HAWC Science Survey of 2 sr (half the sky) up to 100 TeV energies

• Probe knee in cosmic ray spectrum• Identify sources of Galactic cosmic rays

Extended Sources• The Galactic Plane and Molecular Clouds• Supernova Remnants and Pulsar Wind Nebula• Galaxy Clusters

Transient Sources• Active Galactic Nuclei (AGN)• Gamma Ray Bursts (GRBs)• Solar Energetic Particles

Fundamental Physics Measurements• Tests of Lorentz Invariance at High Energies• Indirect Detection of Dark Matter

Increase Scientific Return of Other Projects• Identifies new and flaring TeV sources for VERITAS and IceCube• Extends GLAST and VERITAS spectra to higher energies

From Milagro to HAWC

High Altitude Water Cherenkov (HAWC)• Increase Altitude to 4100 m from 2650 m

• Increase Area to 22000 m2 from 4000 m2

• Reuse Milagro PMTs and electronics

• HAWC ~15x Sensitivity of Milagro• HAWC: Detect Crab in ~ 1 day (5)• Milagro: Detects Crab in ~1/2 yr

e

150 meters

4 meters

e

HAWC Design:Single layer of 900 PMTs (4 m depth vs Milagro’s 2 layers at 1.5 and 6 m) optically separated by curtains or in individual tanks

4100m

2600m

Difference between 2600m (Milagro) and 4100m (HAWC):~ 5x number of particles

HAWC’s median trigger energy ~1 TeV vs Milagro’s ~4 TeV

Higher Altitude is Closer to Shower Max.

Lateral Distribution

• Protons have BROAD lateral distribution of muons

• Gammas have NARROW lateral distribution of electrons

HAWC sensitivity calculation

Milagro MC is used to calculate HAWC sensitivity increase of 15x• Milagro Crab flux is within 10% of ACT flux• Milagro Cosmic Ray flux is within 30-50% of balloon flux and is

used to correct the HAWC background calculation

B.O.T.E.C. (back of the envelope calculation) is similar• Energy Threshold 3x lower than Milagro (Approx. B gives

6x more particles, but density of PMTs is less)– Sensitivity increase depends on spectrum, but is ~3x

• Area for Triggering is 5x larger than Milagro– Sensitivity increase is ~2x

• Angular resolution improves because of increased lever arm, better core location, …

– Sensitivity increase is 1.5-2x• Gamma/hadron rejection improves due to increased probability

of detecting muon away from the core– Sensitivity increase is >1.5x

~10~6

~15

HAWC Sensitivity calculation

Milagro MC is used to calculate the HAWC sensitivity increase of 15x• Milagro Crab flux is within 10% of ACT flux• Milagro Cosmic Ray flux is within 30-50% of balloon flux and is

used to correct the HAWC background calculation

Milagro MC of gamma/hadron separation parameter for gamma rays, cosmic rays, and data

Milagro

Gamma-Ray Sensitivity to Crab-like Source

GeV

VERITAS, HESS, MAGIC, Whipple sensitivity in 50 hours, (~0.2 sr/year)

GLAST sensitivity in 1 year (4 sr)

HAWC, Milagro, sensitivity in 1 year (2 sr)

~ 6 TeV

Angular Resolution

HAWC Angular Resolution

Flaring Blazars detectable by HAWC at 5 Crab in 10 minutes

HAWC & Transients

Orphan Flare

Full Moon

X-ray binary periods unobstructed by Moon or Sun

GRBs out to z~0.3 (0.7) for 10-6 (10-5) ergs/cm2

Plus Solar EnergeticParticles and …

TeV

10 keV

Ecutoff= 700 260 170 GeV

HAWC and GLAST Transient Sensitivity

GLAST and HAWC sensitivity for a source of spectrumdN/dE=KE-2

above 10 GeV

z=0 no E cutoffz=0.1 Eexp~700GeVz=0.3 Eexp~260GeVz=0.5 Eexp~170GeV10

-12

10-1

010

-810

-6

AGN flares1-15 x Crab

GRB <1 MeVFlux

Site Location is Sierra Negra, Mexico

• 4100 m above sea level• Easy Access

• 2 hr drive from Puebla • 4 hr drive from Mexico City

• Existing Infrastructure• Few km from the US/Mexico

Large Millimeter Telescope• Power, Internet, Roads• Sierra Negra Scientific

Consortium of ~7 projects • Excellent Mexican Collaborators• ~15 Faculty at 7 institutions

have submitted proposal to CONACYT for HAWC

• Experience in HEP, Auger, and astrophysics (including TeV)

HAWC Baseline Design

Fiducial volume: 150m x 150m x 4m

4,100 m elevation

5m PMT spacing under 4m of water

~35mCrab sensitivity over the northern sky (5 in 2 year)

170m

150m

6m

roof

8” Hamamatsu R5912 PMTs

columns

Polypropylene-nylon liner

~115Ml Filtered water

Curtains

LANL Design of Pond

Top of Pond at 4098 m a.s.l.Topographic Survey of Site

Steel Building with Structural Supports in the Water

LANL Engineering Study: Pond Cover

Floating Cover with Access Ports for Installation and Repairs

Individual Plastic Tanks of ~4-5m height and ~4-5m diameter in

30 x 30 array

Tanks

• Simplifies construction, deployment. Modular design.• Auger Tanks were manufactured in Mexico by RotoblasCan purchase special 4m tanks off the shelf.• Possibly special order 5m tanks, fabricated locally in Mexico.

HAWC Proposal and Budget

Joint Proposal to NSF and DoE High Energy Physics

Additional Collaborators – University of New Mexico, University of Utah and International Partners

Construction Budget

Milagro Construction Budget was $3.4M ($2.7M from NSF and $0.7M from DoE HEP)

Site Preparation & Water Acquisition $0.6M

Pond or Tanks $3.2M

PMT Refurbishment & Calibration System $0.4M

Cabling, Electronics, Computers $0.8M

Contingency 20% $1.0M

Total ~$6 M

Conclusion

• Milagro has demonstrated the power of the water Cherenkov technique

• Detection of Crab Nebula and Mrk 421, known TeV sources• Discovery of new TeV sources• 1st detection of TeV diffuse emission from the Galactic plane

• Future: HAWC • Building on expertise with Milagro• Design improvements in Size, Altitude, Curtains . . . • 15x Milagro sensitivity

• Milagro /HAWC complementary to other particle astrophysics observatories

TeV -rays: A New Window on the Sky

0.1 GeV

Milagro 10 TeV gamma-rayTeV gamma ray

Milagro HESS

Survey Sensitivity

Gamma/Hadron Separation

Gam

mas

Pro

ton

s30 GeV 70 GeV 230 GeV

20 GeV 70 GeV 270 GeVSize of HAWC

Size of Milagro deep layer Energy Distribution at ground level

Larger Area implies better angular resolution + better cosmic ray background rejection