PENeLOPE: Measuring a precise neutron lifetime with an ultracold neutron magneto-gravitational trap

Synopsis

The neutron lifetime from beta decay, τ_n , is a significant value for predictions in particle physics and cosmology. It is used to verify unitarity of the Cabbibo-Kobayashi-Maskawa (CKM) matrix, the Standard Model’s weak force quark mixing matrix, and for evaluating the abundances of light elements such as Helium-4, created during big bang nucleosynthesis. Furthermore, there is a 3.6 σ discrepancy of neutron lifetime results from beam experiments (τ_{n beam} = 887.7 ± 1.2 ± 1.9s), and ultracold neutron (UCN) trap experiments (τ_{n trap} = 877.75± 0.28^{+ 0.22}_{− 0.16}s). The measurements should agree, since beam experiments measure daughter particles from beta decay, and trap experiments measure surviving neutrons. Thus, the discrepancy may be evidence of Physics beyond the Standard Model. A more precise value of the neutron lifetime from beam or trap experiments provides more constraint on the value of the first element of the CKM matrix used in verifying unitarity. It also provides constraint on the neutron-proton ratio during Big Bang Nucleosynthesis which influences the abundance of light elements created, as well as providing constraint on the discrepancy between the beam and trap methods. PENeLOPE (Precision Experiment on the Neutron Lifetime Operating with Proton Extraction), located at Technical University of Munich, Germany, is a UCN magneto-gravitational trap experiment with a goal of determining the neutron lifetime to a precision of 0.1s. In this presentation, I will briefly discuss the motivation for the measurement, how UCN are trapped in PENeLOPE, and how the experiment cycle of PENeLOPE is optimized to reach a sensitivity of 0.1s.