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###### 日期：2020-05-01 09:14

2020/4/28 cosmic_presentation
Presentation Notebook - Final Project 1: cosmic
This notebook contains physics questions to be answered as part of the cosmic final project - see companion assignment notebook for details.
Honor Code Pledge
Please type your name in the box below to agree to the Honor Code Pledge for this assignment:
"On my honor, as a University of Colorado Boulder student, I have neither given nor received unauthorized assistance."
In?[?]:
Physics Questions
Add cells below as necessary to answer each of the physics questions.
Make sure your notebook runs with no errors by using the "Restart & Run All" command before you submit!
1. Testing with simple showers
As a simple test of your Monte Carlo code, find the "shower" induced by an initial electron, initial muon, and initial pion, each traveling at 0.999c
towards the ground. (None of these will produce a complicated shower; the electron doesn't interact, and the other interactions can only happen once.)
Make a plot or plots showing the particle trajectories, and explain them.
Once you think your plots make sense, check conservation of energy and momentum for the muon decay (not true for downscatters since the air
nuclei provide/absorb energy!)
2. Simulating a single proton shower
Simulate a cosmic-ray shower with a single incoming proton with initial velocity , and starting at km.
Make a two-dimensional figure showing the trajectories of all particles produced in the shower, and use the figure to explain cosmic rays at a level that
a freshman physics major would understand. (How does it compare to a real cosmic ray shower?)
(????, ?? ) = (0.95999, ?0.28) ??
(??, ??) = (0, 20)
3. Ground flux of cosmic muons
For protons with an initial total energy of 30 GeV, the flux of cosmic rays (rate at which they bombard the Earth's atmosphere) is roughly equal to
( denotes "steradian", a unit of solid angle; integrating over the whole sky from a point on earth would give about as the total solid angle.)
Run your Monte Carlo simulation several times for protons incident on the upper atmosphere at an altitude of 15 km, incoming towards the point
on the surface at height above sea level (you can check for dependence on the initial angle, or try to average over it somehow.) Based on how many
muons cross through ground level in your simulation results, what is the total flux of muons (number of muons observed per second) at ground level?
If you had a detector which was 0.1 square meters in size, how long would you have to wait per muon on average at sea level ( )?
4. [Extra-credit challenge!] Cosmic muons in underground laboratories
Cosmic ray muons are a nuisance if you're trying to do a very sensitive search for rare particles, like hunting for dark matter. To shield against these
muons, most dark matter detectors are placed deep underground. When traveling through the solid rock that makes up the Earth's crust, muons suffer
energy losses as described in section 30.4.1 of this document (http://pdg.lbl.gov/2017/reviews/rpp2017-rev-cosmic-rays.pdf) (don't worry about
understanding the rest of the document!) Implement energy loss for muons passing below in your Monte Carlo simulation. How far underground
would a detector have to be for the muon detection rate (in your model) to pass below 1 muon per year?
?? = 0
# Import cell
from cosmic import *