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.

Bc → J/ψ tensor form factors at large momentum recoil

2021 ◽  
pp. 2150135
Author(s):  
Dandan Shen ◽  
Huimin Ren ◽  
Fan Wu ◽  
Ruilin Zhu
Keyword(s):  
Form Factors ◽  
Distance Matrix ◽  
Relativistic Correction ◽  
Large Momentum ◽  
Matrix Elements ◽  
Leading Order ◽  
Lattice Data ◽  
Tensor Form ◽  
Long Distance ◽  
Current Form

We present a next-to-leading order (NLO) relativistic correction to [Formula: see text] tensor form factors within nonrelativistic QCD (NRQCD). We also consider complete Dirac bilinears [Formula: see text] with [Formula: see text] matrices [Formula: see text] in the [Formula: see text] transition. The relation among different current form factors is given and it shows that symmetries emerge in the heavy bottom quark limit. For a phenomenological extension, we propose to extract the long-distance matrix elements (LDMEs) for [Formula: see text] meson from the recent HPQCD lattice data and the NLO form factors at large momentum recoil.

scholarly journals Nucleon’s energy–momentum tensor form factors in light-cone QCD

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
K. Azizi ◽  
U. Özdem
Keyword(s):  
Perturbation Theory ◽  
Lattice Qcd ◽  
Chiral Perturbation Theory ◽  
Light Cone ◽  
Energy Momentum Tensor ◽  
Form Factors ◽  
Momentum Tensor ◽  
Tensor Form ◽  
Chiral Perturbation ◽  
Theoretical Predictions

Abstract We use the energy–momentum tensor (EMT) current to compute the EMT form factors of the nucleon in the framework of the light cone QCD sum rule formalism. In the calculations, we employ the most general form of the nucleon’s interpolating field and use the distribution amplitudes (DAs) of the nucleon with two sets of the numerical values of the main input parameters entering the expressions of the DAs. The directly obtained results from the sum rules for the form factors are reliable at $$ Q^2\ge 1$$Q2≥1 GeV$$^2 $$2: to extrapolate the results to include the zero momentum transfer squared with the aim of estimation of the related static physical quantities, we use some fit functions for the form factors. The numerical computations show that the energy–momentum tensor form factors of the nucleon can be well fitted to the multipole fit form. We compare the results obtained for the form factors at $$ Q^2=0 $$Q2=0 with the existing theoretical predictions as well as experimental data on the gravitational form factor d$$_1^q(0)$$1q(0). For the form factors M$$_2^q (0)$$2q(0) and J$$^q(0)$$q(0) a consistency among the theoretical predictions is seen within the errors: our results are nicely consistent with the Lattice QCD and chiral perturbation theory predictions. However, there are large discrepancies among the theoretical predictions on d$$_1^q(0)$$1q(0). Nevertheless, our prediction is in accord with the JLab data as well as with the results of the Lattice QCD, chiral perturbation theory and KM15-fit. Our fit functions well define most of the JLab data in the interval $$ Q^2\in [0,0.4]$$Q2∈[0,0.4] GeV$$^2 $$2, while the Lattice results suffer from large uncertainties in this region. As a by-product, some mechanical properties of the nucleon like the pressure and energy density at the center of nucleon as well as its mechanical radius are also calculated and their results are compared with other existing theoretical predictions.

scholarly journals Electromagnetic transition form factors, E2/M1 and C2/M1 ratios of the baryon decuplet

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
June-Young Kim ◽  
Hyun-Chul Kim
Keyword(s):  
Lattice Qcd ◽  
Empirical Data ◽  
Pion Mass ◽  
Form Factors ◽  
The Self ◽  
Transition Form ◽  
Lattice Data ◽  
Electromagnetic Transition ◽  
Self Consistent ◽  
Good Agreement

AbstractWe investigate the electromagnetic transition form factors of the baryon decuplet to the baryon octet, based on the self-consistent SU(3) chiral quark-soliton model, taking into account the effects of explicit breaking of flavor SU(3) symmetry. We emphasize the $$Q^2$$ Q 2 dependence of the electromagnetic $$N\rightarrow \Delta $$ N → Δ transition form factors and the ratios of E2/M1 and C2/M1 in comparison with the experimental and empirical data. In order to compare the present results of the electromagnetic transition form factors of the $$N\rightarrow \Delta $$ N → Δ with those from lattice QCD, we evaluate the form factors with the pion mass deviated from its physical value. The results of the E2/M1 and C2/M1 ratios are in good agreement with the lattice data. We also present the results of the electromagnetic transition form factors for the decuplet to the octet transitions.

scholarly journals HQET form factors for Bs → Klv decays beyond leading order

2018 ◽  
Vol 175 ◽  
pp. 13025
Author(s):  
Debasish Banerjee ◽  
Mateusz Koren ◽  
Hubert Simma ◽  
Rainer Sommer
Keyword(s):  
Form Factor ◽  
Heavy Quark ◽  
Form Factors ◽  
Good Control ◽  
Effective Theory ◽  
Ratio Method ◽  
Heavy Quark Effective Theory ◽  
Leading Order ◽  
Decay Form ◽  
Static Order

We compute semi-leptonic Bs decay form factors using Heavy Quark Effective Theory on the lattice. To obtain good control of the 1 /mb expansion, one has to take into account not only the leading static order but also the terms arising at O (1/mb): kinetic, spin and current insertions. We show results for these terms calculated through the ratio method, using our prior results for the static order. After combining them with non-perturbative HQET parameters they can be continuum-extrapolated to give the QCD form factor correct up to O (1/[see formula in PDF]) corrections and without O (αs(mb)n) corrections.

scholarly journals Improvement of heavy-heavy current for calculation of B̅ → D(*)lv̅ form factors using Oktay-Kronfeld heavy quarks

2018 ◽  
Vol 175 ◽  
pp. 14010 ◽  
Author(s):  
Jon A. Bailey ◽  
Yong-Chull Jang ◽  
Weonjong Lee ◽  
Jaehoon Leem
Keyword(s):  
Matrix Element ◽  
Lattice Qcd ◽  
Heavy Quark ◽  
Recent Progress ◽  
Form Factors ◽  
Heavy Quarks ◽  
Power Counting ◽  
Ckm Matrix ◽  
Combining Data ◽  
Discretization Errors

The CKM matrix element |Vcb| can be extracted by combining data from experiments with lattice QCD results for the semileptonic form factors for the B̅ → D(*)lv̅ decays. The Oktay-Kronfeld (OK) action was designed to reduce heavy-quark discretization errors to below 1%, or through O(λ3) in HQET power counting. Here we describe recent progress on bottom-to-charm currents improved to the same order in HQET as the OK action, and correct formerly reported results of our matching calculations, in which the operator basis was incomplete.

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 Radiative decays of heavy-light mesons and the $$ {f}_{H,{H}^{\ast },{H}_1}^{(T)} $$ decay constants

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Ben Pullin ◽  
Roman Zwicky
Keyword(s):  
Sum Rules ◽  
Form Factors ◽  
Radiative Decays ◽  
Matrix Elements ◽  
Leading Order ◽  
Sum Rule ◽  
Decay Constants ◽  
Leptonic Decays ◽  
Shell Matrix ◽  
First Time

Abstract The on-shell matrix elements, or couplings $$ {g}_{H{H}^{\ast}\left({H}_1\right)\upgamma} $$ g H H ∗ H 1 γ , describing the $$ B{(D)}_q^{\ast } $$ B D q ∗ → B(D)qγ and B1q → Bqγ (q = u, d, s) radiative decays, are determined from light-cone sum rules at next-to-leading order for the first time. Two different interpolating operators are used for the vector meson, providing additional robustness to our results. For the D*-meson, where some rates are experimentally known, agreement is found. The couplings are of additional interest as they govern the lowest pole residue in the B(D) → γ form factors which in turn are connected to QED-corrections in leptonic decays B(D) → ℓ$$ \overline{\nu} $$ ν ¯ . Since the couplings and residues are related by the decay constants $$ {f}_{H^{\ast}\left({H}_1\right)} $$ f H ∗ H 1 and $$ {f}_{H^{\ast}\left({H}_1\right)}^T $$ f H ∗ H 1 T , we determine them at next-leading order as a by-product. The quantities $$ \left\{{f}_{H^{\ast}}^T,{f}_{H_1}^T\right\} $$ f H ∗ T f H 1 T have not previously been subjected to a QCD sum rule determination. All results are compared with the existing experimental and theoretical literature.

scholarly journals Double parton correlations in mesons within AdS/QCD soft-wall models: a first comparison with lattice data

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
Matteo Rinaldi
Keyword(s):  
Lattice Qcd ◽  
Parton Distribution ◽  
General Procedure ◽  
Form Factors ◽  
Distribution Functions ◽  
Lattice Data ◽  
Parton Distribution Functions ◽  
Model Calculations ◽  
Double Parton Scattering ◽  
Soft Wall

Abstract Double parton distribution functions (dPDFs), entering the double parton scattering (DPS) cross section, are unknown fundamental quantities encoding new interesting properties of hadrons. Here, the pion dPDFs are investigated within different holographic QCD quark models in order to access their basic features. Results of the calculations obtained within the AdS/QCD soft-wall approach, have been compared with predictions of lattice QCD evaluations of the pion two-current correlation functions. The present analysis confirms that double parton correlations, affecting dPDFs, are very important and not direct accessible from generalised parton distribution functions and electromagnetic form factors. The comparison between lattice data and quark model calculations unveils the relevance of the contributions of high partonic Fock states in the pion. Nevertheless, by using a complete general procedure, results of lattice QCD have been used, for the first time, to estimate the mean value of the so called $$\sigma _{eff}$$σeff, a relevant experimental observable for DPS processes. In addition, the results of the first calculations of the $$\rho $$ρ meson dPDFs are discussed in order to make predictions.

scholarly journals The $$ \overline{B} $$ → π form factors from QCD and their impact on |Vub|

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Domagoj Leljak ◽  
Blaženka Melić ◽  
Danny van Dyk
Keyword(s):  
Form Factor ◽  
Lattice Qcd ◽  
Sum Rules ◽  
Semileptonic Decay ◽  
Form Factors ◽  
Scalar Form Factor ◽  
Small Momentum Transfer ◽  
Scalar Form ◽  
Sum Rule ◽  
First Time

Abstract We revisit light-cone sum rules with pion distribution amplitudes to determine the full set of local $$ \overline{B} $$ B ¯ → π form factors. To this end, we determine all duality threshold parameters from a Bayesian fit for the first time. Our results, obtained at small momentum transfer q2, are extrapolated to large q2 where they agree with precise lattice QCD results. We find that a modification to the commonly used BCL parametrization is crucial to interpolate the scalar form factor between the two q2 regions. We provide numerical results for the form factor parameters — including their covariance — based on simultaneous fit of all three form factors to both the sum rule and lattice QCD results. Our predictions for the form factors agree well with measurements of the q2 spectrum of the semileptonic decay $$ {\overline{B}}^0\to {\pi}^{+}{\mathrm{\ell}}^{-}{\overline{\nu}}_{\mathrm{\ell}} $$ B ¯ 0 → π + ℓ − ν ¯ ℓ . From the world average of the latter we obtain |Vub| = (3.77 ± 0.15) · 10−3, which is in agreement with the most recent inclusive determination at the 1 σ level.

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