Milagro Status Report - October 1998

October 1998 The Milagro Project Physics Goals Overall Design Milagrisimo - Milagrito - Milagro Comparison of Milagro to other detectors  Milagrito The Detector Operations Results  Status - Milagro Installation Schedule Budget History Physics Goals and Status of Milagro

The Milagro Collaboration October 1998 M.L.Chen, and J.A. Goodman,* G. Sullivan, D. Evans University of Maryland At College Park A. Shoup, and G.B. Yodh, S. Hugenberger, I. leonor University of California, Irvine D.G. Coyne, D.E. Dorfan, L.A. Kelley D.A. Williams S. Westerhoff W. Benbow, J. McCullough, M. Morales, T. Yang University of California, Santa Cruz A.I. Mincer, and P. Nemethy, L. Fleysher, R. Fleysher New York University R.W. Ellsworth George Mason University D. Berley National Science Foundation G. Gisler, T. J. Haines, C.M. Hoffman*, R. Miller, and C. Sinnis Los Alamos National Laboratory B. Shen, A. Smith, O.T. Tumer, K. Wang, M. Wascko University of California, Riverside M. McConnell, J. Ryan, A. Falcone University of New Hampshire B. Dingus, J. McEnery, R. Atkins University of Utah *Spokesmen Students NSF EP Supported Groups Doe & other Supported Groups

High Energy Cosmic Ray Detectors GeV1 TeV1 PeV1 EeV The Cosmic Ray Spectrum Satellites Fly’s Eye / HiRes Air Cherenkov Milagro EAS Arrays Solar Arrays Akeno /Auger

 A Water Cherenkov Detector Sensitive over 100% of the area Sensitive to Photons and Electrons  A Low Threshold - Open Aperture Detector Threshold < 300 GeV  Significant Area at 100 GeV Large Duty Cycle Acceptance ~ 1sr Angular Resolution < (better for large showers) Milagro

Milagro  Built in an Existing 60x80x8m Pond 450 Top layer 8” PMT’s on 3m grid 273 Hadron/  layer PMT’s (facing up)  High Altitude Location ’ Existing Lab Tech Area Support Facilities at the Site

Physics with Milagro  First All Sky Survey of the Northern Sky Search for DC Signals Look for New Sources Search for Bursts on Many Time Scales  Study the Signal from the Crab Milagro will observe the Crab with >5  in a few months (using the Whipple Flux) Milagro will study the spectrum & flux  Absolute flux normalization from ACT’s is important and needs to be confirmed  Data on the high energies is needed for acceleration models  Search for Gamma Ray Bursts EGRET has seen burst events up to ~20 GeV with A eff of ~400 cm 2 Milagro at 100 GeV will have A eff   20 m 2 (more than ~500 x EGRET) Milagro’s acceptance grows like E 2 up to 1 TeV Milagro operates continuously with a wide aperture - It will be the best high energy GRB detector! Measuring a cutoff above a TeV would constrain GRB models and distance to the source

The Crab

Physics with Milagro  Study AGN’s MRK 501 has be seen by Milagrito EGRET has seen >30 AGN’s Milagro will search for variability in AGN’s at TeV energies  Sources have shown increases x ~100  All northern sources can be viewed every day with Milagro  Correlation with Radio Observations HEGRA has events at >20 TeV from Mrk501 The nature of the spectrum above a few TeV is important in determining where / if absorption is occurring  Primordial Black Holes PBH’s will radiate energetic particles at the end of their lifetime  The spectrum of particles radiated will be depend on physics model - SUSY etc. Milagro will be sensitive to the last few minutes of a PBH explosion Cygnus set limits on PBH that were 100x better than any other Milagro should do about 2-3 orders of magnitude better

Primordial Black Holes  PBH’s will radiate particles at the end of their life The radiation will depend on the number of degrees of freedom Milagro will be sensitive to particles produced in the last ~1000 seconds

Physics with Milagro  Solar Physics Milagro will detect the shadow of the sun in a few days The position and disappearance of the shadow are a measure of the solar B perp  Currently measurements are poor GeV Solar flares give muons in the bottom layer  2500 m 2 will allow us to measure solar flare structure on a 1 sec time scale vs 10’s of minutes Milagrito already has a probable detection of a CME event Proposal to ATM from UNH (muon direction)  Antimatter Search There will be a second displaced shadow if there is a significant amount of antimatter  Composition Studies Wide Area Cherenkov Telescope Proposal

Milagrisimo  Milagrisimo was the first stage of Milagro 30 PMTs were operated in the Milagro Pond in winter of Single layer on the bottom of the Pond ~1.5m of water above tubes Design studies and analysis presented in at Durban ICRC

Milagrito  Milagrito was the second stage of the Milagro detector It was a large area water detector  Area ~ 2/3 Milagro  No Muon Layer Milagrito data was used for:  design studies and development And it will be used for physics & theses  Physics (MRK 501, GRB’s etc)  Student Theses  Milagrito operated at >250Hz from February 1997 to April 1998 (>85% livetime)  More than 9 billion events - 9 Terabytes

Milagrito

Milagrito  One Month Coverage

Milagrito Results  Moon Shadow Offset is approximately what is expected at our energies. Antimatter shadow location

Milagrito Results  Mrk501

Nov Coronal Mass Ejection

Milagro Site HDR Site Milagro Site Ops Building Million Gallon Pond

Milagro Site Counting House Pond Utility Building (PUB) Office Trailer Testing Trailer

Milagro Construction  Cover Inflated with new webbing  Lightning protection system

Late Light

Baffles

Milagro Construction 4 Muon Boxes deployed to provide redundant ID

Milagro Construction

Milagro  Milagro will have a trigger rate of ~2 kHz Data will be processed in real time Will perform online search for bursts Time and pulse height on each channel  The muons will provide substantial background reduction for showers above a few TeV detected = 1 at 1 TeV At high energies Milagro will have low background  Muon/Hadron layer may provide other methods of background rejection A real gamma signal can be studied from sources like the Crab to develop better rejection algorithms  Water tanks are needed to surround the pond to get core position Core position is needed for angular resolution and energy determination

Milagro

Milagro

Milagro

Event Reconstruction

Milagrito

Why We Need Outriggers  What are outriggers? An array of water tanks outside the pond We have built & operated a prototype Outriggers were part of the original Milagro proposal  Outriggers are essential for locating core position Need counters outside the pond to tell if cores are inside or outside  Energy Determination needs core position Need core to determine shower size and lateral distribution - This is vital for AGNs and GRBs  Angular Resolution Curvature correction needs core position  Proton/Gamma Discrimination Proton showers trigger further from the pond Gammas trigger more often on the pond

Major Responsibilities on Milagro Major Responsibilities on Milagro  Milagro is a strong collaboration of University Groups and Los Alamos A project supported by both NSF & DoE All groups share responsibility for operating the detector  Irvine PMTs - testing, encapsulation…  Los Alamos Operations Site  Santa Cruz Electronics Cover Inflation system Lightning Protection  Maryland DAQ  New Hampshire Solar Outriggers  NYU PMT structure and deployment  Utah WACT

 1994 Funding begins toward a $2.6M Project (80%NSF 20%DoE)  1995 Site Preparation - New liner & cover - PUB - Counting House - PMT structure installed  Milagrisimo run - 38 tubes on pond bottom  Milagrito installed - Data taking begins Feb 1997  1997 Lightning protection system  1998 Milagro tubes installed, modifications to electronics, cover, water system completed (based on Milagrito experience)  Winter Running to begin Site Work MilagrisimoMilagritoMilagro Timeline & Funding Profile

Summary  Milagro is an important new detector that will produce significant new physics results GRB, AGNs, Solar Physics, PBH, Antimatter, Composition  Milagro has a strong collaboration NSF Groups, DoE Groups & Los Alamos  Milagro has been built in stages We have learned how to build and operate the detector through prototypes  The project has been on time and on budget We built it for the cost proposed in 1991 We built as fast as the cash flow allowed We have met all the technical challenges  Outriggers are essential to finish to Milagro Core position is central to Milagro’s goals Proposal this winter for outriggers  Solar Physics is an added bonus Solar Proposal to ATM

Primordial Black Holes  Why might they exist? Density Fluctuations in the early universe- Some regions of space could become overdense and collapse  What did COBE tell us? COBE studied density fluctuations on a huge scale (10 55 gm) and found    Other evidence Standard inflation says  is scale invariant If Standard inflation and COBE are correct - There should be virtually no PBH’s Diffuse 100 MeV  ’s set a limit on the number of PBH’s  PBH <10 -8  If PBH’s do exist - We might see them when they evaporate T ~ 1/M They would radiate all species of particles at the end of their lifetime Initial mass of ~10 15 gm would be going off now We should look at a scale 40 orders below COBE

Physics Questions  The Sources of VHE/UHE Cosmic Rays Northern Sky Survey Crab Spectra  Active Galactic Nuclei Why do we see only the closest and weakest at TeV energies? What is their source spectra?  Gamma Ray Bursts What are they? How high does their energy spectra extend?  Absorption of TeV Photons Do we we absorption of photons due to  e + e - on IR or CMBR?  Primordial Black Holes Do they exist?  Solar Physics Solar Magnetic Fields Solar Energetic Particles

Milagro

Sensitivity to a Single Source

Milagro