Conveners
Hadron Structure: Session 5-1 A
- Weonjong Lee (Seoul National University)
Hadron Structure: Session 5-2 A
- Zhaofeng Liu (IHEP)
Hadron Structure: Session 7-1 A
- James Zanotti (University of Adelaide)
Hadron Structure: Session 7-2 A
- Ross Young (University of Adelaide)
There exists a long standing discrepancy of around 3.5 sigma between experimental measurements and standard model calculations of the magnetic moment of the muon. Current experiments aim to reduce the experimental uncertainty by a factor of 4, and Standard Model calculations must also be improved by a similar order. The largest uncertainty in the Standard Model calculation comes from the QCD...
Understanding the tension between the Standard Model prediction and the experimental results on the anomalous magnetic moment of the muon (a_\mu) has been an active research field over the past two decades. The theoretical uncertainty mainly comes from the hadronic contributions, among which the hadronic light-by-light scattering ($a_\mu^{hlbl}$) process plays an important role. We investigate...
The leading finite-volume corrections to the HVP contribution to the muonic (g-2) are related to the forward Compton amplitude of the pion in a completely model-independent fashion. The developed formalism is able to capture a few leading contributions, up to errors of order exp(-wML) where w~1.93 and M is the pion mass. By using models and chiPT for the forward Compton tensor, the...
We use a method to calculate the hadron's charge radius without model-dependent momentum extrapolations. The method does not require the additional quark propagator inversions on the twisted boundary conditions or the computation of the momentum derivatives of quark propagators and thus is easy to implement. We apply this method to the calculation of pion charge radius ⟨r^2⟩. For comparison,...
For the first time the openQD code was used to generate fully dynamical Nf=1+2+1 QCD+QED configurations with C boundary conditions and degenerate down and strange quarks at an unphysical value of the electromagnetic coupling alpha~0.04. In this talk, technical details about the generation, will be presented. In particular the stability of the algorithm, diagnostic observables and neutral and...
We will present the current status of nucleon structure studies with physical light quarks (m_pi = 135 MeV) in a large spatial extent of about 10 fm. Our calculations are carried out with the PACS10 gauge configurations generated by the PACS Collaboration with the stout-smeared O(a) improved Wilson fermions and Iwasaki gauge action at beta=1.82 corresponding to the lattice spacing of 0.084 fm....
The hadronic form factors at large momentum transfers often suffer from substantial excited state contributions and poor signal-to-noise ratios. Using the Feynman-Hellmann theorem allows for calculations of the hadronic form factors which only rely on two-point functions this allows access to higher momenta while still controlling the excited state contributions. We will present results from...
In this talk we present the first lattice QCD calculation of unpolarized and helicity generalized parton distributions (GPDs) for the proton. We use the quasi-distribution approach, which relies on computations of correlation functions that, for sufficiently fast moving hadrons, can be matched to light-cone distributions using perturbation theory. The calculations are...
We will present the first calculation of the nucleon vector and axial-vector charges with a single 2+1+1 flavors Highly Improved Staggered Quarks (HISQ) ensemble generated by the MILC collaboration and a matching valence action. We will focus on the theoretical foundation of staggered baryons and outline the methods to calculate physical observables with staggered valence quarks.
Current status of LHP+RBC joint nucleon structure calculations using RBC+UKQCD 2+1-flavor domain-wall fermions lattice-QCD ensembles is summarized.
We extract structure functions corresponding to the first moment of the gluon GPDs from the matrix elements of the gluon energy momentum tensor on a clover ensemble with m_{\pi} = 450 MeV. We present the various GFFs for states of different spins with a focus on the D-terms. We then compare extracted physical quantities like the pressure and shear forces between the different hadrons.
The Heavy quark Operator Product Expansion (HOPE) method allows one to extract information about light-cone matrix elements via local, instant form matrix elements. When applied to the calculation of the pion's light cone distribution amplitude, it allows (in principle) the full x dependence of the distribution amplitude to be determined. In practice, finite statistics and finite momenta mean...
The moments of the pion light-cone distribution amplitude (LCDA) can be extracted by comparison with the operator product expansion of the pion hadronic tensor with an artificially heavy intermediate quark. We perform a preliminary lattice calculation of this hadronic tensor in the quenched approximation at multiple lattice spacings and use it to extract the continuum limit of the second...
We present a detailed study of the nucleon unpolarized parton distribution function (PDF) using the approach of parton pseudo-distribution functions. We use this method to extract PDFs from the lattice results obtained using simulations with the
light quark mass fixed to its physical value. Then, the physical Ioffe time distributions are obtained from the nucleon matrix elements extracted...
We present a high-statistics lattice QCD determination of the valence parton distribution function (PDF) of pion, with a mass of 300 MeV, using two very fine lattice spacings of a = 0.06 fm and 0.04 fm. Our analysis use both RI-MOM and ratio-based schemes to renormalize the equal-time bi-local quark-bilinear matrix elements of pions boosted up to 2.4 GeV momenta. We reconstruct the x-dependent...
We present a Lattice QCD investigation of the pion electromagnetic form factor based on gauge configurations generated by Extended Twisted Mass Collaboration with N_f = 2+1+1 dynamical quark flavors. The calculation is carried out at two different lattice spacing values directly at the physical point. Employing Wilson clover twisted mass fermions at maximal twist guarantees O(a) improved...
The need to reach high hadron momentum is key to calculations of Parton Distribution Functions and other measures of hadron structure within lattice QCD. Meanwhile, the distillation framework provides a valuable means both of more fully sampling the lattice, and of controlling the contribution of excited states. In this talk, we extend the distillation framework through the implementation of...
In this talk, we highlight our group's recent developments on computing the Compton amplitude in a lattice approach. We briefly discuss how to access the Compton amplitude directly via the second-order Feynman-Hellmann theorem. As an application, we compute the nucleon Compton tensor across a range of photon momenta at an unphysical quark mass. This enables us to study the $Q^2$ dependence of...
An understanding of the partonic structure of hadrons is an essential ingredient in making precise predictions and measurements of hadronic cross-sections and various Standard, and Beyond Standard, Model parameters. Several encouraging proposals have been developed in the past decade that relate lattice calculable quantities with PDFs via frameworks akin to QCD factorization. We report results...
The light-cone definition of Parton Distribution Functions (PDFs) does not allow for a direct ab initio determination employing methods of Lattice QCD simulations that naturally take place in Euclidean spacetime. In this presentation we focus on pseudo-PDFs where the starting point is the equal time hadronic matrix element with the quark and anti-quark fields separated by a finite distance. We...
We report on our computation of the pseudoscalar-photon transition form factors from twisted mass lattice QCD for three pseudoscalar states, i.e. the neutral pion and the eta and eta' mesons, to determine the corresponding light pseudoscalar pole contributions in the dispersive analysis of hadronic light by light scattering in the muon g-2.
The neutral pion transition form factor is computed...
We perform a first calculation for the unpolarized parton distribution function of the $\Delta^+$ baryon using lattice QCD simulations within the framework of Large Momentum Effective Theory. Two ensembles of $N_f=2+1+1$ twisted mass fermions are utilized with a pion mass of 270 MeV and 360 MeV, respectively. The baryon, which is treated as a stable single-particle state, is boosted with...
