NA62: Measuring rare kaon decays
The main aim of the NA62 experiment is to study rare kaon decays. Understanding these decays will help physicists to check some of the predictions that the Standard Model makes about short-distance interactions.
Specifically, NA62 will measure precisely the rate at which the charged kaon decays into a charged pion and a neutrino-antineutrino pair. To make beams rich in kaons, the NA62 team uses high-energy protons from the Super Proton Synchrotron (SPS) sent into a stationary beryllium target. The collision creates a beam which transmits almost one billion particles per second, about 6% of which are kaons.
Before entering into a large vacuum tank, each particle is measured by a silicon-pixel detector. A detector called CEDAR determines the types of particle in the beam from their Cherenkov radiation. Further detectors look for decay particles: a magnetic spectrometer in the tank measures charged tracks from kaon decays and a ring imaging Cherenkov detector (RICH) tells the team the nature of each decay particle. A large system of photon and muon detectors reject unwanted decays.
In 2 years of data taking the experiment is expected to detect about 80 decay candidates if the Standard Model prediction is correct.
This data will enable the NA62 team to determine the value of a quantity called |Vtd|, which defines the likelihood that top quarks decay to down quarks.
Understanding with precision the relations between quarks is one effective way to check the consistency of the Standard Model.