Speaker
Description
Recently, a nuclear physicists team from ATOMKI (Debrecen, Hungary) observed three significant anomalies in the emission of electron-positron pairs in the $^7$Li(p,e$^+$e$^−$)$^8$Be, $^3$H(p,e$^+$e$^−$)$^4$He and $^{11}$B(p,e$^+$e$^−$)$^{12}$C nuclear reactions [1-3]. These anomalies have been interpreted as the signature of the existence of a boson (referred as X17) of mass M$_{X17}$ = 16.8 MeV/c$^2$, that could be a mediator of a fifth force characterised by a strong coupling suppression of protons compared to neutrons (protophobic force). To clarify the present scenario the n_TOF Collaboration at CERN is engaged to realise an experimental program to probe the X17 existence and to study its properties through the first study of the $^3$He(n,e$^+$e$^−$)$^4$He reaction and performing a renewed measurement of the $^7$Li(p,e$^+$e$^−$)$^8$Be process. In case of a positive result, the n_TOF program also foresees the study of the conjugate $^2$H(n,e$^+$e$^−$)$^3$He and $^2$H(p,e$^+$e$^−$)$^3$H reactions, that offers a unique opportunity to study the supposed protophobic nature of the fifth force.
The experimental set-up described here is based on the use of four large $\mu$Rwell chambers properly arranged to surround the target, providing the 3D reconstruction of electron and positron tracks. The $\mu$Rwell chambers are inside to an array of scintillating bar, which provides the trigger. Finally, all the detectors are immersed in a magnetic field of 500 Gauss, to measure charge and momentum of e$^+$e$^−$ ejectiles through their curvature. In this talk is described the experimental setup and the experimental program. The results of tests using proton and neutron beams are also discussed.
[1] A. J. Krasznahorkay et al., Phys. Rev. Lett. 116, (2016) 042501.
[2] A. J. Krasznahorkay et al., Phys. Rev. C 104, (2021) 044003.
[3] A. J. Krasznahorkay et al., Phys. Rev. C 106, (2022) 061601.
| Collaboration | n_TOF |
|---|---|
| Role of Submitter | The presenter will be selected later by the Collaboration |
