0000000000122376
AUTHOR
Jonas Wilhelm
showing 11 related works from this author
Nucleon isovector charges and twist-2 matrix elements with Nf=2+1 dynamical Wilson quarks
2019
We present results from a lattice QCD study of nucleon matrix elements at vanishing momentum transfer for local and twist-2 isovector operator insertions. Computations are performed on gauge ensembles with nonperturbatively improved ${N}_{f}=2+1$ Wilson fermions, covering four values of the lattice spacing and pion masses down to ${M}_{\ensuremath{\pi}}\ensuremath{\approx}200\text{ }\text{ }\mathrm{MeV}$. Several source-sink separations (typically $\ensuremath{\sim}1.0$ to $\ensuremath{\sim}1.5\text{ }\text{ }\mathrm{fm}$) allow us to assess excited-state contamination. Results on individual ensembles are obtained from simultaneous two-state fits across all observables and all available sou…
The hadronic contribution to the running of the electromagnetic coupling and the electroweak mixing angle
2019
37th International Symposium on Lattice Field Theory, Wuhan, China, 16 Jun 2019 - 22 Jun 2019; PoS(LATTICE 2019)010 (2019).
Nucleon average quark momentum fraction with Nf = 2+1 Wilson fermions
2018
We report on an analysis of the average quark momentum fraction of the nucleon and related quantities using Nf = 2 + 1 Wilson fermions. Computations are performed on four CLS ensembles covering three values of the lattice spacing at pion masses down to Mπ ≈ 200 MeV. Several source-sink separations (~ 1:0 fm to ~ 1:4 fm) are used to assess the excited-state contamination. To gain further insight, the generalized pencil-of-functions approach has been implemented to reduce the excited-state contamination in the relevant two-and three-point functions. Preliminary results are shown for the isovector nucleon charges from vector, axial vector and tensor derivative (twist-2) operators.
Strange Electromagnetic Form Factors of the Nucleon with Nf=2+1 O(a) -Improved Wilson Fermions
2019
We present results for the strange contribution to the electromagnetic form factors of the nucleon computed on the coordinated lattice simulation ensembles with N_{f}=2+1 flavors of O(a)-improved Wilson fermions and an O(a)-improved vector current. Several source-sink separations are investigated in order to estimate the excited-state contamination. We calculate the form factors on six ensembles with lattice spacings in the range of a=0.049-0.086 fm and pion masses in the range of m_{π}=200-360 MeV, which allows for a controlled chiral and continuum extrapolation. In the computation of the quark-disconnected contributions, we employ hierarchical probing as a variance-reduction technique.
Continuum Goldstone spectrum of two-color QCD at finite density with staggered quarks
2019
We carry out lattice simulations of two-color QCD and spectroscopy at finite density with two flavors of rooted-staggered quarks and a diquark source term. As in a previous four-flavor study, for small values of the inverse gauge coupling we observe a Goldstone spectrum which reflects the symmetry-breaking pattern of a Gaussian symplectic chiral random-matrix ensemble (GSE) with Dyson index $\beta_D=4$, which corresponds to any-color QCD with adjoint quarks in the continuum instead of QC$_2$D wih fundamental quarks. We show that this unphysical behavior occurs only inside of the bulk phase of $SU(2)$ gauge theory, where the density of $Z_2$ monopoles is high. Using an improved gauge action …
Lattice calculation of the hadronic leading order contribution to the muon g − 2
2019
The European physical journal / Web of Conferences Web of Conferences : proceedings proceedings 234, 01016 - (2020). doi:10.1051/epjconf/202023401016
Isovector electromagnetic form factors of the nucleon from lattice QCD and the proton radius puzzle
2021
Physical review / D 103(9), 094522 (2021). doi:10.1103/PhysRevD.103.094522
Hadronic Contributions to the Anomalous Magnetic Moment of the Muon from Lattice QCD
2021
The Standard Model of Particle Physics describes three of the four known fundamental interactions: the strong interaction between quarks and gluons, the electromagnetic interaction, and the weak interaction. While the Standard Model is extremely successful, we know that it is not a complete description of nature. One way to search for physics beyond the Standard Model lies in the measurement of precision observables. The anomalous magnetic moment of the muon \(a_\mu \equiv \frac{1}{2}(g-2)_\mu \), quantifying the deviation of the gyromagnetic ratio from the exact value of 2 predicted by the Dirac equation, is one such precision observable. It exhibits a persistent discrepancy of 3.5 standar…
The anomalous magnetic moment of the muon in the Standard Model
2020
We are very grateful to the Fermilab Directorate and the Fermilab Theoretical Physics Department for their financial and logistical support of the first workshop of the Muon g -2 Theory Initiative (held near Fermilab in June 2017) [123], which was crucial for its success, and indeed for the successful start of the Initiative. Financial support for this workshop was also provided by the Fermilab Distinguished Scholars program, the Universities Research Association through a URA Visiting Scholar award, the Riken Brookhaven Research Center, and the Japan Society for the Promotion of Science under Grant No. KAKEHNHI-17H02906. We thank Shoji Hashimoto, Toru Iijima, Takashi Kaneko, and Shohei Nis…
Nucleon isovector charges and twist-2 matrix elements with Nf=2+1 dynamical Wilson quarks
2019
We present results from a lattice QCD study of nucleon matrix elements at vanishing momentum transfer for local and twist-2 isovector operator insertions. Computations are performed on gauge ensembles with nonperturbatively improved Nf=2+1 Wilson fermions, covering four values of the lattice spacing and pion masses down to Mπ≈200 MeV. Several source-sink separations (typically ∼1.0 to ∼1.5 fm) allow us to assess excited-state contamination. Results on individual ensembles are obtained from simultaneous two-state fits across all observables and all available source-sink separations with the energy gap as a common fit parameter. Renormalization has been performed nonperturbatively using the R…
Leading hadronic contribution to (g−2)μ from lattice QCD with Nf=2+1 flavors of O(a) improved Wilson quarks
2019
The comparison of the theoretical and experimental determinations of the anomalous magnetic moment of the muon (g−2)μ constitutes one of the strongest tests of the Standard Model at low energies. We compute the leading hadronic contribution to (g−2)μ using lattice QCD simulations employing Wilson quarks. Gauge field ensembles at four different lattice spacings and several values of the pion mass down to its physical value are used. We apply the O(a) improvement program with two discretizations of the vector current to better constrain the approach to the continuum limit. The electromagnetic current correlators are computed in the time-momentum representation. In addition, we perform auxilia…