Open Access

First displaced vertex search for electroproduced dark-sector strongly interacting massive particles by the HPS experiment

P. H. Adrian¹, N. A. Baltzell², M. Battaglieri³, M. Bondí⁴, S. Boyarinov², C. Bravo¹, S. Bueltmann⁵, P. Butti¹, V. D. Burkert² et al. (HPS Collaboration)

V. D. Burkert², D. Calvo⁶, T. Cao^7,2, M. Carpinelli^8,9, A. Celentano³, G. Charles¹⁰, L. Colaneri^11,12, W. Cooper¹³, B. Crowe⁷, C. Cuevas², A. D’Angelo^11,12, N. Dashyan¹⁴, M. De Napoli^15,4, R. De Vita^3,2, A. Deur², M. Diamond^1,16, R. Dupre¹⁰, H. Egiyan², T. Eichlersmith¹⁷, L. Elouadrhiri², R. Essig¹⁸, V. Fadeyev¹⁹, C. Field¹, A. Filippi⁶, A. Freyberger², S. Gaiser²⁰, M. Garçon²¹, N. Gevorgyan¹⁴, F. X. Girod², N. Graf¹, M. Graham ^1,*, K. A. Griffioen²², A. Grillo¹⁹, M. Guidal¹⁰, R. Herbst¹, M. Holtrop⁷, J. Jaros¹, R. P. Johnson¹⁹, G. Kalicy²³, M. Khandaker²⁴, V. Kubarovsky², E. Leonora⁴, K. Livingston²⁵, L. Marsicano³, T. Maruyama^1,†, S. McCarty⁷, J. McCormick¹, B. McKinnon²⁵, K. Moffeit²⁵, O. Moreno^1,19, C. Munoz Camacho¹⁰, T. Nelson¹, S. Niccolai¹⁰, A. Odian¹, R. O’Dwyer²⁰, M. Oriunno¹, M. Osipenko³, R. Paremuzyan², S. Paul²⁶, E. Peets²⁰, N. Randazzo⁴, B. Raydo², B. Reese¹, A. Rizzo^11,12, P. Schuster^1,27, Y. G. Sharabian², G. Simi^28,29, A. Simonyan¹⁰, V. Sipala^30,31, A. Spellman¹⁹, D. Sokhan²⁵, M. Solt¹, S. Stepanyan², H. Szumila-Vance²⁶, L. Tompkins²⁰, N. Toro^1,27, S. Uemura¹, M. Ungaro², H. Voskanyan¹⁴, L. B. Weinstein⁵, and B. Wojtsekhowski² (HPS Collaboration)

¹SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94309, USA
²Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
³INFN, Sezione di Genova, 16146 Genova, Italy
⁴INFN, Sezione di Catania, 95123 Catania, Italy
⁵Old Dominion University, Norfolk, Virginia 23529, USA
⁶INFN, Sezione di Torino, 10125 Torino, Italy
⁷University of New Hampshire, Durham, New Hampshire 03824, USA
⁸University di Milano Bicocca, 20126 Milano, Italy
⁹INFN, Laboratori Nazionali del Sud, 95123 Catania, Italy
¹⁰Université Paris-Saclay, CNRS, IJCLab, 91405, Orsay, France
¹¹Università di Roma Tor Vergata, 00133 Rome Italy
¹²INFN, Sezione di Roma Tor Vergata, 00133 Rome, Italy
¹³Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA
¹⁴Yerevan Physics Institute, 375036 Yerevan, Armenia
¹⁵Università degli Studi di Catania, Dipartimento di Fisica e Astronomia “Ettore Majorana,” 95123 Catania, Italy
¹⁶University of Toronto Department of Physics, Toronto, Ontario M5S1A7 Canada
¹⁷University of Minnesota, Minneapolis, Minnesota 55455, USA
¹⁸C. N. Yang Institute for Theoretical Physics, Stony Brook University, Stony Brook, New York 11794, USA
¹⁹Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, California 95064, USA
²⁰Stanford University, Stanford, California 94305, USA
²¹IRFU, CEA, Université Paris-Saclay, F-91190 Gif-sur-Yvette, France
²²College of William & Mary, Williamsburg, Virginia 23187, USA
²³Catholic University of America, Washington, DC 20064, USA
²⁴Idaho State University, Pocatello, Idaho, 83209, USA
²⁵University of Glasgow, Glasgow G12 8QQ, United Kingdom
²⁶Florida International University, Miami, Florida 33199, USA
²⁷Perimeter Institute, Waterloo, Ontario, Canada N2L 2Y5
²⁸Università di Padova, 35122 Padova, Italy
²⁹INFN, Sezione di Padova, 16146 Padova, Italy
³⁰Università di Sassari, 07100 Sassari, Italy
³¹INFN, Sezione di Cagliari, 09042 Monserrato, Italy

^*Contact author: mgraham@slac.stanford.edu
^†Deceased.

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Phys. Rev. D 113, 032019 – Published 24 February, 2026

DOI: https://doi.org/10.1103/2k3q-9mhj

Abstract

The Heavy Photon Search experiment (HPS) is a fixed-target, electron beam experiment designed to search for $e^{+} e^{-}$ mass resonances and displaced decays using a forward acceptance spectrometer. This paper details the search for naturally long-lived “dark” vector mesons ( $V_{D}$ ) arising from a dark sector of beyond-Standard-Model strongly interacting massive particles, characterized by a QCD-like $S U (3)_{D}$ symmetry and coupled to the Standard Model photon via a new $U (1)_{D}$ gauge interaction mediated by the “heavy photon,” or $A^{'}$ . The results are based on an integrated luminosity of $10 608 {nb}^{- 1}$ collected during the 2016 HPS engineering run. The displaced vertex search for $V_{D} \to e^{+} e^{-}$ in the $e^{+} e^{-}$ invariant mass range 39–179 MeV showed no statistically significant evidence for signal above the QED background.

Physics Subject Headings (PhySH)

Corrections

4 March, 2026

Correction: The previously published Figs. 6, 9, and 11 had duplicate plots and have been replaced with the correct plots.

Article Text

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Phys. Rev. D 113, 032019– Published 24 February, 2026

Vol. 113, Iss. 3 — 1 February 2026

Received 5 November 2025
Accepted 5 February 2026
Corrected 4 March 2026

DOI: https://doi.org/10.1103/2k3q-9mhj

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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First displaced vertex search for electroproduced dark-sector strongly interacting massive particles by the HPS experiment

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