Session R02: Frontier Physics Enabled by New Facilities

Charged Lepton Flavor Violation and the new Mu2e and COMET experiments.

Charged lepton flavor violating (CLFV) transitions are powerful probes of physics beyond the standard model, addressing the question of particle generations and the physics of flavor. Unlike weak decays, CLFV transitions among the muon, electron, and tau proceed without neutrinos. Such processes are extremely suppressed in the standard model, and an observation would be a clear sign of new physics. Worldwide efforts with new experiments will greatly improve on current data. Among future initiatives, the Mu2e experiment at Fermilab and the COMET experiment at J-PARC will search for the neutrino-less muon-to-electron conversion with unprecedented sensitivity. These experiments are expected to improve upon previous bounds by four order of magnitude, probing a wide range of new physics scenarios up to mass scales of nearly 10000 TeV, far beyond the direct reach of current colliders. Several approaches to CLFV searches will be reviewed, focusing on the Mu2e and COMET experiments.   

Exploring new physics with Muon g-2

Precision measurements of the static properties of leptons and baryons are increasingly important in an era where signatures of beyond the Standard Model (SM) physics remain conspicuously absent from experiments operating at the energy frontier. The anomalous magnetic moment of the muon $a_\mu\equiv\frac{(g-2)}{2}$ can be calculated and measured to extraordinary precision, permitting a unique sensitivity to contributions from new particles and forces. To date, the most precise measurement of $a_\mu$, made by the E821 experiment at Brookhaven National Laboratory (BNL), disagrees with the SM calculation by more than three standard deviations. This fact has motivated the development of two new and complementary muon $g-2$ experiments, which are sited at Fermilab and J-PARC. Similarly, the theoretical community has made significant progress towards its goal of reducing the error on the SM prediction for $a_\mu$ by at least a factor of two. \newline \newline Fermilab experiment E989 aims to measure $a_\mu$ to 0.14 parts per million (ppm), a factor of four improvement compared to E821. The relocation, installation, and commissioning of the BNL storage ring is complete, and the magnetic field uniformity has been improved threefold compared that achieved at BNL. A completely new instrumentation suite needed to measure the muon precession frequency has been designed, built, and installed. The experimental beamlines are finished and commissioning of the overall experiment is ongoing. A first physics run begins in early 2018 with the initial goal of making a sub-ppm measurement. The J-PARC experiment is pursuing a unique approach, using a low-energy, ultra-cold muon beam injected into a compact, high-field magnet. They aim in their first phase for a sub-ppm measurement comparable to that achieved by BNL. I will provide the context for the measurements and report on the status of the running experiment at Fermilab.   

Physics reach at JLab with the 12 GeV upgrade

The Continuous Electron Beam Accelerator Facility (CEBAF) and associated experimental equipment at Jefferson Lab comprise a unique facility for nuclear physics research whose upgrade has been just completed. The upgraded facility accelerates electron beams to 11 GeV for experiments in the existing Halls A, B and C. In addition, a 12 GeV beam is provided to a new experimental Hall D to generate a 9 GeV tagged photon beam. This upgrade will quantitatively address the nature of confinement and an era of nuclear femtography through precision measurements of the spectrum and structure of hadrons comprised of light quarks and gluons. This facility also provides new opportunities relevant to neutrino oscillation physics, ``dark photon'' searches, and precision tests of the standard model.