重夸克质量计算：N3LO的魅/底夸克质量分析

88 浏览量更新于2024-07-16 收藏 1.04MB PDF 举报

本文是一篇关于通过N3LO（Next-to-Next-to-Next-to-Leading Order）阶的微扰量子色动力学（QCD）表达式来计算重夸克质量的研究论文。作者 Clara Peset, Antonio Pineda 和 Jorge Segovia 来自德国慕尼黑工业大学和西班牙巴塞罗那自治大学的理论物理组。文章于2018年在JHEP期刊上发表，探讨了如何使用基态（伪标量）能量的N3LO表达式来确定魅力夸克（charm quark）和底夸克（bottom quark）的质量，并在renormalon减法方案下进行，以解决因极质量renormalon导致的摄动级数发散问题。在N3LO的框架下，研究者计算了ηb（底夸克onia）、ηc（魅力夸克onia）和Bc（底魅介子）系统的基态能量。他们得出的MS（Modified Minimal Subtraction）质量结果为：魅力夸克的质量 m_c(m_c) = 1223(33) MeV，底夸克的质量 m_b(m_b) = 4186(37) MeV。这里的括号内的数字表示误差范围。此外，他们还从ηb、ηc和Bc的质量无正则子组合中推导出强相互作用耦合常数 α_s 在 M_z 规范下的值：α_s(M_z) = 0.1195(53)，其中的误差同样给出了不确定性。在研究过程中，作者探讨了弱耦合近似在计算bottom n = 2态时的适用性，这是对更高级别激发态的分析。最后，他们提出了一种替代的计算方法，该方法能精确处理静态势，并对其收敛性进行了研究。这种方法可能提供一个更稳定和精确的框架来处理重夸克的质量计算。这项工作对于理解基本粒子的性质，特别是重夸克的物理特性，以及在强相互作用下的量子色动力学理论有重要意义。通过精确计算这些基本粒子的质量，物理学家可以更准确地预测与重夸克相关的粒子衰变和相互作用过程，进一步推动高能物理的发展。

JHEP09(2018)167

We observe that for scales larger than 2 GeV, δE

is small and well inside uncer-

tainties. It is also comforting that the yellow error band in ﬁgure 1 (associated to the

uncertainty of m

) covers the diﬀerence between the NNLO and N

LO results in the RS

and in the RS’ scheme for the whole scale variation. This diﬀerence is often used as an

alternative determination of the error. Actually, in the RS’ scheme the distance between

the diﬀerent orders is quite small, which may ask for future more aggressive determina-

tions of the bottom mass. We refrain from doing so until a more clear understanding of

the renormalization scale dependence of the observable at low scales and of the role played

by the ultrasoft scale is achieved.

As a ﬁnal check, we have performed the ﬁt to the Υ(1S) mass using the same setup.

We ﬁnd a shift of almost +20 MeV, well within the uncertainties of eq. (2.6).

We now compare our result with previous determinations of m

) from spectroscopy

or from sum rules. We show such comparison in ﬁgure 2. We ﬁnd that all determinations are

perfectly consistent with each other. Determinations from sum rules with small number

of momentums (low n sum rules) seem to give slightly smaller values of the mass than

large n or spectroscopy determinations. We notice that the latter include the Coulomb

resummation. Therefore, the physics they are sensitive to is diﬀerent. Nevertheless, at

this stage this diﬀerence is not statistically signiﬁcant, and we are not in the position to

push this discussion further. It is also worth noting that, at present, partial NNLL sum

rules determinations produce slightly larger errors than other determinations. It would be

interesting to see if the complete result, or its combination with the large n N

LO sum

result, may lead to a more precise determination.

We now turn our discussion to the comparison between diﬀerent spectroscopy determi-

nations. Our value is slightlty smaller than the determinations in [26–28] (but well within

each other’s uncertanties). Compared with the determinations of Ayala et al. [27] and Ma-

teu et al. [28], a part of the diﬀerence can be traced back to the fact that in the two latter

references the Υ plays a predominant role in the ﬁt (which leads to a larger value for the

bottom mass than ﬁts to the η

mass). In the ﬁrst reference because the ﬁt was only made

to the Υ, in the second reference because, even if both the vector and the pseudoscalar

were considered in the ﬁt, their method weights the most the particle that produces the

smaller errror, which in their paper is the vector. It is worth mentioning that if one looks

at the individual ﬁts in [28] to the η

mass one ﬁnds a smaller value of m

), quite close

to ours. As at present all these determinations are consistent with each other, there is not

a clear reason to prefer one versus the other. As we have already discussed before, the

resummation of large logarithms may help to solve this problem. We hope to come back to

this issue in the future. The other fact that produces a diﬀerent central value of m

)

is the choice of the factorization scale µ to ﬁx the central value. In this paper we have

chosen a larger value of the factorization scale than in [27, 28]. We somewhat feel that a

smaller value of the factorization scale leads to a region where the perturbative series does

not behave well enough. In this respect the factorization scales we choose are closer to the

factorization scales used in [26]. Actually, the diﬀerence with respect to the value obtained

in [26] can be traced back to the fact that in that reference an average of the determination

of the bottom mass from the Υ and the η

is made. Again pure determinations from the η

– 5 –

剩余28页未读，继续阅读

weixin_38713039

粉丝: 6
资源: 948

重夸克质量计算：N3LO的魅/底夸克质量分析

N3LO对希格斯玻色子衰变至底部夸克的预测

近似N3LO的上夸克双微分分布

在N3LO的Drell-Yan生产中领先的功率阈值校正

使用N3LO QCD上的q T减法形式在大型强子对撞机上生产希格斯玻色子

夸克的树级分裂幅度分成四个共线的部分

广义大Nc逼近中扰动QCD中的下一个，下一个到前一个阶的夸克光束函数

通过在N3LL上的b b $$ \ overline {\ mathrm {b}} $$ ation灭，对希格斯玻色子产量的恢复预测

三环阶QCD扰动下RI/SMOM双线性夸克算符的重整化

QCD中夸克1S能级的精确测量：mc和mb的质量更新

cairo-devel-1.15.12-4.el7.x86_64.rpm.zip

最新资源