Particle Astrophysics

Questions

• What are the sources of cosmic rays in the range 10¹²-10²⁰ eV?
• What are the expected fluxes of ultra-high-energy neutrinos (10¹⁷-10¹⁹ eV) from these sources?
• What are the expected cosmic ray and neutrino fluxes produced by gamma-ray bursts (GRBs), AGNs, magnetars, hypernovae?

Discoveries and Milestones

• Peter Meszaros has shown that the ultra-high energy cosmic rays observed by Auger, if indeed they are heavy elements,  may be explained by acceleration in radio-quiet AGNs, or alternatively, in hypernovae. He also has shown that newly-born magnetars could be detected through their TeV neutrino birth-cry.
• With the NASA Cosmic Ray Energetics and Mass (CREAM) high-altitude balloon experiment, Stephane Coutu continues to accumulate the world's definitive direct measurements of high-energy cosmic-ray nuclei from H to Fe. The elemental energy spectra lend support to the Galactic supernova shock acceleration origin of cosmic rays.

Current Projects

• Peter Meszaros is calculating the TeV to multi-EeV neutrino flux from a proposed Population III Poynting-dominated GRB model.
• Stephane Coutu is searching for cosmic electrons at unprecedented energies, beyond 2 TeV, with the new NASA Cosmic Ray Electron Synchrotron Telescope (CREST) high-altitude balloon project. Such electrons, if they exist, would have to come from nearby cosmic accelerators such as the GEMINGA or VELA supernova remnants. The detection technique relies on synchrotron emission of electrons in the geomagnetic field, and has never been attempted before.
• Abe Falcone uses the VERITAS TeV gamma-ray telescope, combined with telescopes sensitive to lower energy bands, to study emission processes from particle acceleration at sites with astrophysical jets and shocks, such as blazars, X-ray/TeV binaries, and GRBs.
• Peter Meszaros is calculating the cosmic ray and neutrino spectrum resulting from re-acceleration of the secondary particles following photomeson interactions of the primaries, in sources such as supernovae or GRBs.
• The CREAM balloon missions continue in Antarctica (six completed flights as of 2011). Stephane Coutu is continuing to improve the energy reach and statistical accuracy of the measurements, while also investigating the properties of Galactic transport of cosmic rays through the production of rare secondary nuclei (e.g., boron from the spallation of carbon nuclei).
• Peter Meszaros is involved in theoretical calculations related to ongoing neutrino observations with the IceCube neutrino Cherenkov detector, and is developing astrophysical source models for interpreting ultra-high energy cosmic ray observations from the Pierre Auger Observatory.

Student Highlights

• Shan Gao is calculating the neutrino production and the escaping spectrum from Population III GRBs, as well as calculating the detection probability by large Antarctic detectors such as IceCube and ARIANNA.
• Tyler Anderson designed and constructed an improved readout electronics system for the CREAM experiment, and is exploring the energy spectrum of the more massive cosmic rays (iron and sub-iron).
• Matt Geske developed the plastic scintillators for the veto shield of the CREST experiment, and is looking for cosmic electrons in a regime never explored previously.

Participants

Faculty

Stephane Coutu (Physics)
Doug Cowen (Physics)
Peter Meszaros
Paul Sommers (Physics)
Abe Falcone

Students

Tyler Anderson (Physics)
Matt Geske (Physics)

Links

More details on cosmic ray astrophysics at Penn State
More details on ultra-high energy neutrino astrophysics at Penn State
Center for Particle Astrophysics
Institute for Gravitation and the Cosmos
IceCube
Pierre Auger Cosmic Ray Observatory
Cosmic Ray Energetics And Mass
Cosmic Ray Electron Synchrotron Telescope