Session F3: Particle Physics III

Neutrino nus

Neutrinos are almost massless chargeless particles that only feel the weak interaction. They are hard to make (unless you have a nuclear reactor or particle accelerator lying around) and even harder to detect. Despite these obstacles, a whole new field of neutrino studies has opened up since the definite observation of neutrino oscillations in the late 90’s. I will review a small fraction of the exciting recent results in neutrino physics and outline some of our plans for the future.   

The HALO / HALO-2 Supernova Neutrino Detectors

The Helium and Lead Observatory (HALO) is a dedicated supernova neutrino detector in SNOLAB, which is built from 79 tons of surplus lead and the helium-3 neutron detectors from the SNO experiment. It is sensitive primarily to electron neutrinos, and is thus complementary to water Cerenkov and organic scintillation detectors which are sensitive primarily to electron anti-neutrinos. A comparison of the rates in these complementary detectors will enable a flavor decomposition of the neutrino flux from the next galactic core-collapse supernova. We have tentative ideas to build a 1000-ton detector in the Gran Sasso laboratory by using the lead from the decommissioned OPERA detector. We welcome new collaborators to join us.   

Light detection in nEXO liquid Xenon detector.

The nEXO experiment is being designed to achieve unprecedented sensitivity to the neutrino-less double beta decay of 136Xenon. Efficient light detection is critical for achieving the energy resolution of 2{\%} (FHWM) or better required for efficient background rejection. Simulations show that such an energy resolution can be achieved if at least 5{\%} of the scintillation photons are detected, which requires mirroring most inactive surface and at least 4m$^{\mathrm{2}}$ of single photon detectors. So-called silicon photo-multipliers (SiPMs) are the baseline option for nEXO as they meet or approach all requirements: 1) measured limits for the radio-isotope content of SiPMs are consistent with requirements, 2) the photo-detection efficiency exceeds 15{\%} at the liquid Xenon scintillation wavelength, 3) dark noise and correlated avalanche rates are within specifications. The nEXO collaboration is continuing to work with the SiPM vendors to further improve performances. The nEXO collaboration is also investigating solutions for reading out m$^{\mathrm{2}}$ of SiPMs, which has not been done before. In addition to conventional analog electronics solutions, the nEXO collaboration is investigating using the 3-dimensionally integrated technology (3D-SiPMs) that completely avoid any analog electronics and provide a mean of tagging every photon with minimum power dissipation. We will report the development of solutions for light detection in nEXO highlighting the technology that are pioneered by the collaboration, in particular 3D-SiPMs.   

Parasitic Charge Measurements of VUV-sensitive SiPMs for nEXO

Silicon Photomultipliers (SiPMs) are semiconductor light detectors which are of great interest for future particle Physics experiments due to their low noise level, high gain and high radiopurity. nEXO (next Enriched Xenon Observatory) is a planned multi-ton LXe TPC designed for the search for neutrinoless double beta decay. SiPMs are good candidates for light detectors in nEXO however require sensitivity to the UV scintillation light of Xenon at $175-178\,\mathrm{nm}$ which is not possible with conventional devices. In this work we present measurements of dark noise and parasitic charge probability of three current VUV-sensitive SiPM models produced by manufacturers Hamamatsu, FBK and KETEK and compare their performance with the nEXO requirements.   

Quantum limited amplifiers for the Axion Dark Matter eXperiment (ADMX)

The Axion Dark Matter eXperiment (ADMX) uses the most sensitive microwave receivers in the world to look for photons that might come from axions, hypothetical elementary particles which may constitute the dark matter. The ``Generation 2'' of ADMX is in commissioning for its first ultra-high-sensitivity run this summer. Recent upgrades to ADMX include a dilution refrigerator and tunable quantum-noise-limited amplifiers. These upgrades will significantly decrease the system noise, thereby substantially increasing the experimental sensitivity. I will present an overview of the current status of ADMX and what it aims to achieve in terms of sensitivity improvement with these newly-added components, focusing mainly on the quantum-limited amplifiers.   

First Results From the PIENU Experiment

The PIENU experiment at TRIUMF aims to measure the pion decay branching ratio, $R_{\pi}=\Gamma(\pi\rightarrow e\nu(\gamma))/\Gamma(\pi\rightarrow\mu\nu(\gamma))$ which provides a sensitive test of lepton universality and constraints on new physics scenarios. The theoretical uncertainty on the Standard Model prediction of $R_{\pi}^{SM}$ is 0.02\%, a factor of twenty smaller than the experimental uncertainty. First results from the PIENU experiment $R_{\pi}^{exp}=(1.2344\pm0.0023(stat)\pm 0.0019(syst))\times 10^{-4}$, are consistent with the SM prediction and represent a 0.1\% measurement of lepton non-universality. Analysis of additional data will allow increased precision up to 0.05\%.   

Computer Simulation of the Tri-MeV Electron Beam Accelerator

Tri-MeV is an electron beam accelerator originally built by Pulse Sciences Incorporated capable of producing pulses of 3 MeV and 30 kA with a rise time and duration of 3 and 14 ns respectively. These characteristics make Tri-MeV a good choice for studying the focus of electron beams \footnote{D.R. Welch, B.V. Oliver, S.E. Rosenthal and C.L. Olson, in IEEE Conference Record Abstracts, 1999 IEEE International Conference on Plasma Science, Monterey, California, June 20-24, 1999, IEEE Cat. No. 99CH36297, (Institute of Electrical and Electronic Engineers, Piscataway, NJ, 1999), p. 182.}. Tri-Mev was recently relocated to Idaho State University and since has been reconditioned in preparation for plasma and radiography experiments. In this talk the current status of this project, in particular, SCREAMER \footnote{R. B. Spielman, M. L. Kiefer, K. L. Shaw, K. W. Struve, and M. M. Widner, SCREAMER, a pulsed power design tool, user’s guide for version 3.3.1 (2014).} simulations will be compared to recent experimental observations of the Tri-MeV accelerator.