Study of Ultra-High Energy Cosmic Rays 02. Dec. 2019 Special Topics - - PowerPoint PPT Presentation

Study of Ultra-High Energy Cosmic Rays

20196598 Jeewon SEO

• 02. Dec. 2019

Special Topics in Particle Physics

• 22. Nov. 2019

Particle Astrophysics Lecture

• Introduction
• Cosmic Rays and UHECR
• GZK Cut-Ofg
• Detection
• Air shower
• Experiments and method
• Conclusion

2

Outline

• 22. Nov. 2019

Particle Astrophysics Lecture

• The first observation of a cosmic ray particle with an Ultra

high energy was made by Volcano Ranch experiment in New Mexico.

• The existence of such energetic particles remains a mystery.
• How are UHECR accelerated to the extreme energies?
• Where they come from?
• What is composition of them?

3

Introduction

• 22. Nov. 2019

Particle Astrophysics Lecture

• High energy proton and

atomic nuclei which rain down on the Earth from

• utside of the solar

system.

• Energy range :
• The flux of these particles

decreases as their energy increases.

109eV ∼ 1020eV

4

Cosmic Rays

• 22. Nov. 2019

Particle Astrophysics Lecture

• UHE >
• Would not be trapped in

the magnetic fields of a spiral galaxy.

• The origin of these

particles is expected to be extra galactic.

• GZK limit and cut-ofg

1018eV

5

Ultra High Energy Cosmic Ray

Ultra High Energy Extra galactic origin

• 22. Nov. 2019

Particle Astrophysics Lecture

• Greisen-Zatsepin-Kuzmin limit
• The upper limit on the energy of cosmic ray protons traveling from
• ther galaxies through the intergalactic medium to our galaxy.
• Derived under the assumption that UHE cosmic rays are protons.

Eth = 5 × 1019eV

6

GZK cut-ofg

• The protons of

coming from beyond the local galactic would have their energies attenuated by collisions with the CMB photon.

• The flux above about

should fall ofg sharply

E > Eth 5 × 1019eV

• 22. Nov. 2019

Particle Astrophysics Lecture

• The method of cosmic ray

detection depends on the energy

• f the particles.
• Direct Measurement
• Balloon, satellite and space

shuttle.

• Indirect measurement
• Measured by the showers

generated in the atmosphere.

E < E15eV E > E16eV

7

Detection

Direct Measurement Indirect Measurement

• 22. Nov. 2019

Particle Astrophysics Lecture

• When cosmic rays enter the Earth’s atmosphere they collide with atoms and

molecules, mainly oxygen and nitrogen.

• The interaction produces a cascade of lighter particles, so-called air shower.

8

Air Shower

• Extensive Air Shower (EAS)
• If the primary particle is a high

energy proton or heavier nucleus, cascade can develop through the atmosphere.

• Widely spread

• 22. Nov. 2019

Particle Astrophysics Lecture

• Ground Array Experiments
• Consist of particle detectors that are spaced at difgerent distances from each other.
• Typically composed of scintillation counters or water Cherenkov tanks.
• Determine the arrival direction of an EAS
• Atmospheric Light Emission Experiments
• Two type of emitted light: Cherenkov light and nitrogen scintillation
• The Cherenkov light is highly collimated with respect to the original particle direction.
• > useful for lower energy events and particularly in searching for point sources.
• Nitrogen molecules are excited by the EAS and can radiate their energy by producing

near-ultraviolet photons. The emitted light is isotropic.

• > allows a large collection area which makes it useful for UHECR.
• Some experiments are combined the difgerent technique.

9

Indirect detection experiment

• 22. Nov. 2019

Particle Astrophysics Lecture

10

Pierre Auger Observatory

Ultra high energy cosmic ray Extensive air shower Water Cherenkov Detector Fluorescence detectors

• 22. Nov. 2019

Particle Astrophysics Lecture

11

Cherenkov Detector

• 22. Nov. 2019

Particle Astrophysics Lecture

12

Telescope Array Project

• 22. Nov. 2019

Particle Astrophysics Lecture

13

Fluorescent detector

• 22. Nov. 2019

Particle Astrophysics Lecture

14

Scintillation Counter

• 22. Nov. 2019

Particle Astrophysics Lecture

• The source for very energetic particles is still unknown.
• Several projects are looking for possible source of

UHECR to provide a better understanding of the nature

• f the universe.

15

Conclusion