson coefficients of scalar operators that mediate charged-lepton-flavor violation.

M. Abumusabh

I. Adachi

A. Aggarwal

L. Aggarwal

H. Ahmed

Y. Ahn

H. Aihara

N. Akopov

S. Alghamdi

M. Alhakami

A. Aloisio

N. Althubiti

K. Amos

M. Angelsmark

N. Anh Ky

C. Antonioli

D.M. Asner

H. Atmacan

T. Aushev

R. Ayad

V. Babu

H. Bae

N.K. Baghel

S. Bahinipati

P. Bambade

Sw. Banerjee

M. Barrett

M. Bartl

J. Baudot

A. Baur

A. Beaubien

F. Becherer

J. Becker

J.V. Bennett

F.U. Bernlochner

V. Bertacchi

M. Bertemes

E. Bertholet

M. Bessner

S. Bettarini

V. Bhardwaj

F. Bianchi

T. Bilka

D. Biswas

A. Bobrov

D. Bodrov

A. Bondar

G. Bonvicini

J. Borah

A. Boschetti

A. Bozek

M. Bračko

P. Branchini

R.A. Briere

T.E. Browder

A. Budano

S. Bussino

Q. Campagna

M. Campajola

L. Cao

G. Casarosa

C. Cecchi

M.C. Chang

P. Chang

P. Cheema

L. Chen

B.G. Cheon

C. Cheshta

H. Chetri

K. Chilikin

K. Chirapatpimol

H.E. Cho

K. Cho

S.J. Cho

S.K. Choi

S. Choudhury

S. Chutia

J. Cochran

J.A. Colorado-Caicedo

I. Consigny

L. Corona

J.X. Cui

E. De La Cruz-Burelo

S.A. De La Motte

G. De Nardo

G. De Pietro

R. de Sangro

M. Destefanis

S. Dey

R. Dhayal

A. Di Canto

J. Dingfelder

Z. Doležal

I. Domínguez Jiménez

T.V. Dong

X. Dong

G. Dujany

P. Ecker

D. Epifanov

J. Eppelt

Searches for Charged-Lepton-Flavor Violation in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mrow><mi>b</mi><mi>J</mi></mrow></msub><mo stretchy="false">(</mo><mn>1</mn><mi>P</mi><mo stretchy="false">)</mo></math> Decays

We investigate the modification of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> meson mass in asymmetric nuclear matter at zero and finite temperatures employing an effective Lagrangian approach that considers the contributions of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mi>D</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msup><mi>D</mi><mo>*</mo></msup></math> meson loops. The medium dependence of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi></math> meson masses is determined using the hadronic chiral SU(3) model, where scalar condensates are calculated and subsequently utilized in the QCD sum rules approach. Our findings indicate that an increase in baryonic density results in a negative mass shift of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> meson. This suggests that the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> meson is attracted to nuclear mean fields indicating the possibility of the formation of meson-nucleus bound states. Moreover, we have also determined the binding energy and absorption decay width of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> meson for both the ground and excited states of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">O</mi><mn>16</mn></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Ca</mi><mn>40</mn></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Zr</mi><mn>90</mn></msup></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Pb</mi><mn>208</mn></msup></math> nuclei. These results are expected to contribute to the understanding of experimental data from upcoming studies at Jefferson lab and the facility for antiproton and ion research, where low-momentum charmed mesons can be produced and examined within nuclei.

India

Manpreet Kaur

Arvind Kumar

Study of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> mass shift and bound states: Impact of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mi>D</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msup><mi>D</mi><mo>*</mo></msup></math> meson loops

We present our results for the twist-3 gluon contribution to the single transverse-spin asymmetry (SSA) in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> production in proton-proton collisions. Although the data were reported by the RHIC experiment more than a decade ago, a theoretical calculation based on rigorous collinear factorization has remained unavailable for the dominant gluonic contribution. Our results show that only the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi></math>-even type twist-3 gluon distribution, which has a direct relationship with the gluon transverse-momentum-dependent distribution function, contributes to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> SSA. Therefore, this observable serves as a key probe to understand the three-dimensional motion of gluons inside the proton. We also perform numerical simulations of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> SSA at RHIC and LHC energies. Our simulations indicate that a sizable SSA could be generated through a mechanism different from that responsible for the SSA in light hadron and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi></math>-meson production.

Poland

Longjie Chen

Shinsuke Yoshida

Twist-3 gluon contribution to the single transverse-spin asymmetry in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> production in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math> collisions

Searching for dark matter is a primary goal of modern astronomy and particle physics. Invisible decays of heavy quarkonia are particularly promising for probing light dark matter, attracting broad interest due to their unique sensitivity. Experiments searching for radiative invisible decays of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> have steadily improved upper limits, and upcoming facilities will push sensitivity further—making the precise determination and subtraction of the neutrino background indispensable. Here, we present the first lattice QCD calculation of the Standard Model 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>ν</mi><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover></math>, an irreducible background to <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><mo>+</mo><mtext>invisible</mtext></math>. Our result for the branching fraction is <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Br</mi><mo stretchy="false">(</mo><mi>J</mi><mo>/</mo><mi>ψ</mi><mo stretchy="false">→</mo><mi>γ</mi><mi>ν</mi><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">)</mo><mo>=</mo><mn>1.04</mn><mo stretchy="false">(</mo><mn>7</mn><mo stretchy="false">)</mo><mo stretchy="false">(</mo><mn>8</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>10</mn></mrow></msup></math>, where the first uncertainty is statistical and the second is our systematic estimate. This work advances lattice-based determinations of neutrino backgrounds to quarkonium invisible decays, delivering an ab initio benchmark for <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><mo>+</mo><mtext>invisible</mtext></math>. Our approach generalizes to other quarkonium channels (e.g., <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">ϒ</mi><mo>/</mo><mi>ϕ</mi><mo stretchy="false">→</mo><mi>γ</mi><mo>+</mo><mtext>invisible</mtext></math>) and provides critical theoretical support for dark matter searches at colliders.

Yu Meng

Ning Li

Chuan Liu

Haobo Yan

Ke-Long Zhang

Xue-Ze Zhang

Lattice determination of the neutrino background for <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><mo>+</mo><mi>invisible</mi></math>

We analyze the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo></mrow></msup><mi>p</mi><mo stretchy="false">→</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi mathvariant="normal">Ξ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo></mrow></msup><mi>p</mi><mo stretchy="false">→</mo><msup><mrow><mi>K</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi mathvariant="normal">Ξ</mi></mrow><mrow><mn>0</mn></mrow></msup></mrow></math> processes in the energy region <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1.8</mn><mo>&lt;</mo><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>&lt;</mo><mn>2.8</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> within an effective Lagrangian approach. The <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Λ</mi><mo stretchy="false">(</mo><mn>1800</mn><mo stretchy="false">)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>2250</mn><mo stretchy="false">)</mo></math> resonances, along with the ground states <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Λ</mi></math>, are included. Additionally, a possible <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>J</mi><mi>P</mi></msup><mo>=</mo><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup><mtext> </mtext><mtext> </mtext><msup><mi mathvariant="normal">Σ</mi><mo>*</mo></msup></math> or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Λ</mi><mo>*</mo></msup></math> resonance with a mass around 1.9 GeV and a width of approximately 200 MeV is introduced to describe the structure at 2.0 GeV in the total cross section and reproducing the threshold behavior. The two possible solutions corresponding to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup><mo stretchy="false">)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Λ</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup><mo stretchy="false">)</mo></math> cannot be distinguished by the existing data. Predictions for the polarization of the final-state <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Ξ</mi></math> and the cross section of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>−</mo></msup><mi>n</mi><mo stretchy="false">→</mo><msup><mi>K</mi><mn>0</mn></msup><msup><mi mathvariant="normal">Ξ</mi><mo>−</mo></msup></math> are compared with the experimental data, we find that the results of solution-II with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Λ</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup><mo stretchy="false">)</mo></math> are much better. We also discuss the possible interpretations of the introduced <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup></math> hyperon as a pentaquark candidate, e.g., an <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math>-wave <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi><mi mathvariant="normal">Ξ</mi><mo stretchy="false">(</mo><mn>1530</mn><mo stretchy="false">)</mo></math> hadronic molecule. However, since the polarization data suffer from rather large uncertainties, more data inputs are needed in future experiments, for example, J-PARC, HIAF, and JLab.

Zheng-Li Luo

Jia-Jun Wu

Bing-Song Zou

Possible <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi mathvariant="normal">Σ</mi></mrow><mrow><mo>*</mo></mrow></msup></mrow></math> or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Λ</mi><mo>*</mo></msup></math> resonance with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>J</mi><mi>P</mi></msup><mo>=</mo><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup></math> in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>−</mo></msup><mi>p</mi><mo stretchy="false">→</mo><mi>K</mi><mi mathvariant="normal">Ξ</mi></math> scattering

We perform coupled channel analysis for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mi>π</mi></math>, and related meson pairs for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>3900</mn><mo stretchy="false">)</mo></math> channel in an effective model of hadrons and quarks. The model incorporates meson exchange potential such as one pion and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mrow><mo stretchy="false">(</mo><mo>*</mo><mo stretchy="false">)</mo></mrow></msup></math> meson exchanges, and quark exchanges. It turns out that the meson exchange potential is small, while the off-diagonal interactions by the quark exchanges at short distances, particularly for transitions between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup><mo>−</mo><mi>J</mi><mo>/</mo><mi>ψ</mi><mi>π</mi></math> are strong, which plays a main role for the scattering amplitudes for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>3900</mn><mo stretchy="false">)</mo></math> channel, in consistent with the results of the lattice simulations of the HALQCD group.

Japan

Yukihiro Abe

Yasuhiro Yamaguchi

Atsushi Hosaka

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup><mo>−</mo><mi>π</mi><mi>J</mi><mo>/</mo><mi>ψ</mi></math> coupled-channel scattering for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>3900</mn><mo stretchy="false">)</mo></math>

In this paper, we calculate the decay widths and branching fractions for the decays $$Z \rightarrow J/\psi +\Upsilon (nS)$$ ( $$n=1,2,3$$ ) at future super $\textit{Z}$ factory and at the CEPC/FCC-ee, including both the relativistic and QCD corrections within the framework of nonrelativistic QCD. Both the relativistic and QCD corrections are found to be large and negative. Compared to the leading-order results, the decay widths are significantly reduced by the higher-order corrections due to significant numerical cancellations. Despite the resulting large theoretical uncertainties, sizable event rates from these rare decay channels could still be anticipated at future high-luminosity electron-positron colliders running around the Z-pole. Ultimately, our results provide an essential theoretical baseline, highlighting the necessity of incorporating even higher-order corrections and resummation techniques for future precision phenomenological studies.

Guang-Yu Wang

Xu-Chang Zheng

Guang-Zhi Xu

Next-to-leading order QCD and relativistic corrections to $$Z \rightarrow J/\psi +\Upsilon (nS)$$

Using a data sample of (10087 ± 44) × 10 $\textit{J}$/$\textit{ψ}$ events collected with the BESIII detector at a center-of-mass energy of $$ \sqrt{s}=3.097 $$ GeV, a dedicated search for the charmonium semileptonic weak decay $$ J/\psi \to {D}_s^{-}{e}^{+}{\nu}_e+\mathrm{c}.\mathrm{c}. $$ is performed. No significant signal is observed. An upper limit on the branching fraction is set at $$ \mathcal{B}\left(J/\psi \to {D}_s^{-}{e}^{+}{\nu}_e+\mathrm{c}.\mathrm{c}.\right)&lt;9.9\times {10}^{-8} $$ at the 90% confidence level. This result improves upon previous constraints by an order of magnitude, representing the most stringent experimental limit to date. It thus provides a critical test of Standard Model predictions and new physics scenarios in heavy-quark dynamics.

M. Ablikim

Russia

M. Achasov

Sweden

P. Adlarson

X. Ai

Germany

R. Aliberti

Italy

A. Amoroso

Q. An

Y. Bai

O. Bakina

Y. Ban

H.R. Bao

V. Batozskaya

Mongolia

K. Begzsuren

N. Berger

M. Berlowski

M. Bertani

D. Bettoni

E. Bianco

A. Bortone

I. Boyko

United States

R. Briere

A. Brueggemann

H. Cai

M. Cai

X. Cai

A. Calcaterra

G. Cao

N. Cao

Türkiye

S. Cetin

X. Chai

J. Chang

T. Chang

G. Che

Y. Che

C. Chen

Chao Chen

G. Chen

H. Chen

M. Chen

S. Chen

T. Chen

Search for the charmonium semi-leptonic weak decay $$ J/\psi \to {D}_s^{-}{e}^{+}{\nu}_e+\mathrm{c}.\mathrm{c}. $$