Märkisch B, Mest H, Saul H, Wang X, Abele H, Dubbers D, Klopf M, Petoukhov A, Roick C, Soldner T, Werder D
Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany.
Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany.
Phys Rev Lett. 2019 Jun 21;122(24):242501. doi: 10.1103/PhysRevLett.122.242501.
We present a precision measurement of the axial-vector coupling constant g_{A} in the decay of polarized free neutrons. For the first time, a pulsed cold neutron beam was used for this purpose. By this method, leading sources of systematic uncertainty are suppressed. From the electron spectra we obtain λ=g_{A}/g_{V}=-1.27641(45){stat}(33){sys}, which confirms recent measurements with improved precision. This corresponds to a value of the parity violating beta asymmetry parameter of A_{0}=-0.11985(17){stat}(12){sys}. We discuss implications on the Cabibbo-Kobayashi-Maskawa matrix element V_{ud} and derive a limit on left-handed tensor interaction.
我们展示了在极化自由中子衰变中对轴矢量耦合常数(g_{A})的精确测量。首次为此使用了脉冲冷中子束。通过这种方法，系统不确定性的主要来源得到了抑制。从电子能谱中我们得到(\lambda = g_{A}/g_{V} = -1.27641(45){统计}(33){系统})，这证实了近期精度有所提高的测量结果。这对应于宇称破坏贝塔不对称参数(A_{0} = -0.11985(17){统计}(12){系统})的值。我们讨论了对卡比博 - 小林 - 益川矩阵元(V_{ud})的影响，并得出了左手张量相互作用的一个限制。
