Session T09: Future and Upgraded Cosmic-Ray and Ground Based Gamma-Ray Experiments

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The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is a ground-based air shower array designed to detect Cherenkov light produced in water by secondary particles from atmospheric air showers. In order to improve the sensitivity at the highest energies, especially for showers with cores falling outside the main array, an outrigger array of 345 smaller Water Cherenkov Detectors (WCDs) was installed around the main array. This extension increases the instrumented area of HAWC by a factor of four and improves the containment of high energy showers. The outrigger array significantly improves HAWC's sensitivity above 10 TeV as well as its angular and energy resolution. In this contribution, we will present the current status and the performance of the upgrade.   

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The prototype Schwarzschild-Couder Telescope (SCT) is a new imaging Cherenkov telescope for gamma-ray astronomy located at the Fred Lawrence Whipple Observatory in Amado, Arizona. The SCT is a candidate design concept for the planned Cherenkov Telescope Array (CTA). CTA will consist of two arrays (north and south) consisting of dozens of different imaging gamma-ray telescopes of various sizes. CTA will provide a significant increase in sensitivity to astrophysical sources in the 20 GeV to 300 TeV energy range relative to prior experiments. SCT has a unique dual-mirror design that provides unprecedented angular resolution for air shower images. The focal plane of the SCT is instrumented with a large area modular solid-state silicon photomultiplier camera. We describe the operations and performance of the prototype SCT telescope and camera system which has been deployed since early 2019. Results include progress toward full optical alignment of the precision mirror systems and initial operations of the prototype camera for nighttime observations. We also summarize progress toward completing the planned upgrade to the full-sized camera system which will increase the size of the camera from 1,600 to 11,136 pixels.   

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The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is designed to identify the sources of ultra-high energy cosmic rays (UHECRs) and to observe cosmic neutrinos. Developed as NASA Astrophysics Probe-class mission, POEMMA consists of two spacecraft flying in a loose formation at 525 km altitudes. Each spacecraft hosts a large Schmidt telescope with a novel focal plane optimized to observe both the UV fluorescence signal from extensive air showers (EASs) and the optical Cherenkov signals from EASs. In UHECR stereo fluorescence mode, POEMMA will measure the spectrum, composition, and full-sky distribution of the UHECRs above 20 EeV along with remarkable sensitivity to UHE neutrinos. POEMMA is designed to quickly re-orient to a Target-of-Opportunity (ToO) neutrino mode to observe transient astrophysical sources with unique sensitivity. In this mode, POEMMA will be measure cosmic tau neutrino events above 20 PeV by measuring the upward-moving EASs induced from tau neutrino interactions in the Earth. POEMMA's science goals, instrument & mission designs, and simulated UHECR and neutrino measurement performance will be presented.   

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Cosmic-ray accelerators capable of reaching ultra-high energies are expected to also produce very-high energy neutrinos via hadronic interactions within the source. Many of the candidate astrophysical source classes are either transient in nature or exhibit flaring activity. Leveraging the Earth as a neutrino converter, the Probe of Extreme Multi-Messenger Astrophysics (POEMMA) will be able to detect cosmic tau neutrinos at energies $\sim$10 PeV and above. As a space-based mission, POEMMA will have orbital characteristics and slewing capability that will ensure full-sky coverage and enable rapid follow up, making it uniquely suited for searching for neutrinos from astrophysical transient events. We present the latest results of a study exploring the prospects of detecting tau neutrino events with POEMMA from a variety of astrophysical transient source classes.   

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The highest energy cosmic rays and PeV astrophysical neutrinos are tantalizing multi-messengers from some of the most extreme energetic environments in the Universe. As a precursor for the Probe of Extreme Multi-Messenger Astrophysics (POEMMA), the Extreme Universe Space Observatory on a Super Pressure Balloon II (EUSO-SPB2) will use the calorimetric properties of atmosphere to target Ultra High Energy Cosmic Rays and background signatures toward future observations of astrophysical tau-neutrinos using the earth skimming technique. The EUSO-SPB2 science payload will feature an air Cherenkov telescope (CT) and a UV fluorescence telescope (FT) each with 1 m diameter entrance pupils and schmidt optics. With vantage points from the sub-orbital altitude of 33 km, EUSO-SPB2 will record EeV cosmic rays by looking down with the FT. The CT will look slightly below the Earth's limb to search for tau signatures and measure backgrounds. The first direct cherenkov measurements of air showers from near space is also planned by looking slightly above the limb with the CT. The launch is planned from Wanaka NZ in 2022. This overview of EUSO-SPB2 will include the mission plan, the science and technical goals, the instrument, and status.   

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The Extreme Universe Space Observatory on a Super Pressure Balloon II (EUSO-SPB2) is a long-duration balloon based cosmic ray experiment is in preparation, as a successor to EUSO-SPB1 which flew in 2017. A science payload of two telescopes will measure ultra-high energy cosmic rays (EeV scale) via fluorescence and background Cherenkov measurements towards future tau neutrino observations. To understand the performance of the fluorescence telescope, extensive air showers and the response of the detector to these showers have been simulated. By comparison with simulations and field tests done for EUSO-SPB1, the expected performance of EUSO-SPB2 is estimated. In this talk I will describe the expected performance of the EUSO-SPB2 fluorescence telescope based on the results of these simulations and quantify the expected improvement over EUSO-SPB1.   

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The detection of astrophysical neutrinos by IceCube and the potential to constrain source models of ultra-high energy cosmic rays (UHECRs) motivate the development of instruments for the observation of very-high energy (VHE) cosmic neutrinos. In the Earth-skimming technique for VHE (above $10^7$ GeV) cosmic neutrino detection, a tau lepton produced in a tau neutrino interaction inside the Earth can emerge from the ground and decay initiating an upward going extensive air shower (EAS). This event can be detected by measuring its optical Cherenkov signal. UHECRs above the Earth’s horizon can be detected similarly. We discuss the development of a Cherenkov telescope for the detection of tau neutrino associated events and their background. This telescope will be deployed on the Extreme Universe Space Observatory Super Pressure Balloon 2 (EUSO-SPB2) as a precursor for the Probe of Extreme Multi-Messenger Astrophysics. The 1m diameter Cherenkov telescope for EUSO-SPB2 will have a focal plane comprised of silicon photomultipliers (SiPMs) coupled to a 100 MS/s readout based on the GET switch capacitor ring sampler. We present details of the development of the instrumentation and the simulated Cherenkov signal response.   

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The Southern Wide field-of-view Gamma-ray Observatory (SWGO) is a planned next generation very high energy gamma-ray detector to be built in the southern hemisphere. Building on the demonstrated capabilities of HAWC and ARGO, which will be further extended by LHASSO, SWGO will be the world’s most sensitive gamma-ray surface detector and the first wide-field TeV scale instrument to operate in the southern hemisphere. With its wide field and high duty cycle (~100%), SWGO will be an excellent complement to CTA. In this contribution, I will present an overview of the science case for this next-generation observatory and introduce the instrument designs under consideration by the SWGO collaboration.