 Award ID(s):
 1653405
 Publication Date:
 NSFPAR ID:
 10097106
 Journal Name:
 The 36th Annual International Symposium on Lattice Field Theory (LATTICE2018)
 Volume:
 334
 Page Range or eLocationID:
 123
 Sponsoring Org:
 National Science Foundation
More Like this

We study and demonstrate the groundstate extrapolation of the unpolarized and polarized nucleon quark quasiPDF matrix elements in a highly boosted hadron frame on the lattice. The calculation is done using the Wilson clover quark on a MILC’s dynamical Nf = 2+1+1 highly improved staggered quarks (HISQ) ensemble with one step hypercubic smearing, and with the lattice spacing a∼0.09 fm and pion mass 310 MeV. Applying the Gaussian momentumsmeared quark sources and comparing various fits in 1, 2, and 3state fitting models, we show that excited state contributions can be under control in the lattice calculation of the nucleon quark quasiPDF matrix elements.

Abstract We present the first unquenched latticeQCD calculation of the form factors for the decay
at nonzero recoil. Our analysis includes 15 MILC ensembles with$$B\rightarrow D^*\ell \nu $$ $B\to {D}^{\ast}\ell \nu $ flavors of asqtad sea quarks, with a strange quark mass close to its physical mass. The lattice spacings range from$$N_f=2+1$$ ${N}_{f}=2+1$ fm down to 0.045 fm, while the ratio between the light and the strangequark masses ranges from 0.05 to 0.4. The valence$$a\approx 0.15$$ $a\approx 0.15$b andc quarks are treated using the Wilsonclover action with the Fermilab interpretation, whereas the light sector employs asqtad staggered fermions. We extrapolate our results to the physical point in the continuum limit using rooted staggered heavylight meson chiral perturbation theory. Then we apply a modelindependent parametrization to extend the form factors to the full kinematic range. With this parametrization we perform a joint latticeQCD/experiment fit using several experimental datasets to determine the CKM matrix element . We obtain$$V_{cb}$$ ${V}_{\mathrm{cb}}$ . The first error is theoretical, the second comes from experiment and the last one includes electromagnetic and electroweak uncertainties, with an overall$$\left V_{cb}\right = (38.40 \pm 0.68_{\text {th}} \pm 0.34_{\text {exp}} \pm 0.18_{\text {EM}})\times 10^{3}$$ $\left({V}_{\mathrm{cb}}\right)=(38.40\pm 0.{68}_{\text{th}}\pm 0.{34}_{\text{exp}}\pm 0.{18}_{\text{EM}})\times {10}^{3}$ , which illustrates the tensions between the experimental data sets, and between theory and experiment. This result is inmore »$$\chi ^2\text {/dof} = 126/84$$ ${\chi}^{2}\text{/dof}=126/84$ 
We present the first determination of the xdependent pion gluon distribution from lattice QCD using the pseudoPDF approach. We use lattice ensembles with 2+1+1 flavors of highly improved staggered quarks (HISQ), generated by MILC Collaboration, at two lattice spacings a≈0.12 and 0.15~fm and three pion masses Mπ≈220, 310 and 690 MeV. We use clover fermions for the valence action and momentum smearing to achieve pion boost momentum up to 2.29 GeV. We find that the dependence of the pion gluon parton distribution on lattice spacing and pion mass is mild. We compare our results from the lightest pion mass ensemble with the determination by JAM and xFitter global fits.

We apply the densityfunctional theory to study various phases (including nonmagnetic (NM), antiferromagnetic (AFM), and ferromagnetic (FM)) in monolayer magnetic chromium triiodide (CrI 3 ), a recently fabricated 2D magnetic material. It is found that: (1) the introduction of magnetism in monolayer CrI 3 gives rise to metaltosemiconductor transition; (2) the electronic band topologies as well as the nature of direct and indirect band gaps in either AFM or FM phases exhibit delicate dependence on the magnetic ordering and spin–orbit coupling; and (3) the phonon modes involving Cr atoms are particularly sensitive to the magnetic ordering, highlighting distinct spin–lattice and spin–phonon coupling in this magnet. Firstprinciples simulations of the Raman spectra demonstrate that both frequencies and intensities of the Raman peaks strongly depend on the magnetic ordering. The polarization dependent A 1g modes at 77 cm −1 and 130 cm −1 along with the E g mode at about 50 cm −1 in the FM phase may offer a useful fingerprint to characterize this material. Our results not only provide a detailed guiding map for experimental characterization of CrI 3 , but also reveal how the evolution of magnetism can be tracked by its lattice dynamics and Raman response.

Abstract On a lattice with 2+1flavor dynamical domainwall fermions at the physical pion mass, we calculate the decay constants of
, , and . The lattice size is , which corresponds to a spatial extension of fm, with a lattice spacing of fm. For the valence light, strange, and charm quarks, we use overlap fermions at several mass points close to their physical values. Our results at the physical point are MeV, MeV, MeV, MeV, and MeV. The couplings of and to the tensor current ( ) can be derived from ratios and , respectively, which are the first lattice quantum chromodynamics (QCD) results. We also obtain ratios and , which reflect the size of heavy quark symmetry breaking in charmed mesons. Ratios and can be taken as a measure ofSU (3) flavor symmetry breaking.