United States

Samuel Ting

Discovery of the J particle at Brookhaven National Laboratory and the physics of electrons and positrons

The photoproduction of <math altimg='si1.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi></math> meson off the nucleon is investigated using a dynamical model based on a Hamiltonian that describes the reaction mechanisms involving meson-exchange and direct <math altimg='si1.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi></math>-radiation terms. Pomeron exchange is also included to account for the monotonically increasing high-energy behavior of the cross section. To explore the low-energy mechanism, we scrutinize the role of light-meson [ <math altimg='si2.svg'><msup><mrow><mi>&#960;</mi></mrow><mrow><mn>0</mn></mrow></msup><mo stretchy='false'>(</mo><mn>135</mn><mo stretchy='false'>)</mo></math>, <math altimg='si3.svg'><mi>&#951;</mi><mo stretchy='false'>(</mo><mn>548</mn><mo stretchy='false'>)</mo></math>, <math altimg='si4.svg'><msup><mrow><mi>&#951;</mi></mrow><mrow><mo>&#8242;</mo></mrow></msup><mo stretchy='false'>(</mo><mn>958</mn><mo stretchy='false'>)</mo></math>, <math altimg='si5.svg'><msub><mrow><mi>f</mi></mrow><mrow><mn>1</mn></mrow></msub><mo stretchy='false'>(</mo><mn>1285</mn><mo stretchy='false'>)</mo></math>] and charmonium-meson [ <math altimg='si27.svg'><msub><mrow><mi>&#951;</mi></mrow><mrow><mi>c</mi></mrow></msub><mo stretchy='false'>(</mo><mn>1</mn><mi>S</mi><mo stretchy='false'>)</mo></math>, <math altimg='si28.svg'><msub><mrow><mi>&#967;</mi></mrow><mrow><mi>c</mi><mn>0</mn></mrow></msub><mo stretchy='false'>(</mo><mn>1</mn><mi>P</mi><mo stretchy='false'>)</mo></math>, <math altimg='si29.svg'><msub><mrow><mi>&#967;</mi></mrow><mrow><mi>c</mi><mn>1</mn></mrow></msub><mo stretchy='false'>(</mo><mn>1</mn><mi>P</mi><mo stretchy='false'>)</mo></math>, <math altimg='si30.svg'><msub><mrow><mi>&#951;</mi></mrow><mrow><mi>c</mi></mrow></msub><mo stretchy='false'>(</mo><mn>2</mn><mi>S</mi><mo stretchy='false'>)</mo></math>, <math altimg='si10.svg'><msub><mrow><mi>&#967;</mi></mrow><mrow><mi>c</mi><mn>1</mn></mrow></msub><mo stretchy='false'>(</mo><mn>3872</mn><mo stretchy='false'>)</mo></math>] exchanges in the <italic>t</italic>-channel diagram. Most of the coupling constants are determined from the radiative decays of the <math altimg='si1.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi></math> or the relevant charmonium mesons. The final <math altimg='si1.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi></math>- <italic>N</italic> interaction is described by gluon-exchange and direct <math altimg='si11.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi><mi>N</mi></math> coupling. The parameters of the Hamiltonian are fitted using the latest GlueX and <math altimg='si1.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi></math>-007 experiments at the Jefferson Laboratory (JLab). We find that among the meson-exchange terms, the light mesons <math altimg='si3.svg'><mi>&#951;</mi><mo stretchy='false'>(</mo><mn>548</mn><mo stretchy='false'>)</mo></math> and <math altimg='si4.svg'><msup><mrow><mi>&#951;</mi></mrow><mrow><mo>&#8242;</mo></mrow></msup><mo stretchy='false'>(</mo><mn>958</mn><mo stretchy='false'>)</mo></math> make the most significant contributions to <math altimg='si12.svg'><mi>&#947;</mi><mi>p</mi><mo stretchy='false'>&#8594;</mo><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi><mi>p</mi></math>, while the effect of charmonium mesons is relatively minor. The final-state interaction (FSI) contribution is found to be 1 - 2 orders of magnitude smaller than that of the Born term, but becomes significant near the threshold when a Yukawa-type potential is employed for the charmonium-nucleon interaction. The resulting total and <italic>t</italic>-dependent differential cross sections show good agreement with the JLab data. High-precision angular measurements near the threshold energy ( <math altimg='si13.svg'><msub><mrow><mi>E</mi></mrow><mrow><mi>&#947;</mi></mrow></msub><mo>&#10877;</mo><mn>8.9</mn></math> GeV) are highly desirable to clarify the role of the FSI term.

South Korea

Sang-Ho Kim

<italic>J</italic>/ <italic>&#968;</italic>-meson photoproduction off the nucleon in a dynamical model

A study of the charmless baryonic decays $$ {B}_{(s)}^0\to {K}^0p\overline{p} $$ is presented, where $$ {B}_{(s)}^0 $$ denotes either a $\textit{B}$ or a $$ {B}_s^0 $$ meson. The analysis is based on proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb . The decay $$ {B}_s^0\to {K}^0p\overline{p} $$ is observed for the first time, with a measured branching fraction of (9$\textit{.}$14 $\textit{±}$ 1$\textit{.}$69 $\textit{±}$ 0$\textit{.}$90 $\textit{±}$ 0$\textit{.}$33 $\textit{±}$ 0$\textit{.}$20) $\textit{×}$ 10 and a significance of 5.6$\textit{σ}$. The uncertainties respectively account for statistical and systematic contributions, the precision of the branching fraction of the normalisation channel $\textit{B}$ $\textit{→ K}$ $\textit{π}$ $\textit{π}$ and the fragmentation fraction ratio $\textit{f}$ $\textit{/f}$ . The branching fraction determined for $$ {B}^0\to {K}^0p\overline{p} $$ is (2$\textit{.}$82 $\textit{±}$ 0$\textit{.}$08 $\textit{±}$ 0$\textit{.}$12 $\textit{±}$ 0$\textit{.}$10) $\textit{×}$ 10 , which is the most precise measurement to date.

Netherlands

R. Aaij

United Kingdom

A. Abdelmotteleb

Switzerland

C. Abellan Beteta

F. Abudinén

T. Ackernley

A. Adefisoye

Spain

B. Adeva

M. Adinolfi

Sweden

P. Adlarson

France

C. Agapopoulou

C. Aidala

Z. Ajaltouni

S. Akar

K. Akiba

Italy

P. Albicocco

Germany

J. Albrecht

F. Alessio

Z. Aliouche

P. Alvarez Cartelle

R. Amalric

Brazil

S. Amato

J. Amey

Y. Amhis

China

L. An

L. Anderlini

M. Andersson

A. Andreianov

P. Andreola

M. Andreotti

D. Andreou

A. Anelli

D. Ao

F. Archilli

M. Argenton

Costa Rica

S. Arguedas Cuendis

A. Artamonov

M. Artuso

E. Aslanides

R. Ataíde Da Silva

M. Atzeni

B. Audurier

D. Bacher

I. Bachiller Perea

S. Bachmann

M. Bachmayer

J. Back

P. Baladron Rodriguez

V. Balagura

A. Balboni

W. Baldini

L. Balzani

H. Bao

J. Baptista de Souza Leite

C. Barbero Pretel

M. Barbetti

I. Barbosa

R. Barlow

M. Barnyakov

S. Barsuk

W. Barter

J. Bartz

Poland

S. Bashir

B. Batsukh

P. Battista

A. Bay

A. Beck

M. Becker

F. Bedeschi

I. Bediaga

N. Behling

S. Belin

K. Belous

I. Belov

I. Belyaev

G. Benane

G. Bencivenni

E. Ben-Haim

A. Berezhnoy

R. Bernet

S. Bernet Andres

A. Bertolin

C. Betancourt

F. Betti

J. Bex

Ia. Bezshyiko

Ukraine

O. Bezshyyko

J. Bhom

M. Bieker

N. Biesuz

P. Billoir

A. Biolchini

M. Birch

F. Bishop

A. Bitadze

A. Bizzeti

T. Blake

F. Blanc

J. Blank

S. Blusk

V. Bocharnikov

Observation of the decay $$ {B}_s^0\to {K}^0p\overline{p} $$ and measurement of the $$ {B}_{(s)}^0\to {K}^0p\overline{p} $$ branching fractions

<p>By analyzing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">(</mo><mn>2712.4</mn><mo>±</mo><mn>14.3</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>6</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>ψ</mi><mo stretchy="false">(</mo><mn>3686</mn><mo stretchy="false">)</mo></mrow></math> events collected with the BESIII detector operating at the BEPCII collider, the decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>χ</mi></mrow><mrow><mi>c</mi><mn>0</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>2</mn></mrow></msub><mo stretchy="false">→</mo><mn>3</mn><msubsup><mrow><mi>K</mi></mrow><mrow><mi>S</mi></mrow><mrow><mn>0</mn></mrow></msubsup><msup><mrow><mi>K</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>∓</mo></mrow></msup></mrow></math> are observed for the first time with statistical significances greater than <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>10</mn><mi>σ</mi></math>. The branching fractions of these decays are determined to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msub><mrow><mi>χ</mi></mrow><mrow><mi>c</mi><mn>0</mn></mrow></msub><mo stretchy="false">→</mo><mn>3</mn><msubsup><mrow><mi>K</mi></mrow><mrow><mi>S</mi></mrow><mrow><mn>0</mn></mrow></msubsup><msup><mrow><mi>K</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>∓</mo></mrow></msup><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>7.95</mn><mo>±</mo><mn>0.50</mn><mo>±</mo><mn>0.65</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msub><mrow><mi>χ</mi></mrow><mrow><mi>c</mi><mn>1</mn></mrow></msub><mo stretchy="false">→</mo><mn>3</mn><msubsup><mrow><mi>K</mi></mrow><mrow><mi>S</mi></mrow><mrow><mn>0</mn></mrow></msubsup><msup><mrow><mi>K</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>∓</mo></mrow></msup><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>2.62</mn><mo>±</mo><mn>0.08</mn><mo>±</mo><mn>0.19</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup></mrow></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msub><mrow><mi>χ</mi></mrow><mrow><mi>c</mi><mn>2</mn></mrow></msub><mo stretchy="false">→</mo><mn>3</mn><msubsup><mrow><mi>K</mi></mrow><mrow><mi>S</mi></mrow><mrow><mn>0</mn></mrow></msubsup><msup><mrow><mi>K</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>∓</mo></mrow></msup><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mn>1.72</mn><mo>±</mo><mn>0.07</mn><mo>±</mo><mn>0.15</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup></mrow></math>, where the first uncertainties are statistical and the second systematic.</p>

M. Ablikim

Russia

M.N. Achasov

X.C. Ai

R. Aliberti

A. Amoroso

Q. An

Y. Bai

JINR

O. Bakina

Y. Ban

H.R. Bao

V. Batozskaya

Mongolia

K. Begzsuren

N. Berger

M. Berlowski

M. Bertani

D. Bettoni

F. Bianchi

E. Bianco

A. Bortone

I. Boyko

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

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

X.T. Chen

Y.B. Chen

Y.Q. Chen

Z.J. Chen

Z.K. Chen

S.K. Choi

X. Chu

G. Cibinetto

F. Cossio

J.J. Cui

H.L. Dai

J.P. Dai

A. Dbeyssi

R.E. de Boer

D. Dedovich

C.Q. Deng

Z.Y. Deng

A. Denig

I. Denysenko

M. Destefanis

F. De Mori

B. Ding

X.X. Ding

Y. Ding

Y.X. Ding

J. Dong

L.Y. Dong

M.Y. Dong

Observation of <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>3</mn><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msup><mi>K</mi><mo>±</mo></msup><msup><mi>π</mi><mo>∓</mo></msup></math>