We measure the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> asymmetry in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>+</mo></msup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup></math> decays reconstructed 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 Belle II experiment using a dataset corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>428</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. A control sample of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>+</mo></msup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup></math> decays is used to correct for detection and production asymmetries. The result <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>A</mi><mrow><mi>C</mi><mi>P</mi></mrow></msub><mo stretchy="false">(</mo><msup><mi>D</mi><mo>+</mo></msup><mo stretchy="false">→</mo><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><mo>−</mo><mn>1.8</mn><mo>±</mo><mn>0.9</mn><mo>±</mo><mn>0.1</mn><mo stretchy="false">)</mo><mo>%</mo></math>, where the first uncertainty is statistical and the second systematic, is the most precise determination to date. It agrees with the prediction of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> symmetry from the standard model and with results of previous measurements.

I. Adachi

L. Aggarwal

H. Ahmed

H. Aihara

N. Akopov

S. Alghamdi

M. Alhakami

A. Aloisio

K. Amos

M. Angelsmark

N. Anh Ky

C. Antonioli

D.M. Asner

H. Atmacan

V. Aushev

M. Aversano

R. Ayad

V. Babu

H. Bae

N.K. Baghel

P. Bambade

Sw. Banerjee

S. Bansal

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

B. Bhuyan

F. Bianchi

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. Cheema

L. Chen

B.G. Cheon

K. Chilikin

J. Chin

K. Chirapatpimol

H.E. Cho

K. Cho

S.J. Cho

S.K. Choi

S. Choudhury

I. Consigny

L. Corona

J.X. Cui

S. Das

E. De La Cruz-Burelo

S.A. De La Motte

G. De Pietro

R. de Sangro

M. Destefanis

A. Di Canto

Z. Doležal

I. Domínguez Jiménez

T.V. Dong

X. Dong

M. Dorigo

K. Dugic

G. Dujany

P. Ecker

D. Epifanov

J. Eppelt

R. Farkas

P. Feichtinger

T. Ferber

T. Fillinger

C. Finck

G. Finocchiaro

F. Forti

A. Frey

B.G. Fulsom

Measurement of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> asymmetry in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>+</mo></msup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mn>0</mn></msup></math> decays at Belle II

The nature of the <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> and other exotic hadrons has been a subject of extensive investigation since the first observation of the <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> in 2003. While various theoretical models have been proposed, including hadronic molecular and compact tetraquark interpretations, some experimental evidence suggests that the <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> may be a mixture state of a hadronic molecule and a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math> core. In this work, we perform a systematic study of the hidden-charm tetraquark candidates <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>3860</mn><mo stretchy="false">)</mo></math>, <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>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi><mo stretchy="false">(</mo><mn>3930</mn><mo stretchy="false">)</mo></math> using a coupled-channel model that incorporates both <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math> states and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>D</mi></mrow><mrow><mo stretchy="false">(</mo><mo>*</mo><mo stretchy="false">)</mo></mrow></msup><msup><mrow><mover accent="true"><mrow><mi>D</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover></mrow><mrow><mo stretchy="false">(</mo><mo>*</mo><mo stretchy="false">)</mo></mrow></msup></mrow></math> hadronic molecular components. The <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math> sector is described based on the constituent quark model predictions for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>χ</mi><mrow><mi>c</mi><mi>J</mi></mrow></msub><mo stretchy="false">(</mo><mn>2</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, 2) states, while the meson-meson interactions are modeled using pseudoscalar and vector-meson exchange potentials. The model parameters are fixed to reproduce the masses of the <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> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi><mo stretchy="false">(</mo><mn>3930</mn><mo stretchy="false">)</mo></math>, and the resulting framework is used to predict the mass and structure of 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><msup><mn>0</mn><mrow><mo>+</mo><mo>+</mo></mrow></msup></math> state associated with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>3860</mn><mo stretchy="false">)</mo></math>. Our results support the mixture interpretation of these exotic hadrons, exhibiting strong attractions from the transition potential between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math> 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><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> components. The molecular component is found to dominate in the <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>, while the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math> component plays a more prominent role in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>3860</mn><mo stretchy="false">)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi><mo stretchy="false">(</mo><mn>3930</mn><mo stretchy="false">)</mo></math>.

Japan

Kotaro Miyake

Yasuhiro Yamaguchi

Hidden-charm tetraquarks in a mixture model: Coupled-channel analysis with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math> and hadronic molecular components

The arrival time of electromagnetic signals traveling in chiral cosmic media is investigated in the context of Maxwell-Carroll-Field-Jackiw electrodynamics. Considering the interstellar medium (ISM) as a cold, ionized, chiral plasma, we derive the time delay between two traveling signals, expressed in terms of a modified dispersion measure (DM) which receives additional contribution from the chiral parameters. Faraday rotation angle is also addressed in this chiral plasma scenario, yielding modified rotation measures (RM). Using DMs data from five pulsars, we establish constraints on the chiral parameter magnitude at the order of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>23</mn></mrow></msup><mi>–</mi><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>22</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>. On the other hand, the Faraday rotation retrieved from RM measurements implied upper constraints as tight as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>36</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>.

Brazil

Filipe S. Ribeiro

Pedro D.S. Silva

Manoel M. Ferreira

Constraining <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi><mi>T</mi></mrow></math>-odd electromagnetic chiral parameters with pulsar timing

The difference in the proton and neutron separation energies ( <math altimg='si2.svg'><mrow><mstyle mathvariant='normal'><mi>&#916;</mi></mstyle><mi>S</mi></mrow></math>) of the weakly bound <math altimg='si5.svg'><msup><mrow /><mn>15</mn></msup></math>C ground state is -19.86 MeV, an extreme value. Data from intermediate-energy heavy-ion induced (HI-induced) knockout reactions on nuclei spanning <math altimg='si20.svg'><mrow><mo>&#8722;</mo><mn>20</mn><mo>&#8818;</mo><mstyle mathvariant='normal'><mi>&#916;</mi></mstyle><mi>S</mi><mo>&#8818;</mo><mo>+</mo><mn>20</mn></mrow></math> MeV, suggest that the degree to which single-particle strength is quenched, <math altimg='si13.svg'><msub><mi>R</mi><mrow><mi mathvariant='normal'>s</mi></mrow></msub></math>, has a negative correlation with <math altimg='si2.svg'><mrow><mstyle mathvariant='normal'><mi>&#916;</mi></mstyle><mi>S</mi></mrow></math>, decreasing from unity around <math altimg='si21.svg'><mrow><mo>&#8722;</mo><mn>20</mn></mrow></math> MeV to around 0.2 at <math altimg='si22.svg'><mrow><mo>+</mo><mn>20</mn></mrow></math> MeV. For the <math altimg='si5.svg'><msup><mrow /><mn>15</mn></msup></math>C ground state ( <math altimg='si23.svg'><mrow><msub><mi>R</mi><mi>s</mi></msub><mo linebreak='goodbreak'>=</mo><mn>0.96</mn><mrow><mo>(</mo><mn>4</mn><mo>)</mo></mrow></mrow></math> in HI-induced knockout), contrasting results have recently been obtained via the neutron-adding transfer reaction, which reveal a value of <math altimg='si24.svg'><mrow><msub><mi>R</mi><mi>s</mi></msub><mo linebreak='goodbreak'>=</mo><mn>0.64</mn><mrow><mo>(</mo><mn>15</mn><mo>)</mo></mrow></mrow></math>, similar to the value observed at modest <math altimg='si2.svg'><mrow><mstyle mathvariant='normal'><mi>&#916;</mi></mstyle><mi>S</mi></mrow></math> and more extreme values of <math altimg='si2.svg'><mrow><mstyle mathvariant='normal'><mi>&#916;</mi></mstyle><mi>S</mi></mrow></math> with reaction probes other than HI knockout. In order to explore the any potential differences between <math altimg='si25.svg'><mrow><mi>a</mi><mi>d</mi><mi>d</mi><mi>i</mi><mi>n</mi><mi>g</mi></mrow></math> and <math altimg='si26.svg'><mrow><mi>r</mi><mi>e</mi><mi>m</mi><mi>o</mi><mi>v</mi><mi>i</mi><mi>n</mi><mi>g</mi></mrow></math> processes in transfer reactions at extreme <math altimg='si2.svg'><mrow><mstyle mathvariant='normal'><mi>&#916;</mi></mstyle><mi>S</mi></mrow></math>, single-neutron removal transfer reactions on <math altimg='si5.svg'><msup><mrow /><mn>15</mn></msup></math>C were performed at 7.1 MeV/u in inverse kinematics. The removal of a valence neutron in 2 <math altimg='si19.svg'><msub><mi>s</mi><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msub></math> orbit using both ( <math altimg='si7.svg'><mrow><mi>p</mi><mo>,</mo><mi>d</mi></mrow></math>) and ( <math altimg='si8.svg'><mrow><mi>d</mi><mo>,</mo><mi>t</mi></mrow></math>) reactions shows consistent quenching factors and agrees with those from the neutron-adding reaction. The present results, which can be compared with neutron knockout reaction, suggest that correlations, represented by the quenching factor, show limited dependence on neutron-proton asymmetry under the most extreme asymmetry conditions so far achieved in transfer reactions.

China

Y.C. Jiang

United States

J. Chen

B.P. Kay

C.R. Hoffman

T.L. Tang

I.A. Tolstukhin

M.R. Xie

J.G. Li

N. Michel

M.L. Avila

Spain

Y. Ayyad

D. Bazin

United Kingdom

S. Bennett

J.A. Clark

Switzerland

S.J. Freeman

H. Jayatissa

G. Li

W.P. Liu

J.L. Lou

A. Munoz-Ramos

C. Müller-Gatermann

T. Nathan

D. Santiago-Gonzalez

D.K. Sharp

Y.P. Shen

A.H. Wuosmaa

C.X. Yuan

Quenching of single-particle strength inferred from nucleon-removal transfer reactions on <math altimg='si5.svg'><msup><mrow /><mn>15</mn></msup></math>C

We search, for the first time, for an exotic molecular state with quantum numbers <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><msup><mn>1</mn><mrow><mo>−</mo><mo>+</mo></mrow></msup></math>, called <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi></math>, via the process <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>γ</mi><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><msubsup><mi>D</mi><mrow><mi>s</mi><mn>1</mn></mrow><mo>−</mo></msubsup><mo stretchy="false">(</mo><mn>2536</mn><mo stretchy="false">)</mo><mo>+</mo><mi mathvariant="normal">c</mi><mo>.</mo><mi mathvariant="normal">c</mi><mo>.</mo></math> using data samples corresponding to a luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>5.8</mn><mtext> </mtext><mtext> </mtext><mrow><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></mrow></math> across center-of-mass energies from 4.612 to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>4.951</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>, collected with the BESIII detector operating at the BEPCII Collider. No statistically significant signal is observed. The upper limits on the product of cross section and branching fraction <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>σ</mi><mo stretchy="false">(</mo><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>γ</mi><mi>X</mi></mrow><mo stretchy="false">)</mo><mo>·</mo><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><mi>X</mi><mo stretchy="false">→</mo><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><msubsup><mi>D</mi><mrow><mi>s</mi><mn>1</mn></mrow><mo>−</mo></msubsup><mo stretchy="false">(</mo><mn>2536</mn><mo stretchy="false">)</mo><mo>+</mo><mi mathvariant="normal">c</mi><mo>.</mo><mi mathvariant="normal">c</mi><mo>.</mo><mo stretchy="false">)</mo></math> at 90% confidence level are reported for each energy point, assuming the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi></math> mass to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>4.503</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo>/</mo><msup><mi>c</mi><mn>2</mn></msup></mrow></math> and the width 25, 50, 75, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>100</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></mrow></math>, respectively.

M. Ablikim

Russia

M.N. Achasov

Sweden

P. Adlarson

Germany

O. Afedulidis

X.C. Ai

R. Aliberti

Italy

A. Amoroso

Y. Bai

JINR

O. Bakina

I. Balossino

Y. Ban

H.R. Bao

Poland

V. Batozskaya

Mongolia

K. Begzsuren

N. Berger

M. Berlowski

M. Bertani

D. Bettoni

E. Bianco

A. Bortone

I. Boyko

A. Brueggemann

H. Cai

X. Cai

A. Calcaterra

G.F. Cao

N. Cao

Türkiye

S.A. Cetin

X.Y. Chai

J.F. Chang

G.R. Che

Y.Z. Che

G. Chelkov

C. Chen

C.H. Chen

Chao Chen

G. Chen

H.S. Chen

H.Y. Chen

M.L. Chen

S.J. Chen

S.L. Chen

S.M. Chen

T. Chen

X.R. Chen

Search for a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>1</mn><mrow><mo>−</mo><mo>+</mo></mrow></msup></math> molecular state via <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>γ</mi><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><msubsup><mi>D</mi><mrow><mi>s</mi><mn>1</mn></mrow><mo>−</mo></msubsup><mo stretchy="false">(</mo><mn>2536</mn><mo stretchy="false">)</mo><mo>+</mo><mi mathvariant="normal">c</mi><mo>.</mo><mi mathvariant="normal">c</mi><mo>.</mo></math>