Palestrante
Descrição
Hadronic tau decays are one of the cleanest processes to study perturbative Quantum Chromodynamics (QCD). Combining the theoretical description of $\tau\to\text{hadrons}+\nu_\tau$ with the experimental data, it is possible to extract the strong coupling, $\alpha_s$, with good precision. The perturbative contribution is obtained as a weighted integral on the complex contour of the perturbartive expansion of the Adler function in the chiral limit, which nowadays is exactly known up to $\alpha_s^4$. To extract the coupling we need to choose the weight function so as to reduce non-perturbative contributions. The work of Ref.(1) has shown that some of the weight functions employed in the literature may have a bad perturbative behaviour, and are therefore not an ideal choice in precise $\alpha_s$ analyses. The main purpose of this work is to explain why some weight functions are better behaved than others in terms of the analytic structure of their Laplace-Borel transform, in particular,in terms of the singularities of the transform, known in this context as renormalons. We will investigate this problem in the large-$\beta_0$ limit of QCD, where the perturbative expansion is known to all orders. Next we will show that using a modified Borel-Laplace transform (2) we can simplify the analytic structure of renormalons in full QCD. Finally we will use a description of higher-orders perturbative coefficients that we developed recently using the method of Padé Approximants (3)to study in detail the perturbative behaviour of the weight functions QCD.
Referências
1 BENEKE, M.;BOITO, D.; JAMIN, M. Perturbative expansion of tau hadronic spectral function moments and alpha_s extractions. Journal High Energy Physics, v.1301, p.125 2013 doi:10.1007/JHEP01(2013)125.
2 BROWN, L. S.;YAFFE, G.;ZAHAI, C. X. Large order perturbation theory for the electromagnetic current current correlation function. Physical Review D, v. 46,p.4712,1992. doi:10.1103/PhysRevD.46.4712.
3 BOITO, D.;MASJUAN, P.; OLIANI, F. Higher-order QCD corrections to hadronic τ decays from Padé approximants. Journal High Energy Physics, v. 1808, p.075,2018. doi:10.1007/JHEP08(2018)075.
| Apresentação do trabalho acadêmico para o público geral | Não |
|---|---|
| Subárea | Física de Altas Energias, Partículas e Campos |
