Apr 8 – 12, 2024
Maison MINATEC, Grenoble, FRANCE
Europe/Paris timezone

Probing gluon and strange quark helicity distribution in the proton at STAR

Apr 9, 2024, 2:30 PM
Maison MINATEC, Grenoble, FRANCE

Maison MINATEC, Grenoble, FRANCE

3 Parv. Louis Néel, 38054 Grenoble
Regular parallel talk WG5: Spin and 3D Structure WG5


Yi Yu


Unraveling the proton spin composition, comprising intrinsic spins and angular momenta of quarks and gluons, stands as one of the most fundamental and challenging questions in QCD. Tremendous progress has been made since the first surprising result by the EMC experiment in the late 1980s, significantly contributing to our understanding of this question. However, the helicity distributions of strange quarks and anti-quarks inside the proton are still not well constrained by the experimental data.
Measurement of the longitudinal double spin asymmetry, $A_{LL}$, of $\Lambda$, $\overline{\Lambda}$ and $K_S^0$ in the longitudinally polarized proton-proton collisions may shed light on the strange quark and anti-quark helicity distributions. In addition, the $A_{LL}$ of the inclusive jets tagged with a $\pi^+/\pi^-$ carrying high jet momentum fraction, $z$, in proton-proton collisions can provide further constraints on the gluon helicity distribution in the proton.

In this talk, we will present the preliminary results of the $A_{LL}$ for $\Lambda$, $\overline{\Lambda}$ and $K_S^0$, and the inclusive jets tagged with a high-$z$ $\pi^{\pm}$. These results are based on the longitudinally polarized proton-proton collisions at $\sqrt{s}=200$ $\rm{GeV}$ collected by the STAR experiment with an integrated luminosity of about 52 $\rm{pb^{-1}}$.

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