# ZEU-NIC

 2019-03-1415:26 [PUBDB-2019-01546] Preprint/Report et al Conformal field theory and the hot phase of three-dimensional U(1) gauge theory [arXiv:1903.00491; DESY-19-027]   We study the high-temperature phase of compact U(1) gauge theory in 2+1 dimensions, comparing the results of lattice calculations with analytical predictions from the conformal-field-theory description of the low-temperature phase of the bidimensional XY model. We focus on the two-point correlation functions of probe charges and the field-strength operator, finding excellent quantitative agreement with the functional form and the continuously varying critical indices predicted by conformal field theory.. OpenAccess: PDF PDF (PDFA); 2019-02-1913:14 [PUBDB-2019-01169] Report/Journal Article Sommer, R. Large $N$ scaling and factorization in SU($N$) Yang-Mills gauge theory [DESY-18-075; arXiv:1805.11070]   The large $N$ limit of SU($N$) gauge theories is well understood in perturbation theory. Also non-perturbative lattice studies have yielded important positive evidence that t Hoofts predictions are valid. [...] OpenAccess: PDF PDF (PDFA); 2019-02-1109:44 [PUBDB-2019-01028] Journal Article Meyer, H. B. Nonperturbative renormalization and $O(a )$-improvement of the nonsinglet vector current with $N_f = 2 + 1$ Wilson fermions and tree-level Symanzik improved gauge action Physical review / D 99(1), 014519 (2019) [10.1103/PhysRevD.99.014519]   In calculating hadronic contributions to precision observables for tests of the Standard Model in lattice QCD, the electromagnetic current plays a central role. Using a Wilson action with $O(a)$ improvement in QCD with $N_ f$ flavors, a counterterm must be added to the vector current in order for its on-shell matrix elements to be $O(a)$ improved. [...] OpenAccess: PDF PDF (PDFA); 2019-01-2910:01 [PUBDB-2019-00846] Report/Journal Article et al Separated Kaon Electroproduction Cross Section and the Kaon Form Factor from 6 GeV JLab Data [JLAB-PHY-18-2645; arXiv:1801.01536] Physical review / C covering nuclear physics C97(2), 025204 (2018) [10.1103/PhysRevC.97.025204]   The H1(e,e′K+)Λ reaction was studied as a function of the Mandelstam variable −t using data from the E01-004 (FPI-2) and E93-018 experiments that were carried out in Hall C at the 6 GeV Jefferson Laboratory. The cross section was fully separated into longitudinal and transverse components, and two interference terms at four-momentum transfers Q2 of 1.00, 1.36, and 2.07GeV2. [...] OpenAccess: PDF PDF (PDFA); 2019-01-1611:53 [PUBDB-2019-00523] Report/Contribution to a conference proceedings Green, J. Systematics in nucleon matrix element calculations [DESY-18-224, arXiv:1812.10574] 36th International Symposium on Lattice Field Theory, LATTICE 2018, East LansingEast Lansing, USA, 22 Jul 2018 - 28 Jul 2018 15 pp. (2018) [10.3204/PUBDB-2019-00523]   The current status of calculations of simple nucleon structure observables is reviewed, with a focus on the axial charge. A major challenge is the combination of an exponentially decaying signal-to-noise ratio and the need for large source-sink separations to eliminate excited-state contributions; efforts to understand and deal with this problem are the focus of the largest section of this review. [...] OpenAccess: PDF PDF (PDFA); 2019-01-1415:08 [PUBDB-2019-00443] Preprint/Report et al Proton and neutron electromagnetic form factors from lattice QCD [arXiv:1812.10311; DESY-18-033]   The electromagnetic form factors of the proton and the neutron are computed within lattice QCD using simulations of maximally twisted mass fermions with masses fixed to their physical values. We analyse two new ensembles of $N_f=2$ and $N_f=2+1+1$ and use several values of the sink-source time separation in the range of 1.0 fm to 1.6 fm to ensure ground state identification. [...] OpenAccess: PDF PDF (PDFA); 2019-01-0315:05 [PUBDB-2019-00034] Report/Journal Article Steffens, F. Nonperturbative Renormalization of Nonlocal Quark Bilinears for Parton Quasidistribution Functions on the Lattice Using an Auxiliary Field [DESY-17-109; arXiv:1707.07152] Physical review letters 121(2), 022004 (2018) [10.1103/PhysRevLett.121.022004]   Quasi-PDFs provide a path toward an ab initio calculation of parton distribution functions (PDFs) using lattice QCD. One of the problems faced in calculations of quasi-PDFs is the renormalization of a nonlocal operator. [...] OpenAccess: PDF PDF (PDFA); 2019-01-0311:25 [PUBDB-2019-00019] Journal Article/Report/Contribution to a conference proceedings et al Hadronic light-by-light scattering contribution to the muon $g-2$ on the lattice [DESY-18-007; MITP-18-001; arXiv:1801.04238] International Workshop on “Flavour Changing and Conserving Processes, FCCP2017, AnacapriAnacapri, Italy, 7 Sep 2017 - 9 Sep 2017   We briefly review several activities at Mainz related to hadronic light-by-light scattering (HLbL) using lattice QCD. First we present a position-space approach to the HLbL contribution in the muon g-2, where we focus on exploratory studies of the pion-pole contribution in a simple model and the lepton loop in QED in the continuum and in infinite volume. [...] OpenAccess: PDF PDF (PDFA); 2019-01-0311:18 [PUBDB-2019-00018] Journal Article/Report/Contribution to a conference proceedings et al Connected and disconnected contributions to nucleon axial form factors using $\mathrm{N_f = 2}$ twisted mass fermions at the physical point [arXiv:1807.11203] 35th International Symposium on Lattice Field Theory, Lattice 2017, GranadaGranada, Spain, 18 Jun 2017 - 24 Jun 2017   We present results on the isovector and isoscalar nucleon axial form factors including disconnected contributions, using an ensemble of N$_f$ = 2 twisted mass cloverimproved 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. [...] OpenAccess: PDF PDF (PDFA); 2019-01-0311:12 [PUBDB-2019-00017] Journal Article/Report/Contribution to a conference proceedings et al Nucleon spin structure from lattice QCD [arXiv:1807.11214] XXVI International Workshop on Deep-Inelastic Scattering and Related Subjects, DIS2018, KobeKobe, Japan, 10 Apr 2018 - 20 Apr 2018   In this lattice QCD study we evaluate the nucleon spin decomposition to quarks and gluons con-tributions. We employ one gauge ensemble of maximally twisted mass fermions with two degen-erate light quarks tuned to approximately reproduce the physical pion mass [...] OpenAccess: PDF PDF (PDFA);