Speaker: Stephen Pate (New Mexico State University)
Title: "Don't Forget to Measure $\Delta s$"
Abstract:
Measurements of the strange quark form factors of the nucleon are intimately related
to measurements of the strange quark contribution to the spin structure of the nucleon,
as the value of the strange axial form factor $G_A^s$ at $Q^2=0$ is $\Delta s$, the
first moment of the helicity-dependent strange quark momentum distribution $\Delta s(x)$.
The program of parity-violating electron-nucleon scattering measurements at Bates, Mainz,
and Jefferson Lab, seeking to measure the strange electromagnetic form factors, are also
sensitive to the strange axial form factor, and usually take $\Delta s$ to be a measured
quantity. But there has never been a direct measurement of $\Delta s$. The value
typically used is derived from a combination of theoretical and experimental input, and
hangs on a number of assumptions for which the theoretical uncertainties are completely
unknown. I will discuss the implications of this situation for the current program of
electron-nucleon experiments and look ahead to a proposed experiment that could address
this important issue.
Send comments to:
bdob@fnal.gov
