Cross Sections and Transverse Single-Spin Asymmetries in Forward Jet Production from Proton Collisions at $\sqrt{s}=500$ GeV

Abstract

Measurements of the production of forward jets from transversely polarized proton collisions at $\sqrt{s}=500$ GeV conducted at the Relativistic Heavy Ion Collider (RHIC) are reported. Our measured jet cross section is consistent with hard scattering expectations. Our measured analyzing power for forward jet production is small and positive, and provides constraints on the Sivers functions that are related to partonic orbital angular momentum through theoretical models.

Figures (8)

• Figure 1: A top view from the GEANT model of A$_N$DY configuration for the 2011 run. The Blue beam travels in the positive $z$ direction, and Yellow beam in the opposite direction. IR indicates the center of the collision region.
• Figure 2: Cluster pair mass distributions, normalized by number of minimum-bias triggers, for single-tower clusters that are primarily photons, showing $\pi^0\rightarrow\gamma\gamma$. (left and middle) Data to simulation comparison for the HCal modules. (right) Association analysis of the simulation showing contributions to the cluster pair mass.
• Figure 3: Cluster pair mass distributions, where each cluster is required to have energy deposition in the matching BBC detector corresponding to a minimum-ionizing particle, from data and simulation. The peak in the data is consistent with the known mass PDG of $K^{0*}$, reconstructed via $K^{0*}\rightarrow K^-\pi^+$ (and charge conjugates), as determined from a fit to the data using a Gaussian peak (centroid, $\mu$) plus background.
• Figure 4: Tower multiplicity distributions for forward jets for data compared to full simulation for (left) jets from $\sqrt{s}=500\,$GeV collisions, as used for the jet analyzing power; and for (middle) jets from $\sqrt{s}=510\,$GeV collisions, as used for the jet cross section. (right) Multiplicity of particles produced by PYTHIA 6.222 PYTHIA6222 that gives rise to the forward jet.
• Figure 5: (left) Event averaged jet shape, corresponding to how the energy depends on R, the distance of a tower from the thrust axis in ($\eta,\phi$) space. (right) Correlation between jet $x_F$ and $p_T$. The color scale is the number of events.