| 摘 要： | We study the triply heavy baryons Ω_(QQQ)(Q=c,b) in the QCD sum rules by performing the first calculation of the next-to-leading order(NLO) contribution to the perturbative QCD part of the correlation functions.Compared with the leading order(LO) result,the NLO contribution is found to be very important to the Ω_(QQQ).This is because the NLO not only results in a large correction but also reduces the parameter dependence,making the Borel platform more distinct,especially for the Qbbb in the ■ scheme,where the platform appears only at NLO but not at LO.Particularly,owing to the inclusion of the NLO contribution,the renormalization schemes(■ and On-Shell) dependence and the scale dependence are significantly reduced.Consequently,after including the NLO contribution to the perturbative part in the QCD sum rules,the masses are estimated to be 4.53_(-0.11) ~(+0.26) GeV for Ω_(ccc) and14.27_(-0.32) ~(+0.33) GeV for Ω_(bbb),where the results are obtained at μ=M_B with errors including those from the variation of the renormalization scale μ in the range(0.8-1.2)M_B.A careful study of the μ dependence in a wider range is further performed,which shows that the LO results are very sensitive to the choice of μ whereas the NLO results are considerably better.In addition to the μ=M_B result,a more stable value,(4.75-4.80) GeV,for the Ω_(ccc) mass is found in the range of μ=(1.2-2.0)M_B,which should be viewed as a more relevant prediction in our NLO approach because of μ dependence.
|
