Session 2WCB: Polarized Drell-Yan Physics at Fermilab II

SpinQuest/E1039 Status

The SpinQuest/E1039 experiment is being conducted at the Fermi National Accelerator Laboratory and aims to pioneer the measurement of the Sivers function for sea quarks using the Drell-Yan process. By using the Drell-Yan process in proton-proton scattering and observing transverse single spin asymmetry, the experiment seeks to provide the evidence for the presence of orbital angular momentum in light antiquarks within the nucleon. The experiment employs a 120-GeV extracted proton beam colliding with transversely-polarized NH₃ and ND₃ cryogenic targets, and a spectrometer that detects pairs of positive and negative muons from Drell-Yan production on polarized nucleons. This will allow a measurement of the transverse single spin asymmetry for a number of physics processes, including J/ψ and Drell-Yan production. This talk will provide an overview of the SpinQuest experiment, explain its physics objectives, and provide insights into its current progress.   

Transverse spin physics programs at colliders

Transversely polarized proton-proton collisions provide a unique opportunity to improve our understanding of transverse spin structure of the proton. The complex spin structure of the proton leads to emergent properties such as spin-momentum and spin-spin correlations analogous to the fine and hyperfine structure of atoms. These correlations in protons are experimentally accessible through observables known as transverse single-spin asymmetries (TSSAs). TSSAs quantify azimuthal modulations of particle production in collisions of transversely polarized nucleons with unpolarized particles, and have been measured to reach magnitudes up to 40% in hadron-hadron collisions. Two complementary theoretical frameworks have been developed for describing large TSSAs in which contributions arise from nonperturbative elements of the factorized cross section 1) transverse-momentum-dependent (TMD) factorization, and 2) twist-3 factorization. Both frameworks have demonstrated success in modeling TSSAs in complementary regions of transverse momentum, and are relevant for constraining orbital angular momentum of quarks and gluons in protons 

In order to disentangle these underlying mechanisms of the transverse spin structure of proton, TSSAs were measured for various observables in transversely polarized proton+proton collisions at the Relativistic Heavy Ion Collider (RHIC). In this talk, I will present latest results from STAR and  PHENIX experiments as well as future prospects in the sPHENIX experiment.    

The Transverse Structure of the Deuteron with Drell-Yan at SpinQuest

This talk discusses the proposed measurement of the neutron and deuteron transversity TMDs at the Fermilab SpinQuest experiment.  The quark transversity distributions are decoupled from the deuteron gluon transversity in the Q² evolution due to the chiral-odd property in the transversely-polarized target. The gluon transversity TMD only exists for targets of spin greater or equal to 1 and does not mix with quark distributions at leading twist, thereby providing a particularly clean probe of gluonic degrees of freedom. This experiment would be the first of its kind and would probe the gluonic structure of the deuteron, investigating exotic glue contributions in the nucleus not associated with individual nucleons. This experiment can be performed with the SpinQuest polarized target at Fermilab. This new experiment would require a specialized RF-driven solid-state target system

to align the spins to probe linearly polarized gluons.  Dedicated beam time with this novel target system is required to achieve these new physics goals at SpinQuest.