Bullet Statements

The Sivers function describes the correlation between the momentum direction of the struck quark and the spin of its parent nucleon.

A non-vanishing Sivers function for the sea quarks is evidence there is sea quark orbital angular momentum (OAM).

If sea-quark Sivers asymmetry is non-zero, then sea quarks have non-zero OAM.

A non-zero Sivers asymmetry from SpinQuest is "smoking gun" evidence for sea quark OAM

SpinQuest will measure the correlation between the angular distribution of the di-muons and the proton spin. If this is non-zero, then the antiquarks must have some orbital angular momentum.

The first measurement of the sea quark Sivers function is not SpinQuest but has been performed by the Star collaboration at RHIC using W/Z boson production rather than Drell-Yan. https://arxiv.org/pdf/1511.06003.pdf

This may be replaced by:

Initial attempts to measure the Sivers asymmetry for sea quark Sivers have been reported by the STAR collaboration at RHIC using W/Z boson production. Their data is statistically limited and favor a sign-change only, if TMD evolutions effects are significantly smaller than expected.  Star publication: https://arxiv.org/pdf/1511.06003.pdf and study of the sign change of the Sivers function https://arxiv.org/pdf/1612.06413.pdf

SpinQuest will perform the first measurement of the Sivers asymmetry in Drell-Yan pp scattering from the sea quarks.

The gauge invariant definition of the Sivers function predicts the opposite sign for the Sivers function in SIDIS compared to processes with color charges in the initial state and a colorless final state such at Drell-Yan and W/Z boson production.  In W/Z production, it is guaranteed that an anti-quark is involved as in Drell-Yan process.

SpinQuest will explore properties of the nucleon's spin composition by investigating correlation of the light antiquarks motion relative to the nucleon spin.

SpinQuest will explore the interference between spin-flip and non-flip amplitudes with phase dependence.

SpinQuest can testing the interplay between time-reversal symmetry and gauge symmetry:  This can be understood by applying time-reversal to the quark fields in the operator definitions of the parton densities and how the gauge link provide the phase for the interference.  The Sivers asymmetry is manifest like other naive T-odd observables because one is not integrating in such a measurement over transverse momentum.

The transverse SSA are odd under naive time reversal (time reversal of three momenta and angular momenta) requiring interference of amplitudes with different helicities and phases.

The Sivers function and other TMDs are recognized as a tool to study spin-orbit correlations, providing experimental observables for studying orbital angular momentum.

SpinQuest is attempting to push the proton beam intensity frontier on a solid polarized target (specifically instantaneous intensity).

SpinQuest uses the longest target cell (and most volume) ever ran in a 1 K evaporation polarized target system.

Other Numbers and Important Points

The max intensity is 5X10¹² protons/spill with a 4.4 seconds spill

The max annual proton count is 7X10¹⁷ protons/year

Use 96% max proton polarization (average will be about 75%)

Use 50% max deuteron polarization (average will be about 30%)

Cooling power of the He-evaporation refrigerator is 1.4 W at 1 K assuming a flow rate of 20 SLPM (normal operation).  The pumps and fridge are capable of running at more than twice this flow rate while keeping the target around 1.1 K so the max cooling power while running is around 3 W.

This is the highest cooling power DNP (Dymanic Nuclear Polarization) target in the world due the the high pumping rate and the refrigerator.  This is important since we are attempting to run the highest proton intensity on a solid polarized target ever done.

This is also the highest proton intensity ever attempted on this type of superconducting target magnet.

[Collins, Hermes Sivers, After Star Update,