Conveners
Structure of hadrons and nuclei: Flex2
- Anthony Grebe (Fermi National Accelerator Laboratory)
Structure of hadrons and nuclei: Flex2
- Seyong Kim (Sejong University)
Structure of hadrons and nuclei: Flex2
- Dimitra Pefkou (UC Berkeley)
Structure of hadrons and nuclei: Flex2
- Tie-Jiun Hou (University of South China)
Structure of hadrons and nuclei: Flex2
- Xu Feng (Peking University)
Structure of hadrons and nuclei: Flex2
- Giannis Koutsou (The Cyprus Institute)
Structure of hadrons and nuclei: Flex2
- Roger Horsley (University of Edinburgh)
Structure of hadrons and nuclei: Flex2
- Andrea Shindler (Michigan State University)
We determine the nucleon axial, scalar and tensor charges at the continuum limit including all contributions from valence and sea quarks by analyzing three $N_f = 2 + 1 + 1$ twisted mass fermion ensembles with all quark masses tuned to approximately their physical values. We use the Akaike Information Criterion to evaluate systematic errors due to excited states and the continuum...
This talk will summarize the calculations of the axial, scalar and tensor charges of the nucleons using lattice QCD. These charges quantify the pion-nucleon sigma term, the coupling to dark matter and Higgs-like interactions, the contribution of quark spin to the nucleon spin, the contribution of quark electric dipole moment to the neutron dipole moment and to the transversity moment. The...
We present our progress on the computation of the axial form factor of the nucleon with flavour structure $u+d-2s$ from lattice QCD. We employ a set of $N_f=2+1$ CLS ensembles with O(a)-improved Wilson fermions and the Lรผscher-Weisz gauge action, with lattice spacings ranging from 0.05 fm to 0.086 fm and pion masses spanning between 130 MeV and 350 MeV.
We employ multiple source-sink...
We consider the axial-vector together with its induced pseudo-scalar form factor of the nucleon as computed from the chiral Lagrangian with nucleon and isobar degrees of freedom. The form factors are evaluated at the one-loop level, where particular emphasis is put on the use of on-shell masses in the loop expressions. Our results are presented in terms of a novel set of basis functions that...
We compute the electromagnetic form factors of the proton and neutron using lattice QCD with $N_f=2+1+1$ twisted mass clover-improved fermions and quark masses tuned to their physical values. Three ensembles with lattice spacings of a=0.080 fm, 0.068 fm, and 0.057 fm, and approximately the same physical volume allow us obtain the continuum limit directly at the physical pion mass. Several...
Proton and neutron electromagnetic form factors are some the primary characteristics of their spatial structure. At large momentum transfer $Q^2$, their behavior probes transition from nonperturbative to perturbative QCD dynamics, diquark correlations, quark orbital angular momenta, as well as other phenomenological assumptions about nucleon structure. Recently at JLab, data on the proton form...
In the PACS10 project, the PACS collaboration have generated three sets of the PACS10 gauge configurations at the physical point with lattice volume larger than $(\mbox{10 fm})^4$ and three different lattice spacings. The isovector nucleon form factors had been already calculated by using two sets of the PACS10 gauge configurations. In our strategy, the smearing parameters of the nucleon...
In this talk, I will report on the lattice QCD calculation of pion electroproduction on the nucleon. This process describes how pions are produced when nucleons are struck by electrons and provides insights into the internal structure of nucleon. At pion-production threshold, we extract the multipole amplitudes $E_{0+} $ and $L_{0+} $ from the $N+\gamma^*\to N\pi$ matrix element. The...
We give a status update on our analysis of the pion scalar form factors $F_S^{\pi,f}$, $f=l,0,8$ and the associated radii $\langle r_S \rangle^{l,0,8}_\pi$. Our lattice results are computed on a large set of 18 CLS gauge ensembles with $N_f=2+1$ Wilson Clover-improved sea quarks. These ensembles cover four values of the lattice spacing $a=0.049\mathrm{fm}\ ...\ 0.086\mathrm{fm}$, a pion mass...
We report our preliminary results for the charge radii of $\pi^{+}$ and $K^{+}$ mesons with the PACS10 configuration generated at the physical point using the Iwasaki gauge action and $N_{f}=2+1$ stout-smeared nonperturbatively $\mathcal{O}(a)$ improved Wilson quark action, especially at $a = 0.085$ fm corresponding lattice size $128^4$. The charge radii are obtained from a model-independent...
We present the isovector axial, induced pseudoscalar, and pseudoscalar form factors of the nucleon using three twisted-mass fermion ensembles with degenerate up- and down-, strange-, and charm-quarks with masses tuned to their physical values (physical point). The three ensembles have lattice spacing $a$=0.08, 0.068, and 0.057 fm and approximately equal physical volume allowing for the...
To explore the possibility of H-like dibaryon $\Lambda_c \Lambda_c(0^+)$, we proceed calculation on lattice. Two Wilson-Clover ensembles are used which were generated by CLQCD collaboration with similar settings that $m_\pi \approx 303$ MeV, $m_{D} \approx 1.966$ GeV, $m_{D^\ast} \approx 2.077$ GeV. In this work, finite-volume scattering with single channel L$\mathrm{\ddot{u}}$scher's formula...
We present an implementation of the three-neutron quantization condition (QC) derived in previous work. We construct the QC computationally and numerically determine the solutions. The symmetry of the QC means that it can be projected onto representations of the appropriate little group (depending on frame momentum $\vec{P}$), restricting the size of the matrices and reducing computational...
We investigate an improved method to extract nucleon matrix elements from lattice 3-point functions and generalized eigenvalue problem with nucleon and pion-nucleon interpolating fields. Our method avoids the costly three-point functions with 2-hadron interpolators at both source and sink. We demonstrate minimization of excited state contamination in matrix elements of the scalar, vector,...
The study of two-hadron matrix elements and form factors is critical for the success of several planned experimental searches for new physics which utilize low-energy nuclear environments. Lattice QCD calculations of, e.g., short-distance nn->pp transitions relevant for neutrinoless double beta decay experiments, rely on a recently derived finite-volume formalism for computing 2+J->2...
The TMD soft function may be obtained by formulating the Wilson line in terms of auxiliary 1-dimensional fermion fields on the lattice. We take inspiration from heavy quark effective theory (HQET) in order to define the auxiliary field. Our computation takes place in the region of the lattice that corresponds to the โspacelikeโ region in Minkowski space in order to obtain the Collins soft...
Transverse-momentum-dependent parton distribution functions (TMDPDFs) are important in revealing the 3D structure of hadrons. Among these distributions, the T-odd Boer-Mulders TMDPDF describes the transversely polarized quark distribution in an unpolarized hadron. Within large-momentum effective theory, we perfromed a lattice calculation of the nucleon Boer-Mulders function. The calculation...
Using large momentum effective theory it is possible to calculate transverse momentum dependent parton distribution functions (TMDPDFs) from first principle in lattice QCD. In this work, we present results for the 3 main constituents of the TMD Parton distribution functions, namely the quasi-TMDPDF, the Collins-Soper kernel and the reduced soft function. We construct the physical TMDPDF using...
The formalism of short-distance factorization allows to connect light-cone correlators with spacelike ones. The later being directly accessible in Euclidean lattices, and the former being the key objects for all of parton physics, the possibility of studying hadron structure in the framework of lattice QCD is opened. In this work we take advantage of this formalism --conveyed through the...
We will present a first lattice QCD calculation of gluon Collins-Soper kernel, which relates the transverse momentum-dependent gluon parton distribution functions at different energy scales.
In this talk, we present updates on the measurement of the unpolarized gluon distribution in the nucleon from $N_fโ=2+1$ QCD on the lattice, extending the work published in PRD 104 (2021) 9, 094516, where the estimation is performed with a 358 MeV pion mass and 0.094 fm lattice spacing. Utilizing larger statistical datasets and refining the sGEVP determination through a projection of the...
We describe a novel procedure, based on the gradient flow for fermion and gauge fields, to determine moments of parton distribution functions of any order in lattice QCD. This method resolves the problems that have hampered the determination of moments of any order of parton distribution functions on the lattice. The flowed matrix elements of twist-2 operators renormalize multiplicatively, and...
We implement a recent proposal using gradient flow to compute higher moments of hadron parton distribution functions, circumventing the power divergent mixing problem. We discuss how to efficiently implement this computationally, as well as data analysis approaches. We present preliminary results on the first few moments of the unpolarized flavor non-singlet PDF of the pion in the MSbar...
We calculate the leading-twist light-cone distribution amplitude (LCDA) moments of mesons on MILC ensembles using the hyp-smeared clover action. For pseudoscalar mesons, we compute the first moments of the $K$ meson and the second moments of the $\pi$ and $K$ mesons. For vector mesons, we compute the first moments of the $K^{*}$ meson and the second moments of the $\rho$, $K^{*}$, and $\phi$ mesons.
We present the full decomposition of the momentum fraction carried by quarks and gluons in the pion and the kaon. We employ three gauge ensembles generated with Nf = 2 + 1 + 1 Wilson twisted-mass clover-improved fermions at the physical quark masses. For both mesons we perform a continuum extrapolation directly at the physical pion mass, which allows us to determine for the first time the...
Single-spin asymmetries observed in polarised deep-inelastic scattering are important probes of hadron structure. The Sivers asymmetry provides information about the transverse momentum of the struck quark and can be related to final-state interactions. Understanding these asymmetries at the quark level has been the subject of much interest in QCD phenomenology. In this talk, we present a...
We report a lattice QCD simulation of electric and magnetic polarizabilities of $\pi^0$ using the four-point function method. The connected diagrams are evaluated on the $24^3 \times 48$ lattice using Wilson action with a=0.1 fm and pion mass from 1100 to 370 MeV. Results are compared with existing calculations from the background field method.
We study the electric polarizability of a charged kaon from four-point functions in lattice QCD as an alternative to the background field method. Lattice four-point correlation functions are constructed from quark and gluon fields to be used in Monte Carlo simulations. The elastic form factor (charge radius) is needed in the method which can be obtained from the same four-point functions at...
I will discuss the recent progress in lattice QCD calculations of nucleon four-point correlation functions, with a focus on nucleon electromagnetic polarizability.
We will present a lattice QCD study of the axialvector diquark. We note that obtaining the diquark mass from the bound-state pole of the two-point correlator is not straightforward due to color confinement. To circumvent this issue, we regard the diquark mass as a parameter in the quark-diquark model, constructed using the potential method developed by the HAL QCD Collaboration. For the...
We calculate $c\bar{c}$ potential from the equal-time Nambu-Bethe-Salpeter wave function in Lattice QCD to consider its gauge dependence, i.e., we compare the results with Coulomb gauge and Landau gauge. In previous works by Kawanai, Sasaki and Watanabe, Coulomb gauge is employed. However, the renormalizability of Coulomb gauge is controversial so that we desire to change it to some...
At the large distances compared to the chiral symmetry breaking scale, a four-quark state $\bar Q \bar Q q q$ (with $Q$ as heavy and $q$ as light quarks) can be treated as two asymptotic mesons interacting via strong residual forces. To analyse the long-range strong force in such a system, we study the interaction between two bottom mesons in the heavy quark limit using chiral effective field...
In this study, we explore the renormalization of a comprehensive set of gauge-invariant gluon nonlocal operators on the lattice. We calculate the renormalization factors for these operators in the modified Minimal Subtraction $(\rm \overline{MS})$ scheme up to one-loop, utilizing both dimensional and lattice regularizations in the Wilson gluon action. To facilitate a non-perturbative...
We present a new method for extracting hadronic matrix elements from simultaneous analysis of two- and three-point correlation functions. We demonstrate its advantages over previous approaches in applications to both synthetic and lattice data.
We report the first exploratory study on nuclear $\beta$-decay through nuclear lattice effective field theory, including $^3$H and $^6$He $\beta$-decays. We employ nuclear forces and nuclear one-body and two-body axial currents consistently derived from chiral effective field theory to calculate the Gamow-Teller matrix element(GTME). We first combine the GTME of $^3$H $\beta$-decay ...
We apply the method of pseudo parton distributions to compute the distribution amplitude of the $\eta_c$ meson, which is a necessary ingredient in cross sections of exclusive meson production. We present results in the continuum for physical quark masses and we compare to alternative methods to compute this object, mainly non-relativistic QCD and Dyson-Schwinger equations. We find a large...
The size of the proton is of lasting and high interest in the subatomic physics community. The most well-known example is the electric radius which has been beclouded by the proton radius puzzle for more than a decade. While tremendous progress in $ep$-scattering, atomic spectroscopy and lattice QCD has brought this puzzle closer to its resolution, one also finds discrepant results for the...
We present results of nucleon structures measured in 2+1 flavor QCD with the physical light quarks 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, 2.00 and 2.20 corresponding to the lattice spacings...
Many simulations now have many lattice spacings available, and it is of interest to investigate how they scale.In this talk we first derive renormalisation group equations appropriate for 2+1 clover fermions. This is then used together with pion mass and wilson flow data at five lattice spacings to study scaling.
The parity-odd structure function, $F_3$, accessible via neutrino-nucleon deep-inelastic scattering, plays an important role in estimating the hadronic uncertainties in the extracted weak parameters of the Standard Model (SM). Controlled and reduced uncertainties in SM processes are crucial for beyond the standard model searches progressing via CKM matrix elements or the weak mixing angle....
