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.

China

Russia

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

We report a study of the semileptonic decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mn>0</mn></msup><msup><mi>π</mi><mo>−</mo></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msub><mi>ν</mi><mo>ℓ</mo></msub></math> (where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>ℓ</mo><mo>=</mo><mi>e</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>μ</mi></mrow></math>) based on 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 a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider. Based on an investigation of the decay dynamics in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mn>0</mn></msup><msup><mi>π</mi><mo>−</mo></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msub><mi>ν</mi><mo>ℓ</mo></msub></math> decays, a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">D</mi></mrow></math>-wave component of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><msubsup><mi>K</mi><mn>2</mn><mo>*</mo></msubsup><mo stretchy="false">(</mo><mn>1430</mn><msup><mo stretchy="false">)</mo><mo>−</mo></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msub><mi>ν</mi><mo>ℓ</mo></msub></math> is observed for the first time with a statistical significance of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>8.0</mn><mi>σ</mi></math>, in addition to the dominant <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>892</mn><msup><mo stretchy="false">)</mo><mo>−</mo></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">S</mi></mrow></math>-wave components. The <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">D</mi></mrow></math>-wave component is determined to account for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>0.092</mn><mo>±</mo><mn>0.02</mn><msub><mn>8</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.01</mn><msub><mn>8</mn><mrow><mi>syst</mi></mrow></msub><mo stretchy="false">)</mo><mo>%</mo></math> of the total decay rate. The branching fractions of the dominant <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>K</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>892</mn><msup><mo stretchy="false">)</mo><mo>−</mo></msup></math> components are measured as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><msup><mi>K</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>892</mn><msup><mo stretchy="false">)</mo><mo>−</mo></msup><msup><mi>e</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>e</mi></msub><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>2.043</mn><mo>±</mo><mn>0.01</mn><msub><mn>8</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.01</mn><msub><mn>2</mn><mrow><mi>syst</mi></mrow></msub><mo stretchy="false">)</mo><mo>%</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><msup><mi>K</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>892</mn><msup><mo stretchy="false">)</mo><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>μ</mi></msub><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>1.964</mn><mo>±</mo><mn>0.01</mn><msub><mn>8</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.01</mn><msub><mn>2</mn><mrow><mi>syst</mi></mrow></msub><mo stretchy="false">)</mo><mo>%</mo></math>, which are the most precise measurements to date and represent significant improvements over the previous world averages. The hadronic form-factor parameters are measured to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>r</mi><mi>V</mi></msub><mo>=</mo><mi>V</mi><mo stretchy="false">(</mo><mn>0</mn><mo stretchy="false">)</mo><mo>/</mo><msub><mi>A</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>0</mn><mo stretchy="false">)</mo><mo>=</mo><mn>1.444</mn><mo>±</mo><mn>0.02</mn><msub><mn>6</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.01</mn><msub><mn>0</mn><mrow><mi>syst</mi></mrow></msub></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>r</mi><mn>2</mn></msub><mo>=</mo><msub><mi>A</mi><mn>2</mn></msub><mo stretchy="false">(</mo><mn>0</mn><mo stretchy="false">)</mo><mo>/</mo><msub><mi>A</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>0</mn><mo stretchy="false">)</mo><mo>=</mo><mn>0.752</mn><mo>±</mo><mn>0.02</mn><msub><mn>0</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.00</mn><msub><mn>4</mn><mrow><mi>syst</mi></mrow></msub></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>A</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>0</mn><mo stretchy="false">)</mo><mo>=</mo><mn>0.618</mn><mo>±</mo><mn>0.00</mn><msub><mn>2</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.00</mn><msub><mn>4</mn><mrow><mi>syst</mi></mrow></msub></math>, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>V</mi><mo stretchy="false">(</mo><mn>0</mn><mo stretchy="false">)</mo></math> is the vector form factor and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>A</mi><mrow><mn>1</mn><mo>,</mo><mn>2</mn></mrow></msub><mo stretchy="false">(</mo><mn>0</mn><mo stretchy="false">)</mo></math> are the axial-vector form factors evaluated at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>q</mi><mn>2</mn></msup><mo>=</mo><mn>0</mn></math>. This is the most precise determination of the form-factor parameters to date measured in a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mo stretchy="false">→</mo><msup><mi>K</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>892</mn><mo stretchy="false">)</mo></math> transition. In addition, we report the first model-independent measurement of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">S</mi></mrow></math>-wave phase shift in the hadronic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mn>0</mn></msup><msup><mi>π</mi><mo>−</mo></msup></math> system. We also measure the relative ratio between 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><msup><mi>K</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>892</mn><msup><mo stretchy="false">)</mo><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>μ</mi></msub></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><msup><mi>K</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>892</mn><msup><mo stretchy="false">)</mo><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>μ</mi></msub></math> to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi mathvariant="script">R</mi><mrow><msup><mi>K</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>892</mn><mo stretchy="false">)</mo></mrow><mrow><mi>μ</mi><mo>/</mo><mi>e</mi></mrow></msubsup><mo>=</mo><mn>0.961</mn><mo>±</mo><mn>0.01</mn><msub><mn>2</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.00</mn><msub><mn>5</mn><mrow><mi>syst</mi></mrow></msub></math>, and no violation of lepton flavor universality is found.

M. Ablikim

M.N. Achasov

Sweden

P. Adlarson

X.C. Ai

Germany

R. Aliberti

Italy

A. Amoroso

Q. An

Y. Bai

JINR

O. Bakina

Y. Ban

H.R. Bao

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

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

X.R. Chen

X.T. Chen

X.Y. Chen

Y.B. Chen

Y.Q. Chen

Z.K. Chen

J.C. 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

X.X. Ding

Y. Ding

Y.X. Ding

J. Dong

L.Y. Dong

M.Y. Dong

X. Dong

M.C. Du

S.X. Du

X.L. Du

Y.Y. Duan

Z.H. Duan

P. Egorov

G.F. Fan

J.J. Fan

Y.H. Fan

J. Fang

S.S. Fang

W.X. Fang

Y.Q. Fang

L. Fava

F. Feldbauer

G. Felici

C.Q. Feng

J.H. Feng

L. Feng

Q.X. Feng

Y.T. Feng

M. Fritsch

Precise measurement of the form factors in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><msup><mi>K</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>892</mn><msup><mo stretchy="false">)</mo><mo>−</mo></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msub><mi>ν</mi><mo>ℓ</mo></msub></math> and observation of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><msubsup><mi>K</mi><mn>2</mn><mo>*</mo></msubsup><mo stretchy="false">(</mo><mn>1430</mn><msup><mo stretchy="false">)</mo><mo>−</mo></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msub><mi>ν</mi><mo>ℓ</mo></msub></math>

The triangle singularity interpretation of the $a_1(1420)$ observed by the COMPASS Collaboration has been widely accepted. In this work, we investigate the triangle mechanism in the decay $B^0 \to D^- \pi^+ a_0(980)(\pi^0 \eta)$ , where the $a_0(980)$ is treated as a dynamically generated state. The $\bar{K}^{*0}$ - $K^+$ - $K^-$ triangle loop originates from the decay $B^0 \to D^- K^+ \bar{K}^{*0}$ , which has been observed by the Belle Collaboration, followed by the subsequent decay $\bar{K}^{*0} \to K^- \pi^+$ . The triangle amplitude develops a pronounced peak around 1420 MeV, which is reflected in the invariant mass spectrum of the $\pi a_0(980)$ system. The differential decay width is calculated and exhibits a narrow peak around $980~\mathrm{MeV}$ in the $\pi^0 \eta$ invariant mass distribution. Furthermore, the invariant mass distribution of the $\pi^+ \pi^0 \eta$ system shows a clear peak around $1420~\mathrm{MeV}$ , which further confirms the triangle singularity explanation of the $a_1(1420)$ . We expect that the proposed $B^0$ decay mode could provide a potential platform for further exploring the triangle-singularity nature of the $a_1(1420)$ and could be tested in future experiments such as LHCb, BESIII, and Belle II.

Wei Wang

Dazhuang He

Xuan Luo

The role of triangle singularity in the $ {B^0 \to D^- \pi^+ a_0(980)(\pi^0 \eta)}$ decay * Dazhuang He is supported by the Heze University doctoral fund project (010008002039037). Xuan Luo is supported by the National Natural Science Foundation of China (12205002)

By analyzing <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> collision data corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>7.33</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> collected with the BESIII detector at center-of-mass energies ranging from 4.128 to 4.226 GeV, we report the observations of the hadronic decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo stretchy="false">→</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>π</mi><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msup><mi>K</mi><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup><msup><mi>π</mi><mn>0</mn></msup></math>. Their decay branching fractions are determined to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo stretchy="false">→</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>π</mi><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>4.08</mn><mo>±</mo><mn>0.4</mn><msub><mn>6</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.4</mn><msub><mn>5</mn><mrow><mi>syst</mi></mrow></msub><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msup><mi>K</mi><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup><msup><mi>π</mi><mn>0</mn></msup><mo stretchy="false">)</mo><mo>=</mo><mspace linebreak="goodbreak"></mspace><mo stretchy="false">(</mo><mn>3.32</mn><mo>±</mo><mn>0.6</mn><msub><mn>4</mn><mrow><mi>stat</mi></mrow></msub><mo>±</mo><mn>0.3</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>3</mn></mrow></msup></math>, where the first uncertainties are statistical and the second are systematic.

Measurement of branching fractions of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo stretchy="false">→</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>π</mi><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msup><mi>K</mi><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup><msup><mi>π</mi><mn>0</mn></msup></math>

Experimental analyses of the semileptonic decays $\textit{B}$ → $\textit{D}$ $\textit{ℓν}$ (with $\textit{ℓ}$ = $\textit{μ}$, $\textit{e}$) typically rely on the assumption that the missing energy originates from a massless neutrino, as predicted by the Standard Model. However, this assumption may not hold in scenarios where the invisible final-state particle is instead massive, such as a sterile neutrino or a dark-sector fermion. In this work, we explore how the presence of a massive dark sector fermion modifies the kinematic and angular distributions of these decays. Our analysis is carried out within the framework of a general weak effective theory, and we also discuss effective and simplified models in which these interactions may arise. In addition, we study the implications of these effects for the extraction of the CKM matrix element |$\textit{V}$ |. Overall, our results show that relaxing the standard assumption of a massless neutrino can lead to observable effects and provide a framework for systematically investigating their impact on semileptonic $\textit{B}$- decay distributions.

India

Lipika Kolay

Soumitra Nandi

Shantanu Sahoo

Ria Sain

Probing light dark fermions in $\textit{B}$ → $\textit{D}$ (∗) $\textit{ℓX}$ inv via rate distributions

According to the <italic>B</italic>-mesogenesis framework, the baryon asymmetry of the Universe and dark matter can be simultaneously generated through CP-violating <italic>B</italic>-meson oscillations. In this mechanism, <italic>B</italic>-mesons decay into a Standard Model baryon and a dark-sector antibaryon, denoted by <italic>&#968;<inf>DS</inf></italic>. Within this scenario, we investigate the allowed mass window for <italic>&#968;<inf>DS</inf></italic> using Light Cone Sum Rules (LCSR) for <italic>B<inf>d</inf></italic>&#8239;&#8594;&#8239;&#923;&#8201; <italic>&#968;<inf>DS</inf></italic> decay. To include nonperturbative effects, we employ contributions up to twist-6 of the &#923; distribution amplitudes in the operator product expansion (OPE). We derive the branching fraction as a function of dark antibaryon mass and, by comparing with the experimental limits by the BaBar and Belle collaborations, determine the mass ranges of <italic>&#968;<inf>DS</inf></italic> consistent with the <italic>B</italic>-mesogenesis mechanism.

Iran

M.A. Abri

N. Hajirasouliha

K. Azizi

Constraints on the mass of the dark antibaryon using <italic>B<inf>d</inf></italic>&#8239;&#8594;&#8239;&#923; <italic>&#968;<inf>DS</inf></italic> channel in light cone QCD

The total decay widths of heavy mesons can be systematically calculated in terms of an expansion in the two parameters 1/$\textit{m}$ and $\textit{α}$ ($\textit{m}$ ), where $\textit{Q}$ = $\textit{c}$, $\textit{b}$ denotes the heavy quark. The dominant contributions to meson lifetime splittings stem from terms which are suppressed by $$ 1/{m}_Q^3 $$ with respect to the leading universal contribution to the total decay width. We calculate three-loop contributions of order $$ {\alpha}_s^2/{m}_q^3 $$ to the lifetime ratios $$ \tau \left({B}^{+}\right)/\tau \left({B}_d^0\right) $$ , $\textit{τ}$($\textit{D}$ )/$\textit{τ}$($\textit{D}$ ), and $$ \tau \left({D}_s^{+}\right)/\tau \left({D}^0\right) $$ in the limit of exact isospin and V-spin symmetry, respectively. Furthermore, we present new $$ {\alpha}_s/{m}_q^3 $$ corrections to the Cabibbo-suppressed terms in $$ \tau \left({B}^{+}\right)/\tau \left({B}_d^0\right) $$ . Combining our perturbative coefficients with hadronic matrix elements calculated from Heavy Quark Effective Theory sum rules, we find $$ \tau \left({B}^{+}\right)/\tau \left({B}_d^0\right) $$ = 1.072 ± 0.024. Using hadronic matrix elements from a recent lattice QCD calculation we find $\textit{τ}$($\textit{D}$ )/$\textit{τ}$($\textit{D}$ ) = 2.344 ± 0.170 and $$ \tau \left({D}_s^{+}\right)/\tau \left({D}^0\right) $$ = 1.289 ± 0.042. We find good agreement of our predictions with experimental data, which constitutes a successful probe of the calculations of hadronic matrix elements and permits estimates of the unknown $$ 1/{m}_Q^4 $$ contributions as well as the V-spin breaking terms in $$ \tau \left({D}_s^{+}\right)/\tau \left({D}^0\right) $$ .

Francesco Moretti

Ulrich Nierste

Pascal Reeck

Matthias Steinhauser

Next-to-next-to-leading QCD corrections to the $$ {\mathrm{B}}^{+}-{\mathrm{B}}_{\mathrm{d}}^0 $$ , D+ − D0, and $$ {\mathrm{D}}_{\mathrm{s}}^{+}-{\mathrm{D}}^0 $$ lifetime ratios

We investigate the three-body <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mi>D</mi><mi>K</mi></math> system with quantum numbers <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>I</mi><mo stretchy="false">(</mo><msup><mi>J</mi><mi>P</mi></msup><mo stretchy="false">)</mo><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mo stretchy="false">(</mo><msup><mn>0</mn><mo>−</mo></msup><mo stretchy="false">)</mo></math> within a coupled-channel framework that incorporates the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mi>D</mi><mi>K</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>*</mo></msup><msup><mi>D</mi><mo>*</mo></msup><mi>K</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msub><mi>D</mi><mi>s</mi></msub><mi>η</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msub><mi>D</mi><mi>s</mi></msub><mi>π</mi></math> channels. The <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><msup><mi>D</mi><mrow><mo stretchy="false">(</mo><mo>*</mo><mo stretchy="false">)</mo></mrow></msup></math> interactions are described using the one-boson-exchange model constrained by heavy-quark symmetry and fitted to the pole positions of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>3872</mn><mo stretchy="false">)</mo></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>T</mi><mrow><mi>c</mi><mi>c</mi></mrow><mo>+</mo></msubsup></math>, and <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>. The <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><mi>K</mi></math> interaction is from the chiral effective field theory, motivated by the molecular interpretation of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>D</mi><mrow><mi>s</mi><mn>0</mn></mrow><mo>*</mo></msubsup><mo stretchy="false">(</mo><mn>2317</mn><mo stretchy="false">)</mo></math>, and is further constrained by lattice-QCD results for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mi>K</mi></math> scattering lengths. The resulting three-body problem is solved using the Gaussian expansion method, while the complex scaling method is employed to search for possible resonant states. We find that coupled-channel effects from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>*</mo></msup><msup><mi>D</mi><mo>*</mo></msup><mi>K</mi></math> are negligible, and the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mi>D</mi><mi>K</mi></math> system supports a deeply bound state across a wide range of parameters. Depending on the long-range behavior of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mi>K</mi></math> interaction, an additional shallow state may emerge near the particle-dimer (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>D</mi><mtext>−</mtext><mi>D</mi><mi>K</mi></mrow></math>) threshold. The deeply bound state exhibits a compact three-body structure, whereas the shallow state displays characteristic features of a three-body halo configuration. Similar results are obtained for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>*</mo></msup><msup><mi>D</mi><mo>*</mo></msup><mi>K</mi></math> system. We also observe that the coupled-channel effects originating from the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msub><mi>D</mi><mi>s</mi></msub><mi>η</mi></math> channel produce only minor corrections to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mi>D</mi><mi>K</mi></math> bound state and lead to a modest reduction in its binding energy. By contrast, opening the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><msub><mi>D</mi><mi>s</mi></msub><mi>π</mi></math> channel substantially alters the nature of the three-body <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mi>D</mi><mi>K</mi></math> state and transforms the bound state into a resonance. These findings may provide new insight into few-body dynamics in systems involving charmed mesons and kaons.

Hai-Peng Xie

Si-Yi Chen

Ning Li

Wei Chen

Coupled-channel study of the three-body <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>D</mi><mi>D</mi><mi>K</mi></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>D</mi></mrow><mrow><mo>*</mo></mrow></msup><msup><mrow><mi>D</mi></mrow><mrow><mo>*</mo></mrow></msup><mi>K</mi></mrow></math>

By performing a fit to the merged BES 2008 and BESIII 2024 <math altimg='si15.svg'><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>&#8722;</mo></msup><mo>&#8594;</mo><mi>D</mi><mover accent='true'><mi>D</mi><mo>&#175;</mo></mover></mrow></math> cross-section data, we find that the <italic>&#968;</italic>(2S) subthreshold pole influences this process markedly. The statistical significance of the <italic>&#968;</italic>(2S) as a subthreshold pole is 8 <italic>&#963;</italic>. A fit assuming it and seven resonances excels with the fit quality characterized by <math altimg='si8.svg'><mrow><msup><mi>&#967;</mi><mn>2</mn></msup><mo linebreak='goodbreak'>/</mo><mtext>DOF</mtext><mo linebreak='goodbreak'>=</mo><mn>240.4</mn><mo linebreak='goodbreak'>/</mo><mn>284</mn></mrow></math>, which means a <italic>p</italic>-value of 97%. The interference of resonances with the continuum provided by the subthreshold pole changes their shapes, positions, and widths.

Czechia

Peter Lichard

The <italic>&#968;</italic>(2S) state as a subthreshold pole in electron-positron annihilation into <math altimg='si14.svg'><mrow><mi>D</mi><mover accent='true'><mi>D</mi><mo>&#175;</mo></mover></mrow></math> final states