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 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.

scholarly journals Masses and decay constants of the η and η′ mesons from lattice QCD

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
◽  
Gunnar S. Bali ◽  
Vladimir Braun ◽  
Sara Collins ◽  
Andreas Schäfer ◽  
...  
Keyword(s):  
Quark Mass ◽  
Matrix Elements ◽  
Leading Order ◽  
Decay Constants ◽  
The Matrix ◽  
Spatial Lattice ◽  
Quark Mass Dependence ◽  
The Masses ◽  
First Time ◽  
Energy Constants

Abstract We determine the masses, the singlet and octet decay constants as well as the anomalous matrix elements of the η and η′ mesons in Nf = 2 + 1 QCD. The results are obtained using twenty-one CLS ensembles of non-perturbatively improved Wilson fermions that span four lattice spacings ranging from a ≈ 0.086 fm down to a ≈ 0.050 fm. The pion masses vary from Mπ = 420 MeV to 126 MeV and the spatial lattice extents Ls are such that LsMπ ≳ 4, avoiding significant finite volume effects. The quark mass dependence of the data is tightly constrained by employing two trajectories in the quark mass plane, enabling a thorough investigation of U(3) large-Nc chiral perturbation theory (ChPT). The continuum limit extrapolated data turn out to be reasonably well described by the next-to-leading order ChPT parametrization and the respective low energy constants are determined. The data are shown to be consistent with the singlet axial Ward identity and, for the first time, also the matrix elements with the topological charge density are computed. We also derive the corresponding next-to-leading order large-Nc ChPT formulae. We find F8 = 115.0(2.8) MeV, θ8 = −25.8(2.3)°, θ0 = −8.1(1.8)° and, in the $$ \overline{\mathrm{MS}} $$ MS ¯ scheme for Nf = 3, F0(μ = 2 GeV) = 100.1(3.0) MeV, where the decay constants read $$ {F}_{\eta}^8 $$ F η 8 = F8 cos θ8, $$ {F}_{\eta \prime}^8 $$ F η ′ 8 = F8 sin θ8, $$ {F}_{\eta}^0 $$ F η 0 = −F0 sin θ0 and $$ {F}_{\eta \prime}^0 $$ F η ′ 0 = F0 cos θ0. For the gluonic matrix elements, we obtain aη(μ = 2 GeV) = 0.0170(10) GeV3 and aη′(μ = 2 GeV) = 0.0381(84) GeV3, where statistical and all systematic errors are added in quadrature.

scholarly journals Light-cone sum rules for proton decay

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Ulrich Haisch ◽  
Amando Hala
Keyword(s):  
Lattice Qcd ◽  
Light Cone ◽  
Sum Rules ◽  
State Of The Art ◽  
Form Factors ◽  
Baryon Number ◽  
Proton Decay ◽  
Matrix Elements ◽  
Decay Channels ◽  
Systematic Uncertainties

Abstract We estimate the form factors that parametrise the hadronic matrix elements of proton-to-pion transitions with the help of light-cone sum rules. These form factors are relevant for semi-leptonic proton decay channels induced by baryon-number violating dimension-six operators, as typically studied in the context of grand unified theories. We calculate the form factors in a kinematical regime where the momentum transfer from the proton to the pion is space-like and extrapolate our final results to the regime that is relevant for proton decay. In this way, we obtain estimates for the form factors that show agreement with the state-of-the-art calculations in lattice QCD, if systematic uncertainties are taken into account. Our work is a first step towards calculating more involved proton decay channels where lattice QCD results are not available at present.

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.

RADIATIVE DECAYS OF HEAVY MESON IN THE LIGHT CONE QCD SUM RULE

2000 ◽  
Vol 15 (04) ◽  
pp. 601-608
Author(s):  
H. ROUTH
Keyword(s):  
Light Cone ◽  
D Mesons ◽  
Branching Ratio ◽  
Form Factors ◽  
Heavy Meson ◽  
Radiative Decays ◽  
Long Distance ◽  
Sum Rule ◽  
Penguin Contribution ◽  
Decay Modes

The long-distance contribution of heavy B and D mesons are calculated in the light cone QCD sum rule. Here I have discussed both the parity conserving and parity violating form factors in the radiative decays of B and D mesons e.g. B*, B**, [Formula: see text], D*, D** and [Formula: see text] mesons. I have studied the decay of type P → Vγ and estimated the light cone QCD sum rule form factors and the branching ratio for various decay modes of B and D mesons. Although the short-distance electromagnetic Penguin contribution is the dominant contribution in the P → Vγ decay, it is also necessary to take into account the long distance contribution for completeness of study of the decays discussed in the text.

scholarly journals QCD sum rules analysis of weak decays of doubly heavy baryons: the $$b\rightarrow c$$ processes

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Zhi-Peng Xing ◽  
Zhen-Xing Zhao
Keyword(s):  
Correlation Functions ◽  
Sum Rules ◽  
Form Factors ◽  
Final States ◽  
Qcd Sum Rules ◽  
Leptonic Decays ◽  
Weak Decays ◽  
Heavy Baryons ◽  
Point Correlation ◽  
Comprehensive Study

AbstractA comprehensive study of $$b\rightarrow c$$ b → c weak decays of doubly heavy baryons is presented in this paper. The transition form factors as well as the pole residues of the initial and final states are respectively obtained by investigating the three-point and two-point correlation functions in QCD sum rules. Contributions from up to dimension-6 operators are respectively considered for the two-point and three-point correlation functions. The obtained form factors are then applied to a phenomenological analysis of semi-leptonic decays.

scholarly journals Mass Spectra and Decay Constants of Heavy-Light Mesons: A Case Study of QCD Sum Rules and Quark Model

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Halil Mutuk
Keyword(s):  
Quark Model ◽  
Mass Spectra ◽  
Sum Rules ◽  
Theoretical Studies ◽  
Sum Rule ◽  
Decay Constants ◽  
Oscillator Wave Function ◽  
Light Mesons ◽  
Harmonic Oscillator Wave Function

We visited mass spectra and decay constants of pseudoscalar and vector heavy-light mesons (B, Bs, D, and DS) in the framework of QCD sum rule and quark model. The harmonic oscillator wave function was used in quark model while a simple interpolating current was used in QCD sum rule calculation. We obtained good results in accordance with the available experimental data and theoretical studies.

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.

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