Strange nucleon form factors and isoscalar charges with $N_f=2+1$ $\mathcal{O}(a)$-improved Wilson fermions

Abstract

We report on our calculation of the strange contribution to the vector and axial vector form factors. The strange charge radii, magnetic moment, and axial charge are extracted by model independent z-expansion fits to the Q 2 -dependence of the respective form factors. Furthermore, the isoscalar contribution to the axial and tensor charge is investigated by combining the calculation of connected and disconnected diagrams. The required renormalization is performed with the Rome-Southampton method. We make use of the CLS N f = 2 + 1 O(a)-improved Wilson fermion ensembles. Results are reported for pion masses in the range m π = 200 − 360 MeV and lattice spacings a = 0.05 − 0.086 fm.

Recent results of nucleon structure & matrix elementcalculations

“…8), the u and d quark contributions are known at 4 and 7% accuracy, whereas the s quark contribution differs from zero only by 1.7σ. New calculations from the Mainz [19] and PNDME [17] collaborations give consistent values for the u and d quark contributions. PNDME have reduced the uncertainty on the s quark matrix element, g s T , and it is now negative with > 2σ confidence.…”

“…New results on the disconnected contribution, in particular the strange contribution, were also presented this year by the Mainz collaboration [19].…”

“…New results for the disconnected contributions to the form-factors are available from the ETMC [23] and Mainz [19] collaborations (See Figs. 13 and 12).…”

“…In a parallel talk, Boram Yoon [34], summarized the unrenormalized results for the F 3 form factors, which are reproduced in Fig. 19 [relaxed 2-state] E 0 , A 0 and M 0 , A 0 are taken from nucleon two-point correlator fits. Excited state parameters are free.…”

All about the neutron from lattice QCD

“…This is not practical as it is a (12•10 8 )×(12•10 8 ) complex matrix for a 100 4 lattice. The solution is to construct [3,4] obtained by different collaborations ( PNDME '22 [14] ETM '19 [15], PNDME '18 [16] Mainz '18 [17], χQCD 18 [18], JLQCD '18 [19], ETM '17 [20], χQCD 15A [21], Engelhardt '12 [22]). The points with filled squares meet the FLAG criteria for inclusion in the FLAG average.…”