Abstract
We evaluate the strange nucleon electromagnetic form factors using an ensemble of gauge configurations generated with two degenerate maximally twisted mass clover-improved fermions with mass tuned to approximately reproduce the physical pion mass. In addition, we present results for the disconnected light quark contributions to the nucleon electromagnetic form factors. Improved stochastic methods are employed leading to high-precision results. The momentum dependence of the disconnected contributions is fitted using the model-independent z-expansion. We extract the magnetic moment and the electric and magnetic radii of the proton and neutron by including both connected and disconnected contributions. We find that the disconnected light quark contributions to both electric and magnetic form factors are nonzero and at the few percent level as compared to the connected. The strange form factors are also at the percent level but more noisy yielding statistical errors that are typically within one standard deviation from a zero value.
Highlights
The electromagnetic form factors of the nucleon are important quantities encapsulating information about the distribution of electric charge and magnetism inside the proton and neutron
We evaluate the strange nucleon electromagnetic form factors using an ensemble of gauge configurations generated with two degenerate maximally twisted mass clover-improved fermions with mass tuned to approximately reproduce the physical pion mass
We find that the disconnected light quark contributions to both electric and magnetic form factors are nonzero and at the few percent level as compared to the connected
Summary
The electromagnetic form factors of the nucleon are important quantities encapsulating information about the distribution of electric charge and magnetism inside the proton and neutron. A combined analysis of proton and neutron electromagnetic and weak form factors from elastic electron-nucleon scattering mediated by photon and Z0 exchange provides more recent estimates for the electric and magnetic form factors [4,5,6] for some recent experimental results) These studies deliver results consistent with zero for the strange quark contribution, and as such, provide limits on the contribution of strange quarks in the distribution of nucleon charge and magnetization.
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