1. Wide-Field Gamma-Ray Instruments: Milagro Results Plans for HAWC Gus Sinnis Los Alamos National Lab TeVPA 2008 Beijing Scientific Goals Experimental Techniques Recent Results Future Plans

2. Modern Gamma-Ray Telescopes Large Aperture/High Duty Cycle Milagro, Tibet, ARGO Large Area Good Background Rejection Good Angular Resolution Large Duty Cycle/Large Aperture Unbiased Sky Survey Extended sources Highest energies Transients (GRB’s) Low Energy Threshold EGRET/FERMI Space-based (Small Area) “Background Free” Good Angular Resolution Large Duty Cycle/Large Aperture Sky Survey 100 MeV - 10 GeV AGN Physics Transients (GRBs) < 100 GeV High Sensitivity HESS, MAGIC, VERITAS, CANGAROO Large Area Excellent Background Rejection Excellent Angular Resolution Low Duty Cycle/Small Aperture Surveys of limited regions of sky High Resolution Energy Spectra Source morphology

3. Science Goals of Ground-Based Observatories Cosmic-ray origins –High-energy W and high resolution A spectra of Galactic sources –Galactic diffuse emission W –Discover Galactic cosmic-ray accelerators A Particle acceleration –Transient phenomena (AGN flares and GRBs) prompt emission W & delayed A orphan flares W, TeV duty factors W, fastest phenomena A –Multi-wavelength (GLAST, x-ray, optical, radio) WA, multi-messenger A –Source morphology A –Pulsars A Fundamental Physics –Lorentz invariance (GRB W, AGN A ) –Dark matter detector A (annihilation gammas from neutralinos) Discovery –Unbiased sky survey (2.6  sr) to 2% of Crab Nebula W –Deep Galactic survey to 0.1% of Crab A W Wide field instrument A Air Cherenkov Array

4. Abdo, Allen, Berley, DeYoung, Dingus, Ellsworth, Gonzalez, Goodman, Hoffman, Huentemeyer, Kolterman, Linnemann, McEnery, Mincer, Nemethy, Pretz, Ryan, Saz Parkinson, Shoup, Sinnis, Smith, Williams, Vasileiou, Yodh The Milagro Collaboration

5. TeV gamma at 2600m asl Water Cherenkov Technology CASA-MIA Milagro gammas electrons Provides fully active area Converts  ’s to electrons  : electron ~ 6:1

6. 60 m 80 m Milagro Gamma-Ray Observatory 2600m above sea level 2 sr field-of-view 95% duty factor A. Abdo, B. Allen, D. Berley, T. DeYoung,B.L. Dingus, R.W. Ellsworth, M.M. Gonzalez, J.A. Goodman, C.M. Hoffman,P. Huentemeyer, B. Kolterman, J.T. Linnemann, J.E. McEnery, A.I. Mincer, P. Nemethy, J. Pretz, J.M. Ryan, P.M. Saz Parkinson, A. Shoup, G. Sinnis, A.J. Smith, D.A. Williams, V. Vasileiou, G.B. Yodh 8’ dia. x 3’ deep Angular resolution~0.5 o 1700 Hz trigger rate

7. How Milagro Works Direction via timing (~1 ns) Background rejection via muons Energy via shower size 8 meters e  80 meters 50 meters time position ARGO

8. Background Rejection in Milagro Bottom layer (6 mwe overburden) detects penetrating component of hadronic EAS Reject 95% of background Retain 50% of gammas Rejection is highly energy dependent! Proton MC Data  MC

9. Boomerang PWN Cygnus Region Confirmed by HESS Geminga Milagro Wide Field View of Galaxy (10-50 TeV) Sources are extended Correlated with EGRET GeV catalog Hard spectra (-2.3 connects to EGRET) Clearly visible diffuse component Tibet AS  EGRET

10. Galactic Diffuse Emission Cygnus Region with Matter Density Contours overlaying Milagro Observation  component due to CR-matter interactions Inverse Compton to e -  (~CMB) interactions Cygnus Region 65 o < l < 85 o GALPROP (Strong et al.) EGRET data Milagro EGRET data GALPROP (Strong et al.) 30 o < l < 65 o

11. Large-Scale Cosmic-Ray Anisotropy New analysis technique – forward backward asymmetry Milagro results consistent with Tibet AS  discovery Modulation amplitude ~5x10 -3 with deficit at RA=180 o

12. Large-Scale Cosmic-Ray Anisotropy: Time Dependence 4/1/2001 8/14/2002 5/10/2005 9/22/2006 12/27/2003 Solar Max 2000-2001 Solar Min 2007/8 Amplitude of anisotropy has been increasing over past 6 years (solar max to solar min) Error bars include systematic errors

13. Intermediate-Scale Cosmic-Ray Anisotropy at ~10 TeV Excesses are hadronic particles not gamma rays Anisotropy ~6x10 -4 (~10% of the large-scale anisotropy) Larmor radius of 10 TeV proton in 1  G is.01pc Lifetime of 10 TeV neutron is 0.1 pc Explanations difficult: requires ordered B-field (Drury & Aharonian 2008) B A heliotail Geminga Galactic Plane

14. Straightforward Improvements to Milagro Higher Altitude – closer to shower maximum Larger area (especially of muon detector) Optical isolation of detector elements 5200m 2600m 4100m Approximation B

15. HAWC: High Altitude Water Cherenkov 10-15x more sensitive than Milagro 1 Crab in 5 hrs, 10 Crab in 3 minutes Located at base of volcán Sierra Negra latitude : 18º 59’ altitude : 4100m Inside Parque Nacional Pico de Orizaba 2 hours from Puebla (INAOE)

16. The HAWC Collaboration Instituto Nacional de Astrofísica Óptica y Electrónica Alberto Carramiñana, L. Carasco, E. Mendoza, S. Silich, G. T. Tagle Universidad Nacional Autónoma de México R. Alfaro, E. Belmont, M. Carrillo, M. González, A. Lara, Lukas Nellin, D. Page, V. A. Reese, A. Sandoval, G. Medina Tanco,O. Valenzuela, W. Lee Benemérita Universidad Autónoma de Puebla C. Alvarez, A. Fernandez, O. Martinez, H. Salazar Universidad Michoacana de San Nicolás de Hidalgo L. Villasenor Universidad de Guanajuato David Delepine, Victor Migenes, Gerardo Moreno, Marco Reyes, Luis Ureña UC Irvine G. Yodh University of New Hampshire J. Ryan Los Alamos National Laboratory B. Dingus, J. Pretz, G. Sinnis Uniersity of Maryland D. Berley, R. Ellsworth, J. Goodman, A. Smith, G. Sullivan, V. Vasileiou University of New Mexico J. Matthews University of Utah D. Kieda, P. Huentemeyer Pennsylvania State University Ty DeYoung NASA Goddard J. McEnery Naval Research Laboratory A.Abdo U.C. Santa Cruz M. Schneider

17. HAWC Design ~1000 large tanks (~4m dia x ~4m height) –1 PMT/tank (looking up) –Non-reflective interior 22,000 m 2 enclosed area 4100 m above sea level 150 m 100 MeV  photons shown 100 MeV  1/50 photons shown

18. HAWC Performance: Effective Area At low energies (<1 TeV), HAWC has ~30x the effective area of Milagro larger dense sampling area (5x) higher altitude Larger muon detection area (10x) HAWC w/reconstruction HAWC w/Rejection Milagro w/reconstruction Milagro w/Rejection

19. HAWC Performance: Angular Resolution At similar energies, HAWC’s angular resolution is ~1.5x better than Milagro. larger area higher altitude optical isolation Resolution defined as sigma of a 2-d Gaussian. Resolution at 10 TeV Angular Resolution (degrees)

20. HAWC Background Rejection Gammas Protons Size of Milagro deep layer Size of HAWC 10x better hadron rejection than Milagro above 10 TeV larger muon detection area (10x) optical isolation 2.5x higher gamma efficiency at lower energies (< 10 TeV)

21. HAWC Performance: Energy Resolution I http://www.ast.leeds.ac.uk/~fs/photon-showers.html Fixed first interaction elevation: 30km HAWC elevation 4.1km 10 TeV gamma-ray shower Longitudinal Profile Distribution of height of 1 st interaction Energy Resolution in an EAS is dominated by the fluctuations in the depth of first interaction

22. HAWC Performance: Energy Resolution II EAS arrays can measure shower size very well (<20% resolution) Shower fluctuations (depth of 1st interaction) dominate energy resolution of array. Because of increased altitude HAWC will have much better energy resolution than Milagro

23. Point Source Sensitivity IACTs 50 hrs (~0.06 sr/yr) 1 yr EAS 5 yrs (~2  sr) 2000 km 2 sr hr

24. High-Energy Spectra with HAWC HESS J1616-508 0.2 Crab @ 1 TeV dN/dE  -2.3 Highest energy ~20 TeV Simulated HAWC data 1 year no cutoff Simulated HAWC data 1 year 40 TeV cutoff

25. Transient Phenomena: AGN and GRB PKS J2155-304 (z=0.117) 50x quiescent (1 hr) dN/dE=kE -3.5 6  in HAWC 10 -12 10 -10 10 -8 TeV AGN flares GRB <1 MeV GLAST and HAWC sensitivity for a source of spectrum dN/dE=KE -2 z=0no E cutoff z=0.1E exp ~700GeV z=0.3E exp ~260GeV z=0.5E exp ~170GeV

26. Gus Sinnis AGIS Collaboration Meeting June 2008 Worldwide Dataset of TeV Observations of Mrk421 Transient Phenomena: AGN Flares HAWC will obtain TeV duty factors, search for orphan flares, & notify other observers in real time. All sources within ~2  sr would be observed every day for ~ 5 hrs. HAWC sensitivity: 10 Crab in 3 min and 1 Crab in 5 hrs 3 min 5 hr

27. Conclusions The role of wide-field instruments now established Large sensitivity gain (>10x) is achievable Strong Scientific Motivation –Highest energies (>5-10 TeV) –Extended sources –Galactic diffuse emission –Unique TeV transient detector (GRBs and AGN flares) 4x Crab in 15 minutes HAWC Status –Fall 2007 Full proposal submitted to NSF and CONyCT –July 2008 NSF funds $1M MRI grant for HAWC Develop site infrastructure (roads, power, water, internet) R&D for large tank –US funding decision awaits Particle Astrophysics SAG (early 2009)

28. Thank You! "Confirming an idea is always gratifying. But finding what you don't expect opens new vistas on the nature of reality. And that's what humans, including those of us who happen to be physicists, live for.” -Brian Greene NYT 9/12/2008