Juan I. Collar


Ph.D., University of South Carolina, 1992
Contact Information
Phone: 773-702-4253
Location: ERC 489
Email: collarkicp.uchicago.edu
WWW: Web Site
A prototype bubble chamber sensitive to Weakly Interacting Massive Particles (WIMPs).
My main interest is in the development of innovative methods for the detection for hypothetical astroparticles (WIMPs, axions, magnetic monopoles, any yet-to-be-discovered component of cosmic rays that might constitute a fraction of the 'dark matter'). Needless to say, this is a risky business, but I am equally interested in the journey and the destination: the extreme levels of sensitivity required in some of these experiments force us to devise new detection technologies, in an endless quest for the 'better mouse-trap'. It is a very enjoyable challenge. I am also attracted to other exotica such as double-beta decay and some 'hard' problems in neutrino detection (coherent neutrino scattering, detection of the relic neutrino sea). I enjoy the condensed-matter aspects of detector development and anything having to do with the interactions between radiation and matter. I get easily excited about cross-disciplinary endeavors and real-life applications of detectors that might otherwise be chasing ghost particles.

Together with collaborators at the Groupe de Physique des Solides (Universite Paris VII), University of Lisbon, and Pacific Northwest National Laboratory, I developed large-mass, low-background superheated droplet detectors (SDDs) dedicated to WIMP (Weakly Interacting Massive Particle) searches (The SIMPLE dark matter search). On my arrival to Chicago I started investigating the possibility of making large bubble chambers stable enough for the same goal, using CF3I, a target ideal for WIMP detection. Our collaboration with FNAL and Indiana University (The Chicago Observatory for Underground Particle Physics, COUPP) has already led to the best sensitivity to spin-dependent WIMP interactions. We presently work on a 60 kg and 500 kg CF3I chamber. We expect the first, to be installed in SNOlab during 2010, to provide a similar leading sensitivity also to spin-independent WIMP couplings. At CERN I am involved in CAST, a search for solar axions using a decommissioned LHC test magnet, an interesting astroparticle spin-off from the Large Hadron Collider effort. More recently, I have worked on the application of P-type Point Contact germanium detectors to coherent neutrino-nucleus scattering, double beta decay and searches for light dark matter candidates. These devices have already produced some very interesting results within the CoGeNT and MAJORANA experiments.

Ongoing Scientific Projects:
KICP Highlights & News

Talks, Lectures, & Workshops

Past Students

GRADUATE: Alan Robinson (2015), Nicole Fields (2015), Drew Fustin (2012), Matthew Szydagis (2010), Phil Barbeau (2009), Nathan Riley (2008), Dante Nakazawa (2006)

UNDERGRADUATE: Kevin Baker (2014), William Tahoe Schrader (2014), Vivek Sarma (2014), Berk Diler (2014), Alan Salkanovic (2013), Eli Byers Barrows (2012), Natalie Harrison (2012), Songkiat Nutalaya (2012), Steven Bogacz (2012), Muneeb Hai (2010), Hannes Schimmelpfennig (2009), Jacob Claussen (2008), Adrian Culver (2008), Luke Goetzke (2008), Charles Greenberg (2008), Keith Crum (2007), Smriti Mishra (2007), Julia Rasmussen (2006), Kevin O'Sullivan (2005), Aza Raskin (2005), Taylor Aune (2004)
Currently in Committees
  • Wednesday Colloquium committee

KICP Publications
2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001

Latest Journal Publications
  1. "Measurement of the ionization produced by sub-keV silicon nuclear recoils in a CCD dark matter detector", arXiv:1608.00957 (Aug 2016)
  2. "Measurement of the low-energy quenching factor in germanium using an $^{88}$Y/Be photoneutron source", arXiv:1608.03588 (Aug 2016)
  3. "Improved dark matter search results from PICO-2L Run 2", Physical Review D, Volume 93, Issue 6, id.061101 (Mar 2016)
  4. "Improved dark matter search results from PICO-2L Run 2", arXiv:1601.03729 (Jan 2016)
  5. "Search for chameleons with CAST", Physics Letters B, Volume 749, p. 172-180 (Oct 2015)
  6. "Dark Matter Search Results from the PICO-60 CF$_3$I Bubble Chamber", arXiv:1510.07754 (Oct 2015)
  7. "New solar axion search using the CERN Axion Solar Telescope with 4He filling", Physical Review D, Volume 92, Issue 2, id.021101 (Jul 2015)
  8. "Dark Matter Search Results from the PICO-2L C3F8 Bubble Chamber", Physical Review Letters, Volume 114, Issue 23, id.231302 (Jun 2015)
  9. "Coherent neutrino-nucleus scattering detection with a CsI[Na] scintillator at the SNS spallation source", Nuclear Inst. and Methods in Physics Research, A, Volume 773, p. 56-65 (Feb 2015)
  10. "Comment on "Fitting the Annual Modulation in DAMA with Neutrons from Muons and Neutrinos"", Physical Review Letters, Volume 113, Issue 22, id.229001 (Nov 2014)
  11. "Erratum: First dark matter search results from a 4-kg CF3I bubble chamber operated in a deep underground site [Phys. Rev. D 86, 052001 (2012)]", Physical Review D, Volume 90, Issue 7, id.079902 (Oct 2014)
  12. "Search for Solar Axions by the CERN Axion Solar Telescope with He3 Buffer Gas: Closing the Hot Dark Matter Gap", Physical Review Letters, Volume 112, Issue 9, id.091302 (Mar 2014)
  13. "Quenching and channeling of nuclear recoils in NaI(Tl): Implications for dark-matter searches", Physical Review C, vol. 88, Issue 3, id. 035806 (Sep 2013)
  14. "CoGeNT: A search for low-mass dark matter using p-type point contact germanium detectors", Physical Review D, vol. 88, Issue 1, id. 012002 (Jul 2013)
  15. "Direct measurement of the bubble-nucleation energy threshold in a CF3I bubble chamber", Physical Review D, vol. 88, Issue 2, id. 021101 (Jul 2013)
  16. "The C-4 dark matter experiment", Nuclear Instruments and Methods in Physics Research A, Volume 712, p. 27-33 (Jun 2013)
  17. "CAST constraints on the axion-electron coupling", Journal of Cosmology and Astroparticle Physics, Issue 05, article id. 010, pp. (2013) (May 2013)
  18. "Applications of an Y88/Be Photoneutron Calibration Source to Dark Matter and Neutrino Experiments", Physical Review Letters, vol. 110, Issue 21, id. 211101 (May 2013)
  19. "Characteristics of signals originating near the lithium-diffused N+ contact of high purity germanium p-type point contact detectors", Nuclear Instruments and Methods in Physics Research A, Volume 701, p. 176-185 (Feb 2013)
  20. "First dark matter search results from a 4-kg CF3I bubble chamber operated in a deep underground site", Physical Review D, vol. 86, Issue 5, id. 052001 (Sep 2012)

Latest Conference Proceedings
  1. "A search for WIMPs with the CoGeNT public dataset", APS April Meeting 2016, abstract #D1.034 (Mar 2016)
  2. "Monte Carlo studies of the CoGeNT detector for a variety of dark matter candidates", APS April Meeting 2015, abstract #T1.029 (Apr 2015)
  3. "A search for WIMPs and tests of local dark matter velocity distributions with the CoGeNT public dataset", APS April Meeting 2014, abstract #R12.008 (Mar 2014)
  4. "CosI: Coherent Neutrino Scattering with Cesium Iodide", APS April Meeting 2014, abstract #J7.009 (Mar 2014)
  5. "A measurement of the K-shell decays in the CoGeNT public dataset", American Physical Society, APS April Meeting 2013, April 13-16, 2013, abstract #E2.021 (Apr 2013)
  6. "The MAJORANA experiment: an ultra-low background search for neutrinoless double-beta decay", Journal of Physics: Conference Series, Volume 381, Issue 1, article id. 012044, 6 pp. (2012) (Sep 2012)
  7. "The Majorana Demonstrator: A Search for Neutrinoless Double-beta Decay of Germanium-76", Journal of Physics: Conference Series, Volume 375, Issue 4, id. 042010 (2012) (Jul 2012)
  8. "Dark matter sensitivities of the Majorana Demonstrator", Journal of Physics: Conference Series, Volume 375, Issue 1, id. 012014 (2012) (Jul 2012)
  9. "Status and perspectives of the CAST experiment", Journal of Physics: Conference Series, Volume 375, Issue 2, id. 022001 (2012) (Jul 2012)
  10. "The Majorana Demonstrator: A search for neutrinoless double-beta decay of germanium-76", 19TH PARTICLES AND NUCLEI INTERNATIONAL CONFERENCE (PANIC11). AIP Conference Proceedings, Volume 1441, pp. 480-482 (2012) (Apr 2012)

Past Visitors:
  1. Andrew Sonnenschein, Fermilab (2016)
  2. Miguel Ardid, Universitat Politecnica de Valencia (2014)
  3. Dipak Rimal, University of Florida (2014)
  4. Manuel Bou, Polytechnic University of Valencia (2012)
  5. Alvaro Chavarria, Princeton University (2012)
  6. Rafael Lang, Purdue University (2012)
  7. María Luisa Sarsa, University of Zaragoza (2012)
  8. Miguel Ardid, Universitat Politècnica de València (2011)
  9. Manuel Bou, UPV - IGIC (2011)
  10. Todd Hossbach, Pacific Northwest National Laboratory (2011)
  11. Paolo Gondolo, University of Utah (2010)
  12. Sam Waldman, Massachusetts Institute of Technology (2010)
  13. Juan Gomez-Cadenas, IFIC (CSIC-UV) SPAIN (2009)
  14. Carl Dahl, Princeton University (2008)
  15. Richard Gaitskell, Brown University (2007)
  16. Andrea Pocar, Stanford University (2007)
  17. William Wester, Fermi National Accelerator Laboratory (2007)
  18. Silvia Borghi, CERN (2006)
  19. Dan Akerib, Case Western Reserve University (2004)
  20. Frank Avignone, University of South Carolina (2003)
  21. Robynne Hooper, University of Texas, Austin (2003)
  22. Peter Gorham, University of Hawaii (2002)
  23. Harry Miley, Pacific Northwest National Laboratory (2002)
  24. Andre Sonnenschein, Princeton University (2002)