IntroductionIntroduction - obspm.frluthier/zech/pdap/pdap_intro.pdf · A. Zech, Physics & Detection...

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Physics & Detection of AstroParticles Andreas Zech, LUTH, Observatoire de Paris 2011 Introduction Introduction

Transcript of IntroductionIntroduction - obspm.frluthier/zech/pdap/pdap_intro.pdf · A. Zech, Physics & Detection...

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Physics & Detection of AstroParticles

Andreas Zech, LUTH, Observatoire de Paris2011

IntroductionIntroduction

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Introduction

A Tools

1 overview of special relativity2 standard model of particles (in a nutshell)

B High Energy Photons

1 X-ray astronomy2 γ-ray astronomy

C Cosmic Rays & Neutrinos

1 low energy cosmic rays2 (ultra-) high energy cosmic rays3 neutrino astrophysics

D Dark Matter in Astroparticle Physics

Outline

Detection(detectors, instrumentation, recent projects)

Research Topics (a selection of physics topics in the field)

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What (not) to expect from this courseThis course is intended to give an introduction into several fields of astrophysics, regrouped as "high energy astrophysics" and/or "astro-particle physics".

Such a course cannot be complete. A researcher in a field such as e.g. gamma-ray astrophysics uses methods from many different sources (electro-dynamics, relativity, quantum mechanics, MHD, statistics, electronics ...).

We will discuss a selection of physics topics and introduce the most common detection methods and their application in experiments/projects.

Suggestions for further reading are given to allow a deeper understanding of the different subjects...

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Particle interactions (1)Interactions of massive particles and photons (both are 'particles') with matter and electromagnetic fields will play a central role in this course. We need to understand them to get an insight into:

- the physical mechanisms of particle detectors

- the underlying processes in astrophysical objects emitting high energy particles

interactions of high energy photons with matter

- photoelectric absorption, spectral absorption and emission lines

- (inverse) Compton scattering

- electron-positron pair production

e.g. Compton scattering

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Particle interactions (2)interactions of massive high energy particles with matter and e.m. fields

- ionization

- bremsstrahlung (free-free emission)

- Cherenkov radiation

- nuclear interactions and spectral lines

- (electron-positron) pair creation

- synchrotron radiation

e.g. bremsstrahlung

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Some Detector Types in High Energy (Astro)physics

– proportional and Geiger counters– wire chambers, drift chambers– spark chambers

– semiconductor devices (e.g. CCDs, photodiodes, silicon strip detectors)

– scintillation detectors– transition detectors – photo-multiplier tubes

– calorimeters

e.g. photo-multiplier tube from the Antares experiment

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experiments / projects we will discuss● cosmic rays

– AMS● ultra-high energy cosmic rays

– HiRes telescopes– Pierre Auger Observatory

● (astro-) neutrinos

– Super-Kamiokande– Antares, IceCube

● dark matter

– Edelweiss (?)

● X-ray astronomy

– Chandra satellite● gamma-ray astronomy

– Compton Gamma-Ray Observatory

– Suzaku– Fermi

● VHE gamma-ray astronomy

– HESS (Cherenkov telescopes)

– Milagro (air shower array)

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● High Energy Astro(particle) physics:

– Malcolm S. Longair: High Energy Astrophysics I & II, (Second Edition) Cambridge University Press 1992

– Charles D. Dermer & Govind Menon: High Energy Radiation from Black Holes, Princeton Series in Astrophysics, 2009

● Radiative Processes

– G.B. Rybicki, A.P. Lightman: Radiative Processes in Astrophysics, Wiley-VCH 2004

● Instrumentation in Particle Physics:

– Dan Green: The Physics of Particle Detectors , Cambridge University Press 2000

– Particle Detector BriefBook: http://rkb.home.cern.ch/rkb/titleD.html

– Particle Data Group: http://pdg.lbl.gov/2006/reviews

● Astroparticle physics:

– Donald H. Perkins: Particle Astrophysics , Oxford Master Series, 2003

● Particle physics:

– Donald H. Perkins: Introduction to High Energy Physics , Cambridge University Press 2005

● Everything you ever wanted to know about Electrodynamics and Special Relativity (and more):

– J.D.Jackson, Classical Electrodynamics , John Wiley & Sons, Inc.

● Details on different experiments:Webpages of NASA, ESA, H.E.S.S., Auger, etc. ...

Bibliography

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● ~40h de cours; 20h de TD et "journal club"

● polycopies seront disponibles sur internet (mises à jour régulièrement)

● TD sous forme d'exercices (petits calculs)

● "journal club":

lecture de papiers scientifiques, présentations des papiers (un par étudiant(e)), questions et discussion (en groupe)

● Au lieu d'un examen: Rédaction d'un rapport sur un sujet dans l'astrophysique des hautes énergies sous la forme d'un court papier scientifique (projet de bibliographie). Des détails seront donnés plus tard.

● Notes:

– 60% : TD (exercices, présentations)– 40% : rapport

● Possibilité d'avoir (quelques) cours en anglais (aussi présentations, rapports) !

Organisation du cours

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Introduction to High Energy Astro(particle) physics

© ASDC

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What is "High Energy Astrophysics" ?There is not a really precise definition of "High Energy Astrophysics". Two characteristics are:

- In "High Energy" observations, the particle character of light (= photons) becomes significant. => instruments resemble detectors from particle physics

experiments

- "High Energy" radiation and particles are often connected to non-thermal sources (this is not true in general for X-rays).

=> observation of highly energetic particle accelerators (shocks, accretion, ...)

There is also no clear difference between "High Energy Astrophysics" and "Astroparticle Physics". We will discuss observation of X-rays and Gamma-rays (electromagnetic radiation), but also of cosmic rays and neutrinos (massive particles).

Certain aspects of dark matter (and gravitational waves) fall into the domain of Astroparticle physics. We will discuss dark matter briefly in this course.

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Thermal radiation

I =2h 3

c² ⋅1

eh kT −1

Planck's law:I(ν)dν : thermal emission of a «black body»(erg cm-2 s-1 sr-1 in interval between ν and dν)

Thermal radiation is the transfer of heat from a material by means of electromagnetic radiation and depends on the material's characteristic emissivity and temperature. Thermal radiation results from the movement of charged particles (protons and electrons) in a material.

Thermal radiation is responsible for much of the radiation observed in the radio/IR/optical/UV and up to the X-ray band.

Black-body radiation is thermal radiation from an idealized object, a black body in thermal equilibrium. Black bodies absorb all radiation that falls onto them (no reflection or transmission, emissivity=1) and re-emit radiation in a continuous spectrum, depending only on their temperature. Celestial objects can often be described as black bodies (stars, gas clouds, CMB, etc. ). The black-body emission spectrum is described by Planck's law:

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Non-thermal radiationIn high-energy astrophysics, we often deal with non-thermal radiation. This is e.m. emission from particles with kinetic energy not due to heat, but due to some acceleration process. Charged particles can for example be accelerated by shock fronts inside a plasma, by electromagnetic fields, magnetic reconnection etc.

Non-thermal radiation is often characterized by a power-law distribution of the emitted light. A typical example would be the synchrotron emission from AGNs that is seen from the radio to the X-ray range.

T. Berghöfer et al., ApJ 535, 615 (2000)

synchrotron emission from M87

Even though certain emission processes, like synchrotron radiation, are often linked to non-thermal radiation, the "non-thermal" aspect is really determined by the underlying particles' distribution and not by the emission process.

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High energy vs. low energy astronomy

h << kT

energy of radiation is much smaller than T of sky, telescope or detector.

h >> kT

energy of radiation is much larger than T of sky, telescope or detector.

description of radiation as particles (photons); wave properties negligible

=> angular resolution of telescopes determined by geometric optics

=> sensitivity of telescopes limited by statistics of source photons and background photons (or cosmic rays)

description of radiation as electromagnetic waves

=> angular resolution of telescopes determined by diffraction optics

=> important thermal/optical background from sky, telescope and detector limits the sensitivity

high energy astronomy UV optical IR radio (X-ray, γ-ray) astroparticle physics

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The electromagnetic and cosmic ray spectrum

energy: eV meV eV keV MeV GeV TeV

Solar c.r. Galactic c.r.

energy: TeV PeV EeV ZeV

Galactic c.r. Extra-galactic c.r. (?) ------> |

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astrophysical sources in different wavebands● radio (3MHz – 30 GHz / 100m – 1cm)

– thermal bremsstrahlung from ionised hydrogen

– neutral hydrogen (21 cm line)

– synchrotron radiation from relativistic plasma (interstellar magnetic field, radio lobes of active galaxies, quasars, pulsars...)

● (sub-)millimeter (30 GHz – 3 THz /10 – 0.1 mm)

– thermal bremsstrahlung from ionised hydrogen

– observation of molecular lines

– Cosmic Microwave Background

● infrared (3 THz – 30 THz / 0.1 mm – 1 μm)

– thermal emission from stars, galaxies, AGN...

– emission from dust grains

● optical (30 THz – 1 PHz / 1 μm – 300 nm)

– planets, stars, galaxies ...

– emission and absorption features

● ultraviolet (1 PHz – 30 PHz / 300 – 10 nm)

– thermal radiation, non-thermal radiation from active galaxies and quasars

– resonance lines of ions, atoms

● X-ray (30 PHz – 30 EHz / 10 nm – 10 fm)

– supernova remnants, AGN, pulsars, binaries

– thermal bremsstrahlung in galaxy clusters

● γ-ray (> 30 EHz / < 10 fm / E > 100 keV)

– non-thermal processes (bremsstrahlung, inverse Compton, decay of pions...)

– radioactive elements (line emission)

– e+e- annihilation line (511 keV)

– SN remnants, AGN, pulsars, -γ ray bursts

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Atmospheric Absorption of Electromagnetic Radiation

image taken from NASA

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Observation in different wavebands● radio (3MHz – 30 GHz / 100m – 1cm)

– at low frequencies reflection of radio waves in plasma (ionosphere, interplanetary, interstellar)

– radio antennas, arrays of antennas

● (sub-)millimeter (30 GHz – 3 THz / 1cm – 0.1 mm)

– at short wavelengths, absorption in atmosphere (water vapour, molecules) -> high, dry sites

● infrared (3 THz – 30 THz / 0.1 mm – 1 μm)

– large thermal background, absorption in atmosphere -> high, dry sites for certain wavebands, balloons, aircraft, satellite

● optical (30 THz – 1 PHz / 1 μm – 300 nm)

– at short wavelengths, absorption by ozone in upper atmosphere; scattering (Rayleigh & Mie)

– telescopes, CCDs ...

● ultraviolet (1 PHz – 30 PHz / 300 – 10 nm)

– ozone & molecular absorption in atmosphere -> satellites

– at short wavelengths, photoelectric absorption by Lyman continuum of neutral hydrogen (interstellar gas)

● X-ray (30 PHz – 30 EHz / 10 nm – 10 fm)

– atmosphere is opaque to X-rays -> satellites

– grazing incidence optics, particle physics type detectors

● γ-ray (> 30 EHz / < 10 fm / E > 100 keV)

– photoelectric absorption, Compton scattering, pair production -> satellites

– particle physics type detectors

– E > 100 GeV : indirect detection (air shower)

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A bit of history of High Energy Astrophysics● Until ~1945 astronomy was restricted to

optical astronomy.

● Advances in electronics, radio techniques and computers led then to radio astronomy and the study of highly energetic sources (radio galaxies, AGN, pulsars...)

● First rocket flights with X-ray detectors in 1962 and 1963. Detection of Crab nebula, M87...

● First dedicated X-ray satellite UHURU in 1970s maps the X-ray sky.

● γ-ray emission from the Galactic plane was first discovered in 1967 by the OSO III satellite.

● First evidence of γ-ray line emission found in balloon observations in the early 1970s.

● Ground based Air Cherenkov telescopes allow today the indirect observation of TeV γ-rays. (e.g. Whipple in 1980s)

● Ground based cosmic ray detectors observe indirectly cosmic rays of much higher energies than was possible with balloon flights. One of the first ground arrays was Volcano Ranch in the 1960s. The air fluorescence technique has helped to improve the energy resolution significantly.

● Detection of solar neutrinos (Cl37) and of neutrinos from the SN1987A supernova in 1987 (Kamiokande) laid the foundation for neutrino astronomie. This is today still a field in its infancy.