1. U N C L A S S I F I E D High-Energy Astrophysics Probing the Extreme Universe Gus Sinnis P-23

2. U N C L A S S I F I E D Outline  Milagro Tera-Volt Gamma-Ray Telescope Physics Goals The Milagro Detector Recent results  Future Directions Milagro at TA-57

3. U N C L A S S I F I E D The Milagro Collaboration  LANL Sinnis (PI/co-spokesman), Dingus (TSM), Walker, Casanova, Spaulding (UGS)  U. Maryland Goodman (PI/co-spokesman), Smith, Lansdell (at LANL), Vasilios (GRA), Noyes (GRA)  U.C. Irvine Yodh, Shoup, Allen (GRA), Amarotto (UGS), Delay (tech at LANL)  U.C. Santa Cruz Williams, Saz-Parkinson, Schneider (tech)  Michigan State University Jim Linnemann, Aous Abdo (GRA), Iris Gebauer (GRA)  New York University Nemethy, Mincer  George Mason University Ellsworth

4. U N C L A S S I F I E D Milagro: A Tera-Volt Astrophysical Observatory  Physics Goals Particle acceleration Astrophysical shocks Black hole environments Neutron star environments Gamma-ray bursts Solar physics Space weather  Open aperture/continuous observation Monitoring of variable sources Study large-scale structure of sources Discovery potential

5. U N C L A S S I F I E D Active Galactic Nuclei  ~10 8 M sun black hole  Relativistic particle jets  10 48 ergs/sec  TeV emission is along jet  Highly variable  Open questions what is being accelerated? how large is the bulk Lorentz factor of shock? B-field in shock?  Need multi-wavelength observations many objects many flares long-term monitoring

6. U N C L A S S I F I E D Water Cherenkov Technology e  Time Top layer detects 50% of particles that enters the pond ( ,e +,e - ) Measure relative timing across pond (~1ns) Reconstruct direction ~0.5 o

7. U N C L A S S I F I E D Background Rejection in Milagro Protons Gammas Reject 90% of proton background Retain 50% of  -ray signal

8. U N C L A S S I F I E D Galactic Plane in TeV Gamma Rays  Cosmic rays interacting with matter in Galaxy produce  ’s that decay into  rays  Gamma ray spectrum is sensitive to cosmic ray source models inverse Compton component point sources  EGRET observations up to 20 GeV indicated an excess > 1 GeV  Higher energy observations have proven elusive despite 20 years of effort  Milagro has made the first detection of TeV gamma rays from the Galactic plane  S/B level ~3:10 -4 – a very difficult analysis  Submitted to PRL EGRET data

9. U N C L A S S I F I E D Galactic Plane in TeV Gamma Rays  Demonstrates the strength of Milagro in finding diffuse and extended sources Due to good “inherent” background rejection ACTs get most of their rejection from angular resolution Large observation time Large field of view  Our flux measurement is ~1/10 of previous upper limits E -2.51±0.05

10. U N C L A S S I F I E D TeV Point-Source Survey of the Northern Hemisphere  Crab Nebula and active galaxy Mrk421 detected  9 regions of interest identified (>4  ) – 3 coincident with “roi’s” from Tibet array (Walker et al. ApJ)

11. U N C L A S S I F I E D Extended Source Survey  Two of the regions of interest are actually extended sources  ~6 degree source in Cygnus arm of Galaxy  ~3 degree source near the Crab Nebula  HESS telescope now performing follow-up observations

12. U N C L A S S I F I E D Solar Physics  Coronal mass ejections are an ideal laboratory to study particle acceleration in the cosmos  By monitoring the singles rates in all PMTs we are sensitive to “low”-energy particles (>10 GeV)  Milagro has detected 4 events from the Sun with >10 GeV particles

13. U N C L A S S I F I E D X7-Class flare Jan. 20, 2005  GOES proton data >10 MeV >50 MeV >100 MeV  Milagro scaler data > 10 GeV protons ~1 min rise-time ~5 min duration

14. U N C L A S S I F I E D Milagro Status and Future  Milagro is running in stable mode  We are discovering new source of TeV gamma rays Galactic plane Extended sources (not anticipated)  Online GRB analysis continuing Tied into global alert network (GCN)  Several exciting solar events detected  NSF anticipates 2 more years of operations

15. U N C L A S S I F I E D Future Plans: miniHAWC  Reuse Milagro PMTs and electronics  Build pond at extreme altitude (Tibet – 4300m asl)  Incorporate new design Optical isolation between PMTs Larger PMT spacing Deeper PMT depth (in top layer)  Increase collaboration Added IHEP (Beijing), MSU, UNM, and Utah  $2-3M for complete detector  >15x sensitivity of Milagro Crab Nebula in 2-3 days (now 1 year) GRBs to redshift of >1 (now 0.4)

16. U N C L A S S I F I E D miniHAWC Sensitivity: Galactic Emission  Extrapolate from Milagro detection of Galactic plane  Use neutral H map to predict TeV intensity  Maps on left show 1-year of data from Milagro, miniHAWC and HAWC

17. U N C L A S S I F I E D Conclusion  Milagro has made several discoveries TeV emission from the Galactic plane 2 extended sources of TeV gamma rays  Milagro is a completely new technique and we are still learning. The best days lie ahead.  Design of next generation instrument in progress  For modest cost (~$2-3M) we can build an instrument >15x more sensitive than Milagro  Needed for monitoring of GLAST sources, ICECUBE sources, and discovery of new phenomena

18. U N C L A S S I F I E D

19. HAWC Sensitivity: Active Galaxies  Assume theoretical model of 27 AGN  Account for IR absorption  Add in 5 known TeV sources

20. U N C L A S S I F I E D Forbush Decreases – The interplanetary field

21. U N C L A S S I F I E D The High Resolution Fly’s Eye  Studying the most energetic particles in the universe E=10 18 eV to 10 21 eV  Outstanding Issues The shape of the spectrum (is there an endpoint to the spectrum?) The composition of these particles (protons, gammas, Fe, ?) Are there any anisotropies in their arrival directions?  LANL’s role in HiRes Post 9/11 Dugway closed to non- cleared personnel LANL “rescued” HiRes – operated HiRes with Q-cleared personnel 2004 Dugway allowed US citizen’s on base – LANL no longer operates LANL receives ~100k/year from NSF for a postdoc (starting now)

22. U N C L A S S I F I E D The HiRes Detector The fluorescence yield is proportional to the number of electrons We directly measure the development of the extensive air shower and the energy of the primary particle

23. U N C L A S S I F I E D The Ultra-High-Energy Cosmic Ray Spectrum  Griesen, Zatsepin, and Kuzmin (GZK) predicted an endpoint to the UHECR spectrum at 10 19.6 eV protons interacting with the 3K CMBR lose energy via pion production  AGASA measures a continuing spectrum  HiRes mono consistent with endpoint  HiRes stereo in progress

24. U N C L A S S I F I E D Anisotropy of Ultra-High Energy Cosmic Rays  Outstanding questions Are there point sources of UHECRs? Is there large-scale structure to the UHECR arrival directions?  Motivated by results from the AGASA array Found event clusters (2 or more events from same direction) Claimed strong evidence for neutral particles from the Galactic plane  LANL work Hoffman working with Westerhoff (Columbia) developed maximum likelihood analysis to search for point sources (paper accepted) Sinnis searched for enhancement from Galactic plane (paper in progress)

25. U N C L A S S I F I E D Point Source Search  Combining data from AGASA and HiRes > 4x10 19 eV  Most likely “point source” position consists of 3 AGASA events and 1 HiRes event  Chance probability is 24% - no evidence for point sources of UHECRs

26. U N C L A S S I F I E D Galactic Plane Enhancement AGASA Long-standing claim of excess from Galaxy between 10 18 eV and 10 18.4 eV – interpreted as neutral particles HiRes 4 years of stereo data No evidence of Galactic enhancement. 90% CL upper limit ~ to AGASA signal level

27. U N C L A S S I F I E D HiRes Status and Future  Operations will continue until ~March 2006  Stereo data analysis is our major effort  Spectrum – Utah and Nevis  Anisotropy – LANL and Columbia Galactic plane Point sources Correlations with known objects  Expect 1-2 more years of analysis than effort shifting