C. Alexandrou, M. Constantinou, T Korzec, J. Carbonell, P. A. Harraud, M. Papinutto, P. Guichon, K. Jansen
We present results on the nucleon form factors and moments of generalized parton distributions obtained within the twisted mass formulation of lattice QCD. We include a discussion of lattice artifacts by examining results at different volumes and lattice spacings. We compare our results with those obtained using different discretization schemes and to experiment.
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Flavor Twisted Boundary Conditions and the Nucleon Axial Current
在夸克场的扭曲边界条件下，利用扭曲重子手征微扰理论研究了轴流的核子矩阵元。人们可以探索的轴向形状因子的动量转移依赖性更容易比单独使用普通的晶格量子化动量。作为例子，我们导出了核子轴半径和赝标形状因子的表达式。
We present results on the nucleon electromagnetic form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 and a=0.056 fm. The nucleon magnetic moment, Dirac and Pauli radii are obtained in the continuum limit and chirally extrapolated to the physical pion mass allowing for a comparison with experiment.
We study the nucleon matrix elements of the quark scalar-density operator using maximally twisted mass fermions with dynamical light ($u$,$d$), strange and charm degrees of freedom. We demonstrate that in this setup the nucleon matrix elements of the light and strange quark densities can be obtained with good statistical accuracy, while for the charm quark counterpart only a bound can be provided. The present calculation which is performed at only one value of the lattice spacing and pion mass serves as a benchmark for a future more systematic computation of the scalar quark content of the nuc…
We present results on the electromagnetic and axial nucleon form factors using two degenerate flavors of twisted mass fermions on lattices of spatial size 2.1 fm and 2.7 fm and a lattice spacing of about 0.09 fm. We consider pion masses in the range of 260-470 MeV. We chirally extrapolate results on the nucleon axial ch arge, the isovector Dirac and Pauli root mean squared radii and magnetic moment to the physical point and co mpare to experiment.
We present results on the nucleon form factors, momentum fraction and helicity moment for $N_f=2$ and $N_f=2+1+1$ twisted mass fermions for a number of lattice volumes and lattice spacings. First results for a new $N_f=2$ ensemble at the physical pion mass are also included. The implications of these results on the spin content of the nucleon are discussed taking into account the disconnected contributions at one pion mass.
Nucleon form factors with dynamical twisted mass fermions
在具有两种简并轻夸克的扭曲质量QCD中计算了核子的电磁和轴向形状因子。在300 MeV ~ 500 MeV范围内，确定了轴向电荷g_A、磁矩、狄拉克半径和泡利半径。
We investigate scalar matrix elements of the nucleon using $N_f=2+1+1$ flavors of maximally twisted mass fermions at a fixed value of the lattice spacing of $a\approx 0.078{\rm fm}$. We compute disconnected contributions to the relevant three-point functions using an efficient noise reduction technique. Using these methods together with an only multiplicative renormalization applicable for twisted mass fermions, allows us to obtain accurate results in the light and strange sector.
We present results on the nucleon scalar, axial and tensor charges, as well as, on the first moments of the unpolarized, polarized and transversity parton distributions using $N_f=2$ and $N_f=2+1+1$ twisted mass fermions. These include an ensemble that yields the physical value of the ratio of the nucleon to the pion mass. Results on the axial charges of hyperons and charmed baryons are also presented for a range of pion masses including the physical one.
Flavor Twisted Boundary Conditions and the Nucleon Vector Current
利用味扭曲边界条件，研究了矢量流的核子矩阵元。我们只扭曲与电流耦合的活跃夸克。利用我们发展的阶跃群SU（7）的部分扭曲、部分猝灭的重子手征微扰理论，确定了扭曲边界条件引起的有限体积修正|5）。渐近地，这些修正在体积上是指数小的，但是对于小的扭转角可以变得明显。利用Breit框架不会减轻核子矢量流矩阵元素的体积校正。导出的表达式将允许更好地控制提取的等矢量磁矩和电磁半径从模拟在零晶格动量。此外，我们的形式可以应用于任何核子矩阵元。
We present results for the nucleon electromagnetic and axial form factors using an N$_f$=2 twisted mass fermion ensemble with pion mass of about 131 MeV. We use multiple sink-source separations to identify excited state contamination. Dipole masses for the momentum dependence of the form factors are extracted and compared to experiment, as is the nucleon magnetic moment and charge and magnetic radii.
Nucleon and Delta masses in twisted mass chiral perturbation theory
在扭曲质量重子手征微扰理论中计算了核子和δ的质量。我们工作的二次顺序的功率计数计划，其中我们对待的晶格间距和夸克质量是相同的顺序。我们给出了核子的质量和质量分裂的表达式，以及在同位旋极限内和远离同位旋极限时的δ。我们用手征拉格朗日处理方法证明了在强同位旋极限下，手征微扰理论中的δ多重态分裂为两个简并对，而核子仍保持简并.我们发现，质量分裂之间的退化对的三角洲第一次出现在二次秩序中的晶格间距。我们讨论的微妙之处，在有效手征理论所产生的列入同位旋破缺。
We present results on the axial and the electromagnetic form factors of the nucleon, as well as, on the first moments of the nucleon generalized parton distributions using maximally twisted mass fermions. We analyze two N_f=2+1+1 ensembles having pion masses of 210 MeV and 354 MeV at two values of the lattice spacing. The lattice scale is determined using the nucleon mass computed on a total of 18 N_f=2+1+1 ensembles generated at three values of the lattice spacing, $a$. The renormalization constants are evaluated non-perturbatively with a perturbative subtraction of ${\cal O}(a^2)$-terms. The…
We compute the disconnected quark loops contributions entering the determination of nucleon observables, by using a $N_f = 2$ ensemble of twisted mass fermions with a clover term at a pion mass $m_π= 133$ MeV. We employ exact deflation and implement all calculations in GPUs, enabling us to achieve large statistics and a good signal.
We present results on the isovector and isoscalar nucleon axial form factors including disconnected contributions,using an ensemble of $N_f =2$ twisted mass clover- improved Wilson fermions simulated with approximately the physical value of the pion mass. The light disconnected quark loops are computed using exact deflation, while the strange and the charm quark loops are evaluated using the truncated solver method. Techniques such as the summation and the two-state fits have been employed to access ground-state dominance.
We present the first lattice calculation of nucleon matrix elements using four dynamical flavors. We use the $N_f=2+1+1$ maximally twisted mass formulation. The renormalization is performed non-perturbatively in the RI$^\prime$-MOM scheme and results are given for the vector and axial vector operators with up to one-derivative. Our calculation of the average momentum of the unpolarized non-singlet parton distribution is presented and compared to our previous results obtained from the $N_f=2$ case.
Results on the electromagnetic form factors of the nucleon using twisted mass fermion configurations are presented. These include a gauge field ensemble simulated with two degenerate light quarks yielding a pion mass of around 130 MeV, as well as two ensembles that include strange and charm quarks in the sea yielding pion masses of 210 MeV and 373 MeV. Details of the methods used and systematic errors are discussed, such as noise reduction techniques and the effect of excited states contamination.
We present lattice QCD simulation results from the European Twisted Mass Collaboration (ETMC) for the light, strange and charm quark contents of the nucleon. These quantities are important ingredients to estimate the cross-section for the detection of WIMPs as Dark Matter candidates. By employing a particular lattice QCD formulation, i.e. twisted mass fermions, accurate results of the light and strange scalar contents of the nucleon can be obtained. In addition, we provide a bound for the charm quark content of the nucleon.
We present results on the nucleon tensor form factors and first moment of the transversity distribution using maximally twisted mass fermions. We analyze two Nf=2+1+1 ensembles having pion masses of 213 MeV and 373 MeV with lattice spacing a=0.064 fm and a=0.082 fm, respectively. First results using an Nf=2 ensemble of twisted mass fermions with a clover term at a physical pion mass and lattice spacing a=0.094 fm are also presented. The renormalization function for the local tensor form factors is evaluated non-perturbatively with a perturbative subtraction of O(a^2)-terms, while for the first…
To understand the structure of hadrons it is important to know the PDF of their constituents, the quarks and gluons. In our work we aim to compute the first moment of the gluon PDF $\langle x \rangle_g$ for the nucleon. We follow two possible approaches in order to extract the gluon moment: the Feynman-Hellmann theorem and a direct method with smearing of the gluon operator. We present preliminary results computed on $24^3 \times 48$ lattices for the case where the Feynman-Hellman theorem is used and $32^3 \times 64$ lattices for the direct method, employing $N_f=2+1+1$ maximally twisted mass …
We investigate excited state contaminations in a direct computation of the nucleon $σ$-terms. This is an important source of systematic effects that needs to be controlled besides the light quark mass dependence and lattice artefacts. We use maximally twisted mass fermions with dynamical light ($u$,$d$), strange and charm degrees of freedom. Employing an efficient stochastic evaluation of the disconnected contribution available for twisted mass fermions, we show that the effect of excited states is large in particular for the strange $σ$-terms, where it can be as big as $O(\gtrsim 40%$). This …
We present results from an ongoing computation of masses of $D$ mesons, $D_s$ mesons and charmonium, including both ground states and several parity and angular momentum excitations. We employ 2+1+1 flavours of dynamical maximally twisted mass fermions at three lattice spacings and three $u/d$ quark masses at each lattice spacing. We consider different combinations of valence quark discretizations, with either identical or opposite signs in front of the twisted mass terms. In the end, our setup allows for a good control of different kinds of systematic effects, in particular the quark mass dep…
We present results on the electroweak form factors and on the lower moments of parton distributions of the nucleon, within lattice QCD using two dynamical flavors of degenerate twisted mass fermions. Results are obtained on lattices with three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm, allowing the investigation of cut-off effects. The volume dependence is examined by comparing results on two lattices of spatial length L=2.1 fm and L=2.8 fm. The simulations span pion masses in the range of 260-470 MeV. Our results are renormalized non-perturbatively…
Disconnected Loops with Twisted Mass Lattice QCD
本文对格点费米子的扭曲质量公式在不连通圈计算中的应用进行了介绍和讨论，并对核子奇异夸克形状因子的实验现状作了简要的介绍。本文描述了核子标量形状因子不连续部分的原型计算。
Wilson Fermions with untwisted and twisted mass are widely used in lattice simulations. Therefore one important question is whether the twist angle and the lattice spacing affect the phase diagram. We briefly report on the study of the phase diagram of QCD in the parameter space of the degenerate quark masses, isospin chemical potential, lattice spacing, and twist angle by employing chiral perturbation theory. Moreover we calculate the pion masses and their dependence on these four parameters.
Twisted Mass, Overlap and Creutz Fermions: Cut-off Effects at Tree-level of Perturbation Theory
本文研究了最大扭曲质量Wilson、重叠和最近提出的Creutz费米子在微扰理论树水平上的截止效应。我们证明了这三种格点费米子在格点间距上都具有O（a^2）标度行为。此外，这些截止效应的大小是可比的三种格费米子考虑这里。此外，我们分析的情况下，扭曲的质量费米子不完全是在最大扭曲和重叠费米子的研究相比，扭曲的质量费米子时，夸克质量不匹配。
Wilson twisted mass fermions in the epsilon regime
在这一过程中的贡献，我们报告正在进行的努力，以了解和模拟威尔逊扭曲质量费米子在所谓的非对称制度。
Two--dimensional lattice Gross--Neveu model with Wilson twisted mass fermions
我们研究了具有Wilson扭曲质量费米子的二维格点Gros-Neveu模型，以探索这种设置下的相结构。特别是，我们调查的行为发现早期与标准威尔逊费米子作为扭曲的质量参数$μ$的函数的相变。我们发现相变对$μ$的依赖性定性地与格点量子色动力学的情况非常相似。
We present a preliminary lattice calculation of the leading-order electromagnetic and strong isospin-breaking corrections to the Hadronic Vacuum Polarization (HVP) contribution of the light quarks to the anomalous magnetic moment of the muon. The results are obtained in the quenched-$QED$ approximation using the $QCD$ gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with $N_f = 2 + 1 + 1$ dynamical quarks, at three values of the lattice spacing varying from $0.089$ to $0.062 ~ \mbox{fm}$, at several lattice volumes and with pion masses in the range $M_π\simeq 22…
We present the nucleon axial and electromagnetic form factors using \Nf{2}{1}{1} ensembles of twisted mass fermions with clover improvement and with masses tuned to their physical values. Excited state effects are studied using several sink-source time separations in the range 0.8 fm - 1.6 fm, exponentially increasing statistics with the separation such that statistical errors remain approximately constant. In addition, quark loop disconnected diagrams are included in order to extract the isoscalar axial form factors and the proton and neutron electromagnetic form factors, as well as their str…
Exploring the epsilon regime with twisted mass fermions
在这一过程中的贡献，我们报告的第一项研究，以探索所谓的威尔逊扭曲质量（WTM）费米子的超导制度。为了显示这种方法的潜力，我们给出了手性缩合物的初步测定。
A lattice determination of moments of unpolarised nucleon structure functions using improved Wilson fermions
在猝灭格点量子色动力学框架下，利用O（a）改进的Wilson费米子和非微扰重整化，给出了非极化核子结构函数低阶矩的高统计计算.特别注意手征和连续外推。
Iterative methods for overlap and twisted mass fermions
本文比较了几种求解格点量子色动力学中费米子传播子的线性方程组迭代解法。特别是，我们认为手征不变的重叠和手征改进威尔逊（最大）扭曲质量费米子。在230 MeV和720 MeV之间的四个固定π介子质量值下，比较了两种格点量子色动力学公式。对于重叠费米子，我们解决自适应精度和低模式预处理，而扭曲质量费米子，我们讨论偶/奇预处理。在每一种情况下，我们发现最好的算法与重叠算子的计算是由一个因素的30-120更昂贵的扭曲质量算子。
Twisted valence quarks and hadron interactions on the lattice
我们考虑具有价态的QCD和海夸克服从不同边界条件。我们指出，低两个强子态的能量不依赖于海夸克的边界条件（直到指数小修正）。因此，在格点量子色动力学中使用扭曲边界条件提取核子-核子相移的优点可以在不需要新规范位形的情况下获得，即使在完全非淬灭的计算中也是如此。
We present a lattice QCD calculation of the heavy-light decay constants f_B and f_Bs performed with Nf=2 maximally twisted Wilson fermions, at four values of the lattice spacing. The decay constants have been also computed in the static limit and the results are used to interpolate the observables between the charm and the infinite-mass sectors, thus obtaining the value of the decay constants at the physical b quark mass. Our preliminary results are f_B=191(14) MeV, f_Bs=243(14) MeV, f_Bs/f_B=1.27(5). They are in good agreement with those obtained with a novel approach, recently proposed by ou…
Dynamical twisted mass fermions
我们总结了动力学扭曲质量费米子的四个贡献。所得到的报告包括了N_f=2时三种不同规范作用量的结果，即标准Wilson Plaquette规范作用量、DBW 2规范作用量和树级Symanzik改进规范作用量。此外，还讨论了N_f=2+1+1味的扭曲质量费米子的初步结果。
The flavour singlet axial Ward identity with Osterwalder-Seiler twisted mass Wilson fermion action is studied on a finite lattice, with finite fermion mass and the Wilson parameter r up to 1. Approach to the infinite volume chiral limit and emergence of the anomaly is significantly better than that obtained with O(a) and O(a^2) improved fermion actions. We have shown explicitly that up to O(g^2), parity violating terms cancel in the Ward identity even at finite volume and finite lattice spacing.
Two dimensional twisted chiral fermions on the lattice
结果表明，晶格重叠正确地再现了手征行列式的存在下，非平凡的背景Polyakov循环变量的二维环面。
We present results for the eta prime meson and the topological susceptibility in two flavour lattice QCD. The results are obtained using Wilson twisted mass fermions at maximal twist with pion masses ranging from 340 MeV down to the physical point. A comparison to literature values is performed giving a handle on discretisation effects.
Comparison between overlap and twisted mass fermions towards the chiral limit
我们比较重叠费米子，这是手征不变的，威尔逊扭曲质量费米子的手征极限的方法。我们的淬火模拟表明，这两种配方的晶格费米子π质量的O（250兆电子伏）可以达到在实际的模拟。我们的比较是在固定的晶格间距a=0.123 fm处进行的。测量了几个量，如强子质量和赝标衰变常数。
Comparing iterative methods for overlap and twisted mass fermions
我们提出了一个系统的比较各种迭代方法，以获得重叠和扭曲质量的费米子在固定的π介子质量在淬火近似的费米子传播子。在每种情况下，我们发现，在这里考虑的参数值，计算与重叠算子是由一个因素的20-40更昂贵的比扭曲质量算子。对于重叠算子，我们也比较了各种方法计算拓扑指数的效率。
We investigate the temperature dependence of the Landau gauge gluon and ghost propagators in lattice QCD with two flavors of maximally twisted mass fermions. For these propagators we provide and analyze data which corresponds to pion mass values between 300 and 500 MeV. For the gluon propagator we find that both the longitudinal and transversal component change smoothly in the crossover region, while the ghost propagator exhibits only a very weak temperature dependence. For momenta between 0.4 and 3.0 GeV we give a parametrization for our lattice data. It may serve as input to studies which em…
The Adaptive Aggregation-based Domain Decomposition Multigrid method (arXiv:1303.1377) is extended for two degenerate flavors of twisted mass fermions. By fine-tuning the parameters we achieve a speed-up of the order of hundred times compared to the conjugate gradient algorithm for the physical value of the pion mass. A thorough analysis of the aggregation parameters is presented, which provides a novel insight into multigrid methods for lattice QCD independently of the fermion discretization.
We present the Adaptive Aggregation-based Domain Decomposition Multigrid method extended to the twisted mass fermion discretization action. We show comparisons of results as a function of tuning the parameters that enter the twisted mass version of the DDalphaAMG library (https://github.com/sbacchio/DDalphaAMG). Moreover, we linked the DDalphaAMG library to the tmLQCD software package and give details on the performance of the multigrid solver during HMC simulations at the physical point.
Hadronic contribution to g-2 from twisted mass fermions
我们计算的真空极化张量的π介子质量从480兆电子伏至270兆电子伏使用动态扭曲质量费米子在晶格间距为0.086微米。我们分析的形式的极化张量的晶格使用扭曲QCD的对称性，我们研究了有限尺寸效应和晶格文物在310兆电子伏的π质量。最低阶强子贡献的g-2的结果和系统误差的影响进行了讨论。
Hadronic light-by-light contribution to the muon $g-2$ using twisted-mass fermions
本文报告了利用ETMC的扭曲质量格点QCD系综，初步计算缪子反常磁矩中强子光-by-光贡献的结果。
Overlap fermions on a twisted mass sea
我们提出了一个混合行动项目的第一个结果。我们分析了两种动力学扭曲质量费米子产生的规范配置。价区采用Neuberger重叠Dirac算子。讨论了模拟设置中的各种选择。我们采用手征微扰理论来描述在非零晶格间距下，在海和价扇区中使用不同作用的影响。
The calculation of the strangeness and charmness of the nucleon is presented with overlap fermion action on 2+1 flavor domain wall fermion configurations. We adopt stochastic grid sources and the low mode substitution technique to improve the signals of nucleon correlation functions and the loops. The calculation is done on a $24^3\times 64$ lattice with $m_l=0.005$, $m_h=0.04$, and $a^{-1}=1.73\,{\rm GeV}$. We find $ f_{T_{s}} = 0.048(15)$ and $f_{T_{c}} = 0.029(43)$.
We present the N_f=2+1 clover fermion lattice QCD calculation of the nucleon strangeness form factors. We evaluate disconnected insertions using the Z(4) stochastic method, along with unbiased subtractions from the hopping parameter expansion. We find that increasing the number of nucleon sources for each configuration improves the signal significantly. We obtain G_M^s(0) = -0.017(25)(07), where the first error is statistical, and the second is the uncertainties in Q^2 and chiral extrapolations. This is consistent with experimental values, and has an order of magnitude smaller error.
We discuss the recent progress in extracting partonic functions from the quasi-distribution approach, using twisted mass fermions. This concerns, among others, the investigation of several sources of systematic effects. Their careful analysis is a prerequisite to obtain precise determinations of PDFs from the lattice with realistic estimates of all uncertainties. In these proceedings, we shortly discuss systematic effects in the matching procedure. Moreover, we present preliminary results from our new simulations at the physical point. They involve, additionally, the dynamical strange and char…
Stout Smearing for Twisted Mass Fermions
在数值模拟中，研究了扭曲质量Wilson夸克的Stout拖尾效应。本文研究了12^3 × 24、16^3 × 32和24^3 × 48格点上夸克质量近零的相变，格点间距a = 0.1 - 0.125 fm。
We discuss recent progress in studying Quantum Chromodynamics at finite temperature using $N_f=2+1+1$ Wilson twisted mass fermions. Particular interest is in QCD symmetries and their breaking and restoration. First, we discuss the behaviour of the $η'$ meson at finite temperature, which is tightly connected to the axial and chiral symmetries. The results suggest a small decrease of the $η'$ mass in the pseudo-critical region coming close to the non-anomalous contribution and subsequent growth at large temperatures. Second, we present the first results of lattice simulations of Quantum Chromody…
We present results for the flavor non-singlet u-d parton distribution functions within the nucleon using the quasi-PDF approach. The lattice calculation is performed by employing the twisted mass formulation and two gauge ensembles, having $N_f = 2$ and $N_f = 2 + 1 + 1$ dynamical fermions with masses tuned to their physical value. For the $N_f = 2$ physical point ensemble, the unpolarized, helicity and transversity distributions are computed for three values of the nucleon momentum, namely [6, 8, 10]$π/L$ corresponding to [0.83,1.11,1.38] GeV. Upon renormalization, we find that, as the nucleo…
We discuss the computation of the topological susceptibility using the method of spectral projectors and dynamical twisted mass fermions. We present our analysis concerning the O(a)-improvement of the topological susceptibility and we show numerical results for Nf=2 and Nf=2+1+1 flavours, performing a study of the quark mass dependence in terms of leading order chiral perturbation theory.
Nucleon matrix elements with domain wall fermions
本文介绍了核子结构函数前几阶矩的计算现状。我们的计算是使用畴壁费米子在淬火近似与DBW2规范行动在1.3GeV的逆晶格间距。
We discuss an extension of the QUDA library for the Wilson twisted mass operator. A performance analysis is presented for both degenerate and non-degenerate flavor doublets. The degenerate twisted mass fermion operator runs at up to 190, 487 and 856 Gflops, for double, single and half precisions respectively on recent NVIDIA Kepler GPUs, while our implementation for the non-degenerate flavor doublet allows to reach 163, 516 and 879 GFlops, respectively. The code is currently in production for the hadron structure study.
Going chiral: overlap versus twisted mass fermions
我们比较的行为重叠费米子，这是手征不变的，威尔逊扭曲的质量费米子在全扭曲的手征极限的方法。我们的淬火模拟表明，这两种配方的晶格费米子π质量的O（250兆电子伏）可以达到在实际应用中。我们的比较是在晶格间距a=0.123 fm的固定值下进行的。从沃德恒等式得到了强子质量、赝标衰变常数和夸克质量等一系列物理量。我们还确定了重叠费米子情况下的轴向矢量重整化常数。
Wilson fermions with chirally twisted mass
具有Wilson费米子和手征扭曲夸克质量矩阵的QCD格点公式为非微扰数值研究提供了一个有吸引力的框架。由于重参数化不变性，极限连续统理论就是QCD。在夸克质量有限的情况下，不会出现导致特殊组态问题的伪夸克零模。此外，可以调整的晶格配方的细节，以简化重整化和O（$a$）改善的几个数量的唯象相关性。淬火近似的第一次探索性研究产生了非常令人鼓舞的结果。
Light quarks with twisted mass fermions
我们在淬灭近似下研究了Wilson扭曲质量费米子，采用不同的临界裸夸克质量mc定义，实现了最大扭曲，相应地，物理观测量的O（a）自动改进。通过外推由PCAC关系得到的非零裸扭夸克质量μ的m_c值到μ =0，给出了m_c的一个特殊定义。采用这种改进的临界质量定义，威尔逊扭曲质量公式提供了一种可能性，可以在控制O（a^2）的截止效应的同时，用相应的小π介子质量（m_pi \simeq 250 MeV），对小到非常小的夸克质量进行可靠的模拟。
Pi-Pi scattering is investigated for the first time for Nf=2+1+1 dynamical quark flavours using Wilson twisted mass fermions. Lüscher's finite size method is used to relate energy shifts in finite volume to scattering quantities like the scattering length in the I=2 channel. The computation is performed at several pion masses and lattice spacings utilising the stochastic LapH method.
Previous Lattice QCD calculations of nucleon transverse momentum-dependent parton distributions (TMDs) focused on the case of transversely polarized nucleons, and thus did not encompass two leading-twist TMDs associated with longitudinal polarization, namely, the helicity TMD and the worm-gear TMD corresponding to transversely polarized quarks in a longitudinally polarized nucleon. Based on a definition of TMDs via hadronic matrix elements of quark bilocal operators containing staple-shaped gauge connections, TMD observables characterizing the aforementioned two TMDs are evaluated, utilizing a…
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