UNDERGRADUATE AND GRADUATE STUDENTS: PLEASE INQUIRE ABOUT RESEARCH AND THESIS PROJECTS!

My research focuses on understanding the nature of Dark Matter and on the exploration of the medium energy gamma-ray sky. Dark Matter is one of the great puzzles of cosmology. Even though it was first found by astronomers seven decades ago through its gravitational effects, we have uncovered some of its basic properties only more recently. Most importantly, we have learned that it constitutes the bulk of matter in the universe. A wealth of astrophysical observations indicates that the universe consists of two principal ingredients: so-called Dark Energy, an energy leading to an accelerated expansion of the universe today, and Dark Matter, the principal driver for structure formation in the universe, dominating cosmic evolution in the first few billion years after the Big Bang. On the other hand, all the familiar matter that we see around us and that we are made of, in fact all matter consisting of protons, neutrons, and electrons, constitutes a mere 4% of the content of the universe. In yet another twist to the Copernican Revolution, we are learning that we are made of rather exotic matter in a sea of much more common but invisible "dark" matter, which, however, barely interacts with the "regular" matter we are accustomed to. In other words, some 85% of the total mass in the universe remains to be discovered. But what is it? Reports by the National Research Council and other national and international science committees have recognized the puzzle of the nature of Dark Matter as one of the great puzzles in science today. As one of the founding members of the international XENON collaboration, I pursue with my research group a search for so-called Weakly Interacting Massive Particles (WIMPs) as the most promising candidate for Dark Matter in the Universe. XENON applies a novel detector technology based on liquefied xenon as detection medium to the measurement of expected elastic scatterings of WIMPs and xenon nuclei. The resulting recoil energy can be detected and distinguished from more frequent background events resulting from trace amounts of natural radioactivity within the detector or its surroundings. With our first Dark Matter detector, XENON10, operated beneath >1 km of rock at the Gran Sasso National Laboratory (LNGS) in central Italy, we provided the world’s most stringent limits on Dark Matter particle interactions with regular matter in 2007. The next step in our search for Dark Matter, XENON100, will explore the parameter space 20 times deeper, extending well into the domain of potential detections. My group is heavily involved in this project with hardware development as well as in software, simulation, and analysis efforts. XENON100 is now taking data, and we are already planing the next step to the ton-scale, XENON1T. My Dark Matter research is supported by NSF.

My second major research interest lies in the field of medium energy gamma-ray astronomy, which provides astrophysical insights that are difficult or impossible to obtain at other wavelengths. Cosmic gamma-rays are emitted by the most energetic cosmic explosions in gamma-ray bursts, by cosmic accelerators in the jets of mass-accreting supermassive or stellar black holes, by rotating magnetized neutron stars, or by cosmic-ray interactions with the interstellar medium. Nuclear line fingerprints of radioisotopes and the matter-antimatter (electron-positron) annihilation line are produced in various astrophysical environments, in particular in supernova explosions. Imaging spectroscopy of these lines provides deep insight into their nucleosynthesis and probes the physics of these sources. Observing the gamma-ray sky in the energy band of nuclear transitions is as challenging as it is promising. Even though gamma-rays can pass the entire Milky Way galaxy without being absorbed, Earth's atmosphere is opaque to this radiation. Consequently, we must put our telescopes on satellites or high altitude balloons. In space, cosmic rays and trapped particles in Earth's radiation belts constantly bombard the detector as well as any support structures, leading to a bright glow of gamma-rays just in the energy range to be observed. At the same time, fluxes from astrophysical sources are comparatively weak. Gamma-rays cannot easily be focused as is done, e.g., with telescopes at optical wavelengths. As a consequence, the signal/background ratio is relatively low. These challenges require large gamma-ray detectors with fine position resolution, good energy resolution, and means of background suppression. The detector technology my group is developing, with NASA funding, is based on modules of so-called Liquid Xenon Time Projection Chambers, which are a promising technology for a future satellite mission in gamma-ray astronomy.

E. Aprile et al. (XENON10 Collaboration) "Design and Performance of the XENON10 Dark Matter Experiment." PRD: (arxiv:1001.2834).Submitted

J. Angle et al. (XENON10 Collaboration) "Constraints on Inelastic Dark Matter from XENON10." PRD (2009) : 115005.

P. Shagin, R. Gomez, U. G. Oberlack, P. Cushman, B. Sherwood, M. McClish, R. Farrell "Test of avalanche photodiodes for liquid xenon scintillation: Quantum efficiency and gain." Journal of Instrumentation (JINST) (2009) : 010P 0808.

P. Sorensen et al. (XENON10 Collaboration) "The scintillation and ionization yield of liquid xenon for nuclear recoils." Nucl. Instr. Meth. A, 601 (2009) : 339-346.

A. Curioni, E. Aprile, T. Doke, K. L. Giboni, M. Kobayashi, and U. G. Oberlack "A study of the LXeGRIT detection efficiency for MeV gamma-rays during the 2000 balloon flight campaign." Nucl. Instr. Methods Phys. Res., Sect. A, 576 (2007) : 350-361.

E. Aprile, A. Curioni, K. L. Giboni, M. Kobayashi, U. G. Oberlack, S. Zhang "Compton Imaging of MeV Gamma-Rays with the Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT)." Nucl. Instr. Meth. A, 593 (2008) : 414.

J. Angle et al. (XENON10 Collaboration) "First Results from the XENON10 Dark Matter Experiment at the Gran Sasso National Laboratory." Phys. Rev. Lett., 100 (2008) : 021303.

J. Angle et al. (XENON10 Collaboration) "Limits on spin-dependent WIMP-nucleon cross-sections from the XENON10 ex- periment." Phys. Rev. Lett., 101 (2008) : 091301.

J. Angle et al. (XENON Collaboration) "First Results from the XENON10 Dark Matter Experiment at the Gran Sasso Laboratory." Phys. Rev. Lett., 100 (2008) : 021303.

Boggs, S. E. for the ACT Study Team "The Advanced Compton Telescope Mission ." New Astronomy Reviews, 50 (2006) : 604.

Wunderer, C. B.; Kippen, R. M.; Bloser, P. F.; Boggs, S. E.; McConnell, M. L.; Harris, M.; Hoover, A.; Klimenko, A.V.; Novikova, E.I.; Oberlack, U.; Sturner, S.; Tournear, D.; Weidenspointner, G.; Zoglauer, A. "The ACT Vision Mission Study Simulation Effort." New Astronomy Reviews, 50 (2006) : 608.

E. Aprile, K.L. Giboni, P. Majewski, K. Ni, M. Yamashita, R. Gaitskell, P. Sorensen, L. DeViveiros, L. Baudis, A. Bernstein, C. Hagmann, C. Winant, T. Shutt, J. Kwong, U. Oberlack, D. McKinsey, R. Hasty "The XENON Dark Matter Search Experiment." New Astronomy Reviews, 49 (2004) : 289-295.

E. Aprile, A. Curioni, K. L. Giboni, M. Kobayashi, K. Ni, and U. Oberlack "A new light readout system for the LXeGRIT time projection chamber." IEEE Transactions on Nuclear Science, 50 (2003) : 1303-1308.

E. Aprile, A. Curioni, K. L. Giboni, M. Kobayashi, K. Ni, and U. Oberlack "An Upgraded Data-acquisition System for the Balloon-borne Liquid Xenon Gamma-Ray Imaging Telescope LXeGRIT." IEEE Trans. Nucl. Sci., 48(4) (2001) : 1299.

Oberlack, U., et al. "Performance of the Light-Trigger System in the Liquid Xenon Gamma-Ray Imaging Telescope LXeGRIT." IEEE Trans. Nucl. Sci., 48(4) (2001) : 1041.

U. Oberlack (for the XENON Collaboration) "First Limits on WIMP Dark Matter from the XENON10 Experiment." Journal of Physics: Conf. Series, 110 (2008) : 062020.

E. Aprile et al. (XENON Collaboration) "Xenon." Nucl. Phys. B, Proc. Suppl., 173 (2007) : 113-116.

J. Angle et al. (XENON Collaboration) "3D Position Sensitive XeTPC for Dark Matter Search." Nucl. Phys. B, Proc. Suppl., 173: 117-120.

Aprile, E.; Curioni, A.; Giboni, K. L.; Kobayashi, M.; Oberlack, U. G.; Ventura, S.; Chupp, E. L.; Dunphy, P. P.; Doke, T.; Kikuchi, J. "Calibration and in-flight performance of the Compton telescope prototype LXeGRIT." New Astronomy Reviews, 48 (2004) : 257-262.

A. Pullia, F. Zocca, C. Olsen, P. Shagin, and U. Oberlack "A Cold Low Noise Preamplifier for Use in Liquid Xenon." IEEE Conf. Ser., 1 (2007) : 424.

ACT Study Team "The Advanced Compton Telescope." Proceedings of the SPIE, 6266 (2006)

E. Aprile for the XENON Collaboration "The XENON Dark Matter Search: Status of XENON10." Journal of Physics: Conference Series, 39 (2006) : 107.

A. Curioni, E. Aprile, K. L. Giboni, M. Kobayashi, U. G. Oberlack, S. Ventura, E. L. {Chupp}, P. P. Dunphy, T. Doke and J. Kikuchi "On the Background Rate in the LXeGRIT Instrument during the 2000 Balloon Flight." Proc. of SPIE, 4851 (2003) : 1281-1293.

E. Aprile, A. Curioni, K. L. Giboni, M. Kobayashi, U. G. Oberlack, S. Ventura, E. L. {Chupp}, P. P. Dunphy, T. Doke and J. Kikuchi "The LXeGRIT Compton Telescope Prototype: Current Status and Future Prospects." Proc. of SPIE, 4851 (2003) : 1281-1293.

Speaker.  "Direct Search for WIMP Dark Matter with XENON." New Lights on Dark Matter, Waterloo, Canada. (2009-06-13)

Speaker.  "The Hunt for Particle Dark Matter - Direct Detection." SnowPAC 2009, Snowbird, UT. (2009-02-04)

Speaker.  "Dark Matter Searches – The XENON Suite of Experiments." PPC2008: 2nd Intnatl Work- shop on the Interconnection between Particle Physics and Cosmology, Albuquerque, NM. (2008-05-19)

Speaker.  "Direct Dark Matter Searches." PASCOS'08 Symposium, Waterloo, Canada. (2008-06-03)

Speaker.  "Direct Searches for WIMP Dark Matter." Cosmo'08, Madison, WI. (2008-08-25)

"Liquid Xenon TPCs in Dark Matter Detection." TPC Applications Workshop, Lawrence Berkeley National Laboratory. (April 7, 2006)

"Nuclear Recoil Techniques for the Detection of Dark Matter." Internat. Symp. on the Development of Detectors for Particle Astro-Particle and Synchrotron Radiation Experiments, SLAC, Palo Alto, CA. (April 4, 2006)

"Direct Search for WIMP Dark Matter." Visiting engineering students from Monterrey Tech, Rice University, Houston, TX. (10/25/2007)

Co-author.  "A Cold Low Noise Preamplifier for Use in Liquid Xenon." IEEE Nucl. Sci. Symp., Honolulu, Hawaii. (10/30/2007) With A. Pullia, F. Zocca, U. Oberlack, C. Olsen, P. Shagin

"A Compact Liquid Xenon Compton Telescope with High Energy Resolution and Time-Of-Flight." HEAD Meeting of the AAS, San Francisco, CA. (October 7, 2006) With R. Gomez, C. Olsen, P. Shagin (Rice - Oberlack Lab) & E. Aprile, K.L. Giboni, G. Plante, R. Santorelli (Columbia Univ.)

Co-author.  "Avalanche Photodiodes as Photosensors for Liquid Xenon Scintillation Light." APS April Meeting, Tampa, FL. (April 22, 2006) With P. Shagin & R. Gomez (Rice - Oberlack Lab); P.Cushman & B. Sherwood (UMN); R. Farrell & M. McClich (RMD, Inc.)

Co-author.  "Application of Gas Electron Multipliers (GEMs) in a Dual-Phase Xenon Ionization Chamber." APS Meeting, Tampa, FL. (April 16-19, 2006) With R. Gomez, P. Shagin

Co-author.  "Background Simulations of Advanced Compton Telescopes for Nuclear Gamma-ray Astronomy." HEAD Meeting of the AAS, New orleans, LA. (9/7/2004) With Tournear, D. M. et al.

"The Xenon Advanced Compton telescope." HEAD meeting of the AAS, New Orleans, LA. (9/7/2004) With E. Aprile, A. Curioni, K. Giboni, S. Zhang, E. Osmundsen

Speaker.  "Direct Search for Dark Matter with XENON." Institute of Physics, Johannes Gutenberg University, Mainz, Germany. (2009-09-21)

Speaker.  "Direct Search for WIMP Dark Matter with XENON." Nikhef, Amsterdam, The Netherlands. (2009-05-28)

Speaker.  "Direct Dark Matter Search with XENON." Dept. of Physics and Astronomy, Rheinische Friedrich Wilhelms Universität Bonn, Germany. (2008-08-08)

Speaker.  "Direct Search for WIMP Dark Matter – A XENON Perspective." Colloquium Dept. of Physics, University of Notre Dame, IN. (2008-03-12)

Speaker.  "Experimental Search for WIMP Dark Matter with XENON." Advanced Instrumentation Seminar, SLAC, Menglo Park, CA. (2008-05-29)

Speaker.  "The Hunt for Particle Dark Matter." Astronomy & Astrophysics Seminar, Rice University. (2008-09-10)

"Bringing Light to the Dark Universe: Direct Search for WIMP Dark Matter." Colloquium, Department of Physics and Astronomy, Texas Tech University, Lubbock, TX. (01/18/2007)

"Direct Search for WIMP Dark Matter." Colloquium, Department of Physics, University of New Hampshire, Durham, NH. (03/05/2007)

"Direct Search for WIMP Dark Matter – A XENON Perspective." Colloquium, Max Planck Institute for Physics, Munich, Germany. (10/16/2007)

"Direct Search for WIMP Dark Matter and other Cosmic Explorations with Liquid Xenon Time Projection Chambers." Seminar, I. Physikalisches Institut, RWTH Aachen, Germany. (04/17/2007)

"R&D towards a Liquid Xenon Advanced Compton Telescope for MeV Gamma-Ray Astrophysics." Seminar, Department of Physics & Astronomy, Rice University, Houston, TX. (10/24/2007)

"The Direct Search for WIMP Dark Matter." Colloquium, Department of Physics and Astronomy, Rice University, Houston, TX. (09/05/2007)

"Bringing Light to the Dark Universe: The Hunt for WIMP Dark Matter." Colloquium, Space Science Laboratory, University of California, Berkeley. (October 13, 2006)

"The Hunt for WIMP Dark Matter." Colloquium, Dept. of Physics & Astronomy, Clemson University. (November 16, 2006)

"The Liquid Xenon Advanced Compton Telescope for MeV Gamma-Ray Astrophysics." Astronomy & Astrophysics Seminar, Clemson University. (November 15, 2006)

"The Advanced Compton Telescope: The Next Leap in Nuclear Line Spectroscopy." Rice University. (Sep/14, 2005)

"A Compton Telescope for MeV Gamma-Ray Astronomy." Astrophysics Seminar, Washington University in St. Louis, MO. (12/3/2004)

Speaker.  "The XENON100 Dark Matter Experiment." APS April Meeting, Denver, CO. (2009-05-05) With XENON100 Collaboration

"New Limits on SUSY WIMP Dark Matter from the XENON10 Experiment." HEP2007, Manchester, UK. (07/19/2007) With XENON Collaboration

"R&D towards a Liquid Xenon Advanced Compton Telescope for MeV Gamma-Ray Astrophysics." APS April Meeting, Jacksonville, FL. (04/14/2007)

"Avalanche Photodiodes as Photosensors for Liquid Xenon Scintillation Light." IEEE Nuclear Science Symposium, San Diego. (October 30, 2006)

"Current Developments towards a Xenon Compton Telescope." APS Meeting, Tampa, FL. (April 16-19, 2005) With D. Kocevski, E. Aprile, K. L. Giboni

"Overview of Liquid Xenon TPC Technology: Status and Goals." Advanced Compton Telescope Workshop, University of New Hampshire, Durham, NH. (March 10-11, 2005) With E. Aprile

"LXeTPC Instrument Concept for ACT." Advanced Compton Telescope Workshop, UC Berkeley. (4/23/2004) With E. Aprile, A. Curioni, K. Giboni, S. Zhang