Moriond 2001Jordan GoodmanMilagro Collaboration The Milagro Gamma Ray Observatory The Physics of...
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Transcript of Moriond 2001Jordan GoodmanMilagro Collaboration The Milagro Gamma Ray Observatory The Physics of...
Jordan Goodman Milagro Collaboration Moriond 2001
The Milagro Gamma Ray Observatory
• The Physics of Milagro• Milagrito
– Mrk 501– GRB 970417a
• Milagro– Description– Recent Results - Crab– Future Directions
Jordan Goodman
University of Maryland
Jordan Goodman Milagro Collaboration Moriond 2001
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
Jordan Goodman Milagro Collaboration Moriond 2001
Observing the High Energy Sky
10 9 10 11 10 10 10 1013 15 17 19
1 GeV 1 TeV 1 PeV 1 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
Jordan Goodman Milagro Collaboration Moriond 2001
Milagro Site
Located near Los Alamos, NM, USA
8650’ Elevation
60m X 80m X 8m covered pond
Jordan Goodman Milagro Collaboration Moriond 2001
Milagro Site
Counting House
Pond Utility Building (PUB)
Office Trailer
Testing Trailer
Jordan Goodman Milagro Collaboration Moriond 2001
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
M ilagrito
Jordan Goodman Milagro Collaboration Moriond 2001
Mrk 501 Flare
Jordan Goodman Milagro Collaboration Moriond 2001
Milagrito Results – MRK 501
Jordan Goodman Milagro Collaboration Moriond 2001
MRK 501
Jordan Goodman Milagro Collaboration Moriond 2001
Milagrito - GRB 970417a
• Searching 54 Batse bursts (T90)
• One burst 970417a 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
Jordan Goodman Milagro Collaboration Moriond 2001
Milagrito - GRB 970417a
Jordan Goodman Milagro Collaboration Moriond 2001
Milagrito Moon Shadow
Jordan Goodman Milagro Collaboration Moriond 2001
Milagro
Air Shower Layer
Hadron/Muon layer
2m
8" PMTs
Light-tight Cover
8 m
80m50m
450 Top Layer 8” PMTs
273 Bottom Layer 8” PMTs
Jordan Goodman Milagro Collaboration Moriond 2001
Milagro Construction
Jordan Goodman Milagro Collaboration Moriond 2001
Milagro
Jordan Goodman Milagro Collaboration Moriond 2001
Milagro
Jordan Goodman Milagro Collaboration Moriond 2001
Angle Reconstruction
For large showers, the angle can be reconstructed to better than 0.50o. (However, there are systematics associated with core
location)
Jordan Goodman Milagro Collaboration Moriond 2001
Events
Jordan Goodman Milagro Collaboration Moriond 2001
Milagro Energy Response
Jordan Goodman Milagro Collaboration Moriond 2001
Milagro Moon Shadow: Aug 2000 – Jan 2001
Nhit >150, Nfit > 20
Jordan Goodman Milagro Collaboration Moriond 2001
Gamma / Hadron Separation in Milagro
Gammas (MC)
Data
Gammas (MC)
Jordan Goodman Milagro Collaboration Moriond 2001
P
Jordan Goodman Milagro Collaboration Moriond 2001
Crab Nebula
Jordan Goodman Milagro Collaboration Moriond 2001
Jordan Goodman Milagro Collaboration Moriond 2001
Crab Data
Jordan Goodman Milagro Collaboration Moriond 2001
Crab Signal - Time Evolution
Jordan Goodman Milagro Collaboration Moriond 2001
Predicted Crab Signal in Milagro from ACTs
Events per Day in Milagro
Flux
F(E) x (10-7/s/m2/TeV)
Whipple1 22.5 3.2 ± 0.70 x E(TeV)-(2.49 ± 0.08)
HEGRA1 16.8 2.7 ± 0.82 x E(TeV)-(2.61 ± 0.12)
CAT1 17.3 2.7 ± 0.43 x E(TeV)-(2.57 ± 0.16)
Tibet2 49.8 8.2 ± 1.6 x E(TeV)-(2.62 ± 0.17)
1 Cantenese and Weeks (1998)
2 Amenomori et al (1999)
Jordan Goodman Milagro Collaboration Moriond 2001
Milagro Sensitivity to the Crab
Events per Day
No /had Separation
With /had Separation
Complete Milagro
Whipple 22.5 2.8 9.5
HEGRA 16.8 2.1 3.8 6.9
CAT 17.3 2.2 3.9 7.0
Tibet 49.8 6.2 11.1 21.0
Milagro Prelim.
~20 1.6 5.0
Jordan Goodman Milagro Collaboration Moriond 2001
Outrigger array
• Adding ~150 tanks• Used for Core location
– Improved angle– Improved Energy
Reconstructed Energy in TeV
Energy Resolution
0.75 76%3.5 65%7 64%
11 45%
Jordan Goodman Milagro Collaboration Moriond 2001
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
Jordan Goodman Milagro Collaboration Moriond 2001
Lowering the trigger threshold
Jordan Goodman Milagro Collaboration Moriond 2001
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%
Jordan Goodman Milagro Collaboration Moriond 2001
Conclusions
• Milagro is now online
• We are seeing sources
• We are improving the detector
• We hope for many important Physics results soon!