A search for 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><msub><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1270</mn><msup><mo stretchy="false">)</mo><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>+</mo></msup><mo stretchy="false">→</mo><mi>γ</mi><msub><mi>K</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1270</mn><msup><mo stretchy="false">)</mo><mo>+</mo></msup></math> is conducted using <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 <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>3.773</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> by the BESIII detector operating at the BEPCII collider. No significant signals are observed, and upper limits on the 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><msub><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1270</mn><msup><mo stretchy="false">)</mo><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>+</mo></msup><mo stretchy="false">→</mo><mi>γ</mi><msub><mi>K</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1270</mn><msup><mo stretchy="false">)</mo><mo>+</mo></msup></math> at 90% confidence level are determined to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>7.8</mn><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"><mn>3.9</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></math>, respectively. This represents the first test of the vector meson dominance mechanism in the radiative decays of charmed mesons to axial-vector mesons.

China

M. Ablikim

Russia

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

X.L. 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

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

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

Search for 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><msub><mover accent="true"><mi>K</mi><mo stretchy="false">¯</mo></mover><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1270</mn><msup><mo stretchy="false">)</mo><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>+</mo></msup><mo stretchy="false">→</mo><mi>γ</mi><msub><mi>K</mi><mn>1</mn></msub><mo stretchy="false">(</mo><mn>1270</mn><msup><mo stretchy="false">)</mo><mo>+</mo></msup></math>

We performed searches for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>K</mi></mrow><mrow><mi>L</mi></mrow></msub><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><mi>X</mi></mrow></math> where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi></math> may be an axionlike particle that promptly decays to two photons, and the first search for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>K</mi></mrow><mrow><mi>L</mi></mrow></msub><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><mi>γ</mi><mi>γ</mi></mrow></math> at the KOTO experiment using data taken in 2021. The search is performed for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi></math> mass in the range of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>160</mn><mi>–</mi><mn>220</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi><mo>/</mo><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math>. Three events were observed in the signal region, with two events near an <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi></math> mass of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>177</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi><mo>/</mo><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math>. This result led to a range of upper limits on the branching ratio, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mrow><mi>BR</mi><mo stretchy="false">(</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>L</mi></mrow></msub><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><mi>X</mi></mrow><mo stretchy="false">)</mo></mrow></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo>&lt;</mo><mo stretchy="false">(</mo><mn>1</mn><mo>−</mo><mn>20</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>7</mn></mrow></msup></mrow></math> at the 95% confidence level (CL). No events were observed for the analysis of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>K</mi></mrow><mrow><mi>L</mi></mrow></msub><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><mi>γ</mi><mi>γ</mi></mrow></math>, setting an upper limit on the branching ratio, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mrow><mi>BR</mi><mo stretchy="false">(</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>L</mi></mrow></msub><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><mi>γ</mi><mi>γ</mi></mrow><mo stretchy="false">)</mo></mrow></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo>&lt;</mo><mn>1.69</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>6</mn></mrow></msup></mrow></math> at the 95% CL.

J. Redeker

Taiwan

C. Lin

Y.W. Wah

J.K. Ahn

Japan

M. Gonzalez

K. Hanai

Y.B. Hsiung

T. Kato

E.J. Kim

T.K. Komatsubara

K. Kotera

S.K. Lee

G.Y. Lim

T. Matsumura

H. Nanjo

T. Nomura

T. Nunes

K. Ono

K. Shiomi

R. Shiraishi

Y. Tajima

Y.C. Tung

H. Watanabe

T. Wu

T. Yamanaka

H.Y. Yoshida

Search for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>K</mi></mrow><mrow><mi>L</mi></mrow></msub><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><mi>γ</mi><mi>γ</mi></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>K</mi></mrow><mrow><mi>L</mi></mrow></msub><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><mi>X</mi></mrow></math> Where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>X</mi><mo stretchy="false">→</mo><mi>γ</mi><mi>γ</mi></mrow></math> at the KOTO Experiment

Muon-electron universality is tested in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>B</mi></mrow><mrow><mn>0</mn></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>*</mo><mn>0</mn></mrow></msup><msup><mrow><mo>ℓ</mo></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mo>ℓ</mo></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> decays, in the dilepton-invariant-mass region above the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ψ</mi><mrow><mo stretchy="false">(</mo><mn>2</mn><mi>S</mi><mo stretchy="false">)</mo></mrow></math> resonance. The analysis uses beauty mesons produced in proton-proton collisions recorded by the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>9</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. The ratio of branching fractions between the muon and electron channels <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><msup><mi>K</mi><mrow><mo>*</mo><mn>0</mn></mrow></msup></msub></math> is measured to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msubsup><mrow><mn>1.08</mn></mrow><mrow><mo>−</mo><mn>0.12</mn></mrow><mrow><mo>+</mo><mn>0.14</mn></mrow></msubsup><mrow><mo stretchy="false">(</mo><mi>stat</mi><mo stretchy="false">)</mo></mrow><mo>±</mo><mn>0.07</mn><mrow><mo stretchy="false">(</mo><mi>syst</mi><mo stretchy="false">)</mo></mrow></mrow></math> for a dilepton-invariant-mass squared above <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>14.0</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>GeV</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>/</mo><msup><mrow><mi>c</mi></mrow><mrow><mn>4</mn></mrow></msup></mrow></math>, consistent with the standard model prediction. This result represents the most precise measurement of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><msup><mi>K</mi><mrow><mo>*</mo><mn>0</mn></mrow></msup></msub></math> in this region and the first such measurement performed at a hadron collider.

Netherlands

R. Aaij

M. Abdelfatah

A.S.W. Abdelmotteleb

Switzerland

C. Abellan Beteta

F. Abudinén

T. Ackernley

A.A. Adefisoye

Spain

B. Adeva

M. Adinolfi

France

C. Agapopoulou

C.A. Aidala

Z. Ajaltouni

S. Akar

K. Akiba

P. Albicocco

J. Albrecht

R. Aleksiejunas

CERN

F. Alessio

P. Alvarez Cartelle

R. Amalric

Brazil

S. Amato

J.L. Amey

Y. Amhis

L. An

L. Anderlini

M. Andersson

P. Andreola

M. Andreotti

S. Andres Estrada

A. Anelli

D. Ao

C. Arata

F. Archilli

Z. Areg

M. Argenton

Costa Rica

S. Arguedas Cuendis

L. Arnone

M. Artuso

E. Aslanides

R. Ataíde Da Silva

M. Atzeni

B. Audurier

J.A. Authier

D. Bacher

I. Bachiller Perea

S. Bachmann

M. Bachmayer

J.J. Back

Z.B. Bai

P. Baladron Rodriguez

V. Balagura

Test of Lepton Flavor Universality with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>B</mi><mn>0</mn></msup><mo stretchy="false">→</mo><msup><mi>K</mi><mrow><mo>*</mo><mn>0</mn></mrow></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> Decays at Large Dilepton Invariant Mass