Speaker
Description
The spin of the nucleon is well established but the contribution to this intrinsic
value from its constituent partons is still under intense investigation. As part of
a global effort to map out these individual contributions, the SpinQuest experiment at Fermilab aims to add significantly to the level of information available
on sea-quarks by measuring their Sivers function. To separate the contributions
of ̄u and ̄d quarks to the Sivers asymmetry, the experiment uses both NH3 and
ND3 polarized targets, interacting with an incoming unpolarized 120 GeV/c
proton beam. The dimuons from the Drell-Yan process are detected to analyze
the azimuthal asymmetry. The incoming proton beam will also interact with
other materials that are present in the experimental beam path, such as the
target cell walls, the aluminum insert ladder, the microwave horn, liquid helium
and nitrogen in the ammonia target. The figure of merit in our extracted Sivers
function is directly dependent on both the magnitude of polarization and the
interaction rate from these various unwanted materials resulting in a dilution
factor. With the use of MCFM (Monte Carlo simulation at femtobarn), a par-
ton distribution based cross-section generator we can analyze the contributions
from unmeasured cross-sections from these various materials to find the degree
of dilution and the corresponding kinematic sensitivity. This contribution to
the experimental systematic error and its management is reviewed in this presentation.