NLO effects for Ω_QQQ baryons in QCD Sum Rules

【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.更多还原

【Abstract】 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.更多还原