Erice July 2004Jordan GoodmanUniversity of Maryland Air Shower Gamma Ray Detectors Outline Air...

Jordan Goodman University of Maryland Erice July 2004

Air Shower Gamma Ray Detectors

Outline• Air Shower Physics

– Extensive Air Showers– Gamma/Hadron sep.

• Why use EAS Detectors• Detecting showers on the ground

– Water Cherenkov - Milagro– RPCs – ARGO

• Recent Milagro Results– Known Sources– New Detections

• Future Detectors - HAWC

Milagro


Extensive Air Shower Development


From Ralph Engel


Effect of Altitude

Low Energy Threshold Requires High Altitude

Milagro

ARGO


Cascade Development

ARGO Milagro

1 TeV

10 TeV


Shower Content

NgammasNelectrons

Primary Energy (GeV)


Photon Shower 2 Gamma (movies by Miguel Morales)

Blue – Electrons Muons – Yellow Pions – Green Nucleons – Purple


Proton Shower 2 TeV (movies by Miguel Morales)

Blue – Electrons Muons – Yellow Pions – Green Nucleons – Purple


Techniques in TeV Astrophysics

Low energy thresholdGood background rejectionSmall field of viewLow duty cycleGood for sensitive studies of known point sources.

High energy thresholdModerate background rejectionLarge field of view (~2sr)High duty cycle (>90%)Good for all sky monitor and for investigation of transient and diffuse sources.

Pointed instruments

Non-pointed instruments


Why Use EAS Detectors

• Transient Sources– GRB’s

• Don’t know when

or where to look• Some indications

of 2nd hard comp.

– Variable Sources• Diffuse Sources

– Galactic Plane– New Sources


Cherenkov Radiation

Boat moves throughwater faster than wavespeed.

Bow wave (wake)


Cherenkov Radiation

Aircraft moves throughair faster than speed ofsound.

Sonic boom


Cherenkov Radiation

When a charged particle moves throughtransparent media fasterthan speed of light in thatmedia.

Cherenkov radiationCone oflight


Cherenkov Radiation


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


The Milagro Collaboration

D. Berley, E. Blaufuss, J.A. Goodman,* A. Smith , G. Sullivan, E. Hayes, D. Noyes

University of Maryland At College ParkShoup, and G.B. Yodh

University of California, IrvineD.G. Coyne, D.E. Dorfan, L.A. Kelley D.A. Williams S. Westerhoff, W. Benbow, J. McCullough, M. Morales

University of California, Santa CruzA.I. Mincer, and P. Nemethy, L. Fleysher, R. Fleysher

New York University

R.W. Ellsworth

George Mason UniversityG. Gisler, T. J. Haines, C.M. Hoffman*, F. Samuelson, C. Sinnis

B. Dingus, Los Alamos National LaboratoryJ. Ryan, R. Miller, A. Falcone

University of New HampshireJ. McEnery, R. Atkins

University of Wisconsin*Spokesmen Students


Milagro


Inside Milagro


Milagro Site


Milagro Outriggers


Shower hitting the pond at an angle


2 Tev Proton Shower hitting the pond


2 Tev E/M Shower hitting the pond


Angle Reconstruction

For large showers, the angle can be reconstructed to better than 0.50o. (However, there are systematics associated with core

location)


Events


Shower Curvature


Operations

• Milagro has been operating since 2000 at 2650m– 0.22 Trillion Events

• Outriggers were finished in 2003• We run with ~96% on-time• Data rate is ~ 1700 Hz

– 8-9% deadtime• We reconstruct in real-time

– We look for GRBs and send out alerts– Three months of raw data saved for archival

analysis• Data is sent via network to LANL & UMD• Nearly total remote capability


Milagro Energy Response (before/after new trigger)

1 TeV1 TeV

Ratio of response to new trigger

New Trigger installed March 2002 – removes muon triggers at large angles to allow triggering on lower energy showers


Milagro Sensitivity

Our energy threshold increases with the zenith angle.

Energy threshold is not well defined.Even though our peak sensitivity isat a few TeV, we have substantial sensitivity at lower energies.

GLAST

Milagro Effective Area

EGRET


P

Gamma – Hadron Separation


Gamma / Hadron Separation in Milagro

Gammas (MC)

Data

Proton (MC)

This cut removes 90% of the protons and keeps 50% of the gammas

Q is improvement of signal to root BG which equates to sigma

This gives a Q of ~1.5 (same signif in ½ the time)


Tibet – 4300m

• ARGO


ARGO Technique


Limited Streamer Tubes


ARGO Design


ARGO Building


Inside the ARGO Building


ARGO Event

ARGO will be a very capable detector when completed in several years!


Recent Milagro Results


Milagro Point Sources

Data taken in the Crab Nebula region with 6.4 at the position of the Crab (2000-2002)

Signal map of Mrk 421 during the 2001 flare (1/17/01-4/26/01). The circle shows the position of Mrk 421 with our angular bin. The center corresponds to ~5


Milagro All Sky Survey

Crab Mrk 421

Hot Spot


Effect of the Outriggers

This improved ang. resolution give us an increase in Q factor of ~1.7

This means we see the same signal ~ 3 times faster!

More improvement (~1.5 – 2 in Q) is expected with better /h separation

With outriggers

With outriggers

Before outriggers 0.75o

Before outriggers

Core Error


Effect of the Outriggers

12 months of recent data on the Crab

~3 times faster to get same signal

Another factor of ~1.5 - 2 is expected from /h sep

Andy/Tony will provide a new plot


EGRET Observation of the Galactic Plane

Note that their coordinates run opposite from ours…

•Black is EGRET Diffuse Flux > GeV

•Red is Milagro Exposure (TeV)

Cygnus region

Inner Galaxy

Outer Galaxy


Milagro Galactic Plane

5 excess for the “inner galaxy” - Flux fraction ~ 4 x 10-5 of CR

This is the first detection of the galactic plane at these energies (~TeV)

Cygnus regionPre

liminary


Milagro Galactic Plane

Cygnus region

Prelim

inary

Inner Galaxy

Outer Galaxy


Galactic Plane


The Cygnus Region


3EG_J0520+2556 – Milagro Hot Spot


3EG_J0520+2556 – Milagro Hot Spot

This source is now ~6 and appears to be ~0.8deg wide!

This will be hard for an ACT to see!

When we reported a 3 source - Whipple looked, but didn’t see it…


GRB970417a

● 18 signal events with an expected background of 3.46 -> Poisson prob. 2.9e-8 (5.2). Prob. after correcting for size of search area: 2.8e-5 (4). Chance prob. of this excess in any of the 54 GRB examined for TeV emission by Milagrito: 54x2.8e-5 = 1.5e-3 (3).

Evidence for a TeV signal from GRB970417 was seen by Milagrito (a smaller, single layer prototype of Milagro)


Luminosity of GRB970417a

More luminosity at TeV energies than MeV energies.But the GRB must be close due to TeV-IR absorption, so the total energy released is not unusually large.

If z~0.1 => E < 700 GeV so L < 5 x 1051 ergsIf z~0.03 => E < 10 TeV so L < 1 x 1049 ergs

Atkins, 2003, Ap J 583 824


GRB 941017 (pre-Milagro)

• M.M. González, B.L. Dingus, Y. Kaneko, R.D. Preece, C.D. Dermer and M.S. Briggs, Nature, 424, 749 (14 Aug 2003)

• This burst is the first observation of a distinct higher energy spectral component in a GRB

• Lower energy component decays faster than higher energy component

• Peak of higher energy component is above the energy range of the detector

• Power released in higher energy component is more than twice the lower energy component

-18 to 14 sec

14 to 47 sec

47 to 80 sec

80 to 113 sec

113 to 200 sec


Theories of the High Energy Component of GRB941017

• Requires GRBs to more energetic phenomena

• Different timescale of low and high energy implies an evolving source environment or different high energy particles

• Shape of high energy component applies tight constraints to ambient densities and magnetic fields

• Or evidence of origin of Ultra High Energy Cosmic Rays

• More and Higher Energy observations are needed

Pe’er & Waxman (astroph/0310836) constrain source parameters for Inverse Compton emission of GRB941017

Milagro Sensitivityz=0.2

z=0.02


Operations in the Swift era

Swift will be launched in September 2004

It will detect ~100-150 bursts per year with redshift information

Milagro observes ~ 1/6 the sky with some reasonable efficiency

Therefore we should expect ~20 GRBs per year in our FOV with redshift information

This will improve our sensitivity by ~ factor of 3

And allow us to put limits on bursts we don’t detect

Note: EGRET saw 6 bursts in 9 years!


Milagro Summary

• Running well with outriggers• Q factor is improving steadily• Improved sensitivity to GRBs• Two recent “discoveries”

– The galactic plane + Cygnus Region– A new diffuse source in the crab region

• More to come– Spectral information, etc.


HAWC – The Next Generation


HAWC Requirements

• Low Energy Threshold < 50 GeV• GRBs visible to redshift ~1• Near known GRB energy• AGN to redshift ~0.3

• Large fov (~2 sr) / High duty cycle (~100%)• GRBs prompt emission• AGN transients• Time domain astrophysics

• Large Area / Good Background Rejection– High signal rate– Ability to detect Crab Nebula in single transit

• Moderate Energy Resolution (~40%)– Measure GRB spectra (inter-pulse spectra)– Measure AGN flaring spectra


Effect of Altitude

Low Energy Threshold Requires High Altitude


HAWC Strawman Design

• 200m x 200m water Cherenkov detector• Two layers of 8” PMTs on a 2.7 meter grid

– Top layer under 1.5m water (trigger & angle)– Bottom layer under 6m water (energy & particle ID)– ~10,000 PMTs total (5,000 top and 5000 bottom)– Trigger: >50 PMTs in top layer

• Two altitudes investigated– 4500 m (~Tibet, China)– 5200 m (Atacama desert Chile)

6 meters

e

200 meters

Jordan Goodman University of Maryland Erice July 2004Reconstructed events


Effect of EBL on Distant Sources

z = 0.03z = 0.1z = 0.2

z = 0.3

z = 0.0


Energy Distribution After EBL


Point Source Sensitivity


Gam

mas

Pro

tons

Background Rejection: Bottom Layer

30 GeV 70 GeV 230 GeV

20 GeV 70 GeV 270 GeV


HAWC Conclusions

• A large area, high altitude all sky VHE detector will:– Detect the Crab in a single transit– Detect AGN to z = 0.3– Observe 15 minute flaring from AGN– Detect GRB emission at ~50 GeV / redshift ~1– Detect 6-10 GRBs/year (EGRET 6 in 9 years)– Monitor GLAST sources– Perform Time Domain Astrophysics in VHE Regime

• Extreme States of Extreme Systems• Continuing work

– Improve background rejection & event reconstruction• Increase sensitivity by ~50% - 100%? • Develop energy estimator

– Detailed detector design (electronics, DAQ, trigger, infrastructure)– Reliable cost estimate needed (~$30M???)– Site selection (Chile, Tibet, White Mountain)

• Time Line– 2004 R&D proposal to NSF & DOE (LANL & UNM)– 2006 full proposal to NSF & DOE– 2007-2010 construction


Conclusions on Air Shower Detectors

• They are complimentary to ACTs• Their features of wide field of view and continuous

observation gives them the ability to:– Observe transient sources– Observe diffuse objects– Discover new objects

Erice July 2004Jordan GoodmanUniversity of Maryland Air Shower Gamma Ray Detectors Outline Air...

Documents

Transcript of Erice July 2004Jordan GoodmanUniversity of Maryland Air Shower Gamma Ray Detectors Outline Air...