We propose an evolution of the Mu2e experiment, called Mu2e-II, that would leverage advances in detector technology and utilize the increased proton intensity provided by the Fermilab PIP-II upgrade to improve the sensitivity for neutrinoless muon-to
-electron conversion by one order of magnitude beyond the Mu2e experiment, providing the deepest probe of charged lepton flavor violation in the foreseeable future. Mu2e-II will use as much of the Mu2e infrastructure as possible, providing, where required, improvements to the Mu2e apparatus to accommodate the increased beam intensity and cope with the accompanying increase in backgrounds.
We report results from the first search for sterile neutrinos mixing with active neutrinos through a reduction in the rate of neutral-current interactions over a baseline of 810,km between the NOvA detectors. Analyzing a 14-kton detector equivalent e
xposure of 6.05$times$10$^{20}$ protons-on-target in the NuMI beam at Fermilab, we observe 95 neutral-current candidates at the Far Detector compared with $83.5 pm 9.7 mbox{(stat.)} pm 9.4 mbox{(syst.)}$ events predicted assuming mixing only occurs between active neutrino species. No evidence for $ u_{mu} rightarrow u_{s}$ transitions is found. Interpreting these results within a 3+1 model, we place constraints on the mixing angles $theta_{24}<20.8^{circ}$ and $theta_{34}<31.2^{circ}$ at the 90% C.L. for $0.05~eV^2leq Delta m^2_{41}leq 0.5~eV^2$, the range of mass splittings that produce no significant oscillations over the Near Detector baseline.
Results are reported from an improved measurement of $ u_mu rightarrow u_e$ transitions by the NOvA experiment. Using an exposure equivalent to $6.05times10^{20}$ protons-on-target 33 $ u_e$ candidates were observed with a background of $8.2pm0.8$ (
syst.). Combined with the latest NOvA $ u_mu$ disappearance data and external constraints from reactor experiments on $sin^22theta_{13}$, the hypothesis of inverted mass hierarchy with $theta_{23}$ in the lower octant is disfavored at greater than $93%$ C.L. for all values of $delta_{CP}$.
This Letter reports new results on muon neutrino disappearance from NOvA, using a 14 kton detector equivalent exposure of $6.05times10^{20}$ protons-on-target from the NuMI beam at the Fermi National Accelerator Laboratory. The measurement probes the
muon-tau symmetry hypothesis that requires maximal mixing ($theta_{23} = pi/4$). Assuming the normal mass hierarchy, we find $Delta m^2 = (2.67 pm 0.11)times 10^{-3}$ eV$^2$ and $sin^2 theta_{23}$ at the two statistically degenerate values $0.404^{+0.030}_{-0.022}$ and $0.624^{+0.022}_{-0.030}$, both at the 68% confidence level. Our data disfavor the maximal mixing scenario with 2.6 $sigma$ significance.
We describe the design, construction, readout, tests, and performance of planar drift chambers, based on 5 mm diameter copperized Mylar and Kapton straws, used in an experimental search for rare kaon decays. The experiment took place in the high-inte
nsity neutral beam at the Alternating Gradient Synchrotron of Brookhaven National Laboratory, using a neutral beam stop, two analyzing dipoles, and redundant particle identification to remove backgrounds.
