Grant: Subatomic Physics Envelope - Project

High precision measurement of the ultra-rare kaon decay K+ to pi+ neutrino anti-neutrino (KPNN) at the CERN experiment NA62 will be one of the most incisive probes of quark flavor physics. The branching ratio is sensitive to new physics models not easily accessible by other reactions which extend the Standard Model (SM) to solve its considerable problems. The SM prediction for the KPNN branching fraction is theoretically robust at the 5% level. Only a precious few accessible 2nd order weak interaction quark processes can be predicted with this level of certainty. The suppression of the KPNN branching fraction in the SM to the level 10-10 allows physics beyond the SM to contribute dramatically to the branching fraction. The certainty with which the SM contribution to KPNN can be predicted permits significant discovery potential for new physics with sensitivity to probe a wide variety of models of new physics with mass scales well beyond the direct reach of the Large Hadron Collider. NA62 expects to have sensitivity for observing 80 events at the SM level for KPNN covering most of the parameter space for new physics models to contribute. It will also study many other rare or forbidden reactions to search for dark matter, heavy sterile neutrinos, neutral pion decays, and radiative processes. In addition, searches for axion-like and hidden sector particles are being investigated using an alternate mode of operation.