Ultra-Cold Neutron measurement of Proton branching in neutron Beta decay (UCNProBe)*

The lifetime of the free neutron has been measured many times, each experiment using one of two methods: measuring the decay products of neutrons in a well calibrated neutron beam (beam experiment), or counting the number of surviving neutrons stored in a UCN trap over time (bottle experiment). The lifetime results from the two different methods of experiments differ by 10 seconds or five standard deviations. Our goal is to resolve the difference between the two measurements by measuring the proton branching ratio of neutron decay using UCNs. Detecting a proton branching ratio of less than one will indicate new physics beyond the Standard Model of particle physics. The experiment is realized by storing the neutrons in a scintillating material trap. To measure the proton branching ratio, we will attempt to measure the absolute number of UCNs inside the trap and the absolute number of electrons from beta decay to 0.1% precision. In this talk, we will describe the concept of the experiment and its systematic error.