Searching for New Phenomena with Leptons

Northern Illinois University, Dekalb IL

Investigators

Abstract

One of the major intellectual achievements of the 20th century was the development of the Standard Model (SM) of particle physics. This model succeeded in classifying all of the elementary particles known at the time into a hierarchy of groups having similar quantum properties. The validity of this model to date was recently confirmed by the discovery of the Higgs boson at the Large Hadron Collider (LHC) at the CERN laboratory near Geneva Switzerland. However, the Standard Model as it currently exists leaves open many questions about the universe, including such fundamental questions as to why the mass of the Higgs boson has the value it has. To answer these questions it is necessary to go beyond the present picture of the Universe described by the Standard Model to the next phase of development, Beyond the Standard Model (BSM). Investigations in BSM physics probe such questions as why matter dominates over anti-matter in the Universe, the values of the masses of the fundamental constituents of matter, the quarks and the leptons, the size of the mixings among the quarks, and separately among the leptons, and the properties of dark matter. This project, which uses the Mu2e detector at Fermilab, will search for BSM physics through the precision measurement of the energy of electrons produced by the decay of muons. The broader impact of this work, in addition to contributions to the scientific collaborations, includes student engagement at Northern Illinois University, public outreach and service, and technology development through generation of patents and the development of technology usable for medical imaging. Undergraduate and graduate students from both physics and engineering participate in all aspects of this research. Technology developed by the R&D program has expanded techniques available for calorimetry and is currently being used for Mu2e and for a second generation proton tomography device, and has led to two patents with a third under consideration. Searches for evidence for new physics beyond the Standard Model can be addressed through direct searches at the Energy Frontier at High Energy Colliding Beam Facilities such as the LHC and through a complementary technique of indirect searches at the Intensity Frontier, in experimental measurements of rare processes such the subject of this award, the decay of a muon into an electron. In the SM such a decay is very rare, but certain BSM physics models, such as SuperSymmetry(SUSY) , predict a higher rate of this decay. In this award, the researchers will use the Mu2e detector at Fermi National Accelerator Laboratory (FNAL). This experiment uses a very intense beam of protons to produce a muon beam which traverses a series of magnets and impinges on a target where the muons are stopped and are captured by Aluminum atoms in the target. After a short period of time, the muons then decay to electrons and if the decay is a direct decay to an electron (with no neutrino) the electron has a unique characteristic energy. The challenge of this experiment is to measure the electron energy very precisely. If the electron energy distribution is correct, it will show evidence of the direct muon to electron decay and provide evidence that there is BSM physics.