LABORATORY INVESTIGATIONS INTO THE EXTREME UNIVERSE

Pisin Chen

Stanford Linear Accelerator Center

Stanford University

• Introduction• Universe as Laboratory• Laboratory Studies of the Universe• Summary

Second ORION Workshop, SLAC, Feb. 18-20, 2003.

LABORATORY ASTROPHYSICSIts relationship with Astrophysics, Particle Physics, and Plasma Physics

National Research Council Committee on the Physics of the Universe:

Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century

• What is the dark matter?

• What is the nature of the dark energy?

• How did the universe begin?

• Did Einstein have the last word on gravity?

• What are the masses of the neutrinos, and how have they shaped the evolution of the universe?

• How do cosmic accelerators work and what are they accelerating?

• Are protons unstable?

• Are there new states of matter at exceedingly high density and temperature?

• Are there additional spacetime dimensions?

• How were the elements from iron to uranium made?

• Is a new theory of matter and light needed at highest energies?

High Energy-Density Physics

• Long history of Plasma Astrophysics (Alfven waves, etc.)

• Modern frontier: Very high density, high pressure, and high temperature astrophysical environments and plasma processes

• Newly emerged discipline: High Energy-Density Physics

“Eleven Science Questions” and Extreme Astrophysical Conditions

• Extremely high energy events, such as ultra high energy cosmic rays (UHECR), neutrinos, and gamma rays

• Very high density, high pressure, and high temperature processes, such as supernova explosions and gamma ray bursts (GRB)

• Super strong field environments, such as that around black holes (BH) and neutron stars (NS)

Particle astrophysics and cosmology partially overlaps with high energy-density physics through some of these connections

Symbiosis between Direct Observations and Laboratory Investigations

Symbiosis should still be true for Particle Astrophysics and Cosmology

Classic example: Laboratory determination of stellar evolution

4p 4He + 2e+ + 2νe + ~ 25 MeV

Three Categories of LabAstro

-Using Lasers and Particle Beams as Tools -1. Calibration of observation - Precision measurements to calibrate observation processes - Development of novel approaches to astro-experimentations - Though mundane, value to astrophysics most certain

2. Investigation of dynamics - Astro-conditions hard to recreate in lab - Many MHD or plasma processes scalable by extrapolation - Value lies in revelation of dynamical underpinnings

3. Probing fundamental physics - Underlying physical principles may yet to be developed - Extreme limits render signatures faint; viability uncertain - Issues at stake too fundamental to be ignored for experimentation

UNIVERSE AS A LABORATORY- Extremely High Energy Events -

• Ultra High Energy Cosmic Rays (UHECR)

- “Knee” and “ankle” in UHECR

spectrum

- Events beyond GZK-limit found

• Very high energy ν’s and γ’s

- ν masses and oscillations

- Extremely high energy γ:

violation of Lorentz

invariance?

“Is a new theory of matter and light

needed at the highest energies?”

UHECR: From Source to Detection

“How do cosmic accelerators work and what are they accelerating?”

Δ

Greisen-Zatsepin-Kuzmin Limit

• Protons above 6×1019 eV will lose sizable energy through CMB

• Super-GZK events have been found with no identifiable local sources

3×1020 eV

50 Mpc ~

Size of local

super-cluster

Cosmic Acceleration Mechanisms• Conventional cosmic acceleration mechanisms encounter limitations:

- Fermi acceleration (1949) (= stochastic accel. bouncing off B-fields)

- Diffusive shock acceleration (70s) (a variant of Fermi mechanism)

Limitations for UHE: field strength, diffusive scattering inelastic

- Eddington acceleration (= acceleration by photon pressure)

Limitation: acceleration diminishes as 1/γ

• New thinking:

- Zevatron (= unipolar induction acceleration) (R. Blandford)

- Alfven-wave induced wakefield acceleration in relativistic plasma

(Chen, Tajima, Takahashi, Phys. Rev. Lett. 89 , 161101 (2002).)

- Additional ideas by M. Barring, R. Rosner, etc.

UNIVERSE AS A LABORATORY- Ultra High Energy-Density Processes -

Shock

Neutrino-plasma

coupling

Neutrinosphere

(proto-neutron star)

Plasma pressure

Bingham, Dawson, Bethe, Phys. Lett. A, 220, 107 (1996)

Phys. Rev. Lett., 88, 2703 (1999)

• Supernova explosion

Gamma Ray Burst• Release of ~ 1052 erg/sec (short bursts)!

• “Standard” relativistic fireball model (Rees-Meszaros, 92, 93)

• Extended model invokes quark-gluon plasma (Chen et al., 01)

“Are there new states of matter at exceedingly high density and temperature?”

UNIVERSE AS A LABORATORY - Super Strong Field Environment -

• Black holes and strong gravitational field

- Testing general relativity

“Did Einstein have the last word on gravity?”

• Neutron stars and strong EM fields

- Schwinger critical field: Bc ~ 4×1013 G or Ec ~ 1016 V/m

- QED Vacuum unstable

UNIVERSE AS A LABORATORY- Extreme Limits of Spacetime and Vacuum -

• ~2/3 of the present energy density

of the universe is in “dark energy”.

“What is the nature of dark energy?”

• Quantum effects of gravity

becomes sizable, or spacetime

becomes unrest, at Planck scale.

“Are there additional spacetime

dimensions?”

Planckscale~10-35m

Human scale~ 1m

LABORATORY STUDIES OF THE UNIVERSE

Suggested in 2001 Workshop on Laboratory Astrophysics (very preliminary): 1. Cline (UCLA): Primordial Black Hole Induced Plasma Instability Expt.2. Sokolsky (Utah): High Energy Shower Expt. for UHECR3. Kirkby (CERN): CLOUD Expt. on Climate Variation4. Chen-Tajima (SLAC-Austin): Plasma Wakefield Acceleration Expt. for UHECR 5. Nakajima (KEK): Laser Driven Dirac Acceleration for UHECR Expt.6. Odian (SLAC): Non-Askaryan Effect Expt.7. Rosner (Chicago): Astro Fluid Dynamics Computer Code Validation Expt.8. Colgate-Li (LANL): Magnetic Flux Transport and Acceleration Expt.9. Kamae (SLAC): Photon Collider for Cold e+e– Plasma Expt.10. Begelman-Marshall (CO-MIT): X-Ray Iron Spectroscopy and Polarization Expt.11. Ng (SLAC): Relativistic e+e– Plasma Expt.12. Katsouleas (USC): Beam-Plasma Interaction Induced Photon Burst Expt.13. Blandford (CalTech): Beam-Plasma Filamentation Instability Expt. 14. Scargle (NASA-Ames): Relativistic MHD Landau Damping Expt.

POSSIBLE LABORATORY ASTROPHYSICS EXPERIMENTS

LABORATORY STUDIES OF THE UNIVERSE- Calibration of Observation -

1. Fluorescence from UHECR induced showers - Two methods of detec-

tion: Fly’s eye (HiRes)

& ground array(AGASA)

- Next generation UHECR

detector Pierre Auger invokes

hybrid detections

- Future space-based

observatories use fluorescence

detection

SLAC E-165 ExperimentFluorescence in Air from Showers (FLASH)

HiRes-SLAC-CosPA (Taiwan) collaboration

2. Neutrino Astrophysics and the Askaryan Effect - During high-energy EM cascade, γ’s and e-’s pull e-’s in from surrounding material - e+’s, on the other hand, annihilate in flight - The two effects lead to a net charge in the shower - Strong coherent radio and microwave Cherenkov emission (First observation at SLAC, Saltzberg, et al., Phys. Rev. Lett., 2000)

- Novel method for UHECR and ν detections (Saltzberg-Gorham)

3. Heavy Element X-Ray Spectroscopy Three “lucky breaks” in black hole accretion: 1. (Many) accretion flows are “cold”; 2. Accretion disks are not fully ionized; 3. Accretion disks are illuminated by flaring coronae. “X-ray observations will allow us to probe the spacetimes of black holes in detail” (M. Begelman)

(M. Begelman, 01)

LABORATORY STUDIES OF THE UNIVERSE- Investigation of Underlying Dynamics -

1. Alfven-Wave induced Plasma Wakefield Accel. Expt. (Chen et al., 01)

• Generation of Alfven waves in relativistic plasma flow• Inducing high gradient nonlinear plasma wakefields• Acceleration and deceleration of trapped e+/e-

• Power-law (n~2) spectrum of stochastic acceleration

2. Relativistic Jet Dynamics Experiments

• Simulations of shock waves induced by jet-plasma interaction

(K. Nishikawa, 02)

• Laboratory experiment with e+e- plasma (J. S.T. Ng)

LABORATORY STUDIES OF THE UNIVERSE- Probing Fundamental Physics -

1. Event Horizon Experiment (Chen and Tajima, 99)

A Conceptual Design of an Experiment for Detecting the Unruh Effect

2. Probing Spacetime Granularity - Brownian motion: microscopic discrete nature of atom revealed in macro-structure fluctuations (Einstein, 1905) - Planck-scale spacetime fluctuations induces stochastic phase shifts of decoherent atomic wavefunction (Power and Percival, 00)

A possible expt., R. Bingham, et al. (Rutherford Appleton Lab, 03)

SUMMARY

• History has shown that symbiosis between direct observation and laboratory investigation instrumental in the progress of astrophysics.

• Particle astrophysics and cosmology, an overlapping frontier between astrophysics and particle physics, faces deep and exciting fundamental issues for the new century.

• Many of these issues further overlap with high energy-density physics.

• Laser and particle beams are powerful tools for LabAstro.

• Three categories of LabAstro: Calibration of observation; Investigation of dynamics; and Probing fundamental physics; Each provides different value to astrophysics.