Constraining nucleon strangeness

Abstract

Determining the nonperturbative ss content of the nucleon has attracted considerable interest and been the subject of numerous experimental searches. These measurements used a variety of reactions and place important limits on the vector form factors observed in parity-violating (PV) elastic scattering and the parton distributions determined by deep inelastic scattering (DIS). In spite of this progress, attempts to relate information obtained from elastic and DIS experiments have been sparse. To ameliorate this situation, we develop an interpolating model using lightfront wave functions capable of computing both DIS and elastic observables. This framework is used to show that existing knowledge of DIS places significant restrictions on our wave functions. The result is that the predicted effects of nucleon strangeness on elastic observables are much smaller than those tolerated by direct fits to PV elastic scattering data alone. Using our model, we find −0.024 ≤ µs ≤ 0.035, and −0.137 ≤ ρ D s ≤ 0.081 for the strange contributions to the nucleon magnetic moment and charge radius. The model we develop also independently predicts the nucleon's strange spin content ∆s and scalar density N |ss|N , and for these we find agreement with previous determinations.2

Strange-quark asymmetry in the proton in chiral effective theory

“…extended previous light-front calculations using a scalar tetraquark spectator model with Gaussian and power-law wave functions [35], finding S − = (−1 to + 5) × 10 −3 .…”

“…1, with the interaction vertices given by the operators in Eqs. (34) and (35). In this section we give the complete set of strange hadron splitting functions in the effective theory.…”

Charge symmetry breaking in electromagnetic nucleon form factors in elastic parity-violating electron-nucleus scattering

“…A third dashed curve sets the strangeness contribution to zero (ρ s = 0). Recent work relates the strangeness contribution to deep inelastic scattering to that to proton electromagnetic form factors [13] through the use of light-front models, and ρ s is limited to values about 10 times smaller than in [8] are obtained. If these models are valid, the dashed curve (with dominant contribution arising from nuclear isospin violation) would be the best prediction.…”

“…We use this range of values in our numerical work. However, experiments on deep inelastic scattering restrict the s and s parton distribution functions to very small values [12] and reality may correspond to an order of magnitude smaller values of ρ s [13].…”

Role of nucleon strangeness in supernova explosions

“…In yet another model-based analysis, Hobbs et al [34] investigated the strange content of the proton using the framework of light-front wave functions (LFWFs). Truncating the nucleon Fock expansion at a twobody quark/scalar tetraquark state containing s and s, Ref.…”