scholarly journals Infinite-order scale-setting using the principle of maximum conformality: A remarkably efficient method for eliminating renormalization scale ambiguities for perturbative QCD

2020 ◽  
Vol 102 (1) ◽  
Author(s):  
Leonardo Di Giustino ◽  
Stanley J. Brodsky ◽  
Sheng-Quan Wang ◽  
Xing-Gang Wu
Keyword(s):  
Perturbative Qcd ◽  
Efficient Method ◽  
Infinite Order ◽  
Renormalization Scale ◽  
Principle Of Maximum

scholarly journals Z-boson hadronic decay width up to $${{\mathcal {O}}}(\alpha _s^4)$$-order QCD corrections using the single-scale approach of the principle of maximum conformality

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Xu-Dong Huang ◽  
Xing-Gang Wu ◽  
Xu-Chang Zheng ◽  
Qing Yu ◽  
Sheng-Quan Wang ◽  
...  
Keyword(s):  
Quantum Chromodynamics ◽  
Perturbative Qcd ◽  
Decay Width ◽  
Z Boson ◽  
Hadronic Decay ◽  
Experimental Measurements ◽  
Renormalization Scale ◽  
Single Scale ◽  
Global Fit ◽  
Principle Of Maximum

AbstractIn the paper, we study the properties of the Z-boson hadronic decay width by using the $$\mathcal {O}(\alpha _s^4)$$ O ( α s 4 ) -order quantum chromodynamics (QCD) corrections with the help of the principle of maximum conformality (PMC). By using the PMC single-scale approach, we obtain an accurate renormalization scale-and-scheme independent perturbative QCD (pQCD) correction for the Z-boson hadronic decay width, which is independent to any choice of renormalization scale. After applying the PMC, a more convergent pQCD series has been obtained; and the contributions from the unknown $$\mathcal {O}(\alpha _s^5)$$ O ( α s 5 ) -order terms are highly suppressed, e.g. conservatively, we have $$\Delta \Gamma _{\mathrm{Z}}^{\mathrm{had}}|^{{{\mathcal {O}}}(\alpha _s^5)}_{\mathrm{PMC}}\simeq \pm 0.004$$ Δ Γ Z had | PMC O ( α s 5 ) ≃ ± 0.004 MeV. In combination with the known electro-weak (EW) corrections, QED corrections, EW–QCD mixed corrections, and QED–QCD mixed corrections, our final prediction of the hadronic Z decay width is $$\Gamma _{\mathrm{Z}}^{\mathrm{had}}=1744.439^{+1.390}_{-1.433}$$ Γ Z had = 1744 . 439 - 1.433 + 1.390 MeV, which agrees with the PDG global fit of experimental measurements, $$1744.4\pm 2.0$$ 1744.4 ± 2.0 MeV.

scholarly journals The P-wave charmonium annihilation into two photons $$\chi _{c0, c2}\rightarrow \gamma \gamma $$ with high-order QCD corrections

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Hua Zhou ◽  
Qing Yu ◽  
Xu-Dong Huang ◽  
Xu-Chang Zheng ◽  
Xing-Gang Wu
Keyword(s):  
Perturbative Qcd ◽  
Scale Dependence ◽  
High Order ◽  
P Wave ◽  
Leading Order ◽  
Scale Invariant ◽  
Central Value ◽  
Setting Approach ◽  
Belle Ii ◽  
Principle Of Maximum

AbstractIn this paper, we present a new analysis on the P-wave charmonium annihilation into two photons up to next-to-next-to-leading order (NNLO) QCD corrections by using the principle of maximum conformality (PMC). The conventional perturbative QCD prediction shows strong scale dependence and deviates largely from the BESIII measurements. After applying the PMC, we obtain a more precise scale-invariant pQCD prediction, which also agrees with the BESIII measurements within errors, i.e. $$R={\Gamma _{\gamma \gamma }(\chi _{c2})} /{\Gamma _{\gamma \gamma }(\chi _{c0})}=0.246\pm 0.013$$ R = Γ γ γ ( χ c 2 ) / Γ γ γ ( χ c 0 ) = 0.246 ± 0.013 , where the error is for $$\Delta \alpha _s(M_\tau )=\pm 0.016$$ Δ α s ( M τ ) = ± 0.016 . By further considering the color-octet contributions, even the central value can be in agreement with the data. This shows the importance of a correct scale-setting approach. We also give a prediction for the ratio involving $$\chi _{b0, b2} \rightarrow \gamma \gamma $$ χ b 0 , b 2 → γ γ , which could be tested in future Belle II experiment.

scholarly journals The renormalization scale problem and novel perspectives for QCD

2015 ◽  
Vol 39 ◽  
pp. 1560108
Author(s):  
Stanley J. Brodsky
Keyword(s):  
Renormalization Scale ◽  
High Transverse Momentum ◽  
Proton Proton ◽  
Direct Production ◽  
Proton Collisions ◽  
Qcd Factorization ◽  
Quarkonium Production ◽  
Proton Proton Collisions ◽  
Principle Of Maximum

I discuss a number of novel tests of QCD, measurements which can illuminate fundamental features of hadron physics. These include the origin of the “ridge” in proton-proton collisions; the production of the Higgs at high [Formula: see text]; the role of digluon-initiated processes for quarkonium production; flavor-dependent anti-shadowing; the effect of nuclear shadowing on QCD sum rules; direct production of hadrons at high transverse momentum; and leading-twist lensing corrections; and the breakdown of perturbative QCD factorization. I also review the “Principle of Maximum Conformalit” (PMC) which systematically sets the renormalization scale order-by-order in pQCD, independent of the choice of renormalization scheme, thus eliminating an unnecessary theoretical uncertainty.

scholarly journals Revisiting the bottom quark forward–backward asymmetry $$A_\mathrm{{FB}}$$ in electron–positron collisions

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
Sheng-Quan Wang ◽  
Rui-Qing Meng ◽  
Xing-Gang Wu ◽  
Long Chen ◽  
Jian-Ming Shen
Keyword(s):  
Experimental Determination ◽  
Bottom Quark ◽  
Model Fit ◽  
Renormalization Scale ◽  
Leading Order ◽  
Electron Positron ◽  
Order Of Magnitude ◽  
Positron Collisions ◽  
Reasonable Behavior ◽  
Principle Of Maximum

Abstract The bottom quark forward–backward asymmetry $$A_\mathrm{{FB}}$$AFB is a key observable in electron–positron collisions at the $$Z^{0}$$Z0 peak. In this paper, we employ the Principle of Maximum Conformality (PMC) to fix the $$\alpha _s$$αs-running behavior of the next-to-next-to-leading order QCD corrections to $$A_\mathrm{{FB}}$$AFB. The resulting PMC scale for this $$A_\mathrm{{FB}}$$AFB is an order of magnitude smaller than the conventional choice $$\mu _r=M_Z$$μr=MZ. This scale has the physically reasonable behavior and reflects the virtuality of its QCD dynamics, which is independent to the choice of renormalization scale. Our analyses show that the effective momentum flow for the bottom quark forward–backward asymmetry should be $$\mu _r\ll M_Z$$μr≪MZ other than the conventionally suggested $$\mu _r=M_Z$$μr=MZ. Moreover, the convergence of perturbative QCD series for $$A_\mathrm{{FB}}$$AFB is greatly improved using the PMC. Our prediction for the bare bottom quark forward–backward asymmetry is refined to be $$A^{0,b}_\mathrm{FB}=0.1004\pm 0.0016$$AFB0,b=0.1004±0.0016, which diminishes the well known tension between the experimental determination for this (pseudo) observable and the respective Standard Model fit to $$2.1\sigma $$2.1σ.

Organization of suburban communication in the conditions of repair work on the railway section

2021 ◽  
Vol 14 (3) ◽  
pp. 44-50
Author(s):  
Elena Popova ◽  
I. Zhuravleva
Keyword(s):  
Efficient Method ◽  
Transport Process ◽  
Point Of View ◽  
Intermodal Transport ◽  
Railway Transport ◽  
Repair Work ◽  
Passenger Traffic ◽  
Passenger Transportation ◽  
Transport Services ◽  
Principle Of Maximum

The organization of transport services for suburban routes during the periods of providing "windows" should be based on logistics approaches and the principle of maximum use of the possibilities of railway transport for the development of a given and predicted passenger traffic. Intermodal transport is the most progressive and efficient method of passenger transportation, which is most convenient and more understandable to a person from the point of view of the organization-the responsibility of one carrier for the entire transport process on the route.

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