1. Erice July 2004Jordan GoodmanUniversity of Maryland Air Shower Gamma Ray Detectors Outline Air Shower Physics –Extensive Air Showers –Gamma/Hadron sep. Why use EAS Detectors Detecting showers on the ground –Water Cherenkov - Milagro –RPCs – ARGO Recent Milagro Results –Known Sources –New Detections Future Detectors - HAWC Milagro

2. Erice July 2004Jordan GoodmanUniversity of Maryland Extensive Air Shower Development

3. Erice July 2004Jordan GoodmanUniversity of Maryland From Ralph Engel

4. Erice July 2004Jordan GoodmanUniversity of Maryland Effect of Altitude Low Energy Threshold Requires High Altitude Milagro ARGO

5. Erice July 2004Jordan GoodmanUniversity of Maryland Cascade Development ARGO Milagro 1 TeV 10 TeV

6. Erice July 2004Jordan GoodmanUniversity of Maryland Shower Content Ngammas Nelectrons Primary Energy (GeV)

7. Erice July 2004Jordan GoodmanUniversity of Maryland Photon Shower 2 Gamma (movies by Miguel Morales) Blue – Electrons Muons – Yellow Pions – Green Nucleons – Purple

8. Erice July 2004Jordan GoodmanUniversity of Maryland Proton Shower 2 TeV (movies by Miguel Morales) Blue – Electrons Muons – Yellow Pions – Green Nucleons – Purple

9. Erice July 2004Jordan GoodmanUniversity of Maryland Techniques in TeV Astrophysics Low energy threshold Good background rejection Small field of view Low duty cycle Good for sensitive studies of known point sources. High energy threshold Moderate background rejection Large field of view (~2sr) High duty cycle (>90%) Good for all sky monitor and for investigation of transient and diffuse sources. Pointed instruments Non-pointed instruments

10. Erice July 2004Jordan GoodmanUniversity of Maryland Why Use EAS Detectors Transient Sources –GRB’s Don’t know when or where to look Some indications of 2 nd hard comp. –Variable Sources Diffuse Sources –Galactic Plane –New Sources

11. Erice July 2004Jordan GoodmanUniversity of Maryland Cherenkov Radiation Boat moves through water faster than wave speed. Bow wave (wake)

12. Erice July 2004Jordan GoodmanUniversity of Maryland Cherenkov Radiation Aircraft moves through air faster than speed of sound. Sonic boom

13. Erice July 2004Jordan GoodmanUniversity of Maryland Cherenkov Radiation When a charged particle moves through transparent media faster than speed of light in that media. Cherenkov radiation Cone of light

14. Erice July 2004Jordan GoodmanUniversity of Maryland Cherenkov Radiation

15. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro 8 m 80m 50m 450 Top Layer 8” PMTs 273 Bottom Layer 8” PMTs

16. Erice July 2004Jordan GoodmanUniversity of Maryland The Milagro Collaboration D. Berley, E. Blaufuss, J.A. Goodman,* A. Smith, G. Sullivan, E. Hayes, D. Noyes University of Maryland At College Park Shoup, and G.B. Yodh University of California, Irvine D.G. Coyne, D.E. Dorfan, L.A. Kelley D.A. Williams S. Westerhoff, W. Benbow, J. McCullough, M. Morales University of California, Santa Cruz A.I. Mincer, and P. Nemethy, L. Fleysher, R. Fleysher New York University R.W. Ellsworth George Mason University G. Gisler, T. J. Haines, C.M. Hoffman*, F. Samuelson, C. Sinnis B. Dingus, Los Alamos National Laboratory J. Ryan, R. Miller, A. Falcone University of New Hampshire J. McEnery, R. Atkins University of Wisconsin *Spokesmen Students

17. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro

18. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro

19. Erice July 2004Jordan GoodmanUniversity of Maryland Inside Milagro

20. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro Site

21. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro Outriggers

22. Erice July 2004Jordan GoodmanUniversity of Maryland Shower hitting the pond at an angle

23. Erice July 2004Jordan GoodmanUniversity of Maryland 2 Tev Proton Shower hitting the pond

24. Erice July 2004Jordan GoodmanUniversity of Maryland 2 Tev E/M Shower hitting the pond

25. Erice July 2004Jordan GoodmanUniversity of Maryland Angle Reconstruction For large showers, the angle can be reconstructed to better than 0.50 o. (However, there are systematics associated with core location)

26. Erice July 2004Jordan GoodmanUniversity of Maryland Events

27. Erice July 2004Jordan GoodmanUniversity of Maryland Shower Curvature

28. Erice July 2004Jordan GoodmanUniversity of Maryland Operations Milagro has been operating since 2000 at 2650m –0.22 Trillion Events Outriggers were finished in 2003 We run with ~96% on-time Data rate is ~ 1700 Hz –8-9% deadtime We reconstruct in real-time –We look for GRBs and send out alerts –Three months of raw data saved for archival analysis Data is sent via network to LANL & UMD Nearly total remote capability

29. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro Energy Response (before/after new trigger) 1 TeV Ratio of response to new trigger New Trigger installed March 2002 – removes muon triggers at large angles to allow triggering on lower energy showers

30. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro Sensitivity Our energy threshold increases with the zenith angle. Energy threshold is not well defined. Even though our peak sensitivity is at a few TeV, we have substantial sensitivity at lower energies. GLAST Milagro Effective Area EGRET

31. Erice July 2004Jordan GoodmanUniversity of Maryland P  Gamma – Hadron Separation

32. Erice July 2004Jordan GoodmanUniversity of Maryland Gamma / Hadron Separation in Milagro Gammas (MC) Data Proton (MC) This cut removes 90% of the protons and keeps 50% of the gammas Q is improvement of signal to root BG which equates to sigma This gives a Q of ~1.5 (same signif in ½ the time)

33. Erice July 2004Jordan GoodmanUniversity of Maryland Tibet – 4300m ARGO

34. Erice July 2004Jordan GoodmanUniversity of Maryland

35. Erice July 2004Jordan GoodmanUniversity of Maryland ARGO Technique

36. Erice July 2004Jordan GoodmanUniversity of Maryland Limited Streamer Tubes

37. Erice July 2004Jordan GoodmanUniversity of Maryland ARGO Design

38. Erice July 2004Jordan GoodmanUniversity of Maryland ARGO Building

39. Erice July 2004Jordan GoodmanUniversity of Maryland Inside the ARGO Building

40. Erice July 2004Jordan GoodmanUniversity of Maryland ARGO Event ARGO will be a very capable detector when completed in several years!

41. Erice July 2004Jordan GoodmanUniversity of Maryland Recent Milagro Results

42. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro Point Sources Data taken in the Crab Nebula region with 6.4  at the position of the Crab (2000-2002) Signal map of Mrk 421 during the 2001 flare (1/17/01-4/26/01). The circle shows the position of Mrk 421 with our angular bin. The center corresponds to ~5 

43. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro All Sky Survey CrabMrk 421 Hot Spot

44. Erice July 2004Jordan GoodmanUniversity of Maryland Effect of the Outriggers This improved ang. resolution give us an increase in Q factor of ~1.7 This means we see the same signal ~ 3 times faster! More improvement (~1.5 – 2 in Q) is expected with better  /h separation With outriggers Before outriggers 0.75 o Before outriggers Core Error

45. Erice July 2004Jordan GoodmanUniversity of Maryland Effect of the Outriggers 12 months of recent data on the Crab ~3 times faster to get same signal Another factor of ~1.5 - 2 is expected from  /h sep Andy/Tony will provide a new plot

46. Erice July 2004Jordan GoodmanUniversity of Maryland EGRET Observation of the Galactic Plane Note that their coordinates run opposite from ours… Black is EGRET Diffuse Flux > GeV Red is Milagro Exposure (TeV) Cygnus region Inner Galaxy Outer Galaxy

47. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro Galactic Plane 5  excess for the “inner galaxy” - Flux fraction ~ 4 x 10 -5 of CR This is the first detection of the galactic plane at these energies (~TeV) Cygnus region Preliminary

48. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro Galactic Plane Cygnus region Preliminary Inner Galaxy Outer Galaxy

49. Erice July 2004Jordan GoodmanUniversity of Maryland Galactic Plane

50. Erice July 2004Jordan GoodmanUniversity of Maryland The Cygnus Region

51. Erice July 2004Jordan GoodmanUniversity of Maryland 3EG_J0520+2556 – Milagro Hot Spot

52. Erice July 2004Jordan GoodmanUniversity of Maryland 3EG_J0520+2556 – Milagro Hot Spot This source is now ~6  and appears to be ~0.8deg wide! This will be hard for an ACT to see! When we reported a 3  source - Whipple looked, but didn’t see it…

53. Erice July 2004Jordan GoodmanUniversity of Maryland GRB970417a ● 18 signal events with an expected background of 3.46 -> Poisson prob. 2.9e-8 (5.2  ). Prob. after correcting for size of search area: 2.8e-5 (4  ). Chance prob. of this excess in any of the 54 GRB examined for TeV emission by Milagrito: 54x2.8e-5 = 1.5e-3 (3  ). Evidence for a TeV signal from GRB970417 was seen by Milagrito (a smaller, single layer prototype of Milagro)

54. Erice July 2004Jordan GoodmanUniversity of Maryland Luminosity of GRB970417a More luminosity at TeV energies than MeV energies. But the GRB must be close due to TeV-IR absorption, so the total energy released is not unusually large. If z~0.1 => E  < 700 GeV so L < 5 x 10 51 ergs If z~0.03 => E  < 10 TeV so L < 1 x 10 49 ergs Atkins, 2003, Ap J 583 824

55. Erice July 2004Jordan GoodmanUniversity of Maryland GRB 941017 (pre-Milagro) M.M. González, B.L. Dingus, Y. Kaneko, R.D. Preece, C.D. Dermer and M.S. Briggs, Nature, 424, 749 (14 Aug 2003) This burst is the first observation of a distinct higher energy spectral component in a GRB Lower energy component decays faster than higher energy component Peak of higher energy component is above the energy range of the detector Power released in higher energy component is more than twice the lower energy component -18 to 14 sec 14 to 47 sec 47 to 80 sec 80 to 113 sec 113 to 200 sec

56. Erice July 2004Jordan GoodmanUniversity of Maryland Theories of the High Energy Component of GRB941017 Requires GRBs to more energetic phenomena Different timescale of low and high energy implies an evolving source environment or different high energy particles Shape of high energy component applies tight constraints to ambient densities and magnetic fields Or evidence of origin of Ultra High Energy Cosmic Rays More and Higher Energy observations are needed Pe’er & Waxman (astroph/0310836) constrain source parameters for Inverse Compton emission of GRB941017 Milagro Sensitivity z=0.2 z=0.02

57. Erice July 2004Jordan GoodmanUniversity of Maryland Operations in the Swift era Swift will be launched in September 2004 It will detect ~100-150 bursts per year with redshift information Milagro observes ~ 1/6 the sky with some reasonable efficiency Therefore we should expect ~20 GRBs per year in our FOV with redshift information This will improve our sensitivity by ~ factor of 3 And allow us to put limits on bursts we don’t detect Note: EGRET saw 6 bursts in 9 years!

58. Erice July 2004Jordan GoodmanUniversity of Maryland Milagro Summary Running well with outriggers Q factor is improving steadily Improved sensitivity to GRBs Two recent “discoveries” –The galactic plane + Cygnus Region –A new diffuse source in the crab region More to come –Spectral information, etc.

59. Erice July 2004Jordan GoodmanUniversity of Maryland HAWC – The Next Generation

60. Erice July 2004Jordan GoodmanUniversity of Maryland HAWC Requirements Low Energy Threshold < 50 GeV GRBs visible to redshift ~1 Near known GRB energy AGN to redshift ~0.3 Large fov (~2 sr) / High duty cycle (~100%) GRBs prompt emission AGN transients Time domain astrophysics Large Area / Good Background Rejection –High signal rate –Ability to detect Crab Nebula in single transit Moderate Energy Resolution (~40%) –Measure GRB spectra (inter-pulse spectra) –Measure AGN flaring spectra

61. Erice July 2004Jordan GoodmanUniversity of Maryland Effect of Altitude Low Energy Threshold Requires High Altitude

62. Erice July 2004Jordan GoodmanUniversity of Maryland HAWC Strawman Design 200m x 200m water Cherenkov detector Two layers of 8” PMTs on a 2.7 meter grid –Top layer under 1.5m water (trigger & angle) –Bottom layer under 6m water (energy & particle ID) –~10,000 PMTs total (5,000 top and 5000 bottom) –Trigger: >50 PMTs in top layer Two altitudes investigated –4500 m (~Tibet, China) –5200 m (Atacama desert Chile) 6 meters e  200 meters

63. Erice July 2004Jordan GoodmanUniversity of Maryland Reconstructed events

64. Erice July 2004Jordan GoodmanUniversity of Maryland Effect of EBL on Distant Sources z = 0.03 z = 0.1 z = 0.2 z = 0.3 z = 0.0

65. Erice July 2004Jordan GoodmanUniversity of Maryland Energy Distribution After EBL

66. Erice July 2004Jordan GoodmanUniversity of Maryland Point Source Sensitivity

67. Erice July 2004Jordan GoodmanUniversity of Maryland Gammas Protons Background Rejection: Bottom Layer 30 GeV70 GeV230 GeV 20 GeV70 GeV 270 GeV

68. Erice July 2004Jordan GoodmanUniversity of Maryland HAWC Conclusions A large area, high altitude all sky VHE detector will: –Detect the Crab in a single transit –Detect AGN to z = 0.3 –Observe 15 minute flaring from AGN –Detect GRB emission at ~50 GeV / redshift ~1 –Detect 6-10 GRBs/year (EGRET 6 in 9 years) –Monitor GLAST sources –Perform Time Domain Astrophysics in VHE Regime Extreme States of Extreme Systems Continuing work –Improve background rejection & event reconstruction Increase sensitivity by ~50% - 100%? Develop energy estimator –Detailed detector design (electronics, DAQ, trigger, infrastructure) –Reliable cost estimate needed (~$30M???) –Site selection (Chile, Tibet, White Mountain) Time Line –2004 R&D proposal to NSF & DOE (LANL & UNM) –2006 full proposal to NSF & DOE –2007-2010 construction

69. Erice July 2004Jordan GoodmanUniversity of Maryland Conclusions on Air Shower Detectors They are complimentary to ACTs Their features of wide field of view and continuous observation gives them the ability to: –Observe transient sources –Observe diffuse objects –Discover new objects