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Milagro at Tibet

Milagro at Tibet. Gus Sinnis LANL/P-23. Challenge and Opportunity. Milagro will run for ~2 more years (or less) No viable candidate to replace Milagro on horizon ARGO marginal sensitivity gain (and technical problems) HD Tibet marginal sensitivity gains

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Milagro at Tibet

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  1. Milagro at Tibet Gus Sinnis LANL/P-23

  2. Challenge and Opportunity • Milagro will run for ~2 more years (or less) • No viable candidate to replace Milagro on horizon • ARGO marginal sensitivity gain (and technical problems) • HD Tibet marginal sensitivity gains • NSF has little money (2% cut this FY) • International Research and Education Grants • 5 years up to $2.5M • What can be done with this budget? • Move Milagro to high altitude

  3. Outline • Detector design and constraints • We now have a chance to do it right (based on what we have learned) • Detector sensitivity calculations • Is it worth it? • Rate expectations • Can we keep existing daq and electronics? • Open challenge(s) • Verification testing at Milagro • Path forward - discussion

  4. Detector Design • Constraints • no new pmts • Keep as much electronics as possible • Funding < $2M • Lessons learned • Bottom layer important (want bigger) • Top layer PMTs not deep enough • Pond not big enough • Outriggers are a pain in the neck • Cross-talk is bad, very bad

  5. Detector Design (II) • 2 layers (equal size) • Grid of 21 x 21 uses up all PMTs (with ~30 spares) • Top depth of 2 meters • Detector spacing of 4 meters • Total area of ~7700 m2 • Black curtains extending from top of water to 3 meter depth (5% reflectivity in MC)

  6. 2 m 6 m 88 meters 4m Detector Schematic

  7. GEANT3.2 Simulation • Modified survey file • Added curtains to ugeom.F • Changed altitude in CORSIKA to 4300m • Ran ~4M gamma and 4M proton showers • 50 GeV – 100 TeV • Gammas E-2.4, protons E-2.7 • 0-45 degrees zenith angles • Flat in core distance to 1000m • Tony’s reconstruction used (modified Milinda code checked into CVS). • Gaussian core fitter • 2-layer angle fitter • Combined curvature and sampling from Tony • Trigger & fit criteria • Tibet nTop>40 PMTs (Milagro nTop>50) • nFit>20 and for gammas dAngle<1.2 degrees

  8. Basic Simulation Results g-ray effective area Tibet Milagro

  9. Basic Results II proton effective area!! Tibet Milagro

  10. Core Distance of Triggers NTop>40 NTop>50 Tibet Milagro

  11. Background Rejection • Use nTop/cxPE as found for HAWC • cxPE is PEs in hottest bottom layer PMT (excluding region <10m of fit core from search) Gammas Protons

  12. Background Rejection II Q-factor ~1.8 possible while retaining ~80% of gamma rays (Require nTop/cxPE > 4) Gammas Protons

  13. Crab Sensitivity • Use Sensi() routine from Andy • Scale from Milagro • Events/day given below (triggered and fit) • ~8x more sensitive than Milagro • ~32s on Crab in year * 50 PMT trigger, nFit>20, dAngle<1.2, pre-Tony reconstruction Gamma/Hadron Cut is X2>2.5

  14. Expected Trigger Rate • From previous slide • Proton rate on Crab of 67 events/day (triggered) • Milagro MC gives 85 events/day (triggered) • With Milagro trigger of 1800 Hz • Tibet trigger rate will be <1500 Hz • Current DAQ can be used • Singles rates will be lower • TOT will work better (fewer late hits) • No new electronics needed

  15. Gamma-Ray Bursts • Under construction (issue of real z in Primack code). • But, to get estimate of improvement over Milagro – look at ratio from Sensi() for a “source-day” for Dec=36. • Second number is Ng/sqrt(p) (arb units in p-flux)

  16. Remaining Challenge • Calibration of PMTs (timing and pulse height) • With curtains PMTs can not see neighbors • Or common light source at top of pond • HAWC-like calibration system would require complete re-design of electronics • Ideas? • Laser balls at bottom of pond (no baffles)? • Bright light on inflated cover? • Muons for pulse heights?

  17. Proposal Issues • IHEP is on board • But have no source of internal funding (ARGO issues) • US will have to provide entire cost • Site prep, etc. • IHEP could provide some manpower to help with overseeing of contracts for pond construction • Skip Neal contacted working on cover quote • Water system – cheaper to ship or purchase in China? • Investigate ITAR issues • Proposal due March 10 • Realistic cost estimates • Needs equipment funding from MPS

  18. Testing at Milagro • Install curtains on 4x4 patch of PMTs • Investigate singles rate • Investigate timing distributions • Should become narrower, but we may be dominated by our angular resolution • Build small water tank to determine altitude effect on singles rates (Dylan S.) • Take to Colorado

  19. Conclusions • With slight design modifications moving Milagro to high altitude can have a significant impact on our sensitivity. • With curtains all electronics will continue to function. • Expect 8x improvement in Crab sensitivity • Crab at 5 sigma in 10 days (1.6 s/sqrt(days)) • GRBs @z~0.8 similar sensitivity to z=0.2 in Milagro • Compare to straight move of Milagro at 4300m • Gary’s talk • Complete sensitivity calculations (GRBs and AGN) • Trigger rate estimate needs scaler simulation • Excellent prototype for HAWC

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