The LHCf experiment in the LHC tunnel

The LHCf (Large Hadron Collider forward) is a special-purpose Large Hadron Collider experiment for astroparticle (cosmic ray) physics, and one of eight detectors in the LHC accelerator complex. LHCf is designed to study the particles generated in the "forward" region of collisions, those almost directly in line with the colliding proton beams. It therefore consists of two detectors, 140 m on either side of the interaction point near the ATLAS detector, the much larger general-purpose ATLAS experiment.