The studies on Z → Υ (1S) g + g at the next-to-leading-order QCD accuracy

In this paper, we carry out the next-to-leading-order (NLO) studies on Z -> Upsilon(1S) + g + g via the color-singlet (CS) b b state. We find the newly calculated NLO QCD corrections to this process can significantly influence its leading-order (LO) results and greatly improve the dependence on the renormalization scale. By including the considerable feeddown contributions, the branching ratio B-Z ->Upsilon(1S)+g+g is predicted to be (0.56-0.95) x10(-6), which can reach up to 19-31% of the LO predictions given by the CS dominant process Z ->Upsilon(1S) + b + b. Moreover, Z -> Upsilon(1S) + g + g also seriously affects the CS predictions on the Upsilon(1S) energy distributions, especially when z is relatively small. In summary, for the inclusive.(1S) productions in Z decay, besides Z -> Upsilon(1S)+ b+ b, the gluon radiation process Z -> Upsilon(1S) + g + g can provide indispensable contributions as well.