This end view of a low-energy collision event at STAR shows particle tracks on the right and detector "hits" from which tracks are derived on the left. Note the abundance of hits recorded by the detector's new inner sectors, which greatly enhance scientists' ability to reconstruct tracks.
The STAR detector at the Relativistic Heavy Ion Collider (RHIC) is the size of a small house. It captures snapshots of tracks left by thousands of particles created when two gold ions collide. Upgrades to STAR's inner core now allow the detector to track even more particles, including those with low momentum and those emerging close to the beamline.
A side view of particle tracks (left) and hits (right) from a collision in STAR, as recorded by the new iTPC sectors (top) compared to the old sectors (bottom). Notice how the new sectors record more hits per track, especially close to the beamline, as well as tracks at more forward and rearward angles (more to the left and right in this view).