本文利用畴壁费米子对超子半轻子衰变Xi ^0-> Sigma^{+} l nu的全部六个形状因子：矢量[f_1（q^2）]、弱磁[f_2（q^2）]、感生标量[f_3（q^2）]、轴矢量[g_1（q^2）]、弱电[g_2（q^2）]和感生赝标[g_3（q^2）]形状因子进行了猝灭晶格计算。在相对较低的q^2区域中，所有形状因子的q^2依赖性被检查，以评估它们在零动量传递时的值。Xi ^0-> Sigma^+跃迁对味SU（3）破缺非常敏感，因为这种衰变对应于下夸克与奇夸克交换下中子β衰变的直接模拟。超子β衰变中味SU（3）破缺效应的模式在与中子β衰变的结果比较中很容易暴露出来。我们测量了对f_1（0），f_2（0）/f_1（0）和g_1（0）/f_1（0）的SU（3）破缺修正。f_1（0）上的首阶修正量可能为负，其大小小于百分之几，而f_2（0）/f_1（0）和g_1（0）/f_1（0）分别得到16%和5%阶的正修正。观测到的偏离精确SU（3）极限值的模式不支持某些模型估计。我们证明了在Xi ^0-> Sigma^+衰变中存在非零的第二类形状因子，测量值为f_3（0）/f_1（0）=0.14（10）和g_2（0）/g_1（0）=0.68（18），这与一阶SU（3）破缺的大小相当。我们还发现SU（3）破缺效应对g_3（0）/g_1（0）的影响与广义π-极优势的预言一致。
英文摘要：
We present a quenched lattice calculation of all six form factors: vector [f_1(q^2)], weak magnetism [f_2(q^2)], induced scalar [f_3(q^2)], axial-vector [g_1(q^2)], weak electricity [g_2(q^2)] and induce pseudoscalar [g_3(q^2)] form factors in hyperon semileptonic decay Xi^0 -> Sigma^{+} l nu using domain wall fermions. The q^2 dependences of all form factors in the relatively low q^2 region are examined in order to evaluate their values at zero momentum transfer. The Xi^0 -> Sigma^+ transition is highly sensitive to flavor SU(3) breaking since this decay corresponds to the direct analogue of neutron beta decay under the exchange of the down quark with the strange quark. The pattern of flavor SU(3) breaking effects in the hyperon beta decay is easily exposed in a comparison to results for neutron beta decay. We measure SU(3)-breaking corrections to f_1(0), f_2(0)/f_1(0) and g_1(0)/f_1(0). A sign of the leading order corrections, of which the size is less than a few %, on f_1(0) is likely negative, while f_2(0)/f_1(0) and g_1(0)/f_1(0) receive positive corrections of order 16% and 5% respectively. The observed patterns of the deviation from the values in the exact SU(3) limit does not support some of model estimates. We show that there are nonzero second-class form factors in the Xi^0 -> Sigma^+ decay, measuring f_3(0)/f_1(0)=0.14(10) and g_2(0)/g_1(0)=0.68(18), which are comparable to the size of first-order SU(3) breaking. It is also found that the SU(3) breaking effect on g_3(0)/g_1(0) agree with the prediction of the generalized pion-pole dominance.
Neutrinoless double beta decays of hyperons in covariant chiral perturbation theory
School of Physics and Electronics, Hunan University（湖南大学物理与电子学院）；Hunan Provincial Key Laboratory of High-Energy Scale Physics and Applications, Hunan University（湖南大学高能标物理与应用湖南省重点实验室）；College of Physics and Hebei Key Laboratory of Photophysics Research and Application, Hebei Normal University（河北师范大学物理学院及河北省光物理研究与应用重点实验室）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；School of Physics, Central South University（中南大学物理学院）
