Search for dark photons from Higgs boson decays in the gluon-gluon fusion channel in proton-proton collisions at √s=13.6 TeV with the ATLAS detector

@article{collaboration2026search,
  title = {{Search for dark photons from Higgs boson decays in the gluon-gluon fusion channel in proton-proton collisions at $$ \sqrts=13.6 $$ TeV with the ATLAS detector}},
  author = {The ATLAS collaboration and G. Aad and E. Aakvaag and B. Abbott and S. Abdelhameed and K. Abeling and N. J. Abicht and S. H. Abidi and M. Aboelela and A. Aboulhorma and H. Abramowicz and B. S. Acharya and A. Ackermann and J. Ackerschott and C. Adam Bourdarios and L. Adamczyk and S. V. Addepalli and M. J. Addison and J. Adelman and A. Adiguzel and T. Adye and A. A. Affolder and Y. Afik and M. N. Agaras and A. Aggarwal and C. Agheorghiesei and A. Ahmad and F. Ahmadov and S. Ahuja and X. Ai and G. Aielli and A. Aikot and M. Ait Tamlihat and T. P. A. Åkesson and D. Akiyama and N. N. Akolkar and S. Aktas and G. L. Alberghi and J. Albert and U. Alberti and P. Albicocco and S. Alderweireldt and Z. L. Alegria and M. Aleksa and I. N. Aleksandrov and C. Alexa and T. Alexopoulos and F. Alfonsi and M. Algren and M. Alhroob and B. Ali and H. M. J. Ali and S. Ali and S. W. Alibocus and M. Aliev and G. Alimonti and C. Allaire and B. M. M. Allbrooke and D. R. Allen and J. S. Allen},
  journal = {Journal of High Energy Physics},
  year = {2026},
  month = oct,
  doi = {10.1007/jhep10(2026)270},
  url = {https://link.springer.com/article/10.1007/JHEP10(2026)270},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - Search for dark photons from Higgs boson decays in the gluon-gluon fusion channel in proton-proton collisions at √s=13.6 TeV with the ATLAS detector
AU  - The ATLAS collaboration
AU  - G. Aad
AU  - E. Aakvaag
AU  - B. Abbott
AU  - S. Abdelhameed
AU  - K. Abeling
AU  - N. J. Abicht
AU  - S. H. Abidi
AU  - M. Aboelela
AU  - A. Aboulhorma
AU  - H. Abramowicz
AU  - B. S. Acharya
AU  - A. Ackermann
AU  - J. Ackerschott
AU  - C. Adam Bourdarios
AU  - L. Adamczyk
AU  - S. V. Addepalli
AU  - M. J. Addison
AU  - J. Adelman
AU  - A. Adiguzel
AU  - T. Adye
AU  - A. A. Affolder
AU  - Y. Afik
AU  - M. N. Agaras
AU  - A. Aggarwal
AU  - C. Agheorghiesei
AU  - A. Ahmad
AU  - F. Ahmadov
AU  - S. Ahuja
AU  - X. Ai
AU  - G. Aielli
AU  - A. Aikot
AU  - M. Ait Tamlihat
AU  - T. P. A. Åkesson
AU  - D. Akiyama
AU  - N. N. Akolkar
AU  - S. Aktas
AU  - G. L. Alberghi
AU  - J. Albert
AU  - U. Alberti
AU  - P. Albicocco
AU  - S. Alderweireldt
AU  - Z. L. Alegria
AU  - M. Aleksa
AU  - I. N. Aleksandrov
AU  - C. Alexa
AU  - T. Alexopoulos
AU  - F. Alfonsi
AU  - M. Algren
AU  - M. Alhroob
AU  - B. Ali
AU  - H. M. J. Ali
AU  - S. Ali
AU  - S. W. Alibocus
AU  - M. Aliev
AU  - G. Alimonti
AU  - C. Allaire
AU  - B. M. M. Allbrooke
AU  - D. R. Allen
AU  - J. S. Allen
PY  - 2026
DA  - 2026/10/28
JO  - Journal of High Energy Physics
DO  - 10.1007/jhep10(2026)270
UR  - https://link.springer.com/article/10.1007/JHEP10(2026)270
AB  - A bstract : This paper presents a search for semi-visible Higgs boson decays in final states with a photon ( γ ) and missing transverse momentum p_T^miss p T miss . The analysis is optimised for the gluon-gluon fusion production channel and exploits a novel trigger deployed in 2023, with reduced thresholds down to 50 GeV on the photon transverse momentum ( p_T^γ  p T γ ) and 70 GeV on the p_T^miss p T miss , in combination with a selection on the transverse mass of the p_T^miss p T miss -γ system ( m T ) above 80 GeV. The results are interpreted in terms of Higgs boson decays into a γ and a dark photon γ d ( H → γγ d ). The analysis is performed using 135 fb − 1 of Run 3 data collected by ATLAS in 2023 and 2024. A boosted decision tree is used to identify events with misreconstructed primary vertices, which can affect the p_T^miss p T miss calculation. Data-driven methods are employed to estimate the backgrounds from jets and electrons misidentified as photons, while the backgrounds with genuine photons are taken from Monte Carlo simulations, normalised to data in control regions with muons. A binned maximum-likelihood fit to the m T distribution is performed to evaluate the compatibility of the observed data with the Standard Model expectation. No significant excess is observed over the Standard Model prediction, and an observed (expected) upper limit on the branching ratio of H → γγ d of 1.4% (1.2%) is obtained at 95% confidence level. Combining this result with previous Run 2 searches improves the observed (expected) upper limit to 0.9% (0.9%).
SN  - 1029-8479
ER  -