"Starting from nuclear and particle physics, my research interest evolved into astroparticle physics in late 1990's, with focus on high energy cosmic rays, muons in cosmic ray showers, and high energy neutrino astronomy. I have worked for about 10 years as a research scientist at Bartol Research Institute and the University of Delaware on high-energy cosmic ray and neutrino astronomy projects SPASE-II/AMANDA/IceCube. I joined South Dakota Mines in 2009 to establish research and education programs in particle and astroparticle physics. Since then my research interest also extends to vetoing cosmic ray induced backgrounds, radiological and airborne contamination control for the detection of extremely rare events such as hypothetical dark matter particles."
Email for questions: Xinhua.Bai@sdsmt.edu
Dr. Bai's Agenda
Dr. Xinhua Bai’s Design Challenge Phase 1: Understanding concepts – Cosmic ray experiments, particle flux and detector geometric acceptance (lecture). Need-to-knows: Geometry, trigonometric functions, introductory-level calculus, online python compiler such as https://www.tutorialspoint.com/execute_python_online.php
Dr. Bai’s Design Challenge Phase 2: From concepts to the geometric acceptance formula (Lecture)
Need-to-knows: Geometry, trigonometric functions, introductory-level calculus, online python compiler such as https://www.tutorialspoint.com/execute_python_online.php
Assignment #1: Write a python script to calculate the geometric acceptance of IceTop and Pierre Auger surface array. The Python text file.
Differentiated options here. <--use a different method to model what we've learned today.
Assignment #2: Discussion – Besides the geometric acceptance, what other factors need to be considered in measuring cosmic ray flux using surface array?
# https://www.tutorialspoint.com/execute_python_online.php
# https://repl.it/languages/python3
import os
import sys
import random
import numpy as np
import math
import matplotlib.pyplot as plt
pi = 3.1415926
NLoop = 15
zenith = 0.0 # zenith angle in degree
zenithRad = 0.0 # zenith angle in rad
area = 3000.0 # surface array area = 3000.0 km^2
#area = 1.0 # surface array area = 3000.0 km^2
Acceptance = 0.0
AcceptanceOld = 0.0
print ('+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++')
print ('+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++')
print (' Maximum Angle Integrated Acceptance Increment')
print (' Theta (degree) [Km^2 sr] [Km^2 sr]')
for n in range (NLoop): # loop to NLoop*5 degrees
zenith = (n+1)*5.0
#print '\n zenith angle = ', zenith, ' (degree)'
zenithRad = pi*zenith/180.0
Acceptance = area*pi*math.sin(zenithRad)*math.sin(zenithRad)
# print zenith, Acceptance, Acceptance-AcceptanceOld # messy output
print (" %8.2f %8.2f %8.2f" % (zenith, Acceptance, Acceptance-AcceptanceOld))
AcceptanceOld = Acceptance
print ('+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++')
print ('++++++++++++++++++++++++++++1111+++++++++++++++++++++++++++')
How does a neutrino interaction make visible light when a neutrino is invisible? Review slides 12-19 on Cherenkov Radiation.
Assignment #3:
Loops learning module assigned (it’s labeled #3 but we’ll do it second) SCREENCAPTURE VIDEO
Complete the Week 3 knowledge check by Sunday, January 31 (to give Dr. Shirey time to process your answers and steer next steps.)
Get started on the design challenge Phase 2: Design Exploration (Google Doc copy, Word file to download, PDF file to download)
I think there are three main things to stress at this level about Cherenkov radiation:
1) There must be a transparent medium in order to "see" the radiation.
2) It is produced by particles with electrical charge.
3) The particle must be going faster than the speed of light in the medium.
Cherenkov radiation could be a topic for a student simulation. The game could allow users to select a particle (electron, muon, tau, proton or more exotic not yet seen particles like a magnetic monopole) and produce a light pattern based on some medium properties like its index of refraction, and more ambitious, including absorption and scattering.
There are two answers to what happens to the neutrino when it interacts. The interaction involves an exchange of either a charged boson (a W+ or W-) which changes an up quark to a down quark or vice versa. This W particle has a large mass which means it is not likely to be created if the incident neutrino is lower in energy. Like trying to buy a mansion with a minimum wage job! There might be some unlikely way it occurs but mostly not.
This is called a charged current interaction because the W boson particle is electrically charged. The neutrino is gone, and it corresponding particle is produced (electron neutrino produces an electron, etc.). Since the energies of the neutrinos we are dealing with are so high, there is a cascade of other particles created in the initial interaction in addition to partner particle. But no more neutrinos....except for the case of tau meutrinos which interact, produce a tau which lives a time based on its energy, and then the tau decays producing another tau neutrino. A detail that is important for another reason I won't go into. By the way, we say neutrinos go right through matter but this is only true for low energy neutrinos. Above about 1 PeV, the Earth starts to adsorb neutrinos and we can only look for neutrinos from increasingly smaller part of the sky. Connecting back to Bai's talk, the solid angle seen goes from being 4pi at lower energies to a little over 2pi for the highest energy neutrinos.
It is also possible to create a neutral particle call a Z boson. In this case, the neutrino is not adsorbed in the interaction but changes direction and loses energy. This transfers a lot of momentum and energy to the proton or neutron involved, basically blowing it up producing a lot of very high energy electrically charged particles that produce bursts of cherenkov light before they interact. The net result is a roughly spherical outgoing ball of light. Neutral current interactions become more likely at higher energies (above PeV).