Hadrons are particles that take part in the strong interactions – the force that binds quarks together and keeps atomic nuclei from falling apart. The SPS Heavy Ion and Neutrino Experiment (NA61/SHINE) studies the properties of the production of hadrons in collisions of beam particles (pions, and protons, beryllium, argon and xenon) with a variety of fixed nuclear targets. NA61 reuses most of the detectors of its predecessor NA49 with important upgrades.
The NA61 team uses particles from the Super Proton Synchrotron (SPS) to measure the production of hadrons in three different types of collisions:
- Nucleus-nucleus (heavy-ion) collisions are used to investigate properties of the transition line between quark-gluon plasma and hadron gas by collision energy scans with various beam and target nuclei
- Proton-proton and proton-nucleus collisions are recorded as reference data, better to understand nucleus–nucleus reactions
- Hadron-nucleus interactions are used to determine neutrino beam properties within the T2K experiment and to model cosmic ray showers within the Pierre Auger Observatory (PAO) in Argentina and KASKADE experiments in Germany
To produce hadrons, 400 GeV/c protons from the SPS are made to collide with a beryllium plate 500 metres upstream of NA61. The H2 beamline selects hadrons with a particular charge and momentum to transport to NA61.
NA61 beam and trigger detectors measure precisely the position and mass of each beam hadron and check whether it interacted in the NA61 target. This allows the team to select collisions of particular hadron types (protons and pions for example). NA61 detectors located downstream of the target measure properties of the collisions, such as the number hadrons produced, their momenta, charges and masses.
About 140 physicists from 15 countries and 28 institutions work in NA61/SHINE.