https://doi.org/10.1140/epjp/s13360-024-04920-x
Regular Article
Thermal noise-limited beam balance as prototype of the Archimedes vacuum weight experiment and B-L dark photon search
1
Università di Napoli Federico II, Via Cinthia, 80126, Naples, Italy
2
INFN, sez. Napoli, Via Cinthia, 80126, Naples, Italy
3
Centro Nazionale Ricerche - Istituto Nazionale di Ottica (CNR-INO), Pozzuoli, Naples, Italy
4
Università di Roma La Sapienza, 00185, Rome, Italy
5
INFN-Sezione di Roma 1, 00185, Rome, Italy
6
Università degli Studi di Milano Bicocca, 20126, Milan, Italy
7
European Gravitational Observatory (EGO), Via E Amaldi, 56021, Cascina, PI, Italy
8
INFN - Laboratori Nazionali del Sud, 95125, Catania, Italy
9
Università degli Studi di Cagliari, S.P Sestu, 09042, Monserrato, Cagliari, Italy
10
INFN - sez. Cagliari, S.P Sestu, 09042, Monserrato, Cagliari, Italy
11
Università degli Studi di Sassari, 07100, Sassari, Italy
12
Centre de Physique Theorique Campus of Luminy - Case 907, 13288, Marseille, France
13
Aix-Marseille Universié Site du Pharo, 58 bd Charles Livon, 13284, Marseille, France
14
Université de Toulon - Campus de La Garde, La Valette Avenue de l’Université, 83130, La Garde, Toulon, France
Received:
3
November
2023
Accepted:
18
January
2024
Published online:
14
February
2024
We describe the behavior of a beam balance used for the measurement of small forces, in macroscopic samples, in tens of mHz frequency band. The balance, which works at room temperature, is the prototype of the cryogenic balance of the Archimedes experiment, aimed at measuring the interaction between electromagnetic vacuum fluctuations and the gravitational field. The balance described has a 50-cm aluminum arm and suspends an aluminum sample of 0.2 Kg and a lead counterweight. The read-out is interferometric, and the balance works in closed loop. It is installed in the low seismic noise laboratory of SAR-GRAV (Sardinia—Italy). Thanks to the low sensing and actuation noise and finally thanks to the low environmental noise, the sensitivity in torque 
is about 
at 10 mHz and reaches a minimum of about 
at tens of mHz, corresponding to the force sensitivity 
of 
. The achievement of this sensitivity, which turns out to be compatible with thermal noise estimation, on the one hand, demonstrates the correctness of the optical and mechanical design and on the other paves the way to the completion of the final balance. Furthermore, since the balance is equipped with weight and counterweight made of different materials, it is sensitive to the interaction with dark B-L photons. A first very short run made to evaluate constraints on B-L dark photon coupling shows encouraging results that will be discussed in view of next future scientific runs.
© The Author(s) 2024
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