Confirmation of the existence of the X17 particle.

Authors :: Mitchell, A.J.
Pavetich, S.
Koll, D.
Firak, D. S.
Krasznahorkay, A. J.
Csatlós, M.
Csige, L.
Gulyás, J.
Koszta, M.
Szihalmi, B.
Timár, J.
Nagy, Á.
Sas, N. J.
Krasznahorkay, A.
Source :: EPJ Web of Conferences; 4/6/2020, Vol. 232, p1-5, 5p
Publication Year :: 2020
Abstract: In a 2016 paper, an anomaly in the internal pair creation on the M1 transition depopulating the 18.15 MeV isoscalar 1+ state on 8Be was observed. This could be explained by the creation and subsequent decay of a new boson, with mass m<subscript>X</subscript>c<superscript>2</superscript> = 16.70 MeV. Further experiments of the same transition with an improved and independent setup were performed, which constrained the mass of the X17 boson (m<subscript>X</subscript>c2) and its branching ratio relative to the γ-decay of the 8Be excited state (B<subscript>X</subscript>), to m<subscript>X</subscript>c<superscript>2</superscript> = 17.01(16) MeV and B<subscript>X</subscript> = 6(1) 10−6, respectively. Using the latter setup, the e+e− pairs depopulating the 21 MeV Jπ = 0<superscript>−</superscript> 0<superscript>+</superscript> transition in 4He were investigated and a resonance in the angular correlation of the pairs was observed, which could be explained by the same X17 particle, with mass m<subscript>X</subscript>c<superscript>2</superscript> = 16.98 ± 0.16(stat) ± 0.20(syst) MeV. [ABSTRACT FROM AUTHOR]