| Popis: |
The contribution of the gluon helicity to the spin of the proton is being studied through the use of the unique capability of the Relativistic Heavy-Ion Collider (RHIC) to collide polarized protons at $\sqrt{s}=200\,$GeV and $\sqrt{s}=510\,$GeV. The kinematic coverage of the Solenoidal Tracker At RHIC (STAR) allows access to gluons through quark-gluon and gluon-gluon scattering processes which dominate jet production at low and medium transverse momentum. The polarized gluon distribution function, $\Delta g(x)$, can be constrained through a global analysis by measuring the longitudinal double-spin asymmetry ($A_{LL}$) of inclusive jet and dijet production. Published inclusive jet results from 2009 at mid-rapidity ($|\eta| < 1$) at $\sqrt{s}=200\,$GeV have been used in global analyses and suggest a statistically significant non-zero truncated first moment of $\Delta g(x)$ for $x>0.05$. An additional data sample with an integrated luminosity of $43\,$pb$^{-1}$ has been collected in 2015, which is over twice as large as the corresponding $20\,$pb$^{-1}$ of the 2009 data. Longitudinal double-spin asymmetry results from this new large data sample will further improve the precision of $\Delta g(x)$ for $x>0.05$. |
