Search for Higgs boson decays into a Z boson and a light hadronically decaying resonance in pp collisions at √s=13 TeV with the ATLAS detector

The ATLAS collaboration

doi:10.1016/j.physletb.2025.139671

Search for Higgs boson decays into a Z boson and a light hadronically decaying resonance in pp collisions at √s=13 TeV with the ATLAS detector

The ATLAS collaboration

Aix-Marseille Université
University of Bergen
University of Oklahoma
New York University Abu Dhabi
University of Göttingen
TU Dortmund University
United States Department of Energy
Southern Methodist University
Mohammed V University in Rabat
Tel Aviv University
New York University
National Institute for Nuclear Physics
Abdus Salam International Centre for Theoretical Physics
King's College London
Heidelberg University
Université Savoie Mont Blanc
AGH University of Science and Technology
SLAC National Accelerator Laboratory
University of Manchester
Northern Illinois University
Istanbul University
Rutherford Appleton Laboratory
University of California at Santa Cruz
The University of Chicago
Institute for High Energy Physics
Johannes Gutenberg University Mainz
Alexandru Ioan Cuza University of Iaşi
Azerbaijan National Academy of Sciences
CERN
Royal Holloway University of London
Zhengzhou University
University of Rome Tor Vergata
University of Valencia
University of Hassan II Casablanca
Lund University
Stony Brook University
Waseda University
University of Bonn
Bogazici University
Columbia University
University of Victoria BC
Université Grenoble Alpes
University of Edinburgh
Oklahoma State University
University of the Witwatersrand
Horia Hulubei National Institute of Physics and Nuclear Engineering
National Technical University of Athens
University of Geneva
University of Warwick
Czech Technical University in Prague
Lancaster University
Al-Imam Muhammad Ibn Saud Islamic University
The California State University
University of Liverpool
University of Johannesburg
Université Paris-Saclay
University of Sussex
Universidad Técnica Federico Santa Maria
University of Birmingham
University of Naples Federico II
Universidad Nacional de La Plata
University of Washington
Universidad Autónoma de Madrid
Universidade Federal do Rio de Janeiro
McGill University
Ludwig Maximilian University of Munich
University of Michigan, Ann Arbor
University of Freiburg
University of Toronto
Laboratório de Instrumentação e Física Experimental de Partículas
Aristotle University of Thessaloniki
High Energy Accelerator Research Organization, Tsukuba
University of Oslo
University of Sheffield
University of Texas at Austin
University of Glasgow
University of Milan
National and Kapodistrian University of Athens
The University of Tokyo
German Electron Synchrotron
Brandeis University
Cracow
Duke University
University of Montreal
University of Rome La Sapienza
Nagoya University
Ochanomizu University
Comenius University
University of California at Irvine
University of Cape Town
Mohammed VI Polytechnic University
University of Pennsylvania School of Arts and Sciences
TRIUMF
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University of Thessaly
Carleton University
Technische Universität Dresden
Humboldt University of Berlin
University of Oregon
Queen Mary University of London
Yale University
University of Belgrade
University of Texas at Arlington
University of Bologna
University of Cambridge
United Arab Emirates University
University of Pittsburgh
University of Melbourne
University of Genoa
University of Amsterdam
Max Planck Institute for Physics (Werner Heisenberg Institute)
Palacký University Olomouc
University of Science and Technology of China
University of Oxford
University College London
CAS - Institute of High Energy Physics
An-Najah National University
University of British Columbia
University of Siegen
University of Innsbruck
Universidad de Buenos Aires
Sorbonne Université
Tufts University
University of Bern
University of Fribourg
Istinye University
Universidade do Estado do Rio de Janeiro
Harvard University
Uppsala University
Lawrence Berkeley National Laboratory
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University of Wuppertal
Gaziantep University
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Ohio State University
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Nanjing University
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Westmont College
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Autonomous University of Barcelona
University of Minho
Universidad Nacional de Colombia
Universidade Federal de Juiz de Fora
Tbilisi State University
Argonne National Laboratory
Shanghai Jiao Tong University
Kyoto University
Tsinghua University
The Collaborative Innovation Center of Quantum Matter (CICQM)
University of Wisconsin
Chinese University of Hong Kong
University of Arizona
National Tsing Hua University
Sofia University
Czech Academy of Sciences
University of Ljubljana
University of Udine
University of Lisbon
University of Naples Parthenope
Institute of Particle Physics
Academia Sinica - Institute of Physics
University of Salento
Roma Tre University
Pontificia Universidad Católica de Chile
Millennium Institute for Subatomic physics at high energy frontier (SAPHIR)
University of Bucharest
Universidade Federal da Bahia
Ibn Tofail University
The University of Hong Kong
Louisiana Tech University
Shandong University
IMB-CNM. CSIC
University of Adelaide
University of Coimbra
City University of New York
National Institute of Physics, College of Science, University of the Philippines, Diliman
University of the Aegean
University of Pisa
University of Sharjah
University of New Mexico
Demokritos National Centre for Scientific Research
Jagiellonian University in Kraków
University of Alberta
The University of Georgia, Tbilisi
West University of Timisoara
ICREA
Henan University
A. Alikhanian Yerevan Institute of Physics
Shinshu University
Technical University of Munich
Osaka University
University of Tsukuba
University Politehnica of Bucharest
Azerbaijan State University of Economics
Universidade de São Paulo
University of Pavia
Yeditepe University
University of Texas at Dallas
Georgian National Academy of Sciences
Ilia State University
Tokyo Institute of Technology
Universidad de Tarapacá
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Iowa State University
Universidad Andrés Bello
Kobe University
University of the Western Cape
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KTH Royal Institute of Technology
Peking University
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University of South Africa
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University of Iowa
Kyushu University
California State University Sacramento
Mohamed I University
University of Colorado Boulder
Universidad Antonio Nariño
University of Sydney
University of Hamburg
Transilvania University of Brasov
National Institute for Research and Development of Isotopic and Molecular Technologies
Bulgarian Academy of Sciences
Washington College
University of West Attica
Universidad de La Serena
TOBB University of Economics and Technology
Stanford University
Mongolian Academy of Sciences
University of California at Berkeley

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Abstract

A search for decays of the Higgs boson into a Z boson and a light resonance, with a mass of 0.5–3.5 GeV, is performed using the full 140 fb⁻¹ dataset of 13 TeV proton–proton collisions recorded by the ATLAS detector during LHC Run 2. Leptonic decays of the Z boson and hadronic decays of the light resonance are considered. The resonance can be interpreted as a J/ψ or η_c meson, an axion-like particle, or a light pseudoscalar predicted in two-Higgs-doublet models. Due to its low mass, this resonance is produced with a high Lorentz boost in the laboratory frame and therefore reconstructed as a single small-radius jet of hadrons. A neural network is used to correct the Monte Carlo simulation of the total expected background using data from sideband regions. Two additional neural networks are used to distinguish signal from background, enhancing the purity of the signal region. A binned profile-likelihood fit is performed on the final-state invariant mass distribution. No significant excess of events relative to the expected background is observed, and upper limits at 95% confidence level are set on the Higgs boson's branching fraction to a Z boson and a light resonance. The exclusion limit is ∼10% for the lower masses, and increases for higher masses. Upper limits on the effective coupling C_ZH ^eff/Λ of an axion-like particle to a Higgs boson and Z boson are also set at 95% confidence level, and range from 0.9 to 2 TeV⁻¹.

Original language	English
Article number	139671
Journal	Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume	868
DOIs	https://doi.org/10.1016/j.physletb.2025.139671
Publication status	Published - Sept 2025

ASJC Scopus subject areas

Nuclear and High Energy Physics

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10.1016/j.physletb.2025.139671

Cite this

@article{12e7c66839b54e32893ab0dfb23aeb85,

title = "Search for Higgs boson decays into a Z boson and a light hadronically decaying resonance in pp collisions at √s=13 TeV with the ATLAS detector",

abstract = "A search for decays of the Higgs boson into a Z boson and a light resonance, with a mass of 0.5–3.5 GeV, is performed using the full 140 fb−1 dataset of 13 TeV proton–proton collisions recorded by the ATLAS detector during LHC Run 2. Leptonic decays of the Z boson and hadronic decays of the light resonance are considered. The resonance can be interpreted as a J/ψ or ηc meson, an axion-like particle, or a light pseudoscalar predicted in two-Higgs-doublet models. Due to its low mass, this resonance is produced with a high Lorentz boost in the laboratory frame and therefore reconstructed as a single small-radius jet of hadrons. A neural network is used to correct the Monte Carlo simulation of the total expected background using data from sideband regions. Two additional neural networks are used to distinguish signal from background, enhancing the purity of the signal region. A binned profile-likelihood fit is performed on the final-state invariant mass distribution. No significant excess of events relative to the expected background is observed, and upper limits at 95\% confidence level are set on the Higgs boson's branching fraction to a Z boson and a light resonance. The exclusion limit is ∼10\% for the lower masses, and increases for higher masses. Upper limits on the effective coupling CZH eff/Λ of an axion-like particle to a Higgs boson and Z boson are also set at 95\% confidence level, and range from 0.9 to 2 TeV−1.",

author = "\{The ATLAS collaboration\} and G. Aad and E. Aakvaag and B. Abbott and S. Abdelhameed and K. Abeling and Abicht, \{N. J.\} and Abidi, \{S. H.\} and M. Aboelela and A. Aboulhorma and H. Abramowicz and Y. Abulaiti and Acharya, \{B. S.\} and A. Ackermann and \{Adam Bourdarios\}, C. and L. Adamczyk and Addepalli, \{S. V.\} and Addison, \{M. J.\} and J. Adelman and A. Adiguzel and T. Adye and Affolder, \{A. A.\} and Y. Afik and Agaras, \{M. N.\} and A. Aggarwal and C. Agheorghiesei and F. Ahmadov and S. Ahuja and X. Ai and G. Aielli and A. Aikot and \{Ait Tamlihat\}, M. and B. Aitbenchikh and M. Akbiyik and {\AA}kesson, \{T. P.A.\} and Akimov, \{A. V.\} and D. Akiyama and Akolkar, \{N. N.\} and S. Aktas and \{Al Khoury\}, K. and Alberghi, \{G. L.\} and J. Albert and P. Albicocco and Albouy, \{G. L.\} and S. Alderweireldt and Alegria, \{Z. L.\} and M. Aleksa and Connell, \{S. H.\} and Gololo, \{M. G.D.\} and N. Govender and L. Truong",

note = "Publisher Copyright: {\textcopyright} 2025 CERN for the benefit of the ATLAS Collaboration",

year = "2025",

month = sep,

doi = "10.1016/j.physletb.2025.139671",

language = "English",

volume = "868",

journal = "Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics",

issn = "0370-2693",

publisher = "Elsevier B.V.",

}

TY - JOUR

T1 - Search for Higgs boson decays into a Z boson and a light hadronically decaying resonance in pp collisions at √s=13 TeV with the ATLAS detector

AU - The ATLAS collaboration

AU - Aad, G.

AU - Aakvaag, E.

AU - Abbott, B.

AU - Abdelhameed, S.

AU - Abeling, K.

AU - Abicht, N. J.

AU - Abidi, S. H.

AU - Aboelela, M.

AU - Aboulhorma, A.

AU - Abramowicz, H.

AU - Abulaiti, Y.

AU - Acharya, B. S.

AU - Ackermann, A.

AU - Adam Bourdarios, C.

AU - Adamczyk, L.

AU - Addepalli, S. V.

AU - Addison, M. J.

AU - Adelman, J.

AU - Adiguzel, A.

AU - Adye, T.

AU - Affolder, A. A.

AU - Afik, Y.

AU - Agaras, M. N.

AU - Aggarwal, A.

AU - Agheorghiesei, C.

AU - Ahmadov, F.

AU - Ahuja, S.

AU - Ai, X.

AU - Aielli, G.

AU - Aikot, A.

AU - Ait Tamlihat, M.

AU - Aitbenchikh, B.

AU - Akbiyik, M.

AU - Åkesson, T. P.A.

AU - Akimov, A. V.

AU - Akiyama, D.

AU - Akolkar, N. N.

AU - Aktas, S.

AU - Al Khoury, K.

AU - Alberghi, G. L.

AU - Albert, J.

AU - Albicocco, P.

AU - Albouy, G. L.

AU - Alderweireldt, S.

AU - Alegria, Z. L.

AU - Aleksa, M.

AU - Connell, S. H.

AU - Gololo, M. G.D.

AU - Govender, N.

AU - Truong, L.

PY - 2025/9

Y1 - 2025/9

N2 - A search for decays of the Higgs boson into a Z boson and a light resonance, with a mass of 0.5–3.5 GeV, is performed using the full 140 fb−1 dataset of 13 TeV proton–proton collisions recorded by the ATLAS detector during LHC Run 2. Leptonic decays of the Z boson and hadronic decays of the light resonance are considered. The resonance can be interpreted as a J/ψ or ηc meson, an axion-like particle, or a light pseudoscalar predicted in two-Higgs-doublet models. Due to its low mass, this resonance is produced with a high Lorentz boost in the laboratory frame and therefore reconstructed as a single small-radius jet of hadrons. A neural network is used to correct the Monte Carlo simulation of the total expected background using data from sideband regions. Two additional neural networks are used to distinguish signal from background, enhancing the purity of the signal region. A binned profile-likelihood fit is performed on the final-state invariant mass distribution. No significant excess of events relative to the expected background is observed, and upper limits at 95% confidence level are set on the Higgs boson's branching fraction to a Z boson and a light resonance. The exclusion limit is ∼10% for the lower masses, and increases for higher masses. Upper limits on the effective coupling CZH eff/Λ of an axion-like particle to a Higgs boson and Z boson are also set at 95% confidence level, and range from 0.9 to 2 TeV−1.

AB - A search for decays of the Higgs boson into a Z boson and a light resonance, with a mass of 0.5–3.5 GeV, is performed using the full 140 fb−1 dataset of 13 TeV proton–proton collisions recorded by the ATLAS detector during LHC Run 2. Leptonic decays of the Z boson and hadronic decays of the light resonance are considered. The resonance can be interpreted as a J/ψ or ηc meson, an axion-like particle, or a light pseudoscalar predicted in two-Higgs-doublet models. Due to its low mass, this resonance is produced with a high Lorentz boost in the laboratory frame and therefore reconstructed as a single small-radius jet of hadrons. A neural network is used to correct the Monte Carlo simulation of the total expected background using data from sideband regions. Two additional neural networks are used to distinguish signal from background, enhancing the purity of the signal region. A binned profile-likelihood fit is performed on the final-state invariant mass distribution. No significant excess of events relative to the expected background is observed, and upper limits at 95% confidence level are set on the Higgs boson's branching fraction to a Z boson and a light resonance. The exclusion limit is ∼10% for the lower masses, and increases for higher masses. Upper limits on the effective coupling CZH eff/Λ of an axion-like particle to a Higgs boson and Z boson are also set at 95% confidence level, and range from 0.9 to 2 TeV−1.

UR - https://www.scopus.com/pages/publications/105010717054

U2 - 10.1016/j.physletb.2025.139671

DO - 10.1016/j.physletb.2025.139671

M3 - Article

AN - SCOPUS:105010717054

SN - 0370-2693

VL - 868

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

M1 - 139671

ER -

Search for Higgs boson decays into a Z boson and a light hadronically decaying resonance in pp collisions at √s=13 TeV with the ATLAS detector

Abstract

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