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A new direct detection electron scattering experiment to search for the X17 particle
- Dutta, D;
- Gao, H;
- Gasparian, A;
- Hague, TJ;
- Liyanage, N;
- Paremuzyan, R;
- Peng, C;
- Xiong, W;
- Achenbach, P;
- Ahmidouch, A;
- Ali, S;
- Avakian, H;
- Ayerbe-Gayoso, C;
- Bai, X;
- Battaglieri, M;
- Bhatt, H;
- Bianconi, A;
- Boyd, J;
- Byer, D;
- Cole, PL;
- Costantini, G;
- Davis, S;
- Napoli, M De;
- Vita, R De;
- Devkota, B;
- Dharmasena, B;
- Dunne, J;
- Fassi, L El;
- Gamage, V;
- Gan, L;
- Gnanvo, K;
- Gosta, G;
- Higinbotham, D;
- Howell, C;
- Jeffas, S;
- Jian, S;
- Karki, A;
- Karki, B;
- Khachatryan, V;
- Khandaker, M;
- Kubarovsky, V;
- Larin, I;
- Leali, M;
- Mascagna, V;
- Matousek, G;
- Migliorati, S;
- Miskimen, R;
- Mohanmurthy, P;
- Nguyen, H;
- Pasyuk, E;
- Rathnayake, A;
- West, J Rittenhouse;
- Shahinyan, A;
- Smith, A;
- Stepanyan, S;
- Nieuwenhuizen, E van;
- Venturelli, L;
- Yu, B;
- Zhao, Z;
- Zhou, J
Abstract
A new electron scattering experiment (E12-21-003) to verify and understand the nature of hidden sector particles, with particular emphasis on the so-called X17 particle, has been approved at Jefferson Lab. The search for these particles is motivated by new hidden sector models introduced to account for a variety of experimental and observational puzzles: excess in $e^+e^-$ pairs observed in multiple nuclear transitions, the 4.2$\sigma$ disagreement between experiments and the standard model prediction for the muon anomalous magnetic moment, and the small-scale structure puzzle in cosmological simulations. The aforementioned X17 particle has been hypothesized to account for the excess in $e^+e^-$ pairs observed from the $^8$Be M1, $^4$He M0, and, most recently, $^{12}$C E1 nuclear transitions to their ground states observed by the ATOMKI group. This experiment will use a high resolution electromagnetic calorimeter to search for or set new limits on the production rate of the X17 and other hidden sector particles in the $3 - 60$ MeV mass range via their $e^+e^-$ decay (or $\gamma\gamma$ decay with limited tracking). In these models, the $1 - 100$ MeV mass range is particularly well-motivated and the lower part of this range still remains unexplored. Our proposed direct detection experiment will use a magnetic-spectrometer-free setup (the PRad apparatus) to detect all three final state particles in the visible decay of a hidden sector particle for an effective control of the background and will cover the proposed mass range in a single setting. The use of the well-demonstrated PRad setup allows for an essentially ready-to-run and uniquely cost-effective search for hidden sector particles in the $3 - 60$ MeV mass range with a sensitivity of 8.9$\times$10$^{-8}$ - 5.8$\times$10$^{-9}$ to $\epsilon^2$, the square of the kinetic mixing interaction constant between hidden and visible sectors.
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