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LDMX -- The Light Dark Matter eXperiment
Authors:
Torsten Akesson,
Layan Alsaraya,
Stephen Appert,
Charles Bell,
Elizabeth Berzin,
Nikita Blinov,
Léo Borrel,
Cameron Bravo,
Liam Brennan,
Lene Kristian Bryngemark,
Pierfrancesco Butti,
Riccardo Catena,
Anthony Chavez,
Owen Colegrove,
Giulia Collura,
Patill Daghlian,
Filippo Delzanno,
E. Craig Dukes,
Valentina Dutta,
Bertrand Echenard,
Ralf Ehrlich,
Thomas Eichlersmith,
Jonathan Eisch,
Einar Elén,
Eric Fernandez
, et al. (94 additional authors not shown)
Abstract:
The Light Dark Matter eXperiment (LDMX) is an electron fixed-target experiment optimized to search for sub-GeV dark matter production through the missing momentum signature. LDMX is designed to operate in End Station A at SLAC, using an 8 GeV electron beam accelerated alongside the LCLS-II drive beam. The design of the apparatus is strongly motivated by the performance requirements of a high-rate…
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The Light Dark Matter eXperiment (LDMX) is an electron fixed-target experiment optimized to search for sub-GeV dark matter production through the missing momentum signature. LDMX is designed to operate in End Station A at SLAC, using an 8 GeV electron beam accelerated alongside the LCLS-II drive beam. The design of the apparatus is strongly motivated by the performance requirements of a high-rate missing momentum search and leverages detector technologies and designs from other experiments along with existing facilities at SLAC. LDMX will improve on previous results by up to three orders of magnitude, enabling broad sensitivity to dark sector scenarios including the dark matter interaction strengths motivated by freeze-out of MeV-GeV mass dark matter to the observed relic abundance. With hermetic forward coverage, LDMX also has sensitivity to visible signatures of dark sectors and provides a unique probe of electron-nuclear interactions important to interpreting data from accelerator-based neutrino experiments. This report encompasses the technical design of the LDMX Detector, its simulated performance, and the physics capabilities of the experiment.
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Submitted 2 October, 2025; v1 submitted 15 August, 2025;
originally announced August 2025.
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ACE Science Workshop Report
Authors:
Stefania Gori,
Nhan Tran,
Karri DiPetrillo,
Bertrand Echenard,
Jeffrey Eldred,
Roni Harnik,
Pedro Machado,
Matthew Toups,
Robert Bernstein,
Innes Bigaran,
Cari Cesarotti,
Bhaskar Dutta,
Christian Herwig,
Sergo Jindariani,
Ryan Plestid,
Vladimir Shiltsev,
Matthew Solt,
Alexandre Sousa,
Diktys Stratakis,
Zahra Tabrizi,
Anil Thapa,
Jacob Zettlemoyer,
Jure Zupan
Abstract:
We summarize the Fermilab Accelerator Complex Evolution (ACE) Science Workshop, held on June 14-15, 2023. The workshop presented the strategy for the ACE program in two phases: ACE Main Injector Ramp and Target (MIRT) upgrade and ACE Booster Replacement (BR) upgrade. Four plenary sessions covered the primary experimental physics thrusts: Muon Collider, Neutrinos, Charged Lepton Flavor Violation, a…
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We summarize the Fermilab Accelerator Complex Evolution (ACE) Science Workshop, held on June 14-15, 2023. The workshop presented the strategy for the ACE program in two phases: ACE Main Injector Ramp and Target (MIRT) upgrade and ACE Booster Replacement (BR) upgrade. Four plenary sessions covered the primary experimental physics thrusts: Muon Collider, Neutrinos, Charged Lepton Flavor Violation, and Dark Sectors. Additional physics and technology ideas were presented from the community that could expand or augment the ACE science program. Given the physics framing, a parallel session at the workshop was dedicated to discussing priorities for accelerator R\&D. Finally, physics discussion sessions concluded the workshop where experts from the different experimental physics thrusts were brought together to begin understanding the synergies between the different physics drivers and technologies.
In December of 2023, the P5 report was released setting the physics priorities for the field in the next decade and beyond, and identified ACE as an important component of the future US accelerator-based program. Given the presentations and discussions at the ACE Science Workshop and the findings of the P5 report, we lay out the topics for study to determine the physics priorities and design goals of the Fermilab ACE project in the near-term.
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Submitted 7 March, 2024; v1 submitted 4 March, 2024;
originally announced March 2024.
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Search for a Dark Photon in Electro-Produced $e^{+}e^{-}$ Pairs with the Heavy Photon Search Experiment at JLab
Authors:
P. H. Adrian,
N. A. Baltzell,
M. Battaglieri,
M. Bondí,
S. Boyarinov,
S. Bueltmann,
V. D. Burkert,
D. Calvo,
M. Carpinelli,
A. Celentano,
G. Charles,
L. Colaneri,
W. Cooper,
C. Cuevas,
A. D'Angelo,
N. Dashyan,
M. De Napoli,
R. De Vita,
A. Deur,
R. Dupre,
H. Egiyan,
L. Elouadrhiri,
R. Essig,
V. Fadeyev,
C. Field
, et al. (52 additional authors not shown)
Abstract:
The Heavy Photon Search experiment took its first data in a 2015 engineering run using a 1.056 GeV, 50 nA electron beam provided by CEBAF at the Thomas Jefferson National Accelerator Facility, searching for an electro-produced dark photon. Using 1.7 days (1170 nb$^{-1}$) of data, a search for a resonance in the $e^{+}e^{-}$ invariant mass distribution between 19 and 81 MeV/c$^2$ showed no evidence…
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The Heavy Photon Search experiment took its first data in a 2015 engineering run using a 1.056 GeV, 50 nA electron beam provided by CEBAF at the Thomas Jefferson National Accelerator Facility, searching for an electro-produced dark photon. Using 1.7 days (1170 nb$^{-1}$) of data, a search for a resonance in the $e^{+}e^{-}$ invariant mass distribution between 19 and 81 MeV/c$^2$ showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the Standard Model photon are set at the level of 6$\times$10$^{-6}$. In addition, a search for displaced dark photon decays did not rule out any territory but resulted in a reliable analysis procedure that will probe hitherto unexplored parameter space with future, higher luminosity runs.
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Submitted 5 December, 2018;
originally announced December 2018.
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Search for a Dark Photon in Electro-Produced $e^{+}e^{-}$ Pairs with the Heavy Photon Search Experiment at JLab
Authors:
P. H. Adrian,
N. A. Baltzell,
M. Battaglieri,
M. Bondí,
S. Boyarinov,
S. Bueltmann,
V. D. Burkert,
D. Calvo,
M. Carpinelli,
A. Celentano,
G. Charles,
L. Colaneri,
W. Cooper,
C. Cuevas,
A. D'Angelo,
N. Dashyan,
M. De Napoli,
R. De Vita,
A. Deur,
R. Dupre,
H. Egiyan,
L. Elouadrhiri,
R. Essig,
V. Fadeyev,
C. Field
, et al. (52 additional authors not shown)
Abstract:
The Heavy Photon Search experiment took its first data in a 2015 engineering run at the Thomas Jefferson National Accelerator Facility, searching for a prompt, electro-produced dark photon with a mass between 19 and 81 MeV/$c^2$. A search for a resonance in the $e^{+}e^{-}$ invariant mass distribution, using 1.7 days (1170 nb$^{-1}$) of data, showed no evidence of dark photon decays above the larg…
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The Heavy Photon Search experiment took its first data in a 2015 engineering run at the Thomas Jefferson National Accelerator Facility, searching for a prompt, electro-produced dark photon with a mass between 19 and 81 MeV/$c^2$. A search for a resonance in the $e^{+}e^{-}$ invariant mass distribution, using 1.7 days (1170 nb$^{-1}$) of data, showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the Standard Model photon are set at the level of 6$\times$10$^{-6}$. Future runs with higher luminosity will explore new territory.
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Submitted 3 August, 2018; v1 submitted 30 July, 2018;
originally announced July 2018.
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US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report
Authors:
Marco Battaglieri,
Alberto Belloni,
Aaron Chou,
Priscilla Cushman,
Bertrand Echenard,
Rouven Essig,
Juan Estrada,
Jonathan L. Feng,
Brenna Flaugher,
Patrick J. Fox,
Peter Graham,
Carter Hall,
Roni Harnik,
JoAnne Hewett,
Joseph Incandela,
Eder Izaguirre,
Daniel McKinsey,
Matthew Pyle,
Natalie Roe,
Gray Rybka,
Pierre Sikivie,
Tim M. P. Tait,
Natalia Toro,
Richard Van De Water,
Neal Weiner
, et al. (226 additional authors not shown)
Abstract:
This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in Dark Matter" held at University of Maryland on March 23-25, 2017.
This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in Dark Matter" held at University of Maryland on March 23-25, 2017.
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Submitted 14 July, 2017;
originally announced July 2017.
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Dark Sectors 2016 Workshop: Community Report
Authors:
Jim Alexander,
Marco Battaglieri,
Bertrand Echenard,
Rouven Essig,
Matthew Graham,
Eder Izaguirre,
John Jaros,
Gordan Krnjaic,
Jeremy Mardon,
David Morrissey,
Tim Nelson,
Maxim Perelstein,
Matt Pyle,
Adam Ritz,
Philip Schuster,
Brian Shuve,
Natalia Toro,
Richard G Van De Water,
Daniel Akerib,
Haipeng An,
Konrad Aniol,
Isaac J. Arnquist,
David M. Asner,
Henning O. Back,
Keith Baker
, et al. (179 additional authors not shown)
Abstract:
This report, based on the Dark Sectors workshop at SLAC in April 2016, summarizes the scientific importance of searches for dark sector dark matter and forces at masses beneath the weak-scale, the status of this broad international field, the important milestones motivating future exploration, and promising experimental opportunities to reach these milestones over the next 5-10 years.
This report, based on the Dark Sectors workshop at SLAC in April 2016, summarizes the scientific importance of searches for dark sector dark matter and forces at masses beneath the weak-scale, the status of this broad international field, the important milestones motivating future exploration, and promising experimental opportunities to reach these milestones over the next 5-10 years.
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Submitted 30 August, 2016;
originally announced August 2016.