scholarly journals Tensor form factor for the D → π(K) transitions with Twisted Mass fermions.

2018 ◽  
Vol 175 ◽  
pp. 13022
Author(s):  
Vittorio Lubicz ◽  
Lorenzo Riggio ◽  
Giorgio Salerno ◽  
Silvano Simula ◽  
Cecilia Tarantino
Keyword(s):  
Form Factor ◽  
Matrix Element ◽  
Form Factors ◽  
Vector Current ◽  
Hadronic Matrix Element ◽  
Tensor Form ◽  
Scalar Form ◽  
Mass Collaboration ◽  
Twisted Mass ◽  
Tensor Current

We present a preliminary lattice calculation of the D → π and D → K tensor form factors fT (q2) as a function of the squared 4-momentum transfer q2. ETMC recently computed the vector and scalar form factors f+(q2) and f0(q2) describing D → π(K)lv semileptonic decays analyzing the vector current and the scalar density. The study of the weak tensor current, which is directly related to the tensor form factor, completes the set of hadronic matrix element regulating the transition between these two pseudoscalar mesons within and beyond the Standard Model where a non-zero tensor coupling is possible. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 + 1 + 1 flavors of dynamical quarks. We simulated at three different values of the lattice spacing and with pion masses as small as 210 MeV and with the valence heavy quark in the mass range from ≃ 0.7 mc to ≃ 1.2mc. The matrix element of the tensor current are determined for a plethora of kinematical conditions in which parent and child mesons are either moving or at rest. As for the vector and scalar form factors, Lorentz symmetry breaking due to hypercubic effects is clearly observed in the data. We will present preliminary results on the removal of such hypercubic lattice effects.

scholarly journals D → π and D → K semileptonic form factors with Nf = 2 + 1 + 1 twisted mass fermions

2018 ◽  
Vol 175 ◽  
pp. 13026
Author(s):  
Vittorio Lubicz ◽  
Lorenzo Riggio ◽  
Giorgio Salerno ◽  
Silvano Simula ◽  
Cecilia Tarantino
Keyword(s):  
Pion Mass ◽  
Form Factors ◽  
Kinematical Region ◽  
Matrix Elements ◽  
Scalar Form ◽  
Mass Collaboration ◽  
Twisted Mass ◽  
The Matrix ◽  
Additional Form

We present a lattice determination of the vector and scalar form factors of the D → π(K)lv semileptonic decays, which are relevant for the extraction of the CKM matrix elements |Vcd| and |Vcs| from experimental data. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 + 1 +1 flavors of dynamical quarks. We simulated at three different values of the lattice spacing and with pion masses as small as 210 MeV. The matrix elements of both vector and scalar currents are determined for a plenty of kinematical conditions in which parent and child mesons are either moving or at rest. Lorentz symmetry breaking due to hypercubic effects is clearly observed in the data and included in the decomposition of the current matrix elements in terms of additional form factors. After the extrapolations to the physical pion mass and to the continuum limit the vector and scalar form factors are determined in the whole kinematical region from q2 = 0 up to [see formula in PDF] accessible in the experiments, obtaining a good overall agreement with experiments, except in the region at high values of q2 where some deviations are visible.

scholarly journals THE ROLE OF $K^*_0(1430)$ IN D → PK AND τ → KPντ DECAYS

1999 ◽  
Vol 14 (26) ◽  
pp. 4161-4175 ◽  
Author(s):  
S. FAJFER ◽  
J. ZUPAN
Keyword(s):  
Experimental Data ◽  
Form Factor ◽  
Matrix Element ◽  
Scalar Meson ◽  
Final State Interaction ◽  
Form Factors ◽  
Decay Rates ◽  
Scalar Form Factor ◽  
Meson Resonance ◽  
Scalar Form

We consider the scalar form factor in the weak current matrix element <PK|jμ|0>, P=π, η, η′. It obtains the contributions from the scalar meson resonance [Formula: see text] and from the scalar projection of the vector meson K*(892) resonance. We analyze decay amplitudes of the Cabibbo suppressed decays D → KP, P=π, η, η′ using the factorization approach. The form factors of the relevant matrix elements are described by assuming the dominance of nearby resonances. The annihilation contribution in these decays arises from the matrix element <PK|jμ|0>. All the required parameters are experimentally known except the scalar meson [Formula: see text] decay constant. We fit the decay amplitudes and we find that final state interaction improves the agreement with the experimental data. Then we extract bounds on scalar form factor parameters and compare them with the experimental data obtained in the analyses of K→πeνe and K→πμνμ. The same scalar form factor is present in the τ → KPντ decay, with P=π, η, η′. Using the obtained bounds we investigate the significance of the scalar meson form factor in the τ→ KPντ, P=π, η, η′ decay rates and spectra. We find that the [Formula: see text] scalar meson dominates in the τ→Kη′ντ decay spectrum.

scholarly journals Tensor form factor of D→π(K)ℓν and D→π(K)ℓℓ decays with Nf=2+1+1 twisted-mass fermions

2018 ◽  
Vol 98 (1) ◽  
Author(s):  
V. Lubicz ◽  
L. Riggio ◽  
G. Salerno ◽  
S. Simula ◽  
C. Tarantino ◽  
...  
Keyword(s):  
Form Factor ◽  
Tensor Form ◽  
Twisted Mass

scholarly journals πe3Form Factorf-Near the Mass Shell

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
M. I. Krivoruchenko
Keyword(s):  
Form Factor ◽  
Mass Shell ◽  
Numerical Estimate ◽  
Mass Difference ◽  
Form Factors ◽  
Vector Current ◽  
Gauge Dependence ◽  
A Value ◽  
Model Independent ◽  
The Difference

The generalized Ward-Takahashi identity (gWTI) in the pion sector for broken isotopic symmetry is derived and used for the model-independent calculation of the longitudinal form factorf-of theπe3vector vertex. The on-shellf-is found to be proportional to the mass difference of the pions and the difference between the vector isospinT=1and scalar isospinT=2pion radii. A numerical estimate of the form factor yields a value two times higher than the previous estimate from the quark model. Off-shell form factors are known to be ambiguous because of the gauge dependence and the freedom in the parameterization of the fields. The near-mass-shellf-appears to be an exception, allowing for experimental verification of the consequences of the gWTI. We calculate the near-mass-shellf-using the gWTI and dispersion techniques. The results are discussed in the context of the conservation of vector current (CVC) hypothesis.

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 Current-Component Independent Transition Form Factors for Semileptonic and Rare D ⟶ π K Decays in the Light-Front Quark Model

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Ho-Meoyng Choi
Keyword(s):  
Form Factor ◽  
Quark Model ◽  
Form Factors ◽  
Light Front ◽  
Recent Analysis ◽  
Identical Result ◽  
Current Component ◽  
Tensor Form ◽  
Zero Modes ◽  
Valence Region

We investigate the exclusive semileptonic and rare D ⟶ π K decays within the standard model together with the light-front quark model (LFQM) constrained by the variational principle for the QCD-motivated effective Hamiltonian. The form factors are obtained in the q + = 0 frame and then analytically continue to the physical timelike region. Together with our recent analysis of the current-component independent form factors f ± q 2 for the semileptonic decays, we present the current-component independent tensor form factor f T q 2 for the rare decays to make the complete set of hadronic matrix elements regulating the semileptonic and rare D ⟶ π K decays in our LFQM. The tensor form factor f T q 2 are obtained from two independent sets J T + ⊥ , J T + − of the tensor current J T u v . As in our recent analysis of f − q 2 , we show that f T q 2 obtained from the two different sets of the current components gives the identical result in the valence region of the q + = 0 frame without involving the explicit zero modes and the instantaneous contributions. The implications of the zero modes and the instantaneous contributions are also discussed in comparison between the manifestly covariant model and the standard LFQM. In our numerical calculations, we obtain the q 2 -dependent form factors ( f ± , f T ) for D ⟶ π K and branching ratios for the semileptonic D ⟶ π K ℓ v ℓ ℓ = e , μ decays. Our results show in good agreement with the available experimental data as well as other theoretical model predictions.

CALCULATION OF SCALAR FORM FACTORS OF NONTOPOLOGICAL SOLITONS

1990 ◽  
Vol 05 (08) ◽  
pp. 1509-1527
Author(s):  
L.S. CELENZA ◽  
A. PANTZIRIS ◽  
C.M. SHAKIN
Keyword(s):  
Wave Function ◽  
Form Factor ◽  
Perturbative Qcd ◽  
Soft Part ◽  
Form Factors ◽  
Bound State ◽  
Mass Scale ◽  
Hard Scattering ◽  
Scalar Form ◽  
The Individual

We study a “toy” model which describes the bound state of two scalar particles. We parameterize the “soft” part of the wave function of the bound state using results obtained in the study of a nontopological soliton model. (This part of the wave function has predominantly lowmomentum components.) We improve this wave function by considering a single “hard” scattering, which we treat in perturbation theory. Thus, we have a model in which the wave function has both “soft” and “hard” parts, in the language used when performing perturbative QCD studies. (The relation of these results to those obtained for electromagnetic form factors in perturbative QCD studies requires further analysis.) We find that the form factor calculated using the “soft” part of the wave function behaves as F(Q2)=F(0)/(1+λ2Q2), where Q2=−q2>0. The individual hard scattering terms yield form factors which have the same form, except for a change of the scale factor, λ. We discuss the approach to the asymptotic form, F(Q2)~Q−2, for the various amplitudes which are summed to obtain the complete form factor. We also discuss the modification of the form factor under a change in mass scale. This modification is relatively simple to study since, in our model, there is only a single dimensionful parameter, κ, which sets the scale for all other dimensional parameters.

Electromagnetic form factor of Ds∗ meson from Nf = 2 twisted mass lattice QCD

2019 ◽  
Vol 34 (30) ◽  
pp. 1950194 ◽  
Author(s):  
Ning Li ◽  
Ya-Jie Wu
Keyword(s):  
Form Factor ◽  
Quantum Chromodynamics ◽  
Electromagnetic Form Factor ◽  
Form Factors ◽  
Electromagnetic Form Factors ◽  
Lattice Quantum Chromodynamics ◽  
Twisted Mass ◽  
Lattice Quantum ◽  
Ds Meson ◽  
Twisted Boundary Conditions

We investigate the electromagnetic form factor of [Formula: see text] meson using [Formula: see text] twisted mass lattice quantum chromodynamics gauge configurations. The numerical simulations are carried out under twisted boundary conditions which are helpful to increase the resolution in momentum space. We determine electromagnetic form factors with more small four-momentum transfer, and further fit the charge radius for [Formula: see text] meson.

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