Title: TPC without charge multiplication: a CMOS direct readout towards
neutrinoless double-beta decay and other applications.

Speaker: Yuan Me (LBNL)

Abstract

Time Projection Chamber (TPC) and silicon-based sensor/Integrated Circuitry (IC) are indispensable elements in modern detector instrumentation. Since its inception, TPC relied on the charge sensing and high-speed sampling capabilities offered by silicon devices. The charge collection elements and the electronics, however, are traditionally separated. We are developing a new kind of TPC by integrating an array of CMOS charge sensors directly into the detection medium. Each CMOS sensor has exposed metal pads (pixels) for direct charge collection, and contains charge sensitive amplifiers as well as digitization/signal processing/data transmission circuitry. For the application in Neutrinoless Double-Beta Decay search in high-pressure gas, the electronic noise is suppressed to a level that the required signal-to-noise ratio is achieved without the need of avalanche charge multiplication. It provides competitive energy resolution while improves on tracking capability, stability, and scalability compared to alternative readout schemes. Moreover, ions drifting in gas can be read directly since the otherwise prohibitive ion avalanche is unnecessary. It enables the use of alternative gases
and double-beta decay candidate isotopes such as SeF6 gas, in which only ion drifting is possible. With modest modifications, the readout plane could be used in liquid noble gas and organic liquid TPCs for a broad range of applications. The design and the progress of the first prototype will be presented.

Title: Understanding the Nature of Neutrinos via Neutrinoless Double Beta Decay

Speaker: Wenqin Xu (University of South Dakota)

Abstract:Neutrinos provide a critical portal to physics beyond the Standard Model, but many neutrino properties are still largely unknown. The seesaw model can readily explain the small but non-zero neutrino mass and it requires neutrinos to be Majorana particles, i.e. fermions that are their own antiparticles. Neutrinoless double beta (0νββ) decay is a hypothetical lepton-number-violating process that is possible only if neutrinos are Majorana particles. The discovery of 0νββ decay would unambiguously establish the Majorana nature of neutrinos and explicitly show that the total lepton number is violated. A measurement of the decay rate may yield information regarding the absolute neutrino mass.

Deploying 44 kg of high-purity Germanium (HPGe) detectors at the 4850′ level of the Sanford Underground Research Facility in South Dakota, the Majorana Demonstrator (MJD) experiment is an ultra-low background experiment searching for  0νββ decay in ⁷⁶Ge. The construction and commissioning of MJD has completed and the multiple-year data-taking has started. At the meantime, more than 200 researchers around the world, including many Majorana collaborators, have formed a new collaboration for the Large Enriched Germanium Experiment for Neutrinoless Double Beta Decay (LEGEND). The LEGEND collaboration aims to develop a phased, ⁷⁶Ge based 0νββ decay experimental program with discovery potential at a half-life beyond 10²⁸ years. In this talk, we will review the physics of 0νββ decay. We will discuss initial results from the Majorana Demonstrator experiment and the status of the LEGEND project.

Title: Cosmic Ray Flux Measurements at Global Scale and the Associated Applications

Speaker: Xiaochun He (Georgia State University)

Abstract: Cosmic ray radiation has galactic origin and consists primarily of protons and a small percentage of heavier nuclei. The primary cosmic ray particles interact with the molecules in the atmosphere and produce showers of secondary particles at about 15 km altitude. In recent years, with the advancement of particle detection technology and massive computing power, there is a growing interest of exploring the applications of cosmic rays ranging from muon tomography, space and earth weather monitoring, etc. In this talk, I will present the recent work at Georgia State University on cosmic ray shower simulation, the development of low-cost cosmic ray detectors, and the plan for building a network of cosmic ray detectors around the globe.