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Prospects for Cross-Correlations of UHECR Events with Astrophysical Sources with Upcoming Space-Based Experiments

Ultra-high energy cosmic rays (UHECRs) are the messengers of the most extreme physics in the cosmos; however, efforts to identify their origins have thus far been thwarted by the fact that they don’t point back to their sources. Using statistical studies cross-correlating UHECR arrival directions with astrophysical catalogs, the ground-based Pierre Auger Observatory has reported hints of a correlation with nearby starburst galaxies, as well as lower-significance correlations with other classes of astrophysical sources. Space-based UHECR experiments, such as POEMMA and ZAP, will monitor large interaction volumes on the Earth or the Moon. Within a few years of mission operation time, both missions will achieve unprecedented exposures at energies above40EeV across the entire sky. In this contribution, we present studies of the cross-correlation between UHECR event arrival directions and astrophysical catalogs as motivated by expectations for the detector performance for POEMMA and ZAP. We find that both POEMMA and ZAP will achieve 5σ discovery reach for many plausible astrophysical scenarios.

Tonia M Venters↗
NASA NTRS2009

The Orbiting Wide-Angle Light Collectors (OWL) Mission for Charged-Particle Astronomy

The space-based OWL mission is designed to perform high-statistics measurements of ultra-high-energy cosmic rays (UHECR) using the Earth's atmosphere as a vast particle calorimeter, furthering the field of charged-particle astronomy. OWL has been developed in formal NASA instrument and mission studies and is comprised of two large telescopes separated by approx.600 km in 1000 km, near-equatorial orbits to stereoscopically image the near-UV air fluorescence emitted by UHECR-induced particle cascades. The High Resolution Fly's Eye (HiRes) Collaboration, and subsequently the Pierre Auger Observatory, recently reported confirmation of the expected Greisen-Zatsepin-Kuzmin (GZK) suppression of the UHECR flux above a few times 10(exp 19) eV. This observation is consistent with the majority of UHECR originating in astrophysical objects and reduces the need to invoke exotic physical processes. Particles observed above the GZK threshold energy must have come from sources within about 100 Mpc from the Earth. The small particle deflection angles expected at UHECR energies, with standard assumptions of extragalactic magnetic fields, are on the order of 1 degree. Thus by observing particles above the GZK threshold with sufficient exposure, there is the potential of identifying and characterizing individual UHECR sources. Auger has reported significant anisotropy in the arrival directions of UHECR at energies above about 6 10(exp 19) eV observed in the South, and a correlation to AGN in the 12th VCV catalog, suggesting that the sources of UHECR are traced by the distribution of luminous matter in the Universe. However, with similar statistics and the same event selection criteria, HiRes observations in the North are consistent with isotropy. Extended observations by Auger-South, by Telescope Array in the North, and possibly by the proposed Auger-North, will further these investigations. However, much greater exposures will be required to fully identify individual sources and measure their cosmic ray spectra. A five-year OWL mission would deliver approximately 10(exp 6)sq km/sr/yr of exposure with full aperture reached at approx. 10(exp 19) eV. The baseline 3 m optical aperture OWL telescopes with 45 degree full field-of-view are easily accomodated on a single conventional launch vehicle. On orbit, the simultaneous viewing of the same volume of atmosphere allows for precise stereo event reconstruction, which is nearly independent of the inclination of the particle track and tolerant of atmospheric conditions. The availability of monocular operation provides increased reliability or can be employed to increase the instantaneous aperture. In stereo mode, OWL is also capable of fully reconstructing horizontal or upward-moving showers and so has unmatched sensitivity to neutrino-induced events. The details of the OWL mission will he presented and its science capabilities will be discussed.

Mitchell, John↗
NASA NTRS2018

POEMMA - Probe of Extreme Multi-Messenger Astrophysics: CRs and Neutrinos

Developed as a NASA Astrophysics Probe mission concept study, the Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) science goals are to identify the sources of ultra-high energy cosmic rays (UHECRs) and to observe cosmic neutrinos above 10 PeV. POEMMA consists of two satellites flying in loose formation at 525 km altitudes. A novel focal plane design is optimized to observe the UV air fluorescence signal in a stereoscopic UHECR observation mode and the Cherenkov signals from air showers from UHECRs and neutrino-induced tauleptons in an Earth-limb viewing mode. POEMMA is designed to achieve full-sky coverage and significantly higher sensitivity to the highest energy cosmic messengers compared to what have been achieved so far by ground-based experiments. POEMMA will measure the spectrum, composition, and full sky distribution of the UHECRs above 10 EeV to identify the most energetic cosmic accelerators in the universe and study the acceleration mechanism(s). POEMMA will also have high sensitivity to cosmogenic neutrinos by observing the upward-moving air showers induced from tau neutrino interactions in the Earth. POEMMA will also be able to re-orient to a Target-of-Opportunity (ToO) neutrino mode to view transient astrophysical sources. In this talk, the science goals, instrument design, launch and mission profile, and simulated UHECR and neutrino measurement capabilities for POEMMA will be presented.

Krizmanic, John↗
NASA NTRS2017

POEMMA: Probe of Extreme Multi-Messenger Astrophysics

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) mission is being designed to establish charged-particle astronomy with ultra-high energy cosmic rays (UHECRs) and to observe cosmogenic tau neutrinos (CTNs). The study of UHECRs and CTNs from space will yield orders-of-magnitude increase in statistics of observed UHECRs at the highest energies, and the observation of the cosmogenic flux of neutrinos for a range of UHECR models. These observations should solve the long-standing puzzle of the origin of the highest energy particles ever observed, providing a new window onto the most energetic environments and events in the Universe, while studying particle interactions well beyond accelerator energies. The discovery of CTNs will help solve the puzzle of the origin of UHECRs and begin a new field of Astroparticle Physics with the study of neutrino properties at ultra-high energies.

Olinto, Angela V.↗
NASA NTRS2008

The Spectrum of Ultrahigh Energy Cosmic Rays and Constraints on Lorentz Invariance Violation

There has been much interest in possible violations of Lorentz invariance, particularly motivated by quantum gravity theories. It has been suggested that a small amount of Lorentz invariance violation (LIV) could turn off photomeson interactions of ultrahigh energy cosmic rays (UHECRs) with photons of the cosmic background radiation and thereby eliminate the resulting sharp steepening in the spectrum of the highest energy CRs predicted by Greisen Zatsepin and Kuzmin (GZK). Recent measurements of the UHECR spectrum reported by the HiRes and Auger collaborations, however, indicate the presence of the GZK effect. We present the results of a detailed calculation of the modification of the UHECR spectrum caused by LIV using the formalism of Coleman and Glashow. We then use a chi-squared analysis to compare our results with the experimental UHECR data and thereby place limits on the amount of LIV. We also discuss how a small amount of LIV that is consistent with the experimental data can still lead to a recovery of the cosmic ray flux at higher energies than presently observed.

Stecker, F. W.↗
NASA NTRS2009

Lorentz Invariance Violation and the Observed Spectrum of Ultrahigh Energy Cosmic Rays

There has been much interest in possible violations of Lorentz invariance, particularly motivated by quantum gravity theories. It has been suggested that a small amount of Lorentz invariance violation (LIV) could turn of photomeson interactions of ultrahigh energy cosmic rays (UHECRs) with photons of the cosmic background radiation and thereby eliminate the resulting sharp steepening in the spectrum of the highest energy CRs predicted by Greisen Zatsepin and Kuzmin (GZK). Recent measurements of the UHECR spectrum reported by the HiRes and Auger collaborations, however, indicate the presence of the GZK effect. We present the results of a detailed calculation of the modification of the UHECR spectrum caused by LIV using the formalism of Coleman and Glashow. We then compare these results with the experimental UHECR data from Auger and HiRes. Based on these data, we find a best fit amount of LIV of 4.5+1:5 ..4:5 x 10(exp -23),consistent with an upper limit of 6 x 10(exp -23). This possible amount of LIV can lead to a recovery of the cosmic ray spectrum at higher energies than presently observed. Such an LIV recovery effect can be tested observationally using future detectors.

Scully, S. T.↗
NASA NTRS2013

Optimization of the Orbiting Wide-Angle Light Collectors (OWL) Mission for Charged-Particle and Neutrino Astronomy

OWL [1] uses the Earth's atmosphere as a vast calorimeter to fully enable the emerging field of charged-particle astronomy with high-statistics measurements of ultra-high-energy cosmic rays (UHECR) and a search for sources of UHE neutrinos and photons. Confirmation of the Greisen-Zatsepin-Kuzmin (GZK) suppression above approx. 4 x 10(exp 19) eV suggests that most UHECR originate in astrophysical objects. Higher energy particles must come from sources within about 100 Mpc and are deflected by approx. 1 degree by predicted intergalactic/galactic magnetic fields. The Pierre Auger Array, Telescope Array and the future JEM-EUSO ISS mission will open charged-particle astronomy, but much greater exposure will be required to fully identify and measure the spectra of individual sources. OWL uses two large telescopes with 3 m optical apertures and 45 degree FOV in near-equatorial orbits. Simulations of a five-year OWL mission indicate approx. 10(exp 6) sq km/ sr/ yr of exposure with full aperture at approx. 6 x 10(exp 19) eV. Observations at different altitudes and spacecraft separations optimize sensitivity to UHECRs and neutrinos. OWL's stereo event reconstruction is nearly independent of track inclination and very tolerant of atmospheric conditions. An optional monocular mode gives increased reliability and can increase the instantaneous aperture. OWL can fully reconstruct horizontal and upward-moving showers and so has high sensitivity to UHE neutrinos. New capabilities in inflatable structures optics and silicon photomultipliers can greatly increase photon sensitivity, reducing the energy threshold for n detection or increasing viewed area using a higher orbit. Design trades between the original and optimized OWL missions and the enhanced science capabilities are described.

Optimization↗
NASA NTRS2021

The Zettavolt Askaryan Polarimeter (ZAP) mission concept: radio detection of ultra-high energy cosmic rays in low lunar orbit

Probing the ultra-high energy cosmic ray (UHECR) spectrum beyond the cutoff at ~40 EeV requires an observatory with large acceptance, which is challenging to implement with ground arrays. We present a concept for radio detection of UHECRs impacting the Moon's regolith from low-lunar orbit called the Zettavolt Askaryan Polarimeter (ZAP). ZAP would observe several thousands of events above the cutoff (~40 EeV) with a full-sky field of view to test whether UHECRs originate from Starburst Galaxies, Active Galactic Nuclei, or other sources associated with the matter distribution of the local universe at a distance $>$ 1 MPc. The unprecedented sensitivity of ZAP to energies beyond 100 EeV would enable a test of source acceleration mechanisms. At higher energies, ZAP would produce the most stringent limits on super heavy dark matter (SHDM) via limits on neutrinos and gamma rays resulting from self-annihilation or decay.

Romero-Wolf, Andrew↗
NASA NTRS2004

Observing the Ultrahigh Energy Universe with OWL Eyes

The goal of the Orbiting Wide-field Light-collectors (0WL) mission is to study the origin and physics of the highest energy particles known in nature, the ultra- high energy cosmic rays (UHECRs). The OWL mission consists of telescopes with UV sensitive cameras on two satellites operating in tandem to view in stereo the development of the giant particle showers induced in the Earth s atmosphere by UHECRs. This paper discusses the characteristics of the 0WL mission.

Stecker, F. W.↗
NASA NTRS2010

Testing Lorentz Invariance with Neutrinos from Ultrahigh Energy Cosmic Ray Interactions

We have previously shown that a very small amount of Lorentz invariance violation (UV), which suppresses photomeson interactions of ultrahigh energy cosmic rays (UHECRs) with cosmic background radiation (CBR) photons, can produce a spectrum of cosmic rays that is consistent with that currently observed by the Pierre Auger Observatory (PAO) and HiRes experiments. Here, we calculate the corresponding flux of high energy neutrinos generated by the propagation of UHECR protons through the CBR in the presence of UV. We find that UV produces a reduction in the flux of the highest energy neutrinos and a reduction in the energy of the peak of the neutrino energy flux spectrum, both depending on the strength of the UV. Thus, observations of the UHE neutrino spectrum provide a clear test for the existence and amount of UV at the highest energies. We further discuss the ability of current and future proposed detectors make such observations.

Scully, Sean T.↗
NASA NTRS2021

The POEMMA (Probe of Extreme Multi-Messenger Astrophysics) Observatory

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is designed to accurately observe ultra-high-energy cosmic rays (UHECRs) and cosmic neutrinos from space with sensitivity over the full celestial sky. POEMMA will observe the air fluorescence produced by extensive air showers (EASs) from UHECRs and potentially UHE neutrinos above 20 EeV. Additionally, POEMMA has the ability to observe the Cherenkov signal from upward-moving EASs induced by Earth-interacting tau neutrinos above 20 PeV. The POEMMA spacecraft are designed to quickly re-orientate to follow up transient neutrino sources and obtain currently unparalleled neutrino flux sensitivity. Developed as a NASA Astrophysics Probe-class mission, POEMMA consists of two identical satellites flying in loose formation in 525 km altitude orbits. Each POEMMA instrument incorporates a wide field-of-view (45°) Schmidt telescope with an optical collecting area of over 6 sq. m. The hybrid focal surface of each telescope includes a fast (1 μs) near-ultraviolet camera for EAS fluorescence observations and an ultrafast (10 ns) optical camera for Cherenkov EAS observations. In a 5-year mission, POEMMA will provide measurements that open new multi-messenger windows onto the most energetic events in the universe, enabling the study of new astrophysics and particle physics at these extreme energies.

A. V. Olinto↗
NASA NTRS2021

The POEMMA (Probe of Extreme Multi-Messenger Astrophysics)Observatory

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is designed to accurately observe ultra-high-energy cosmic rays (UHECRs) and cosmic neutrinos from space with sensitivity over the full celestial sky. POEMMA will observe the air fluorescence produced by extensive air showers (EASs) from UHECRs and potentially UHE neutrinos above 20 EeV. Additionally, POEMMA has the ability to observe the Cherenkov signal from upward-moving EASs induced by Earth-interacting tau neutrinos above 20 PeV. The POEMMA spacecraft are designed to quickly re-orientate to follow up transient neutrino sources and obtain currently unparalleled neutrino flux sensitivity. Developed as a NASA Astrophysics Probe-class mission, POEMMA consists of two identical satellites flying in loose formation in 525 km altitude orbits. Each POEMMA instrument incorporates a wide field-of-view (45°) Schmidt telescope with an optical collecting area of over 6 m2. The hybrid focal surface of each telescope includes a fast (1 μs) near-ultraviolet camera for EAS fluorescence observations and an ultrafast (10 ns) optical camera for Cherenkov EAS observations. In a 5-year mission, POEMMA will provide measurements that open new multi-messenger windows onto the most energetic events in the universe, enabling the study of new astrophysics and particle physics at these extreme energies.

A. V. Olinto↗
NASA NTRS2003

The Light of the Night Sky in EUSO: Duty Cycle and Background

The EUSO detector, which will be installed on the International Space Station, will detect the light produced by the EAS generated by the UHECR when entering the Earth's atmosphere. The EUSO telescope will operate only during dark night. The light background in the EUSO detector is of outmost importance. To determine the detector duty cycle, it is necessary to know the periods in which it will be in the obscurity, taking into account both sun and moon precise ephemerides and the ISS trajectory. For signal to background determination and trigger efficiency study, the photon background has to be evaluated, taking into account the various UV light sources at night: natural sources as airglow, stars and diffuse light of the night sky, and artificial sources.

Adams, J.↗
NASA NTRS2004

Ultrahigh Energy Cosmic Rays: Old Physics or New Physics?

We consider the advantages of and the problems associated with hypotheses to explain the origin of ultrahigh energy cosmic rays (UHECR: E greater than 10 EeV) and the "trans-GZK" cosmic rays (TGZK: E greater than 100 EeV) both through "old physics" (acceleration in cosmic sources) and "new physics" (new particles, topological defects, fat neutrino cross sections, Lorentz invariance violation).

Stecker, F. W.↗