EXPLORING RELATIVITY WITH COSMIC RAY AND -RAY SPACE OBSERVATIONS

F. W. STECKER

NASA GODDARD SPACE FLIGHT CENTER

Beyond Einstein (?)

Group of Lorentz boosts (just like the group of Galilean transformations) is open at the high end (Planck scale?) – possible modifications by quantum gravity, extra dimensions, string theory, etc.

The cosmic background radiation is only isotropic in one preferred frame (may not be significant).

Some classes of quantum gravity models imply a photon velocity dispersion relation which may be linear with energy (e.g. , Amelino-Camelia et al. 1998).

Using GLAST data for distant -ray bursts the difference in arrival times of -rays of different energies could be > 100 ms. But ?? effects intrinsic to bursts?? Look for systematic change with distance.

...)1( +⋅−=QGEE

cV ξ

Testing Lorentz Invariance with GLAST

The GLAST Mission

Two GLAST instruments:

LAT: 20 MeV – >300 GeV

GBM: 10 keV – 25 MeV

Launch: 2007

5-year mission (10-year goal)

Large Area Telescope (LAT)

GLAST Burst Monitor (GBM)

GRBs and Instrument Deadtime

Time between consecutive arriving photons

Distribution for the 20th brightest burst in a year (Norris et al)

LAT will open a wide window on the study of the high energy behavior of bursts.

Time resolution: <10 microsec; Simple deadtime per event:<30 microsec

-Ray Astrophysics Limit on LIV from Blazar Absorption Features

Let us characterize Lorentz invariance violation by the parameter such that

(Coleman & Glashow 1999). If > 0, the -ray photon propagator in the case of pair production

is changed by the quantity

so that the threshold energy condition is now given by

c

e≡c

(1 + )

+ → e+ + e−

εp

2 =−2E

2

2εE

2 (1 −cosθ) > 4m

e2 + 2E

2.

-Ray Astrophysics Limit on LIV from Blazar Absorption Features (continued).Thus, the pair production threshold is raised significantly if

The existence of electron-positron pair production for -ray energies up to ~20 TeV in the spectrum of Mkn 501 therefore gives an upper limit on at this energy scale of

(Stecker & Glashow 2001).

>2m

e2

E2

.

< 1 .3 ×10 −15

Limit on the Quantum Gravity Scale For pair production, + e+ + e- the electron (& positron) energy Ee ~ E / 2. For a third order QG term in the dispersion relation, we find

And the threshold energy from Stecker and Glashow (2001)

reduces to

=E

2MQG

−2m2

E2

,

E2

2≤

m2

E

M

QG≥

E3

8m2

Limit on the Quantum Gravity Scale (continued)Since pair production occurs for energies of at least E = 20 TeV, we then find the numerical constraint on the quantum gravity scale

Arguing against some TeV scale quantum gravity models involving extra dimensions!

Previous constraints on MQG from limits on an energy dependent velocity dispersion of -rays from a TeV flare in Mkn 412 (Biller, et al. 1999) and -ray bursts (Schaefer 1999) were of order

M

QG≥0.3M

Planck,

M

QG≥(5 −7) ×10 −3 M

Planck.

• EGRET has detected ~ 90 AGN.

• GLAST should expect to see dramatically more – many thousands (Stecker & Salamon 1996)

Integral Flux (E>100 MeV) cm-2s-1

• Probe absorption cutoffs with distance (R/UV attenuation).

AGN: What GLAST will do

Two Telescope Operation

Mkn 501 Spectrum (Stecker & De Jager 1998)

Mkn 501 Intrinsic with SSC Fit Using X-ray Data (Konopelko et al. 1999)

Photomeson Production off the Cosmic Microwave Background Radiation

CMB + p → Δ → N + π

Produces “GZK Cutoff” Effect

Shutting off Interactions with LIV With LIV, different particles, i, can have different maximum

attainable velocities ci.

Photomeson production interactions of ultrahigh energy cosmic rays are disallowed if cp – c> 5 x 10-24(ε/TCBR)2

Electron-positron pair production interactions of ultrahigh energy cosmic rays can be suppressed if ce – cp > [(mp + me)mp]/Ep

2

UHECR Spectra with Photomeson Production Both On (Dark) and Turned off by LIV (Light)

High Energy Astrophysics Tests of Lorentz Invariance Violation (LIV) Energy dependent time delay of -rays from GRBs & AGN

(Amelino-Camelia et al. 1997; Biller et al 1999). Cosmic -ray decay constraints (Coleman & Glashow 1999,

Stecker & Glashow 2001). Cosmic ray vacuum Cherenkov effect constraints (Coleman &

Glashow 1999; Stecker & Glashow 2001). Shifted pair production threshold constraints from AGN -rays

(Stecker & Glashow 2001). Long baseline vacuum birefringence constraints from GRBs

(Jacobson, Liberati, Mattingly & Stecker 2004). Electron velocity constraints from the Crab Nebula -ray

spectrum (Jacobson, Liberati & Mattingly 2003). Ultrahigh energy cosmic ray spectrum GZK effect (Coleman &

Glashow 1999; Stecker & Scully 2005).

OWL : ORBITING WIDE-ANGLE LIGHT COLLECTORS

Orbiting Wide-angle Light-collector

• Air fluorescence imagery, night atmosphere

• Stereo viewing unambiguously determines shower height and isolates external influences (e.g., cloud effects, surface light sources)

• Large Field-of-View (~ 45O ) reflective optics at a ~1000 km orbit in a stereo configuration ≈ an asymptotic

• Instantaneous aperture ~ 2.3 x 106 km2-sr

OWL Deployment

Schmidt Optics

Mechanical Configuration

“Jiffy-Pop” Light Shield

Capabilities of OWL

Energy resolution – 15% @ 1020 eV and improves with energy

Angular resolution – 0.2 - 1 degree

Longitudinal profile – Locate shower max within 50 g cm-2

Able to statistically identify protons, nuclei, and photons

Perform event by event identification of near horizontal and earth skimming neutrinos)

Instantaneous stereo aperture AI ≈ 2.3x106 km2 sr, duty

cycle of

~11.5 % defined by requirement of moonless nightside viewing conditions. Cloud cover reduces the duty cycle to ~3.5%.

OWL Instantaneous Proton ApertureSchmidt Optics, 1000 km Orbits

HiRes Auger Ground (Hybrid)

EUSO 1 ISS Instrument

OWL 2 Satellites

Status Running Running

Energy

Range (eV) 1017 - 4 x 10 20 1019 - 1021 5 x 10 19 – 3 x 10 21 3 x 10 19 – 1022

Incident θResolution

0.6O(E=10 18eV)

1.3O(0.3O)(E=10 20eV)

0.2O-3O 0.2O-1O

EnergyResolution

<20%(E=10 18eV)

25%(10%)(E=10 19eV)

<20%(E=10 20eV)

~15%(E=10 20eV)

Instantaneous Aperture(km2-ster)

104 7000/site 5x10 5 2x10 6

DutyCycle 10% 100%(Hybrid10%) 11.5% 11.5%

Time-Averaged Aperture(km2-ster)

1000 7000/site (700/site(hybrid))

58,000 230,000

UHE Cosmic Rays: Status and Prospects

Crucial Role of Stereo-viewing from SpaceMonocular Events Demonstrate Significant Systematic

Errors

Tareq Abu Zayad Astroparticle Phys. 21, (2004) 163

•Simulated “data” of 1021 eV EAS events in an atmosphere with clouds

• are reconstructed as either stereo events or monocular events.

•The presence of clouds does not bias the stereo event reconstruction.

•However, monocular events demonstrate significant systematic errors.

Large Detecting Volume (1012 tons of atmospheric target atoms) opens the

door for observing ultra-high energy

neutrinoInteractions.

Horizontal -initiated airshowers start

deep (> 1500 g/cm2) in the atmosphere,

providing a unique signature forultrahigh energy neutrinos.

Ultrahigh Energy Neutrino-Induced Horizontal Showers Detected via Air Fluorescence

OWL

Instantaneous Electron Neutrino ApertureSchmidt Optics, 1000 km Orbits OWL

UHE-Neutrino Physics: Status and Prospects

Reference Material for OWL

F.W. Stecker, J.F. Krizmanic, L.M. Barbier, E. Loh, J.W. Mitchell, P. Sokolsky and R.E. Streitmatter

Nucl. Phys. B 136C, 433 (2004),

e-print astro-ph/0408162

THE TRUE CONQUESTS, THE ONLY ONES THAT LEAVE NO REGRET, ARE THOSE THAT ARE WRESTED FROM IGNORANCE-

----------------------------

NAPOLEON----------------------------

Backup Slides

Minimum Source Spectrum Local Power Density Requirements in W Mpc-3 for E > 3 EeV With source evolution and including pair

production energy losses: 1.5 x 1031

With source evolution and no pair production energy losses: 1.2 x 1030

With no source evolution and including pair production energy losses: 2.2 x 1031

With no source evolution and no pair production energy losses: 7.7 x 1030

UHECR Spectra with Pair Production Turned Off and with Photomeson Production both On (Light) and Off (Dark)

OWL Major Requirements Overview

• Large Aperture (effective aperture ≈ 100,000 km2-sr)

• Wide-angle optics ( ≈ 25 degree half-angle)

• Stereo viewing of EAS

• Photonics (single photoelectron sensitivity, large

focal plane detector)

• Trigger. space-time pattern recognition

• Ability to handle background light

• Deal with signal distortion by clouds, atmospheric

conditions, lights

Observing EAS from Space: TWO CRUCIAL POINTS

(1) THE INSTANTANEOUS APERTURE (AI) IS NOT

THE TIME-AVERAGED EFFECTIVE APERTURE (AE)

AE = AI • D • εEfficiency, ε , involves fractional cloud cover, atmospheric conditions. The maximum achievable efficiency for space observation of EAS is ≈ 0.30 *.

D • ε≈0.035

= = > AE ≈ AI • 0.035, general approximation

AE ≈ 80,000 km2-sr for OWL specifically

* J.K. Krizmanic et al., Proc. 28th-ICRC (2003), 2, 639

(2) For observation from space, stereo viewing is essential for good energy resolution and neutrino-event characterization.

OWL Mission Overview

* Launch: Delta IV Heavy, dual spacecraft, 5 meter fairing

* Orbit: LEO, 1000 km initial, move to 500 km before end of mission; controlled re-entry

* Life: 3 years minimum, 5 year goal

* Mass / size one satellite: 1730 kg / 8 meter diameter / low density

* ACS: 3-axis stabilized, 2 degree control, 0.01 degree knowledge

* Power: 712 watts, including cloud monitor, 11 m2 solar panels, flat panel, fixed

* Data system: dual redundant, 150 kbits / sec average, 110 Gbit onboard storage,