Sivers Function
The Sivers function describes the correlation between the momentum direction of the struck quark and the spin of its parent nucleon.
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SpinQuest uses the longest target cell (and most volume) ever ran in a 1 K evaporation polarized target system.
Boer-Mulders function
The Boer-Mulders function describes a correlation between the transverse spin (polarization) and the transverse momentum of a quark inside an unpolarized hadron. The Boer-Mulders function (commonly denoted by h1⊥) describes the net polarization of quarks inside an unpolarized proton. Protons and quarks are both spin-1/2 particles that can be polarized in specific directions (they can have spin up or spin down in a specific direction). If one averages over the polarization states of the proton, then we call it an unpolarized proton (the net polarization averaged over many protons in a proton beam for instance is then zero). It turns out that the quarks can be polarized on average even inside such an unpolarized proton, as long as they are not moving exactly along the proton direction. If the proton moves along the z direction say, then the quarks can have some transverse momentum kT with respect to the proton momentum, which together define a plane. The quarks can then have a net polarization orthogonal (or transverse) to that plane. A nonzero Boer-Mulders function means that there is such a net quark polarization.
Other Numbers and Important Points
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