<p>We search for the reaction channel <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>η</mi><mi>η</mi><mi>J</mi><mo>/</mo><mi>ψ</mi></math> in a data sample with center-of-mass energies from 4.226 to 4.950 GeV that was collected by the BESIII detector operating at the Beijing Electron Positron Collider (BEPCII). The data analysis is performed with two different reconstruction methods, exclusive and semi-inclusive, enabling a comparison and combination of the results. Only at a few energy points is a nonzero cross section observed with a statistical significance of more than <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mi>σ</mi></math> using one of the methods. Therefore, the corresponding upper limits of the cross section at the 90% confidence level are determined. The energy-dependent results show clear deviations from the line shape expected from three-body phase space alone. Since the statistical significance for almost all center-of-mass energies is low, the upper limits for the reaction channel <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>η</mi><mi>η</mi><mi>J</mi><mo>/</mo><mi>ψ</mi></math> also serve as limits for the existence of a possible isospin partner to the charmonium-like isospin triplet <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi mathvariant="normal">c</mi></msub><mo stretchy="false">(</mo><mn>3900</mn><mo stretchy="false">)</mo></math> which decays to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi><mi>η</mi></math>.</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

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

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.L. Chen

S.M. Chen

T. Chen

X.R. Chen

X.T. Chen

X.Y. Chen

Y.B. Chen

Y.Q. Chen

Z. Chen

Z.J. Chen

Z.K. Chen

South Korea

S.K. Choi

X. Chu

G. Cibinetto

F. Cossio

United Kingdom

J. Cottee-Meldrum

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

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

L. Feng

Q.X. Feng

Search for the reaction channel <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>η</mi><mi>η</mi><mi>J</mi><mo>/</mo><mi>ψ</mi></math> and the isospin partner of the <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> at center-of-mass energies <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>4.226</mn><mtext> </mtext><mi>−</mi><mtext> </mtext><mn>4.950</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>

<p>This Letter presents a measurement of prompt charged-particle production in proton-oxygen interactions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><msub><mi>s</mi><mi>NN</mi></msub></msqrt><mo>=</mo><mn>9.62</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> center-of-mass energy with the ATLAS detector, corresponding to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>634</mn><mtext> </mtext><mtext> </mtext><mi>μ</mi><mrow><msup><mrow><mi mathvariant="normal">b</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></mrow></math> of integrated luminosity. A total of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>246</mn><mo>×</mo><msup><mn>10</mn><mn>6</mn></msup></math> selected events have at least one track with transverse momentum <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi mathvariant="normal">T</mi></msub><mo>&gt;</mo><mn>500</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> and pseudorapidity <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><mi>η</mi><mo stretchy="false">|</mo><mo>&lt;</mo><mn>2.5</mn></math>. The measured fiducial proton-oxygen cross section is <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>σ</mi><mrow><mi>fid</mi><mo>.</mo></mrow><mrow><mi>p</mi><mi mathvariant="normal">O</mi></mrow></msubsup><mo>=</mo><mn>396</mn><mo>±</mo><mn>6</mn><mo stretchy="false">(</mo><mrow><mi>exp</mi><mo>.</mo></mrow><mo stretchy="false">)</mo><mo>±</mo><mn>9</mn><mo stretchy="false">(</mo><mrow><mi>lumi</mi><mo>.</mo></mrow><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>mb</mi></math> and the extrapolated inelastic proton-air cross section is <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>σ</mi><mrow><mi>inel</mi><mo>.</mo></mrow><mrow><mi>p</mi><mo>+</mo><mi>air</mi></mrow></msubsup><mo>=</mo><mn>406</mn><mo>±</mo><mn>6</mn><mo stretchy="false">(</mo><mrow><mi>exp</mi><mo>.</mo></mrow><mo stretchy="false">)</mo><mo>±</mo><mn>9</mn><mo stretchy="false">(</mo><mrow><mi>lumi</mi><mo>.</mo></mrow><mo stretchy="false">)</mo><mo>±</mo><mn>28</mn><mo stretchy="false">(</mo><mrow><mi>th</mi><mo>.</mo></mrow><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>mb</mi></math>. Measurements of charged-particle multiplicity, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi mathvariant="normal">T</mi></msub></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>η</mi></math> distributions are an order-of-magnitude more precise than differences between hadronic-interaction models. These results enable improved modeling of cosmic-ray air showers, which is important for astroparticle physics.</p>

France

G. Aad

Norway

E. Aakvaag

B. Abbott

United Arab Emirates

S. Abdelhameed

K. Abeling

N.J. Abicht

S.H. Abidi

M. Aboelela

Morocco

A. Aboulhorma

Israel

H. Abramowicz

B.S. Acharya

A. Ackermann

Switzerland

J. Ackerschott

C. Adam Bourdarios

L. Adamczyk

S.V. Addepalli

M.J. Addison

J. Adelman

A. Adiguzel

T. Adye

A.A. Affolder

Y. Afik

Spain

M.N. Agaras

A. Aggarwal

Romania

C. Agheorghiesei

A. Ahmad

F. Ahmadov

S. Ahuja

X. Ai

G. Aielli

A. Aikot

M. Ait Tamlihat

T.P.A. Åkesson

Japan

D. Akiyama

N.N. Akolkar

S. Aktas

G.L. Alberghi

Canada

J. Albert

U. Alberti

P. Albicocco

S. Alderweireldt

Z.L. Alegria

CERN

M. Aleksa

I.N. Aleksandrov

C. Alexa

Greece

T. Alexopoulos

F. Alfonsi

M. Algren

M. Alhroob

Czechia

B. Ali

H.M.J. Ali

S. Ali

S.W. Alibocus

South Africa

M. Aliev

G. Alimonti

C. Allaire

B.M.M. Allbrooke

D.R. Allen

J.S. Allen

J.F. Allen

Australia

C.S. Alley

E.R. Almazan

A. Aloisio

Argentina

F. Alonso

C. Alpigiani

A. Alvarez Fernandez

M. Alves Cardoso

M.G. Alviggi

M. Aly

Brazil

Y. Amaral Coutinho

C. Amelung

M. Amerl

T. Amezza

Measurement of Charged-Particle Production in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><msub><mi>s</mi><mrow><mi>NN</mi></mrow></msub></msqrt><mo>=</mo><mn>9.62</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> Proton-Oxygen Collisions as a Probe of Cosmic-Ray Air Showers with the ATLAS Detector