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EXPLORING RELATIVITY WITH COSMIC RAY AND g-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 g-ray bursts the difference in arrival times of g-rays of different energies could be > 100 ms. But ?? effects intrinsic to bursts?? Look for systematic change with distance. 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)
LAT will open a wide window on the study of the high energy behavior of bursts. GRBs and Instrument Deadtime Distribution for the 20th brightest burst in a year (Norris et al) Time between consecutive arriving photons 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
-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).
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
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
AGN: What GLAST will do Integral Flux (E>100 MeV) cm-2s-1 • EGRET has detected ~ 90 AGN. • GLAST should expect to see dramatically more – many thousands • (Stecker & Salamon 1996) • Probe absorption cutoffs with distance (g-IR/UV attenuation).
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 – cp > 5 x 10-24(e/TCBR)2 • Electron-positron pair production interactions of ultrahigh energy cosmic rays can be suppressed if ce – cp > [(mp + me)mp]/Ep2
UHECR Spectra with PhotomesonProductionBoth On (Dark) and Turned off byLIV (Light)
High Energy Astrophysics Tests of Lorentz Invariance Violation (LIV) • Energy dependent time delay of g-rays from GRBs & AGN (Amelino-Camelia et al. 1997; Biller et al 1999). • Cosmic g-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 g-rays (Stecker & Glashow 2001). • Long baseline vacuum birefringence constraints from GRBs (Jacobson, Liberati, Mattingly & Stecker 2004). • Electron velocity constraints from the Crab Nebula g-ray spectrum (Jacobson, Liberati & Mattingly 2003). • Ultrahigh energy cosmic ray spectrum GZK effect (Coleman & Glashow 1999; Stecker & Scully 2005).
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 “Jiffy-Pop” Light Shield Schmidt Optics Mechanical Configuration
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%.
Crucial Role of Stereo-viewing from Space Monocular Events Demonstrate Significant Systematic Errors • 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. Tareq Abu Zayad Astroparticle Phys. 21, (2004) 163
Ultrahigh Energy Neutrino-Induced Horizontal Showers Detected via Air Fluorescence OWL Large Detecting Volume (1012 tons of atmospheric target atoms) opens the door for observing ultra-high energy neutrino Interactions. Horizontal n-initiated airshowers start deep (> 1500 g/cm2) in the atmosphere, providing a unique signature for ultrahigh energy neutrinos.
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----------------------------
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 • THE INSTANTANEOUS APERTURE (AI) IS NOT THE TIME-AVERAGED EFFECTIVE APERTURE (AE) AE = AI • D • e Efficiency, e , involves fractional cloud cover, atmospheric conditions. The maximum achievable efficiency for space observation of EAS is ≈ 0.30 *. D • e≈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,