scholarly journals Small-momentum expansion of heavy-quark correlators in the large-β0 limit and αs extractions

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Diogo Boito ◽  
Vicent Mateu ◽  
Marcus V. Rodrigues
Keyword(s):  
Heavy Quark ◽  
Strong Coupling ◽  
Sum Rules ◽  
Axial Vector ◽  
Vector Current ◽  
Higher Order ◽  
Lattice Data ◽  
Small Momentum ◽  
Pseudo Scalar

Abstract We calculate the small-momentum expansion of vector, axial-vector, scalar, and pseudo-scalar heavy-quark current correlators in the large-β0 limit of QCD, extending the analysis of Grozin and Sturm beyond the vector current. Our results are used to study the higher-order behaviour of dimensionless ratios of vector and pseudo-scalar moments used for the precise extraction of the strong coupling, αs, from relativistic quarkonium sum rules and lattice data, respectively. We show that these ratios benefit from a partial cancellation of the leading renormalon singularities. Our results can guide the design of combinations of moments with improved perturbative behaviour.

scholarly journals Analysis of the Zc(4200) as axial-vector molecule-like state

2015 ◽  
Vol 30 (30) ◽  
pp. 1550168 ◽  
Author(s):  
Zhi-Gang Wang
Keyword(s):  
Experimental Data ◽  
Sum Rules ◽  
Axial Vector ◽  
Vector Current ◽  
Axial Vector Current ◽  
Qcd Sum Rules ◽  
Color Octet ◽  
Type Molecule

In this paper, we assume the [Formula: see text] as the color octet–octet type axial-vector molecule-like state, and construct the color octet–octet type axial-vector current to study its mass and width with the QCD sum rules. The numerical values [Formula: see text] and [Formula: see text] are consistent with the experimental data [Formula: see text] and [Formula: see text], and support assigning the [Formula: see text] to be the color octet–octet type molecule-like state with [Formula: see text]. Furthermore, we discuss the possible assignments of the [Formula: see text], [Formula: see text] and [Formula: see text] as the diquark–antidiquark type tetraquark states with [Formula: see text].

TWIST-THREE DISTRIBUTION AMPLITUDES AND OCTET CURRENT DECAY CONSTANTS OF η AND η': A QCD SUM RULE APPROACH

2009 ◽  
Vol 18 (05n06) ◽  
pp. 1318-1323
Author(s):  
J. P. SINGH
Keyword(s):  
Sum Rules ◽  
Light Quark ◽  
Axial Vector ◽  
Vector Current ◽  
Axial Vector Current ◽  
Qcd Sum Rules ◽  
Sum Rule ◽  
Decay Constants ◽  
Current Decay ◽  
Rule Approach

We investigate twist-three distribution amplitudes (DAs) of η and η' using QCD sum rules. Zeroth moments of light quark DAs of η and η' are evaluated and compared with those found in other approaches. The decay constants of the octet axial vector current in the η and η' system are also estimated.

scholarly journals Heavy Quark Expansion of Λb→Λ*(1520) Form Factors beyond Leading Order

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 531
Author(s):  
Marzia Bordone
Keyword(s):  
Lattice Qcd ◽  
Heavy Quark ◽  
Form Factors ◽  
Higher Order ◽  
Leading Order ◽  
Lattice Data ◽  
Tensor Form ◽  
Higher Order Terms ◽  
First Time

I review the parametrisation of the full set of Λb→Λ*(1520) form factors in the framework of Heavy Quark Expansion, including next-to-leading-order O(αs) and, for the first time, next-to-leading-power O(1/mb) corrections. The unknown hadronic parameters are obtained by performing a fit to recent lattice QCD calculations. I investigate the compatibility of the Heavy Quark Expansion and the current lattice data, finding tension between these two approaches in the case of tensor and pseudo-tensor form factors, whose origin could come from an underestimation of the current lattice QCD uncertainties and higher order terms in the Heavy Quark Expansion.

scholarly journals QCD parameter correlations from heavy quarkonia

2018 ◽  
Vol 33 (10) ◽  
pp. 1850045 ◽  
Author(s):  
Stephan Narison
Keyword(s):  
Sum Rules ◽  
Axial Vector ◽  
Gluon Condensate ◽  
Sum Rule ◽  
Channel One ◽  
Vector Channel ◽  
Stability Point ◽  
Pseudo Scalar ◽  
First Time ◽  
Good Agreement

Correlations between the QCD coupling [Formula: see text], the gluon condensate [Formula: see text] and the [Formula: see text], [Formula: see text]-quark running masses [Formula: see text] in the [Formula: see text]-scheme are explicitly studied (for the first time) from the (axial-)vector and (pseudo)scalar charmonium and bottomium ratios of Laplace sum rules (LSR) evaluated at the [Formula: see text]-subtraction stability point where perturbative (PT) @N2LO, N3LO and [Formula: see text] @NLO corrections are included. Our results clarify the (apparent) discrepancies between different estimates of [Formula: see text] from [Formula: see text] sum rule and also show the sensitivity of the sum rules on the choice of the [Formula: see text]-subtraction scale which does not permit a high-precision estimate of [Formula: see text]. We obtain from the (axial-)vector [respectively (pseudo)scalar] channels: [Formula: see text] [respectively [Formula: see text] GeV4, [Formula: see text] [respectively 1266(16)] MeV and [Formula: see text] MeV. Combined with our recent determinations from vector channel, one obtains the average: [Formula: see text] MeV and [Formula: see text] MeV. Adding the two above values of the gluon condensate to different previous estimates in Table 1, one obtains the 2018 sum rule average: [Formula: see text] GeV4. The mass-splittings [Formula: see text] give @N2LO: [Formula: see text] in good agreement with the world average.

scholarly journals The fermionic universal one-loop effective action

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Sebastian A. R. Ellis ◽  
Jérémie Quevillon ◽  
Pham Ngoc Hoa Vuong ◽  
Tevong You ◽  
Zhengkang Zhang
Keyword(s):  
Path Integral ◽  
Effective Action ◽  
Covariant Derivative ◽  
Heavy Fermion ◽  
Axial Vector ◽  
Derivative Expansion ◽  
Universal Structure ◽  
Pseudo Scalar ◽  
Matching Techniques ◽  
Analytical Expressions

Abstract Recent development of path integral matching techniques based on the covariant derivative expansion has made manifest a universal structure of one-loop effective Lagrangians. The universal terms can be computed once and for all to serve as a reference for one-loop matching calculations and to ease their automation. Here we present the fermionic universal one-loop effective action (UOLEA), resulting from integrating out heavy fermions (Dirac or Majorana) with scalar, pseudo-scalar, vector and axial-vector couplings. We also clarify the relation of the new terms computed here to terms previously computed in the literature and those that remain to complete the UOLEA. Our results can be readily used to efficiently obtain analytical expressions for effective operators arising from heavy fermion loops [13].

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