The question of the nature of dark matter is one of the major challenges of elementary particle
physics. Not surprisingly, the recent suggestion of a dark decay channel as a solution to persisting discrepancies in neutron lifetime measurements has initiated substantial research activity. We discuss the accurate measurement of the parity violating β-asymmetry using Perkeo III. The result is about five times more precise than the current world average and resolves a long-standing discrepancy. Based on this, we largely rule out the dark decay mode interpretation. We derive a new world average of the weak axial coupling and obtain a competitive value of the first element of the quark mixing matrix Vud from neutron decay.
B. Märkisch, H. Abele, D. Dubbers, H. Saul & T. Soldner
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