1. High Energy Astrophysics with the High Altitude Water Cherenkov Experiment John Pretz – Los Alamos National Lab International Astronomical Union Meeting August 20, 2012 Sensitivity of HAWC Results from Milagro / Prospects for HAWC The High Altitude Water Cherenkov Experiment

2. Comparison of Gamma-Ray Detectors Large Aperture/High Duty Cycle Milagro, Tibet, ARGO, HAWC Moderate Area Good Background Rejection Large Duty Cycle/Large Aperture Unbiased Sky Survey Extended sources Transients (GRB’s) Solar physics/space weather Low Energy Threshold EGRET/Fermi Space-based (Small Area) “Background Free” Large Duty Cycle/Large Aperture Sky Survey (< 10 GeV) AGN Physics Transients (GRBs) < 100 GeV High Sensitivity HESS, MAGIC, VERITAS, CTA Large Effective Area Excellent Background Rejection Low Duty Cycle/Small Aperture High Resolution Energy Spectra Studies of known sources Surveys of limited regions of sky at a time

3. Hit Time PMT Charge Observed Observe sources in the entire overhead sky…

4. Sensitivity of HAWC to Point Sources PRELIMINARY

5. Sensitivity of HAWC to Point Sources PRELIMINARY Survey to 50 mCrab in 1 year over 5 sr of the sky…. Test source Declination of 35 o

6. Milagro Detector 2600 m altitude site in Los Alamos, NM Central water pond – 80x60 meters – 625 PMTs in 2 layers Outrigger array – 2.4m diameter, 1.4m tall – 175 tanks 4000 m 2 pond / 40000 m 2 array footprint Reconstruct events based on arrival time of planar showerfront on the ground. 0.4 – 1.0 degree angular resolution 100 GeV – 100 TeV (20 TeV median) Operated 2000 - 2008

7. Galactic TeV Sources associated with Fermi sources Selected 34 potential Galactic sources from early Fermi data 14/34 observed at 3  or more in Milagro data. TeV emission with 9/16 of the pulsars on the list. 3 potential TeV SN remnants. Selected 34 potential Galactic sources from early Fermi data 14/34 observed at 3  or more in Milagro data. TeV emission with 9/16 of the pulsars on the list. 3 potential TeV SN remnants. Milagro Collaboration: ApJ 700 (2009) New TeV Sources. GeV / TeV asociations are common.

8. Crab Spectral Measurement Demonstration of spectral measurement to 100 TeV. Final validation of water-Cherenkov technique. ApJ. 750. 63. (2012)

9. E. Aliu – VERITAS Collab. HAWC will be a “finder” instrument……

10. Mrk421 Observed at 9  in Milagro. HAWC will observe every day Detect at 5  every week in its quiescent state. “Very high state” observable in less than one hour ph/cm2/sec/TeV @ 1 TeV *10^13 Diff. spec. index Cutoff in TeV σ’s Very low state4782.291.595.7/week High-state A19082.011.9111/day Very high state35771.872.7410/30 mins PRELIMINARY ApJ, 738, 25 (2011)

11. Fermi GRBs Fermi GBM/LAT Collab. Nature 462 (2009) TeV detection with HAWC is very likely. Measure the end of the GRB spectrum. GRB090510

12. Serendipitous discovery of small-scale cosmic-ray anisotropy Milagro – 10 TeV IceCube – 20 TeV 10 TeV proton has less than 0.01 pc gyro-radius Difficult to explain with current understanding of cosmic ray propagation. Milagro Collaboration: PhysRevL 101 (2008) IceCube Collaboration ApJL 718 (2010)

13. What we have learned with Milagro… New sources of TeV emission. First measurement of total TeV flux from the Galactic plane and diffuse emission from the Galactic plane Diffuse emission in the Cygnus region violates predictions in the TeV (and matches predictions in the MeV-GeV). TeV emission from GeV Galactic sources is common. Extended emission is important. Unanticipated anisotropy in cosmic radiation. Utility in unbiased survey. Demonstration of utility of water Cherenkov – Unbiased survey of overhead sky. – Measure the spectrum of sources past 20 TeV.

14. Re-deploying Milagro PMTs and Front- end electronics High altitude site in the mountains of Mexico Much better background rejection due to increased PMT coverage Large tanks of water covering 22500 m 2 area Overall 15x improvement in sensitivity. See sources 225x faster. See the Crab at over 5  every day. High Altitude Water Cherenkov Detector

15. HAWC Collaboration USA: Los Alamos National Laboratory University of Maryland University of Utah University of New Mexico Michigan State University Pennsylvania State University NASA/Goddard Space Flight Center University of New Hampshire Georgia Tech George Mason University University of California, Irvine Colorado State University Michigan Technological University University of Alabama University of Wisconsin, Madison Mexico: Instituto Nacional de Astrofísica Óptica y Electrónica (INAOE) Universidad Nacional Autónoma de México (UNAM) Instituto de Astronomía Instituto de Física Instituto de Ciencias Nucleares Instituto de Geofísica Universidad Autónoma de Chiapas Universidad de Guadalajara Benemérita Universidad Autónoma de Puebla Universidad Michoacana de San Nicolás de Hidalgo CINVESTAV Universidad de Guanajuato UGTO-IF Universidad Autonoma del Estado de Hidalgo Instituto Politecnico Nacional

16. HAWC Water Cherenkov Detectors

17. Gamma / Hadron Separation in HAWC Approx. Size of Milagro Muon Layer

18. HAWC Performance Milagro HAWC

19. HAWC Prototype: VAMOS

20. HAWC Deployment

21. HAWC Timeline Summer 2012 – 30 Tanks. – Anticipate 30-tank data next week! Early 2013 – 100 Tanks – Exceed Milagro sensitivity – Operations begin Summer 2014 – Full detector online

23. Summary TeV observations are a window into the extreme high- energy universe. Existing instruments – Survey the sky up to 300 GeV – Make pointed observations up to 20 TeV Scientific return of wide-field high-energy observatory – Identify new sources of TeV emission. 50 mCrab survey over 5sr of sky. – Monitor entire overhead sky for transient TeV emission from AGN and GRBs. – Provide targets for neutrino telescopes. – Measure diffuse emission from the Galactic plane. – Provide spectral measurements to 100 TeV Water Cherenkov technique, demonstrated by Milagro, will come of age with HAWC.