Stéphane Coutu

Professor of Physics and of Astronomy and Astrophysics
The Pennsylvania State University
Ph.D., California Institute of Technology, 1993

coutu@phys.psu.edu

Office: 303H Osmond Lab: (814) 865-2015
Labs: 6B, 212 Osmond Lab: (814) 865-2013
Fax: (814) 863-3297

Mailing address:
Department of physics
104 Davey Laboratory PMB241
The Pennsylvania State University
University Park, PA 16802

Photo taken at Happy Camper School (survival training course) on the Ross Ice Shelf in Antarctica, January 2010, in preparation for the recovery operations of the CREAM-V balloon payload.


Member:
Penn State Institute for Gravitation and the Cosmos
Penn State Center for Particle Astrophysics

Teaching

Physics 457 Laboratory, Spring 98, Fall 98, Fall 01, Fall 02.
Physics 237 Introduction to Quantum Physics, Spring 99, Fall 99.
Physics 211 General Physics: Mechanics, Spring 00, Fall 00, Fall 03, Spring 06, Spring 07, Spring 08, Fall 08, Spring 11, Spring 12
Physics 559 Graduate Laboratory, Spring 01, Spring 02, Spring 03, Spring 05.
Physics 590 Current Research (Graduate Seminar), Spring 01, Spring 02, Spring 03, Spring 05.

Particle Astrophysics

I am interested in experimental high-energy particle astrophysics, which is the study of the universe at the point where the mind-boggingly vast meets the infinitesimally tiny. I have been studying high-energy cosmic rays, particles that rain down on Earth from the depths of space. Among these are particles of antimatter, which can be used to search for candidates for the elusive dark matter that pervades the universe but is detectable, at present, only through its gravitational influence. Or else they can point to new and interesting mechanisms for particle production and acceleration within the Galaxy. At the very highest energies, an entirely different and essentially unexplored regime opens up, with particles most likely originating from outside our own Galaxy, and carrying more energy than ever achieved artificially in the laboratory by particle accelerators.

I am involved in the Pierre Auger Observatory project. This is an ambitious plan to construct two huge arrays of detectors, one in the northern hemisphere, and one in the southern. These arrays study the highest-energy particles in the Universe, and open up a new window on the physical world. Although these particles are very rare (and therefore require very large arrays of sensitive detectors), they are known to exist from previous measurements done by smaller detectors. At present it is not known how such tremendous energies can ever be attained, and the Auger observatory will provide information crucial to the resolution of the puzzle of their existence. The southern detector site is currently completed and operating in Western Mendoza Province, Argentina. A northern array is considered for deployment in Colorado. My Penn State colleague Paul Sommers is one of the founding fathers of this large international project.
The Pierre Auger Observatory and its science can be explored using 3D structures viewed in Google Earth. The model files are available here. Our activities on the project are supported by the National Science Foundation. Click on the image at left to download an animated video of a Google Earth exploration of Auger.

I am involved in the Cosmic Rays Energetics And Mass (CREAM) project. This is a NASA-sponsored program of studies of high-energy cosmic rays up to the astrophysical "knee" (a spectral feature at an energy of a few times 1015 eV). After 100 years of studies since their initial discovery by Victor Hess, their exact origin (probably supernova remnants) has still not been unambiguously resolved, and increased experimental measurements are required. Direct measurements at such high energies are difficult because of very small particle rates. To remedy this, CREAM achieves long exposures by flying repeatedly on long-duration high-altitude balloon flights in Antarctica. The cosmic-ray nuclei ranging from hydrogen to iron are individually identified and counted, and their energy measured up to hundreds of TeV (a few times 1014 eV), approaching the important knee energy. Click on the image at left for video footage of a CREAM launch in Antarctica.
CRESTlaunch

I am involved in the Cosmic Ray Electron Synchrotron Telescope (CREST) experiment. This is a NASA-sponsored project to fly a novel instrument on high-altitude balloons in Antarctica in an attempt to detect cosmic-ray electrons at energies beyond about 2 TeV (2 x 1012 eV), where they have never been detected. Such electrons would have to come from a relatively local neighborhood of our Galaxy, from sources such as supernova remnants, and their detection would reveal such sources and provide new insights into the high-energy Universe. Click on the photo to the left for a video of the late December 2011 CREST launch from McMurdo Station, Antarctica.
I was involved in the NASA-supported High-Energy Antimatter Telescope (HEAT) program, a series of high-altitude balloon-borne experiments to study antimatter in the primary cosmic radiation. We studied high-energy positrons and antiprotons using two different instruments between 1995 and 2004. We used large and complex detectors with redundant particle identification techniques to unambiguously select out the particles of interest from a large background of ordinary cosmic-ray protons and nuclei. We flew such instruments to the very edges of the atmosphere, essentially into space, by means of enormous helium-filled balloons launched from Ft Sumner, NM and Lynn Lake, Manitoba, Canada. Click on the left for video footage of the HEAT 1994 balloon campaign in Ft Sumner (beware, this is a large file, about 117MB).
I also participated in the Monopole, Astrophysics, and Cosmic Ray Observatory (MACRO) project, an experiment buried deep under a mountain in Italy. The experiment shut down at the end of 2000. MACRO was a very large instrument, 10 meters-high by 12 meters-wide by 72 meters-long, using multiple particle tracking and identification techniques to study those particles capable of traveling through more than 1000 meters of rock. Among the many physics topics covered by this multi-purpose detector was the search for magnetic monopoles, hypothetical particles that would carry magnetic (instead of electric) charge, and that are predicted by some theories but have never been observed experimentally. When cosmic rays strike the Earth's atmosphere after traveling through the Galaxy for many millions of years, they generate a cascade of atmospheric secondary particles, known as an air shower. MACRO studied the very penetrating muon components of air showers, and this information in turn, sometimes combined with measurements at the mountain surface by the separate EAS-TOP experiment, was used to infer the mass of the primary cosmic rays that initiated the air showers. By looking at muons traveling upwards, MACRO detected neutrinos that interacted in the rock underneath the detector. Such neutrinos could arise from dark matter particle annihilation at the center of the Earth or the Sun. Finally, MACRO searched for bursts of neutrino events arising from supernova explosions in our Galaxy.

Research Articles

A few representative recent articles are listed below. A full list of my refereed publications is also available.

  1. With H.S. Ahn et al. (CREAM Collaboration), “The Cosmic Ray Energetics And Mass (CREAM) Timing Charge Detector,” Nucl. Inst. & Meth. A 602, 525-536 (2009).
  2. With E.S. Seo et al. (CREAM Collaboration), “Approaching the Spectral Knee in High Energy Cosmic Rays with CREAM,” J. of the Phys. Soc. of Japan, Suppl. A 78, 63-67 (2009).
  3. H.S. Ahn et al. (CREAM Collaboration), “Energy spectra of cosmic-ray nuclei at high energies,” Ap.J. 707, 593-603 (2009).
  4. J. Abraham et al. (Auger Collaboration), “Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory," Astropart. Phys. 32, 89-99 (2009).
  5. J. Abraham et al. (Auger Collaboration), “Limit on the diffuse flux of ultrahigh energy tau neutrinos with the surface detector of the Pierre Auger Observatory," Phys. Rev. D 79,  102001 (2009).
  6. J. Abraham et al. (Auger Collaboration), "Trigger and Aperture of the Surface Detector Array of the Pierre Auger Observatory," Nucl. Inst. & Meth. A 613, 29-39 (2010).
  7. J. Abraham et al. (Auger Collaboration), "Measurement of the Depth of Maximum of Extensive Air Showers above 1018 eV ," Phys. Rev. Lett. 104, 091101 (2010).
  8. J. Abraham et al. (Auger Collaboration), “The Northern Site of the Pierre Auger Observatory," New J. of Phys. 12, 035001 (2010).
  9. J. Abraham et al. (Auger Collaboration), "A Study of the Effect of Molecular and Aerosol Conditions in the Atmosphere on Air Fluorescence Measurements at the Pierre Auger Observatory," Astropart. Phys. 33, 108 (2010).
  10. J. Abraham et al. (Auger Collaboration), "Measurement of the Energy Spectrum of Cosmic Rays above 1018 eV using the Pierre Auger Observatory," Phys. Lett. B 685, 239 (2010).
  11. H.S. Ahn et al. (CREAM Collaboration), “Discrepant hardening of cosmic-ray elemental spectra,” ApJ 714, L89-L93 (2010).
  12. H.S. Ahn et al. (CREAM Collaboration), “Measurements of the relative abundances of high-energy cosmic-ray nuclei in the TeV/nucleon region,” ApJ 714, L89-L93 (2010).
  13. P. Abreu et al. (Auger Collaboration), “Update on the Correlation of the Highest Energy Cosmic Rays with Nearby Extragalactic Matter,” Astropart. Phys. 34, 314-326 (2010).
  14. J. Abraham et al. (Auger Collaboration), “The Fluorescence Detector of the Pierre Auger Observatory,” Nucl. Inst. & Meth. A620 (2010) 227-251.
  15. 1. P. Abreu et al. (Auger Collaboration), “The Exposure of the Hybrid Detector of the Pierre Auger Observatory,” Astropart. Phys. 34, 368-381 (2011).
  16. Y.S. Yoon et al. (CREAM Collaboration), “Cosmic-Ray Proton and Helium Spectra from the First CREAM Flight ,” Ap.J. 728, 122-129 (2011).
  17. P. Abreu et al. (Auger Collaboration), “Search for first harmonic modulation in the right ascension distribution of cosmic rays detected at the Pierre Auger Observatory,” Astropart. Phys. 34, 627-639 (2011).
  18. P. Abreu et al. (Auger Collaboration), “Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory,” Nucl. Inst. & Meth. A 635, 92-102 (2011).
  19. P. Abreu et al. (Auger Collaboration), “The Pierre Auger Observatory Scaler Mode for the Study of Solar Activity Modulation of Galactic Cosmic Rays,” JINST 6, P01003 (2011).
  20. P. Abreu et al. (Auger Collaboration), “Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory,” JCAP06, 022 (2011).
  21. P. Abreu et al. (Auger Collaboration), “The Lateral Trigger Probability Function for Ultrahigh-Energy Cosmic Rays Showers detected by the Pierre Auger Observatory,” Astropart. Phys. 35, 266-276 (2011). 
  22. P. Abreu et al. (Auger Collaboration), “The effect of the geomagnetic field on cosmic ray energy estimates and large scale anisotropysearches on data from the Pierre Auger Observatory,” JCAP 11, 022 (2011).
  23. P. Abreu et al. (Auger Collaboration), “A search for ultra-high energy neutrinos in highly inclined events at the Pierre Auger Observatory,” Phys. Rev. D, in press (2012). 
  24. P. Abreu et al. (Auger Collaboration), “Search for signatures of magnetically-induced alignment in the arrival directions measured by the Pierre Auger Observatory,” Astropart. Phys. 35, 354 (2012).

Sundry

You can click here for a video montage of wildlife I filmed in Antarctica in January 2010.