• Associate Professor, Physics And Astronomy


  • Abe, M., Abu-Zayyad, T., Allen, M., Azuma, R., Barcikowski, E., Belz, J.W., Bergman, D.R., Blake, S.A., Cady, R., Cheon, B.G., Chiba, J., Chikawa, M., Cho, W.R., Fujii, T., Fukushima, M., Goto, T., Hanlon, W., Hayashi, Y., Hayashida, N., Hibino, K., Honda, K., Ikeda, D., Inoue, N., Ishii, T., Ishimori, R., Ito, H., Ivanov, D., Jui, C.C.H., Kadota, K., Kakimoto, F., Kalashev, O., Kasahara, K., Kawai, H., Kawakami, S., Kawana, S., Kawata, K., Kido, E., Kim, H.B., Kim, J.H., Kim, J.H., Kitamura, S., Kitamura, Y., Kuzmin, V., Kwon, Y.J., Lan, J., Lundquist, J.P., Machida, K., Martens, K., Matsuda, T., Matsuyama, T., Matthews, J.N., Minamino, M., Mukai, Y., Myers, I., Nagasawa, K., Nagataki, S., Nakamura, T., Nonaka, T., Nozato, A., Ogio, S., Ogura, J., Ohnishi, M., Ohoka, H., Oki, K., Okuda, T., Ono, M., Oshima, A., Ozawa, S., Park, I.H., Pshirkov, M.S., Rodriguez, D.C., Rubtsov, G., Ryu, D., Sagawa, H., Sakurai, N., Scott, L.M., Shah, P.D., Shibata, F., Shibata, T., Shimodaira, H., Shin, B.K., Shin, H.S., Smith, J.D., Sokolsky, P., Springer, R.W., Stokes, B.T., Stratton, S.R., Stroman, T.A., Suzawa, T., Takamura, M., Takeda, M., Takeishi, R., Taketa, A., Takita, M., Tameda, Y., Tanaka, H., Tanaka, K., Tanaka, M., Thomas, S.B., Thomson, G.B., Tinyakov, P., Tkachev, I., Tokuno, H., Tomida, T., Troitsky, S., Tsunesada, Y., Tsutsumi, K., Uchihori, Y., Udo, S., Urban, F., Vasiloff, G., Wong, T., Yamane, R., Yamaoka, H., Yamazaki, K., Yang, J., Yashiro, K., Yoneda, Y., Yoshida, S., Yoshii, H., Zollinger, R., Zundel, Z. & Abbasi, R.U. (2016). The energy spectrum of cosmic rays above 1017.2 eV measured by the fluorescence detectors of the Telescope Array experiment in seven years. Elsevier BV. Published, 2016.
  • Search for EeV Protons of Galactic Origin R.U. Abbasi (Utah U.) , M. Abe (Saitama U.) , T. Abu-Zayyad, M. Allen (Utah U.) , R. Azuma (Tokyo Inst. Tech.) , E. Barcikowski, J.W. Belz, D.R. Bergman, S.A. Blake, R. Cady (Utah U.) et al. Aug 22, 2016 - 6 pages Astropart.Phys. 86 (2017) 21-26 (2017-01) DOI: 10.1016/j.astropartphys.2016.11.001 e-Print: arXiv:1608.06306 [astro-ph.HE]. Published, 08/22/2016.
  • First Upper Limits on the Radar Cross Section of Cosmic-Ray Induced Extensive Air Showers R.U. Abbasi, M. Abe, M. Abou Bakr Othman, T. Abu-Zayyad, M. Allen, R. Anderson, R. Azuma, E. Barcikowski, J.W. Belz, D.R. Bergman et al. Mar 16, 2016 - 17 pages Astropart.Phys. 87 (2017) 1-17 (2017-01) DOI: 10.1016/j.astropartphys.2016.11.006 e-Print: arXiv:1603.05217 [astro-ph.IM] | PDF. Published, 03/16/2016.
  • 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 IceCube and Pierre Auger and Telescope Array Collaborations (M.G. Aartsen (Adelaide U.) et al.) Nov 30, 2015 - 40 pages JCAP 1601 (2016) no.01, 037 (2016-01-20) DOI: 10.1088/1475-7516/2016/01/037 FERMILAB-PUB-15-520-AD-AE-CD-TD e-Print: arXiv:1511.09408 [astro-ph.HE] | PDF Experiment: AUGER, IceCube, TELESCOPE-ARRAY. Published, 01/20/2016.
  • The energy spectrum of cosmic rays above 1017.2 eV measured by the fluorescence detectors of the Telescope Array experiment in seven years Telescope Array Collaboration (R.U. Abbasi (Utah U.) et al.) Nov 23, 2015 - 10 pages Astropart.Phys. 80 (2016) 131-140 (2016-07) DOI: 10.1016/j.astropartphys.2016.04.002 e-Print: arXiv:1511.07510 [astro-ph.HE] | PDF Experiment: TELESCOPE-ARRAY. Published, 01/2016.
  • Measurement of the proton-air cross section with Telescope Arrays Middle Drum detector and surface array in hybrid mode R. U. Abbasi et al. [Telescope Array Collaboration]. arXiv:1505.01860 [astro-ph.HE] 10.1103/PhysRevD.92.032007 Phys. Rev. D 92, no. 3, 032007 (2015). Published, 05/2015.
  • The hybrid energy spectrum of Telescope Arrays Middle Drum Detector and surface array R. U. Abbasi et al.. 10.1016/j.astropartphys.2015.02.008 Astropart. Phys. 68, 27 (2015). Published, 02/2015.
  • Study of Ultra-High Energy Cosmic Ray composition using Telescope Arrays Middle Drum detector and surface array in hybrid mode R. U. Abbasi, M. Abe, T. Abu-Zayyad, M. Allen, R. Anderson, R. Azuma, E. Barcikowski, J. W. Belz et al.. arXiv:1408.1726 [astro-ph.HE] 10.1016/j.astropartphys.2014.11.004 Astropart. Phys. 64, 49 (2014). Published, 11/2014.
  • 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 A. Aab et al. [Telescope Array and Pierre Auger Collaborations]. arXiv:1409.3128 [astro-ph.HE] 10.1088/0004-637X/794/2/172 Astrophys. J. 794, no. 2, 172 (2014). Published, 09/2014.
  • Gain monitoring of telescope array photomultiplier cameras for the rst 4 years of operation B. K. Shin, H. Tokuno, Y. Tsunesada, T. Abu-Zayyad, R. Aida, M. Allen, R. Anderson and R. Azuma et al.. 10.1016/j.nima.2014.09.059 Nucl. Instrum. Meth. A 768, 96 (2014). Published, 09/2014.
  • Energy Spectrum of Ultra-High Energy Cosmic Rays Observed with the Telescope Array Using a Hybrid Technique T. Abu-Zayyad et al. [Telescope Array Collaboration]. arXiv:1305.7273 [astro-ph.HE] 10.1016/j.astropartphys.2014.05.002 Astropart. Phys. 61, 93 (2015). Published, 05/2014.
  • Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array Experiment" R. U. Abbasi et al. [Telescope Array Collaboration]. arXiv:1404.5890 [astro-ph.HE] 10.1088/2041-8205/790/2/L21 Astrophys. J. 790, L21 (2014). Published, 04/2014.
  • HiRes and TA spectrum measurements D. R. Bergman [HiRes and Telescope Array Collaborations]. 10.1051/epjconf/20135304001 EPJ Web Conf. 53, 04001 (2013). Published, 10/2013.
  • The Energy Spectrum of Ultra-High-Energy Cosmic Rays Measured by the Telescope Array FADC Fluorescence Detectors in Monocular Mode T. Abu-Zayyad et al. [Telescope Array Collaboration]. arXiv:1305.6079 [astro-ph.HE] 10.1016/j.astropartphys.2013.06.007 Astropart. Phys. 48, 16 (2013). Published, 06/2013.
  • Correlations of the Arrival Directions of Ultra-high Energy Cosmic Rays with Extra-galactic Objects as Observed by the Telescope Array Experiment T. Abu-Zayyad et al. [Telescope Array Collaboration]. arXiv:1306.5808 [astro-ph.HE] 10.1088/0004-637X/777/2/88 Astrophys. J. 777, 88 (2013). Published, 06/2013.
  • Upper limit on the ux of photons with energies above 1019 eV using the Telescope Array surface detector T. Abu-Zayyad et al. [Telescope Array Collaboration]. arXiv:1304.5614 [astro-ph.HE] 10.1103/PhysRevD.88.112005 Phys. Rev. D 88, no. 11, 112005 (2013). Published, 04/2013.
  • The Cosmic Ray Energy Spectrum Observed with the Surface Detector of the Telescope Array Experiment T. Abu-Zayyad et al. [Telescope Array Collaboration]. arXiv:1205.5067 [astro-ph.HE] 10.1088/2041-8205/768/1/L1 Astrophys. J. 768, L1 (2013). Published, 01/2013.
  • NICHE: The Non-Imaging CHErenkov Array D. Bergman and J. Krizmanic AIP Conf. Proc. 1516, 282 (2012) [arXiv:1212.6237 [astro-ph.IM]]. Published, 12/2012.
  • ``Search for Anisotropy of Ultra-High Energy Cosmic Rays with the Telescope Array Experiment'' T.~Abu-Zayyad et al. [TA Collaboration] Astrophys. J. 757, 26 (2012) [arXiv:1205.5984 [astro-ph.HE]]. Published, 05/2012.
  • ``The Energy Spectrum of Telescope Array's Middle Drum Detector and the Direct Comparison to the High Resolution Fly's Eye Experiment'' T.~Abu-Zayyad et al. [TA Collaboration] Astropart. Phys. 39-40, 109 (2012) [arXiv:1202.5141 [astro-ph.IM]]. Published, 02/2012.
  • ``The surface detector array of the Telescope Array experiment'' T. Abu-Zayyad et al. [TA Collaboration] Nucl. Instrum. Meth. A 689, 87 (2012) [arXiv:1201.4964 [astro-ph.IM]]. Published, 01/2012.
  • ``New air fluorescence detectors employed in the Telescope Array experiment'' H. Tokuno et al. [TA Collaboration] Nucl. Instrum. Meth. A 676, 54 (2012) [arXiv:1201.0002 [astro-ph.IM]]. Published, 01/2012.
  • R.U. Abbasi et al, "Measurement of the flux of ultra high energy cosmic rays by the stereo technique," Astroparticle Physics, 32 (2009) 53–60. Published, 06/09/2009.

Research Statement

The field of Ultra-High Energy Cosmic Ray (UHECR) physics is poised to change from exploratory observations and vague speculations to precision measurements and well-constrained theoretical explanations, such as happened in the field of Cosmology a decade ago. The observation of the Griessen-Katsepin-Kuzmin (GZK) Cutoff in the UHECR energy spectrum by the High Resolution Fly’s Eye (HiRes) experiment, of which I was a part, was the beginning of this shift, along with the measurement of changing composition in the Knee region of the cosmic ray energy spectrum by the Kascade Experiment. To continue this move towards precision measurements strongly constraining theoretical models, we must not just measure the features of the UHECR more accurately, but measure the relationships between the features more accurately. The systematic uncertainties involved in comparing different experiments covering different energy ranges currently limits our ability to make these sort of comparisons. A single experiment covering as many of the features of the UHECR spectrum as possible will reduce these uncertainties. The Telescope Array (TA) is just such a project. My current and near future research involves TA and its Low Energy Extension (TALE). TA Monocular Analysis: I am currently analyzing fluorescence detector data from the first three years of TA operation, along with my graduate student Sean Stratton and postdoc Tom Stroman, with the aim of producing an energy spectrum, in the monocular mode, in the very near future. This analysis specifically uses data from the two new fluorescence detector (FD) sites which employ a Flash ADC (FADC) data acquisition system. The third FD site uses reconditioned mirrors from HiRes and a different data acquisition system, so the analysis of that data is a completely separate endeavor. There are a number of spectrum analyses ongoing in TA: monocular, stereo, hybrid, surface detector. The monocular analysis is challenging in that the geometry of air showers is harder to reconstruct using only the timing of signals observed at one site, but it provides the widest energy range of any of the analyses above. Again, it’s only by studying the widest energy range possible that we will improve our understanding of the sources of cosmic rays. The heart of this analysis is to understand the detector itself in all details which are important to observing and reconstructing air showers. We achieve this understanding through simulation of the detector, producing “Monte Carlo” (MC) data in the same format as the actual data coming from the instrument. Our understanding of the detector is only as good as the agreement between distributions of variables in the data and those in the MC. If there is a disagreement between distributions in data and MC, e.g. in the distribution of distances between the shower and the detector, it is a sign of something which should be corrected in the simulation. The extent to which they agree allows us to estimate the systematic uncertainty in our aperture calculation. The great advantage of requiring this kind of understanding of the detector is that we can measure the biases introduced by cuts made to analyze the data. This includes not just cuts made to analyze the data after it has been collected, but “cuts” made by the detector itself when recoding the data, i.e., the cuts imposed by the trigger. TALE Development & Construction: TA itself, using monocular analyses, will only cover energies from 0.3 EeV to just above 100 EeV. This covers the features of the GZK Cutoff and the Ankle. To cover energies an order of magnitude lower, which is necessary to observe the 2nd Knee and the change of composition which should accompany the Galactic-Extragalactic transition of UHECR sources, we have to augment TA with more FDs and an infill array of SDs. I have been primarily involved with the design of the new fluorescence mirrors, which must look higher in the sky to observe the full extent of close-by showers, and I will be extensively involved in the immanent deployment of these detectors. I expect to perform an analysis of the data from the TALE FDs similar to my analysis of TA and HiRes fluorescence data. This analysis will be eased by the fact that the TALE FDs will actually be the reconditioned HiRes-II mirrors and FADC electronics. Non-Imaging Cherenkov Array: To extend the range of TA/TALE even further, I have been designing a non-imaging Cherenkov detector array to work with FDs of the TALE detector. Traditionally non-imaging Cherenkov detectors have been used at lower energies, at around 3 PeV in the Knee region. By extending the usable energy range of Cherenkov arrays to overlap with fluorescence detectors, one gains the ability to cross-calibrate the Cherenkov composition measurement with the unambiguous Xmax measurement available in fluorescence telescopes. The cone of Cherenkov light from an EAS falls primarily within a ring of 120 m about the shower core. The transverse momentum of shower particles broadens this cone, so there is a power law drop-off in intensity outside of the central region. Even with this broadening, the individual counters cannot be placed much more than 150 m apart, so that it is difficult to cover the large areas necessary to see the low fluxes at higher energies. Cherenkov array composition measurements have traditionally used the distribution of light intensity within the ring to determine the depth of shower maximum. This requires very close spacing of detectors. However, the width of the Cherenkov front is also dependent on the depth of shower maximum, and this effect gets bigger with radius, allowing us to have a robust composition measurement even with widely spaced detectors. My preliminary estimates show that we can measure Xmax to about 20 g/cm2 at 300 PeV, comparable to what one can do in fluorescence. The combination of fluorescence with Cherenkov for shower detection has never been done before. If we can achieve it, it promises to give us access to the early development of the air shower, earlier than is visible to the FD alone. Measurement of the early development of the shower will allow us to measure properties of particle interactions at and above the CM energies at the LHC.

Research Keywords

  • Ultra high energy cosmic rays


  • NICHE: Using Cherenkov Radia6on to Extend Telescope Array to Sub-PeV Energies APS April Meeting, Salt Lake City U12.0007. Contributed Talk, Presented, 04/18/2016.
  • The distribution of shower longitudinal pro les widths as measured by Telescope Array in stereo mode, 34th International Cosmic Ray Conference, The Hague, July 2015. Poster, Presented, 07/2015.
  • Imaging and Non-Imaging Cherenkov Hybrid Reconstruction, 34th International Cosmic Ray Conference, The Hague, July 2015. Poster, Presented, 07/2015.
  • The NICHE Array: Status and Plans, 34th International Cosmic Ray Conference, The Hague, July 2015. Poster, Presented, 07/2015.
  • Results from Telescope Array, IceCube Particle Astrophysics Symposium, Madison, May 2015. Invited Talk/Keynote, Presented, 05/2015.
  • The Non-Imaging CHErenkov Array (NICHE): A TA/TALE Extension to Measure the Flux and Composition of Very-High Energy Cosmic Rays, Conference on Ultrahigh Energy Cosmic Rays (UHECR2014), Springdale, UT, Oct. 2014. Invited Talk/Keynote, Presented, 10/2014.
  • Cosmic Ray Measurements at the Highest Energies: Results from Telescope Array, 40th COSPAR Scienti c Assembly, Moscow, Russia, Aug. 2014. Invited Talk/Keynote, Presented, 08/2014.
  • Telescope Array: Recent Results, Future Plans Cosmic Ray Anisotropy Workshop, Madison, WI, Sept. 2013. Invited Talk/Keynote, Presented, 09/2013.
  • TA Spectrum Summary 33rd International Cosmic Ray Conference, Rio de Janeiro, Brazil, July 2013. Invited Talk/Keynote, Presented, 07/2013.
  • An Efficient Technique for the Reconstruction of Extensive Air Showers using Non-Imaging Cherenkov Measurements 33rd International Cosmic Ray Conference, Rio de Janeiro, Brazil, July 2013. Poster, Presented, 07/2013.
  • The Non-Imaging CHErenkov Array (NICHE): A TA/TALE extension to measure the flux and composition of Very-High Energy Cosmic Rays APS April Meeting, Denver, CO, April 2013. Conference Paper, Presented, 04/2013.
  • Telescope Array: Recent Results, Future Plans 4th Workshop on Air Shower Detection at High Altitudes, Naples, Italy, Jan. 2013. Invited Talk/Keynote, Presented, 01/2013.
  • HiRes and TA Spectrum Measurements UHECR2012, Geneva, Feb. 2012. Invited Talk/Keynote, Presented, 02/2012.
  • HiRes and TA Spectrum Measurements The International Symposium on Future Directions in UHECR Physics, Geneva, Switzerland, Feb. 2012. Invited Talk/Keynote, Presented, 02/2012.
  • D.R. Bergman et al., "The Energy Spectrum of UHECRs using the Telescope Array Fluorescence Detectors in Monocular Mode", Proceedings of the 32nd International Cosmic Ray Conference (Beijing), vol 2, pp 265-268. Poster, Presented, 08/15/2011.
  • S.R. Stratton et al., "Using the Monte Carlo Technique in the Observation of Fluorescence from UHECRs", Proceedings of the 32nd International Cosmic Ray Conference (Beijing), vol. 2, pp 262--265. Poster, Presented, 08/15/2011.
  • "Detecting UHECRs Using Cherenkov Light", APS April Meeting (Anaheim). Contributed Talk, Presented, 04/30/2011.
  • "HiRes Results: The Final Word (almost)", Workshop on Hadron-Hadron and Cosmic-Ray Interactions at multi-TeV Energies, ECT*, Trento, Italy. Invited Talk/Keynote, Presented, 12/02/2010.
  • "The HiRes Stereo Measurement of the UHECR Spectrum", Fall 2009 Meeting of the Four Corners Section of the APS, . Conference Paper, Presented, 10/23/2009.
  • "Recent Result from HiRes", CCAPP Symposium 2009: Towards Fundamental Breakthroughs in Astrophysics and Cosmology within the Next Decade, OSU, Columbus, OH, . Invited Talk/Keynote, Presented, 10/12/2009.
  • "The TA Fluorescence Detector Spectrum in Monocular Mode", 31st International Cosmic Ray Conference, Łódź, Poland . Invited Talk/Keynote, Presented, 07/13/2009.
  • "Status of the Telescope Array Fluorescence Detectors", given by J. W. Belz from presentation created by Douglas R Bergman, XXIèmes Rencontres de Blois, Blois, France. Invited Talk/Keynote, Presented, 06/23/2009.

Research Groups

  • Greg Furlich, Graduate Student. Physics & Astronomy. 08/2015 - present.
  • Bingran Wang, Undergraduate Student. 12/2012 - 04/2015.
  • Jian Lan, Graduate Student. 09/2012 - 04/2016.
  • Thomas Stroman, Postdoc. Physics & Astronomy. 07/2010 - 08/2015.
  • Rhett Zollinger, Graduate Student. Physics & Astronomy. 05/2010 - 07/2011.

Grants, Contracts & Research Gifts

  • Experimental Research in Ultrahigh Energy Cosmic Ray Physics. PI: Gordon Thomson. Co-PI(s): Douglas Bergman. National Science Foundation, 05/01/2007 - 04/30/2010. Total project budget to date: $1,173,500.00

Research Equipment and Testing Expertise

  • Photomulitplier tubes, FADC data acquisition.

Software Titles

  • TRUMP. Simulation software for UHECR fluorescence detectors. Release Date: 01/2011. Inventors: Douglas Bergman, Sean Stratton, Tom Stroman, Elliott Barcikowski.
  • TRUMP: TA Rationalized & Upgradable MC Program. A Monte Carlo simulation program for the Telescope Array (TA) fluorescence detectors. Release Date: 2009. Inventors: Douglas Bergman, Lauren Scott, Sean Stratton. Distribution List: Within the TA Collaboration.


  • French, basic.
  • Swedish, basic.

Geographical Regions of Interest

  • Belgium
  • Japan
  • Republic of Korea
  • Russian Federation