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

<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>

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

Poland

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

X. Dong

M.C. Du

S.X. 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

R. Farinelli

L. Fava

F. Feldbauer

G. Felici

C.Q. Feng

J.H. Feng

Y.T. Feng

M. Fritsch

C.D. Fu

J.L. Fu

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>

This paper presents a computer code for analyzing electroweak precision data (EWPD) in the framework of the Standard Model Effective Field Theory (SMEFT), highlights the importance of recent ATLAS and CMS precision measurements, and introduces a novel analysis of the forward–backward asymmetry at the LHC. The computer code provides the likelihood of SMEFT Wilson coefficients based on precision measurements of $\textit{W}$ and $\textit{Z}$ pole observables, interpolation formulas for Standard Model predictions, and modular SMEFT parametrizations. SMEFT predictions including next-to-leading-order (NLO) effects in perturbative and SMEFT expansion are available and five alternative electroweak input parameter schemes are supported. The likelihood addresses shortcomings of previous formulations in the treatment of parametric uncertainties and can be straightforwardly included in SMEFT fits of LHC data. The input parameter scheme dependence and role of NLO corrections is studied for the EWPD fit in the SMEFT. Furthermore, the impact of recent ATLAS and CMS measurements — of the $\textit{W}$ boson mass and width, of the lepton flavour universality (LFU) of $\textit{W}$ branching fractions, and the effective leptonic weak mixing angle, $$ {\sin}^2{\theta}_{\textrm{eff}}^{\ell } $$ — is analyzed. A test of LFU that surpasses the precision of existing measurements is proposed based on the $$ {\sin}^2{\theta}_{\textrm{eff}}^{\ell } $$ measurement. Finally, an ATLAS Drell-Yan triple-differential cross-section measurement is reinterpreted in the SMEFT and combined with the EWPD likelihood. This analysis demonstrates the feasibility of the LFU precision test, improves constraints on muon couplings with respect to the world average, and determines a combination of the quark-coupling asymmetry parameters $\textit{A}$ and $\textit{A}$ with a precision comparable to that of the heavy flavour parameters $\textit{A}$ and $\textit{A}$ .

Hannes Mildner

An EWPD SMEFT likelihood for the LHC — and how to improve it with measurements of W and Z boson properties

A set of measurements for the production of a $$W$$ -boson in association with high-transverse-momentum jets is presented using 140 fb $$^{-1}$$ of proton–proton collision data at a centre-of-mass energy of $$\sqrt{s}=13$$ TeV collected by the ATLAS detector at the LHC. The measurements are performed in final states in which the $$W$$ -boson decays into an electron or muon plus a neutrino and is produced in association with jets with $$p_{\text {T}} {EMPTY}>30$$ GeV, where the leading jet has $$p_{\text {T}} {EMPTY}>500$$ GeV. The angular separation between the lepton and the closest jet with $$p_{\text {T}} {EMPTY}>100$$ GeV is measured and used to define a collinear phase space, wherein measurements of kinematic properties of the $$W$$ -boson and the associated jet are performed. The collinear phase space is populated by dijet events radiating a $$W$$ -boson and events with a $$W$$ -boson produced in association with several jets and it serves as an excellent data sample to probe higher-order theoretical predictions. Measured differential distributions are compared with predictions from state-of-the-art next-to-leading order multi-leg merged Monte Carlo event generators and a fixed-order calculation of the $$W+1$$ -jet process computed at next-to-next-to-leading order in the strong coupling constant.

France

G. Aad

Norway

E. Aakvaag

B. Abbott

United Arab Emirates

S. Abdelhameed

K. Abeling

N. Abicht

S. Abidi

M. Aboelela

Morocco

A. Aboulhorma

Israel

H. Abramowicz

Y. Abulaiti

United Kingdom

B. Acharya

A. Ackermann

C. Bourdarios

L. Adamczyk

S. Addepalli

M. Addison

J. Adelman

A. Adiguzel

T. Adye

A. Affolder

Y. Afik

Spain

M. Agaras

A. Aggarwal

Romania

C. Agheorghiesei

Azerbaijan

F. Ahmadov

S. Ahuja

X. Ai

G. Aielli

A. Aikot

M. Tamlihat

B. Aitbenchikh

M. Akbiyik

T. Åkesson

A. Akimov

Japan

D. Akiyama

N. Akolkar

S. Aktas

G. Alberghi

Canada

J. Albert

P. Albicocco

G. Albouy

S. Alderweireldt

Z. Alegria

Switzerland

M. Aleksa

I. Aleksandrov

C. Alexa

Greece

T. Alexopoulos

F. Alfonsi

M. Algren

M. Alhroob

Czechia

B. Ali

Saudi Arabia

H. Ali

S. Ali

S. Alibocus

South Africa

M. Aliev

G. Alimonti

W. Alkakhi

C. Allaire

B. Allbrooke

J. Allen

Chile

C. Flores

P. Allport

A. Aloisio

Cross-section measurements for the production of a $$W$$ -boson in association with high-transverse-momentum jets in $\textit{pp}$ collisions at $$\sqrt{s}$$ = 13 TeV with the ATLAS detector