We study CP violation induced by neutral kaon mixing in $\textit{a}$ ($\textit{D}$ → $\textit{K}$ $\textit{K}$ ). We show that the contribution from neutral kaon mixing arises only in connection with second-order weak interactions in $\textit{D}$ decays. We estimate this effect to be at the 10 level, and thus negligible compared to current experimental sensitivity and to the expected contribution from CP violation in the charm sector. Similar reasoning can be applied to other systems.

United States

Yuval Grossman

Guglielmo Papiri

United Kingdom

Stefan Schacht

$\textit{CP}$ violation in neutral kaon mixing in $\textit{D}$ 0 → $\textit{K}$ $\textit{S}$ $\textit{K}$ $\textit{S}$

We point out several algebraic and dimensional inconsistencies in the derivation of the teleparallel double-wall dynamics and of the axial torsion coupling bound published in this Journal [Eur. Phys. J. C (2026) 86: 785]. Recomputing the torsion two-forms from the tetrads with vanishing spin connection, we obtain expressions that differ from those used in the paper. Consequently, the equations for the wall separation function do not lead to the reported solution, and the approximation $$h^2\ll z^2$$ does not restore the polynomial form adopted there. We also show that the proposed wave equation for the wall separation and the corresponding gravitational-wave interpretation require rederivation. In the fermionic sector, the zero-mode solutions and the scalar Dirac bilinear must be distinguished from the positive density $$\varPsi ^\dagger \varPsi $$ . With the corrected solutions, the effective coefficient $$A=eB+g_T S$$ determines a localization length $$\ell _{\textrm{loc}}\sim |A|^{-1/2}$$ , so that estimating $$g_T$$ requires specifying an additional physical scale rather than imposing $$A=0$$ . Hence the claimed constant condensate and the bound $$g_T\sim 10^{-4}$$ are not established by the calculations presented.

Brazil

Luis Castro

Comment on “Einstein–Cartan fermion condensates trapped in double walls induce axial torsion coupling bounds [Eur. Phys. J. C (2026) 86: 785]”

Motivated by the recent observation of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>c</mi><mo>*</mo></msubsup></math> meson by the ATLAS Collaboration and its promising discovery potential at future high-luminosity colliders, we investigate the semileptonic decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover><mi>c</mi><mo>*</mo></msubsup><mo stretchy="false">→</mo><mo stretchy="false">(</mo><mi>P</mi><mo>,</mo><mi>V</mi><mo stretchy="false">)</mo><msup><mo>ℓ</mo><mo>−</mo></msup><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mo>ℓ</mo></msub></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>P</mi><mo>=</mo><mi>D</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>B</mi><mrow><mi>d</mi><mo>,</mo><mi>s</mi></mrow></msub></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>η</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>1</mn><mi>S</mi><mo>,</mo><mn>2</mn><mi>S</mi><mo>,</mo><mn>3</mn><mi>S</mi><mo stretchy="false">)</mo></math>; <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>V</mi><mo>=</mo><msup><mi>D</mi><mo>*</mo></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mrow><mi>d</mi><mo>,</mo><mi>s</mi></mrow><mo>*</mo></msubsup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ψ</mi><mo stretchy="false">(</mo><mn>1</mn><mi>S</mi><mo>,</mo><mn>2</mn><mi>S</mi><mo>,</mo><mn>3</mn><mi>S</mi><mo stretchy="false">)</mo></math>) in the Standard Model. Using the relevant form factors obtained in the self-consistent covariant light-front quark model, we present theoretical predictions for several physical observables, including the branching fraction, the ratios of branching fractions <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mrow><mo stretchy="false">(</mo><mi>L</mi><mo stretchy="false">)</mo></mrow></msub></math>, the longitudinal polarization fraction of the daughter vector meson, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> lepton spin asymmetry, and the forward-backward asymmetry. It is found that the branching fractions for the Cabibbo-favored <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover><mi>c</mi><mo>*</mo></msubsup><mo stretchy="false">→</mo><msubsup><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover><mi>s</mi><mo>*</mo></msubsup><msup><mi>e</mi><mo>−</mo></msup><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mi>e</mi></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover><mi>s</mi><mo>*</mo></msubsup><msup><mi>μ</mi><mo>−</mo></msup><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mi>μ</mi></msub></math> decays reach the order of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>6</mn></mrow></msup><mo stretchy="false">)</mo></math>, which might be firstly observed at the future high-luminosity Large Hadron Collider.

China

Qin Chang

Jianying Qian

Liting Wang

Xiaolin Wang

Shuai Xu

Jie Zhu

Semileptonic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mover accent="true"><mi>B</mi><mo stretchy="false">¯</mo></mover><mi>c</mi><mo>*</mo></msubsup><mo stretchy="false">→</mo><mo stretchy="false">(</mo><mi>P</mi><mo>,</mo><mi>V</mi><mo stretchy="false">)</mo><msup><mo>ℓ</mo><mo>−</mo></msup><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mo>ℓ</mo></msub></math> decays within the self-consistent light-front quark model

By analyzing a sample of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>20.3</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> of <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> annihilation data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we have made a first measurement of the absolute branching fractions of the radiative decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mrow><mo>*</mo><mn>0</mn></mrow></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>ϕ</mi></math> to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>3.81</mn><mo>±</mo><mn>0.1</mn><msub><mn>8</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.2</mn><msub><mn>0</mn><mrow><mi>syst</mi></mrow></msub><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>2.51</mn><mo>±</mo><mn>0.4</mn><msub><mn>4</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.1</mn><msub><mn>1</mn><mrow><mi>syst</mi></mrow></msub><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></math>, respectively. The statistical significances of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mrow><mo>*</mo><mn>0</mn></mrow></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>ϕ</mi></math> are <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>26.8</mn><mi>σ</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>7.9</mn><mi>σ</mi></math>, respectively. The obtained branching fractions are consistent with the corresponding world average values. In addition, the measured <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> asymmetry <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="script">A</mi><mrow><mi>C</mi><mi>P</mi></mrow></msub><mo stretchy="false">(</mo><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mrow><mo>*</mo><mn>0</mn></mrow></msup><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mo>−</mo><mn>0.7</mn><mo>±</mo><msub><mn>5.0</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><msub><mn>4.1</mn><mrow><mi>syst</mi></mrow></msub><mo stretchy="false">)</mo><mo>%</mo></math> is consistent with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> conservation.

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

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

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

Z.J. 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

Measurements of the absolute branching fractions of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mrow><mo>*</mo><mn>0</mn></mrow></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>ϕ</mi></math>

The double-logarithmic series of non-relativistic $\textit{B}$ → $\textit{η}$ form factors at large recoil is governed by a coupled set of integral equations, reflecting an intricate interplay between arbitrarily many soft-quark and soft-gluon exchanges. Whereas we previously derived these integral equations with diagrammatic resummation techniques, we analyze the form factors with methods from Soft-Collinear Effective Theory (SCET) in this work. Although the resulting factorization theorem for the so-called soft-overlap contribution is known to be spoilt by endpoint divergences, it can still be used at the level of bare (regularized) quantities at any fixed order in perturbation theory. By calculating the required ingredients, we show that the SCET analysis confirms the predictions of the integral equations up to three-loop order. We also argue that the iterative structure and the intertwined soft-quark and soft-gluon effects can be derived from standard renormalization-group equations of the $\textit{B}$ -meson light-cone distribution amplitudes, provided their inverse moments are regularized with an appropriate cutoff.

Guido Bell

Switzerland

Philipp Böer

Thorsten Feldmann

Dennis Horstmann

Vladyslav Shtabovenko

$\textit{B}$ $\textit{c}$ $\textit{ → η}$ $\textit{c}$ form factors at large recoil: SCET analysis and a three-loop consistency check

In this work, we examine Big Bang Nucleosynthesis (BBN) within the framework of <italic>f</italic>( <italic>Q, C</italic>) gravity by considering three representative functional forms of the gravitational Lagrangian. The first model is constructed from quadratic contributions involving the nonmetricity scalar <italic>Q</italic> and the boundary term <italic>C</italic>. The second employs a separable form containing the standard linear dependence on <italic>Q</italic> together with a logarithmic correction associated with <italic>C</italic>, whereas the third model introduces a multiplicative coupling between <italic>Q</italic> and <italic>C</italic>. For each scenario, we investigate the background dynamics during the radiation-dominated phase and assess whether the resulting expansion history is compatible with the requirements of successful BBN. We subsequently derive constraints on the corresponding model parameters by confronting the predicted primordial abundances of the principal light elements, with particular emphasis on helium-4 and deuterium. Among the three cases considered, the second model yields the most favorable agreement with the observationally inferred primordial abundances of helium-4 and deuterium, thereby identifying a viable region of its parameter space.

India

Subhajit Sarkar

Ujjal Debnath

Big Bang nucleosynthesis constraints on f(Q,C) gravity

The discovery of the hidden-charm pentaquarks <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>P</mi></mrow><mrow><mi>c</mi></mrow></msub><mo stretchy="false">(</mo><mn>4312</mn><mo stretchy="false">)</mo></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>P</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>4440</mn><mo stretchy="false">)</mo></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>P</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>4457</mn><mo stretchy="false">)</mo></math> by the LHCb Collaboration are very likely to identify as the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi mathvariant="normal">Σ</mi><mi>c</mi><mrow><mo stretchy="false">(</mo><mo>*</mo><mo stretchy="false">)</mo></mrow></msubsup><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mo>*</mo><mo stretchy="false">)</mo></mrow></msup></math> molecules. A natural and crucial extension is the existence of excited molecular partners built from a ground-state charmed baryon and a radially excited anticharmed meson, namely <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi mathvariant="normal">Σ</mi><mi>c</mi><mrow><mo stretchy="false">(</mo><mo>*</mo><mo stretchy="false">)</mo></mrow></msubsup><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mo>*</mo><mo stretchy="false">)</mo></mrow></msup><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo></math> molecules. In a framework of the chiral quark model, we systematically study pion-emission decays of such excited molecules into the known ground-state <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>P</mi><mi>c</mi></msub></math> molecules. Our results show that the decay widths are sensitive to the spin structures and the coupled-channel interferences, i.e., the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="normal">Σ</mi><mi>c</mi></msub><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo><mo>/</mo><msub><mi mathvariant="normal">Σ</mi><mi>c</mi></msub><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo><mo>/</mo><msubsup><mi mathvariant="normal">Σ</mi><mi>c</mi><mo>*</mo></msubsup><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mo>*</mo></msup><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo><mo stretchy="false">[</mo><mn>1</mn><mo>/</mo><mn>2</mn><mo stretchy="false">(</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup><mo stretchy="false">)</mo><mo stretchy="false">]</mo></math> state decays to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>P</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>4440</mn><mo stretchy="false">)</mo></math> with a width of several MeV, while the width to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>P</mi><mi>c</mi></msub><mo stretchy="false">(</mo><mn>4457</mn><mo stretchy="false">)</mo></math> is suppressed below 0.3 MeV due to destructive interference. The pion-emission decay can be the key to unveiling the excited molecular spectrum of hidden-charm pentaquarks and provides decisive experimental signatures. We expect that future experiments such as the LHCb and PANDA can verify our predictions.

Yu-Jie Tang

Wen-Yan Peng

Rui Chen

Fu-Lai Wang

Pion radiative decays of excited hidden-charm pentaquark molecules: From <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi mathvariant="normal">Σ</mi><mi>c</mi><mrow><mo stretchy="false">(</mo><mo>*</mo><mo stretchy="false">)</mo></mrow></msubsup><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mrow><mo stretchy="false">(</mo><mo>*</mo><mo stretchy="false">)</mo></mrow></msup><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo></math> molecules to the reported <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>P</mi><mi>c</mi></msub></math> states

We investigate the decays $$ {B}_c^{-}\to {D}_s^{\left(\ast \right)-}{\ell}^{+}{\ell}^{-} $$ and $$ {B}_c^{-}\to {D}_s^{\left(\ast \right)-}\nu \overline{\nu} $$ within the Standard Model (SM), employing perturbative QCD (pQCD) form factors that are sensitive to the wave functions of $\textit{B}$ and $$ {D}_s^{\left(\ast \right)} $$ mesons. We determine the shape parameters of these mesons and the $$ {B}_c\to {D}_s^{\left(\ast \right)} $$ form factors at $\textit{q}$ = 0 from available lattice QCD inputs for $$ {B}_s\to {D}_s^{\left(\ast \right)} $$ and $\textit{B}$ → $\textit{D}$ transitions. To obtain the $\textit{q}$ dependence of the $$ {B}_c\to {D}_s^{\ast } $$ form factors, we employ heavy-quark spin symmetry (HQSS) and an appropriate parametrization scheme over the allowed $\textit{q}$ region. Based on these inputs, we present predictions for branching ratios and lepton-flavour-sensitive observables. Furthermore, we perform a detailed angular analysis of the cascade decay $$ {B}_c^{-}\to {D}_s^{\ast -}\left(\to {D}_s^{-}{\pi}^0\right){\ell}^{+}{\ell}^{-} $$ , providing Standard Model predictions for several angular observables.

Utsab Dey

Soumitra Nandi

Study of form factors and observables in $$ {B}_c^{-}\to {D}_s^{\ast -}{\ell}^{+}{\ell}^{-} $$ and $$ {B}_c^{-}\to {D}_s^{\ast -}\nu \overline{\nu} $$ decays

We present a systematic study of the transition form factors for the semileptonic decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mo stretchy="false">→</mo><mi>P</mi><msup><mi>e</mi><mo>+</mo></msup><msub><mi>v</mi><mi>e</mi></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mo stretchy="false">→</mo><mi>P</mi><msup><mi>μ</mi><mo>+</mo></msup><msub><mover accent="true"><mi>v</mi><mo stretchy="false">¯</mo></mover><mi>μ</mi></msub></math> using QCD light-cone sum rules with chiral currents, with emphasis on the nonperturbative structure of the pion. The distribution amplitudes of the meson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>π</mi></math>, including twist-2 and higher-twist components, are analyzed and incorporated in our computation, employing both Gegenbauer polynomial expansions and the basis light-front quantization method, where the latter yields a distribution that rapidly converges to the asymptotic form. Two relations linking transition form factors are derived and found to be consistent with the chiral symmetry of QCD. Our numerical predictions for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi></math>-to-pion form factors agree well with BESIII measurements and lattice QCD calculations. Furthermore, the differential decay widths obtained thereby for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi></math>-to-pion decay also show consistency with the BESIII data in the high-momentum-transfer (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>q</mi></math>) region with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>q</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>&gt;</mo><mn>1</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>GeV</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math>, implying new opportunities for the precise extraction of the Cabibbo-Kabayashi-Maskawa matrix element and the exploration of physics beyond the standard model.

Di Gao

Jiangshan Lan

Duojie Jia

Xingbo Zhao

Yanjun Sun

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mo stretchy="false">→</mo><mi>π</mi></math> transitions from QCD light-cone sum rules with the chiral currents

We study the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>u</mi><mi>u</mi><mi>d</mi><mi>d</mi><mi>s</mi><mi>s</mi></math> multiquark within a constituent quark model framework, solving the corresponding nonrelativistic Schrödinger equation including the AL1 potential by means of a diffusion Monte Carlo (DMC) method. The total wave function is written as the product of a radial component and an exact spin-color-flavor state, restricted to isospin <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>I</mi><mo indentshift="1em">=</mo><mn>0</mn></math>. For this isospin, all allowed flavor wave functions are included. We explore two distinct constructions of the six-quark system. In the first one, corresponding to a sexaquark, all six quarks are treated as indistinguishable and the wave function is fully antisymmetric with respect to the exchange of any two quarks. In the second one, corresponding to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi></math> dibaryon, the system is partitioned into two sets of three quarks, effectively mimicking a baryon-baryonlike configuration including hidden color terms in which antisymmetry is imposed only within each three-quark cluster. Only when the system is forced into a baryon-baryonlike configuration, and for certain values of the spin, color and flavor quantum numbers, do we obtain states with masses close to, but above, the two-baryon threshold. Those states are characterized by two loosely bound three-quark clusters separated from one another by a distance of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><mn>2.5</mn><mtext> </mtext><mtext> </mtext><mi>fm</mi></math>. The remaining structures are compact objects irrespectively of their internal wave function.

Spain

M.C. Gordillo

Sexaquarks and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>H</mi></mrow></math> dibaryons in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>u</mi><mi>u</mi><mi>d</mi><mi>d</mi><mi>s</mi><mi>s</mi></math> system: A comparison within a constituent quark model