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) 865-0978

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 and Gravitational 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, Spring 13, Spring 14, Spring 15, Fall 15, Spring 17
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 a huge array of detectors in western Mendoza Province of Argentina, at the foothills of the Andes Mountains. It covers an area of about 3000 km2, the largest such array anywhere in the world. The international Auger Collaboration studies the highest-energy particles in the Universe, and opens 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 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. A new version of CREAM (dubbed ISS-CREAM) is at NASA's Kennedy Space Center awaiting a launch and deployment in 2017 to the International Space Station.
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 am involved in a new NASA-sponsored project, the High Energy Light Isotope eXperiment (HELIX). This is a project to fly a complex particle physics instrument on a long-duration balloon in Antarctica, at altitudes of about 120,000 ft where cosmic rays can be observed before they are destroyed in interactions with the atmosphere. The aim of the project is the difficult measurement of various isotopes in the flux of cosmic ray particles arriving at earth. In particular the relative proportion of 10Be and 9Be isotopes at energies between 1 and 10 GeV/nucleon will provide crucial clues on the mechanisms of cosmic ray production and transport in the Milky Way Galaxy. The instrument is challenging as it uses a powerful superconducting magnet, a tracking chamber, timing scintillators and a ring-imaging aerogel detector, with stringent requirements on weight, power, ruggedness for flight under very difficult conditions. The payload is expected to fly in 2018.
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), “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).
  5. 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).
  6. 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).
  7. H.S. Ahn et al. (CREAM Collaboration), “Discrepant hardening of cosmic-ray elemental spectra,” ApJ 714, L89-L93 (2010).
  8. 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).
  9. 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).
  10. J. Abraham et al. (Auger Collaboration), “The Fluorescence Detector of the Pierre Auger Observatory,” Nucl. Inst. & Meth. A620 (2010) 227-251.
  11. Y.S. Yoon et al. (CREAM Collaboration), “Cosmic-Ray Proton and Helium Spectra from the First CREAM Flight ,” Ap.J. 728, 122-129 (2011).
  12. 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).
  13. 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).
  14. 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). 
  15. 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).
  16. P. Abreu et al. (Auger Collaboration), “A Search for Anisotropy in the Arrival Directions of Ultra High Energy Cosmic Rays Recorded at the Pierre Auger Observatory,” JCAP 04, 040, 1-14 (2012).
  17. P. Abreu et al. (Auger Collaboration), “Measurement of the proton-air cross-section at sqrt(s) = 57 TeV with the Pierre Auger Observatory,” Phys. Rev. Lett. 109, 062002, 1-9 (2012).
  18. S. Coutu et al. (Auger Collaboration), “The Pierre Auger Observatory: Challenges at the highest-energy frontier,” Physics Procedia 37, 1355-1364 (2012), presented at the 3rd International Conference on Technology and Instrumentation in Particle Physics, Chicago, IL (2011).
  19. P. Abreu et al. (Auger Collaboration), “Nature and Origin of Very-High Energy Cosmic Rays,” Europhys. News 43, 24-27 (2012).
  20. P. Abreu et al. (Auger Collaboration), “Search for point-like sources of ultra-high energy neutrinos at the Pierre Auger Observatory and improved limit on the diffuse flux of tau neutrinos,” ApJ 755, L4, 1-7 (2012).
  21. P. Abreu et al. (Auger Collaboration), “A Search for Point Sources of EeV Neutrons,” ApJ 760, 148, 1-11 (2012).
  22. P. Abreu et al. (Auger Collaboration), "Large scale distribution of arrival directions of cosmic rays detected above 1018 eV at the Pierre Auger observatory," ApJ Suppl. 203, 34, 1-20 (2012).
  23. P. Abreu et al. (Auger Collaboration), “Constraints on the origin of cosmic rays above 1018 eV from large scale anisotropy searches in data of the Pierre Auger observatory,” ApJL 762, L13, 1-8 (2013).
  24. P. Abreu et al. (Auger Collaboration), “Ultra-High Energy Neutrinos at the Pierre Auger Observatory,” Advances in High Energy Physics 2013, 708680, 1-18 (2013).
  25. S. Coutu, “Positrons Galore,” Physics 6, 40 (2013) (invited Viewpoint article by APS on the release in PRL of the first AMS results: “First Results from the Alpha Magnetic Spectrometer on the International Space Station: Precision Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5-350 GeV”).
  26. P. Abreu et al. (Auger Collaboration), “The Interpretation of the Depths of Shower Maximum of Extensive Air Showers Measured by the Pierre Auger Observatory,” JCAP 02, 026, 1-19 (2013).
  27. M.W.E. Smith et al. (AMON Collaboration), “The Astrophysical Multimessenger Observatory Network (AMON),” Astropart. Phys. 45, 56-70 (2013).
  28. P. Abreu et al. (Auger Collaboration), “Bounds on the density of sources of ultra-high energy cosmic rays from the Pierre Auger Observatory,” JCAP 05, 009, 1-18 (2013).
  29. With E.S. Seo et al. (CREAM Collaboration), “Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM),” Adv. Space Res. 53, 1451-1455 (2014).
  30. A. Aab et al. (Auger Collaboration), “A search for point sources of EeV photons,” ApJ 789, 160-171 (2014).
  31. A. Aab et al. (Auger Collaboration), “A Targeted Search for Point Sources of EeV Neutrons,” ApJL 789, 34-40 (2014).
  32. A. Aab et al. (Auger Collaboration), “Muons in air showers at the Pierre Auger Observatory: measurement of atmospheric production depth,” Phys Rev D 90, 012012, 1-15 (2014).
  33. A. Aab et al. (Auger Collaboration), “Reconstruction of inclined air showers detected with the Pierre Auger Observatory,” JCAP 08, 019, 1-31 (2014).
  34. A. Aab et al. (Auger and TA Collaborations), “Searches for Large-Scale Anisotropy in the Arrival Directions of Cosmic Rays Detected above Energy of 1019 eV at the Pierre Auger Observatory and the Telescope Array,” ApJ 794, 172, 1-15 (2014).
  35. A. Aab et al. (Auger Collaboration), “Depth of Maximum of Air-Shower Profiles at the Pierre Auger Observatory. I. Measurements at Energies above 1017.8 eV,” Phys Rev D 90, 122005, 1-25 (2014).
  36. A. Aab et al. (Auger Collaboration), “Depths of Maximum of Air-Shower Profiles at the Pierre Auger Observatory. II. Composition Implications,” Phys Rev D 90, 122006, 1-12 (2014).
  37. A. Aab et al. (Auger Collaboration), “Muons in air showers at the Pierre Auger Observatory: Mean number in highly inclined events,” Phys Rev D 91, 032003, 1-12 (2015).
  38. A. Aab et al. (Auger Collaboration), “Large scale distribution of ultra high energy cosmic rays detected at the Pierre Auger Observatory with zenith angles up to 80 degrees,” ApJ 802, 111 (2015).
  39. A. Aab et al. (Auger Collaboration), “Searches for Anisotropies in the Arrival Directions of the Highest Energy Cosmic Rays Detected by the Pierre Auger Observatory ApJ 804, 15 (2015).
  40. A. Aab et al. (Auger Collaboration), “An improved limit to the diffuse flux of ultra-high energy neutrinos from the Pierre Auger Observatory,” Phys. Rev. D 91, 092008 (2015); featured on the PRD homepage as a PRD Editor’s Suggestion.
  41. A. Aab et al. (Auger Collaboration), “Search for patterns by combining cosmic-ray energy and arrival directions at the Pierre Auger Observatory,” European Phys. J. C 75, 269 (2015).
  42. A. Aab et al. (Auger Collaboration), “Measurement of the cosmic ray spectrum above 4x1018 eV using inclined events detected with the Pierre Auger Observatory,” JCAP 08, 049 (2015).
  43. A. Aab et al. (Auger Collaboration), “The Pierre Auger Cosmic Ray Observatory,” Nucl. Inst. & Meth. A 798, 172-213 (2015).
  44. M.G. Aartsen et al. (IceCube, Auger and TA Collaborations), “Search for correlations between the arrival directions of IceCube neutrino events and ultrahigh-energy cosmic rays detected by the Pierre Auger Observatory and the Telescope Array,” JCAP01, 037, 1-33 (2016).
  45. A. Aab et al. (Auger Collaboration), “Azimuthal asymmetry in the risetime of the Surface Detector signals of the Pierre Auger Observatory,” Phys. Rev. D 93, 072006, 1-16 (2016).
  46. A. Aab et al. (Auger Collaboration), “Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory,” Phys. Rev. D 93, 122005, 1-15 (2016).
  47. A. Aab et al. (Auger Collaboration), “Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy,” PRL 116, 241101, 1-9 (2016).
  48. G. Snow et al. (Auger Collaboration), “AugerPrime looks to the highest energies,” CERN Courier (cover article), 56, 29-31 (2016).
  49. L. Collica et al. (Auger Collaboration), “Measurement of the Muon Production Depths at the Pierre Auger Observatory,” Eur. Phys. J. Plus 131, 301 (2016).
  50. A. Aab et al. (Auger Collaboration), “Search for Ultra-relativistic Magnetic Monopoles with the Pierre Auger Observatory,” PRD 94, 082002, 1- 12 (2016); selected as editor’s suggestion.

Sundry

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