Moriond 2001Jordan GoodmanMilagro Collaboration The Milagro Gamma Ray Observatory The Physics of Milagro Milagrito –Mrk 501 –GRB a Milagro –Description –Recent Results - Crab –Future Directions Jordan Goodman University of Maryland

Moriond 2001Jordan GoodmanMilagro Collaboration The Physics of Milagro The Sources of VHE/UHE Cosmic Rays –Crab –Super Nova Remnants Active Galactic Nuclei –High variability Gamma Ray Bursts –High energies Absorption of TeV Photons Primordial Black Holes Solar Physics

Moriond 2001Jordan GoodmanMilagro Collaboration Observing the High Energy Sky GeV1 TeV1 PeV1 EeV Satellites Fly’s Eye / HiRes Air Cherenkov Milagro EAS Arrays Solar Arrays Akeno /Auger Milagro Water-Cherenkov Detector Threshold ~300 GeV Wide-angle  /hadron Separation 24 Hour – all year operation

Moriond 2001Jordan GoodmanMilagro Collaboration Milagro Site Located near Los Alamos, NM, USA 8650’ Elevation 60m X 80m X 8m covered pond

Moriond 2001Jordan GoodmanMilagro Collaboration Milagro Site Counting House Pond Utility Building (PUB) Office Trailer Testing Trailer

Moriond 2001Jordan GoodmanMilagro Collaboration Milagrito A prototype for the full Milagro detector Single layer of 230 PMTs with no muon detection Milagrito operated at >250Hz from Feb 97 to April 98 (>85% livetime) More than 9 billion events - 9 Terabytes

Moriond 2001Jordan GoodmanMilagro Collaboration Mrk 501 Flare

Moriond 2001Jordan GoodmanMilagro Collaboration Milagrito Results – MRK 501

Moriond 2001Jordan GoodmanMilagro Collaboration MRK 501

Moriond 2001Jordan GoodmanMilagro Collaboration Milagrito - GRB a Searching 54 Batse bursts (T90) One burst a showed 18 events w/background of 3.46 This has a prob< 2.9x10 -8 Accounting for all search trials – combined accidental chance 1/150 This could mean TeV emission from GRBs Batse 1  error circle

Moriond 2001Jordan GoodmanMilagro Collaboration Milagrito - GRB a

Moriond 2001Jordan GoodmanMilagro Collaboration Milagrito Moon Shadow

Moriond 2001Jordan GoodmanMilagro Collaboration Milagro 8 m 80m 50m 450 Top Layer 8” PMTs 273 Bottom Layer 8” PMTs

Moriond 2001Jordan GoodmanMilagro Collaboration Milagro Construction

Moriond 2001Jordan GoodmanMilagro Collaboration Milagro

Moriond 2001Jordan GoodmanMilagro Collaboration Milagro

Moriond 2001Jordan GoodmanMilagro Collaboration Angle Reconstruction For large showers, the angle can be reconstructed to better than 0.50 o. (However, there are systematics associated with core location)

Moriond 2001Jordan GoodmanMilagro Collaboration Events

Moriond 2001Jordan GoodmanMilagro Collaboration Milagro Energy Response

Moriond 2001Jordan GoodmanMilagro Collaboration Milagro Moon Shadow: Aug 2000 – Jan 2001 Nhit >  150, Nfit > 20

Moriond 2001Jordan GoodmanMilagro Collaboration Gamma / Hadron Separation in Milagro Gammas (MC) Data Gammas (MC)

Moriond 2001Jordan GoodmanMilagro Collaboration P 

Moriond 2001Jordan GoodmanMilagro Collaboration Crab Nebula

Moriond 2001Jordan GoodmanMilagro Collaboration

Moriond 2001Jordan GoodmanMilagro Collaboration Crab Data

Moriond 2001Jordan GoodmanMilagro Collaboration Crab Signal - Time Evolution

Moriond 2001Jordan GoodmanMilagro Collaboration Predicted Crab Signal in Milagro from ACTs Events per Day in Milagro Flux F(E) x (10 -7 /s/m 2 /TeV) Whipple ± 0.70 x E(TeV) -(2.49 ± 0.08) HEGRA ± 0.82 x E(TeV) -(2.61 ± 0.12) CAT ± 0.43 x E(TeV) -(2.57 ± 0.16) Tibet ± 1.6 x E(TeV) -(2.62 ± 0.17) 1 Cantenese and Weeks (1998) 2 Amenomori et al (1999)

Moriond 2001Jordan GoodmanMilagro Collaboration Milagro Sensitivity to the Crab Events per Day No  /had Separation With  /had Separation Complete Milagro Whipple  9.5  HEGRA  3.8  6.9  CAT  3.9  7.0  Tibet  11.1  21.0  Milagro Prelim. ~  5.0 

Moriond 2001Jordan GoodmanMilagro Collaboration Outrigger array Adding ~150 tanks Used for Core location –Improved angle –Improved Energy

Moriond 2001Jordan GoodmanMilagro Collaboration Future Plans Complete Outriggers –34 are now online Put burst/GRB analysis online –GRB alerts to network New trigger processor to lower threshold –Discriminate against muon triggers –Lower energy threshold –Increase reach for GRB and other studies Improve Gamma / Hadron Separation Improve Angle Reconstruction

Moriond 2001Jordan GoodmanMilagro Collaboration Lowering the trigger threshold

Moriond 2001Jordan GoodmanMilagro Collaboration Risetime Trigger Processor Data Gives: At 27PMT threshold: Raw Trigger Rate = 14.5 kHz Not Fit (Muon Rate) = 9 kHz Simulation Predicts (Preliminary) Making a 100ns risetime cut: Total Trigger rate = 2.6kHz Not Fit(Muon Rate) = 0.5kHz Gamma Efficiency = 66% Proton Efficiency = 40%

Moriond 2001Jordan GoodmanMilagro Collaboration Conclusions Milagro is now online We are seeing sources We are improving the detector We hope for many important Physics results soon!