scholarly journals QUASILOCAL QUARK MODELS AS EFFECTIVE THEORY OF NON-PERTURBATIVE QCD

2005 ◽  
Vol 20 (08n09) ◽  
pp. 1850-1854 ◽  
Author(s):  
A. A. ANDRIANOV ◽  
V. A. ANDRIANOV
Keyword(s):  
Perturbative Qcd ◽  
Chiral Symmetry ◽  
Sum Rules ◽  
Axial Vector ◽  
Effective Theory ◽  
Operator Product ◽  
Decay Constants ◽  
Intermediate Energies ◽  
Quark Models ◽  
Meson States

We consider the Quasilocal Quark Model of NJL type (QNJLM) as an effective theory of non-perturbative QCD including scalar (S), pseudoscalar (P), vector (V) and axial-vector (A) four-fermion interaction with derivatives. In the presence of a strong attraction in the scalar channel the chiral symmetry is spontaneously broken and as a consequence the composite meson states are generated in all channels. With the help of Operator Product Expansion the appropriate set of Chiral Symmetry Restoration (CSR) Sum Rules in these channels are imposed as matching conditions to QCD at intermediate energies. The mass spectrum and some decay constants for ground and excited meson states are calculated.

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 Quark–hadron duality: Pinched kernel approach

2016 ◽  
Vol 31 (27) ◽  
pp. 1630026 ◽  
Author(s):  
C. A. Dominguez ◽  
L. A. Hernandez ◽  
K. Schilcher ◽  
H. Spiesberger
Keyword(s):  
Perturbative Qcd ◽  
Sum Rules ◽  
Axial Vector ◽  
Finite Energy ◽  
Aleph Collaboration ◽  
Spectral Functions ◽  
Vector Channel ◽  
Kernel Approach ◽  
Model Independent ◽  
Hadron Duality

Hadronic spectral functions measured by the ALEPH collaboration in the vector and axial-vector channels are used to study potential quark–hadron duality violations (DV). This is done entirely in the framework of pinched kernel finite energy sum rules (FESR), i.e. in a model independent fashion. The kinematical range of the ALEPH data is effectively extended up to s = 10 GeV2 by using an appropriate kernel, and assuming that in this region the spectral functions are given by perturbative QCD. Support for this assumption is obtained by using e[Formula: see text] e[Formula: see text] annihilation data in the vector channel. Results in both channels show a good saturation of the pinched FESR, without further need of explicit models of DV.

scholarly journals Determination of perturbative QCD coupling from ALEPH $$\tau $$ decay data using pinched Borel–Laplace and Finite Energy Sum Rules

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
César Ayala ◽  
Gorazd Cvetič ◽  
Diego Teca
Keyword(s):  
Perturbation Theory ◽  
Perturbative Qcd ◽  
Sum Rules ◽  
Finite Energy ◽  
Operator Product ◽  
Decay Data ◽  
Fixed Order ◽  
Principal Value ◽  
Adler Function

AbstractWe present a determination of the perturbative QCD (pQCD) coupling using the V+A channel ALEPH $$\tau $$ τ -decay data. The determination involves the double-pinched Borel–Laplace Sum Rules and Finite Energy Sum Rules. The theoretical basis is the Operator Product Expansion (OPE) of the V+A channel Adler function in which the higher order terms of the leading-twist part originate from a model based on the known structure of the leading renormalons of this quantity. The applied evaluation methods are contour-improved perturbation theory (CIPT), fixed-order perturbation theory (FOPT), and Principal Value of the Borel resummation (PV). All the methods involve truncations in the order of the coupling. In contrast to the truncated CIPT method, the truncated FOPT and PV methods account correctly for the suppression of various renormalon contributions of the Adler function in the mentioned sum rules. The extracted value of the $${\overline{\mathrm{MS}}}$$ MS ¯ coupling is $$\alpha _s(m_{\tau }^2) = 0.3116 \pm 0.0073$$ α s ( m τ 2 ) = 0.3116 ± 0.0073 [$$\alpha _s(M_Z^2)=0.1176 \pm 0.0010$$ α s ( M Z 2 ) = 0.1176 ± 0.0010 ] for the average of the FOPT and PV methods, which we regard as our main result. On the other hand, if we include in the average also the CIPT method, the resulting values are significantly higher, $$\alpha _s(m_{\tau }^2) = 0.3194 \pm 0.0167$$ α s ( m τ 2 ) = 0.3194 ± 0.0167 [$$\alpha _s(M_Z^2)=0.1186 \pm 0.0021$$ α s ( M Z 2 ) = 0.1186 ± 0.0021 ].

scholarly journals The ground states and the first radially excited states of D-wave vector ρ and ϕ mesons

2021 ◽  
Author(s):  
Guo-Liang Yu ◽  
Zhi-Gang Wang ◽  
Xiu-Wu Wang ◽  
Hui-Juan Wang
Keyword(s):  
Excited States ◽  
Wave Vector ◽  
Operator Product Expansion ◽  
Sum Rules ◽  
Ground States ◽  
Operator Product ◽  
Decay Constants ◽  
Vector Formula ◽  
Vacuum Condensates ◽  
D Wave

In this paper, we first derive two QCD sum rules QCDSR I and QCDSR II which are, respectively, used to extract observable quantities of the ground states and the first radially excited states of the D-wave vector [Formula: see text] and [Formula: see text] mesons. In our calculations, we consider the contributions of vacuum condensates up to dimension-7 in the operator product expansion. The predicted masses for [Formula: see text] [Formula: see text] meson and [Formula: see text] [Formula: see text] meson are consistent well with the experimental data of [Formula: see text]([Formula: see text]) and [Formula: see text]([Formula: see text]), respectively. Besides, our analysis indicates that it is reliable to assign the recent reported [Formula: see text]([Formula: see text]) state as the [Formula: see text] [Formula: see text] meson. Finally, we obtain the decay constants of these states with QCDSR I and QCDSR II. These predictions are helpful not only to reveal the structure of the newly observed [Formula: see text]([Formula: see text]) state, but also to establish [Formula: see text] meson and [Formula: see text] meson families.

scholarly journals XYZ-SU3 breakings from Laplace sum rules at higher orders

2018 ◽  
Vol 33 (16) ◽  
pp. 1850082 ◽  
Author(s):  
R. Albuquerque ◽  
S. Narison ◽  
D. Rabetiarivony ◽  
G. Randriamanatrika
Keyword(s):  
Sum Rules ◽  
Chiral Limit ◽  
Axial Vector ◽  
Operator Product ◽  
Leading Order ◽  
Spectral Functions ◽  
Quark State ◽  
Future Data ◽  
The Masses ◽  
Spectral Sum Rules

We present new compact integrated expressions of SU3 breaking corrections to QCD spectral functions of heavy–light molecules and four-quark [Formula: see text]-like states at lowest order (LO) of perturbative (PT) QCD and up to [Formula: see text] condensates of the Operator Product Expansion (OPE). Including next-to-next-to-leading order (N2LO) PT corrections in the chiral limit and next-to-leading order (NLO) SU3 PT corrections, which we have estimated by assuming the factorization of the four-quark spectral functions, we improve previous LO results for the [Formula: see text]-like masses and decay constants from QCD spectral sum rules (QSSR). Systematic errors are estimated from a geometric growth of the higher order PT corrections and from some partially known [Formula: see text] nonperturbative contributions. Our optimal results, based on stability criteria, are summarized in Tables 18–21 while the [Formula: see text] and [Formula: see text] channels are compared with some existing LO results in Table 22. One can note that, in most channels, the SU3 corrections on the meson masses are tiny: [Formula: see text] (respectively [Formula: see text]) for the [Formula: see text] (respectively [Formula: see text])-quark channel but can be large for the couplings ([Formula: see text]). Within the lowest dimension currents, most of the [Formula: see text] and [Formula: see text] states are below the physical thresholds while our predictions cannot discriminate a molecule from a four-quark state. A comparison with the masses of some experimental candidates indicates that the [Formula: see text] [Formula: see text] might have a large [Formula: see text] molecule component while an interpretation of the [Formula: see text] candidates as four-quark ground states is not supported by our findings. The [Formula: see text] [Formula: see text] and [Formula: see text] are compatible with the [Formula: see text], [Formula: see text] molecules and/or with the axial-vector [Formula: see text] four-quark ground state. Our results for the [Formula: see text], [Formula: see text] and for different beauty states can be tested in the future data. Finally, we revisit our previous estimates1 for the [Formula: see text] and [Formula: see text] and present new results for the [Formula: see text].

scholarly journals The D∗Dπ and B∗Bπ couplings from light-cone sum rules

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Alexander Khodjamirian ◽  
Blaženka Melić ◽  
Yu-Ming Wang ◽  
Yan-Bing Wei
Keyword(s):  
Correlation Function ◽  
Lattice Qcd ◽  
Light Cone ◽  
Sum Rules ◽  
Analytical Form ◽  
Operator Product ◽  
Decay Constants ◽  
Meson Coupling ◽  
Double Dispersion ◽  
First Time

Abstract We revisit the calculation of the strong couplings D∗Dπ and B∗Bπ from the QCD light-cone sum rules using the pion light-cone distribution amplitudes. The accuracy of the correlation function, calculated from the operator product expansion near the light-cone, is upgraded by taking into account the gluon radiative corrections to the twist-3 terms. The double spectral density of the correlation function, including the twist-2, 3 terms at $$ \mathcal{O}\left({\alpha}_s\right) $$ O α s and the twist-4 LO terms, is presented in an analytical form for the first time. This form allows us to use various versions of the quark-hadron duality regions in the double dispersion relation underlying the sum rules. We predict $$ {g}_{D^{\ast } D\pi}={14.1}_{-1.2}^{+1.3} $$ g D ∗ Dπ = 14.1 − 1.2 + 1.3 and $$ {g}_{B^{\ast } B\pi}={30.0}_{-2.4}^{+2.6} $$ g B ∗ Bπ = 30.0 − 2.4 + 2.6 when the decay constants of heavy mesons entering the light-cone sum rule are taken from lattice QCD results. We compare our results with the experimental value for the charmed meson coupling and with the lattice QCD calculations.

scholarly journals XYZ-like spectra from Laplace sum rule at N2LO in the chiral limit

2016 ◽  
Vol 31 (36) ◽  
pp. 1650196 ◽  
Author(s):  
R. Albuquerque ◽  
S. Narison ◽  
F. Fanomezana ◽  
A. Rabemananjara ◽  
D. Rabetiarivony ◽  
...  
Keyword(s):  
Sum Rules ◽  
Chiral Limit ◽  
Operator Product ◽  
Theoretical Studies ◽  
Leading Order ◽  
Spectral Functions ◽  
Decay Constants ◽  
Heavy Quark Mass ◽  
The Masses ◽  
Spectral Sum Rules

We present new compact integrated expressions of QCD spectral functions of heavy-light molecules and four-quark [Formula: see text]-like states at lowest order (LO) of perturbative (PT) QCD and up to [Formula: see text] condensates of the Operator Product Expansion (OPE). Then, by including up to next-to-next leading order (N2LO) PT QCD corrections, which we have estimated by assuming the factorization of the four-quark spectral functions, we improve previous LO results from QCD spectral sum rules (QSSR), on the [Formula: see text]-like masses and decay constants which suffer from the ill-defined heavy quark mass. PT N3LO corrections are estimated using a geometric growth of the PT series and are included in the systematic errors. Our optimal results based on stability criteria are summarized in Tables 11–14 and compared, in Sec. 10, with experimental candidates and some LO QSSR results. We conclude that the masses of the [Formula: see text] observed states are compatible with (almost) pure [Formula: see text], [Formula: see text] molecule or/and four-quark states. The ones of the [Formula: see text], [Formula: see text] molecule/four-quark states are about 1.5 GeV above the [Formula: see text] mesons experimental candidates and hadronic thresholds. We also find that the couplings of these exotics to the associated interpolating currents are weaker than that of ordinary [Formula: see text] mesons [Formula: see text] and may behave numerically as [Formula: see text] (respectively [Formula: see text]) for the [Formula: see text], [Formula: see text] (respectively [Formula: see text], [Formula: see text]) states which can stimulate further theoretical studies of these decay constants.

scholarly journals Triply-charmed hexaquark states with the QCD sum rules

2020 ◽  
Vol 35 (14) ◽  
pp. 2050073
Author(s):  
Zhi-Gang Wang
Keyword(s):  
Spectral Density ◽  
Ground State ◽  
Operator Product Expansion ◽  
Sum Rules ◽  
Axial Vector ◽  
Energy Scale ◽  
Operator Product ◽  
Pole Contribution ◽  
Qcd Sum Rules ◽  
The Masses

In this paper, we construct the charmed-diquark–charmed-diquark–charmed-diquark-type current to study the axial vector triply-charmed hexaquark state with the QCD sum rules in details. In calculations, we take the energy scale formula [Formula: see text] to choose the pertinent energy scale of the QCD spectral density so as to enhance the pole contribution and improve the convergent behavior of the operator product expansion. If the spin-breaking effects are small for the triply-charmed hexaquark states, the ground state hexaquark states with [Formula: see text], [Formula: see text] and [Formula: see text] are estimated to have the masses about 5.8 GeV and narrow widths.

scholarly journals Decay constants and masses of light tensor mesons (JP = 2+)

2015 ◽  
Vol 30 (18n19) ◽  
pp. 1550106
Author(s):  
R. Khosravi ◽  
D. Hatami
Keyword(s):  
Standard Model ◽  
Operator Product Expansion ◽  
Sum Rules ◽  
Operator Product ◽  
Qcd Sum Rules ◽  
Decay Constants ◽  
Quantum Numbers ◽  
The Standard Model ◽  
The Masses

The masses and decay constants of the light tensor mesons were calculated with quantum numbers [Formula: see text] in the framework of the QCD sum rules in the standard model. The non perturbative contributions up to dimension-5 are considered as important terms of the operator product expansion.

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