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arXiv · 2604.14359

Expected Sensitivity of the Light Dark Matter eXperiment to Long-Lived Dark Photons and Axion-Like Particles

Torsten Akesson·Clay Barton·Charles Bell·Elizabeth Berzin·Liam Brennan·Lene Kristian Bryngemark·Lincoln Curtis·Patill Daghlian·E. Craig Dukes·Valentina Dutta·Bertrand Echenard·Ralf Ehrlich·Thomas Eichlersmith·Einar Elén·Andrew Furmanski·Majd Ghrear·Matthew Gignac·Matt Graham·Chiara Grieco·Craig Group·Hannah Herde·Christian Herwig·David G. Hitlin·Tyler Horoho·Joseph Incandela·Nathan Jay·Wesley Ketchum·Gordan Krnjaic·Oscar Lewis·Yuze Li·Jeremiah Mans·Cristina Mantilla Suarez·Sanjit Masanam·Steven Metallo·Sophie Middleton·Timothy Nelson·Rory O'Dwyer·James Oyang·Pritam Palit·Jessica Pascadlo·Emrys Peets·Luis Sarmiento Pico·Ruth Pöttgen·Chelsea Rodriguez·Lincoln Satterthwaite·Philip Schuster·Matt Solt·Lauren Tompkins·Natalia Toro·Nhan Tran·Tamas Vami·Kieran Wall·Erik Wallin·Andrew Whitbeck·Jihoon Yoo·Danyi Zhang
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Abstract

The Light Dark Matter eXperiment (LDMX) is an electron-beam fixed-target experiment primarily designed to achieve world-leading, model-independent sensitivity to sub-GeV dark matter particles. LDMX aims to identify dark sector particle production through the detection of events with substantial missing energy and momentum, a signature of invisible particles escaping detection. Beyond this primary objective, LDMX offers a complementary search strategy for long-lived, visibly decaying particles, such as dark photons and axion-like particles. We present the first detailed evaluation of the ability of LDMX to identify visibly decaying, long-lived particles that couple to electrons using a detailed simulation, based on the Geant4-toolkit, that incorporates realistic detection efficiencies and background levels. We demonstrate that LDMX can achieve a sensitivity that is competitive with other experiments that are currently running. The models explored in this paper are distinct and complementary to those probed in the LDMX flagship missing-momentum analysis. Through searching for both invisible dark matter and visibly decaying long-lived signatures, LDMX will significantly advance the search for light dark matter and provide a broad exploration of the sub-GeV dark sector.

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Torsten Akesson, Clay Barton, Charles Bell, Elizabeth Berzin, Liam Brennan, Lene Kristian Bryngemark, Lincoln Curtis, Patill Daghlian, E. Craig Dukes, Valentina Dutta, Bertrand Echenard, Ralf Ehrlich, Thomas Eichlersmith, Einar Elén, Andrew Furmanski, Majd Ghrear, Matthew Gignac, Matt Graham, Chiara Grieco, Craig Group, Hannah Herde, Christian Herwig, David G. Hitlin, Tyler Horoho, Joseph Incandela, Nathan Jay, Wesley Ketchum, Gordan Krnjaic, Oscar Lewis, Yuze Li, Jeremiah Mans, Cristina Mantilla Suarez, Sanjit Masanam, Steven Metallo, Sophie Middleton, Timothy Nelson, Rory O'Dwyer, James Oyang, Pritam Palit, Jessica Pascadlo, Emrys Peets, Luis Sarmiento Pico, Ruth Pöttgen, Chelsea Rodriguez, Lincoln Satterthwaite, Philip Schuster, Matt Solt, Lauren Tompkins, Natalia Toro, Nhan Tran, Tamas Vami, Kieran Wall, Erik Wallin, Andrew Whitbeck, Jihoon Yoo, Danyi Zhang. 2026-04-15. Expected Sensitivity of the Light Dark Matter eXperiment to Long-Lived Dark Photons and Axion-Like Particles. https://arxiv.org/abs/2604.14359

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