2923599 20250211215510.0 oai:cds.cern.ch:2923599 cerncds:FULLTEXT cerncds:CERN:FULLTEXT cerncds:CERN CERN-EP-2025-016 eng CERN-EP-DRAFT-MISC-2025-001 Andreev, Yu. M. Proof of principle for a light dark matter search with low-energy positron beams at NA64 2025 CERN Geneva 07 Feb 2025 cds-ph-ep-publications-referee-non-lhc [CERN] Thermal light dark matter (LDM) with particle masses in the 1 MeV - 1 GeV range could successfully explain the observed dark matter abundance as a relic from the primordial Universe. In this picture, a new feeble interaction acts as a “portal” between the Standard Model and LDM particles, allowing for the exploration of this paradigm at accelerator experiments. In the last years, the “missing energy” experiment NA64e at CERN SPS (Super Proton Synchrotron) has set world-leading constraints in the vector-mediated LDM parameter space, by exploiting a 100 GeV electron beam impinging on an electromagnetic calorimeter, acting as an active target. In this paper, we report a detailed description of the analysis of a preliminary measurement with a 70 GeV positron beam at NA64e, performed during summer 2023 with an accumulated statistic of 1.6 × 1010 positrons on target. This data set was analyzed with the primary aim of evaluating the performance of the NA64e detector with a lower energy positron beam, towards the realization of the post-LS3 program. The analysis results, other than additionally probing unexplored regions in the LDM parameter space, provide valuable information towards the future NA64e positron campaign. Preprint CC-BY-4.0 Preprint CERN 2025 Public comments CERN EDS SzGeCERN Particle Physics - Experiment electroweak interaction CERN particle and resonance production CERN experimental results CERN CERN PREPRINT CERN SPS NA64 Antonov, A. Ayala Torres, M. A. Banerjee, D. Banto Oberhauser, B. Bautin, V. Bernhard, J. Bisio, P. Bondì, M. Celentano, A. Charitonidis, N. Crivelli, P. Dermenev, A. V. Donskov, S. V. Dusaev, R. R. Enik, T. Frolov, V. N. Gertsenberger, S. V. Girod, S. Gninenko, S. N. Hösgen, M. Kambar, Y. Karneyeu, A. E. Kekelidze, G. Ketzer, B. Kirpichnikov, D. V. Kirsanov, M. M. Kramarenko, V. A. Kravchuk, L. V. Krasnikov, N. V. Kuleshov, S. V. Lyubovitskij, V. E. Lysan, V. Marini, A. Marsicano, L. Matveev, V. A. Mena Fredes, R. Mena Yanssen, R. Molina Bueno, L. Mongillo, M. Peshekhonov, D. V. Polyakov, V. A. Radics, B. Salamatin, K. Samoylenko, V. D. Sieber, H. Shchukin, D. Soto, O. Tikhomirov, V. O. Tlisova, I. Toropin, A. N. Tuzi, M. Ulloa, P. Volkov, P. V. Voronchikhin, I. V. Zamora-Saá, J. Zhevlakov, A. S. PH 2712773 4014638 http://cds.cern.ch/record/2923599/files/CERN-EP-2025-016.pdf 2711888 4014638 http://cds.cern.ch/record/2923599/files/CERN-EP-DRAFT-MISC-2025-001 - draft.pdf Draft (restricted) Stamped by WebSubmit: 06/02/2025 anna.marini@cern.ch Approval requested for number CERN-EP-2025-016 CERN-EP-2025-016 EPPHAPP 2025-02-05 14:57:00 2025-02-07 14:57:00 anna.marini@cern.ch waiting Document approved CERN-EP-2025-016 EPPHAPP 2025-02-06 09:41:10 richard.hawkings@cern.ch approved n 202506 NA64_Papers PREPRINT