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 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 Nucleon axial form factors using Nf=2 twisted mass fermions with a physical value of the pion mass

2017 ◽  
Vol 96 (5) ◽  
Author(s):  
C. Alexandrou ◽  
M. Constantinou ◽  
K. Hadjiyiannakou ◽  
K. Jansen ◽  
C. Kallidonis ◽  
...  
Keyword(s):  
Pion Mass ◽  
Form Factors ◽  
Twisted Mass ◽  
Axial Form

scholarly journals Computation of parton distributions from the quasi-PDF approach at the physical point

2018 ◽  
Vol 175 ◽  
pp. 14008 ◽  
Author(s):  
Constantia Alexandrou ◽  
Simone Bacchio ◽  
Krzysztof Cichy ◽  
Martha Constantinou ◽  
Kyriakos Hadjiyiannakou ◽  
...  
Keyword(s):  
Pion Mass ◽  
Distribution Functions ◽  
Matrix Elements ◽  
Parton Distribution Functions ◽  
Physical Point ◽  
Parton Distributions ◽  
The Matrix ◽  
First Results ◽  
Perturbative Renormalization ◽  
Vector Combination

We show the first results for parton distribution functions within the proton at the physical pion mass, employing the method of quasi-distributions. In particular, we present the matrix elements for the iso-vector combination of the unpolarized, helicity and transversity quasi-distributions, obtained with Nf = 2 twisted mass cloverimproved fermions and a proton boosted with momentum [see formula in PDF] = 0.83 GeV. The momentum smearing technique has been applied to improve the overlap with the proton boosted state. Moreover, we present the renormalized helicity matrix elements in the RI’ scheme, following the non-perturbative renormalization prescription recently developed by our group.

Some QCD/gravity intersections

2016 ◽  
Vol 31 (28n29) ◽  
pp. 1645032
Author(s):  
O. V. Teryaev
Keyword(s):  
Equivalence Principle ◽  
Energy Momentum Tensor ◽  
Form Factors ◽  
Momentum Tensor ◽  
Matrix Elements ◽  
Lattice Data ◽  
Hadron Structure ◽  
The Matrix ◽  
Dimensional Gravity ◽  
Quark Transverse Momentum

Gravitational form factors are the matrix elements of the Belinfante energy momentum tensor (EMT) which naturally incorporate the hadron structure and the equivalence principle. The relocalization property allowing to transform EMT to the Belinfante form provides the “kinematical” counterpart of the famous [Formula: see text] problem. The equivalence principle may be approximately valid for quarks and gluons separately in non-perturbative (NP)QCD, and this conjecture is supported by the experimental and lattice data. The extra-dimensional gravity leading to holographic AdS/QCD is supporting the relation of quark transverse momentum to the Regge slope, discovered by V.N. Gribov.

scholarly journals Progress in computing parton distribution functions from the quasi-PDF approach

2018 ◽  
Vol 175 ◽  
pp. 06021 ◽  
Author(s):  
Constantia Alexandrou ◽  
Krzysztof Cichy ◽  
Martha Constantinou ◽  
Kyriakos Hadjiyiannakou ◽  
Karl Jansen ◽  
...  
Keyword(s):  
Parton Distribution ◽  
Distribution Functions ◽  
Matrix Elements ◽  
Parton Distribution Functions ◽  
Mass Collaboration ◽  
Twisted Mass ◽  
The Future ◽  
Systematic Effects ◽  
Perturbative Renormalization

We discuss the current developments by the European Twisted Mass Collaboration in extracting parton distribution functions from the quasi-PDF approach. We concentrate on the non-perturbative renormalization prescription recently developed by us, using the RI′ scheme. We show results for the renormalization functions of matrix elements needed for the computation of quasi-PDFs, including the conversion to the MS scheme, and for renormalized matrix elements. We discuss the systematic effects present in the Z-factors and the possible ways of addressing them in the future.

Form Factors and Correlation Functions

2020 ◽  
pp. 744-788
Author(s):  
Giuseppe Mussardo
Keyword(s):  
Correlation Functions ◽  
Form Factors ◽  
Vacuum Expectation ◽  
Bound State ◽  
Kernel Functions ◽  
Energy Tensor ◽  
Matrix Elements ◽  
Stress Energy ◽  
The Matrix ◽  
Recursive Equations

At the heart of a quantum field theory are the correlation functions of the various fields. In the case of integrable models, the correlators can be expressed in terms of the spectral series based on the matrix elements on the asymptotic states. These matrix elements, also known as form factors, satisfy a set of functional and recursive equations that can exactly solved in many cases of physical interest. Chapter 19 covers general properties of form factors, Faddeev–Zamolodchikov algebra, symmetric polynomials, kinematical and bound state poles, the operator space and kernel functions, the stress-energy tensor and vacuum expectation values and the Ising model in a magnetic field.

Mass Radius of the Nucleon

1972 ◽  
Vol 50 (11) ◽  
pp. 1163-1168 ◽  
Author(s):  
M. G. Hare ◽  
G. Papini
Keyword(s):  
Mass Distribution ◽  
Intermediate State ◽  
Energy Momentum Tensor ◽  
Form Factors ◽  
Momentum Tensor ◽  
Dispersion Relations ◽  
Matrix Elements ◽  
State Expansion ◽  
The Matrix ◽  
The Mean

The mean radius of the mass distribution of the nucleon is determined to be [Formula: see text]. The calculation makes use of sidewise, unsubtracted, threshold dominated dispersion relations for the form factors appearing in the matrix elements of the contracted energy–momentum tensor. It uses a π meson–nucleon intermediate state expansion.

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