Cosmic Ray Theory
Why can't we observe ultra-high-energy cosmic rays sources directly?
Due to the deflection of Galactic and extragalactic magnetic fields as cosmic rays are charged particles
List the 3 fundamental forces in particle physics and their associated particles
electromagnetism - photon, strong - gluon, weak - W/Z (electroweak - photon/W/Z is also ok)
True or False: The fluorescence detector can be used during a full moon
False: The fluorescence light from the moon will smear the fluorescence yield of the air shower. They are conducted in moonless nights instead.
How can neutrinos help us detect cosmic ray sources?
Since neutrinos are produced from charged pion / kaon decays coming from hadronic interactions from sources, and they do not experience any deflections.
Explain (briefly) the detection mechanism of a water Cherenkov detector
Pure water is filled in a tank. When a particle traverses through the tank, the Cherenkov light emitted by this interaction will be amplified by PMTs and generate a signal. The timing of this interaction is used to determine the direction of the air shower.
What are the main candidate sources for cosmic rays below the knee?
Supernovae remnants, pulsar wind nebulae, stellar clusters, acceleration processes within the Galactic Center region
Why do W/Z bosons have mass?
They interact with the Higgs boson through the Higgs mechanism
What is the "muon puzzle"?
The discrepancy between the number of muons from hadronic interaction models and observations (observations show less number than simulations).
What is the purpose of selecting “up-going” events for neutrino detection?
To filter out background atmospheric muons
True or False: the NKG effect is the main reason for suppression of the energy spectrum at the highest energies
False: the NKG function describes the lateral distribution of the air shower. the GZK effect is what causes this suppression
True or False: Fermi II acceleration is the dominant acceleration process in SNRs
False: Fermi II acceleration is due to deflection by magnetic mirrors. Fermi I acceleration (or diffusive shock acceleration) is due to the repeated crossing of particles across the shock front.
True or False: Charged pions primarily decay to electrons
False: muons are heavier thus allowing more left & right-handed particles for pions to decay into. Parity violation is more prominent for lighter particles
What is the elongation rate, and how is it connected to Xmax?
Elongation rate is d Xmax / d (log E). It is an indicator of the multiplicity of high energy particles and the interaction cross section.
True or False: Gamma rays are attenuated over large distances.
True: They are affected by the extragalactic background light
change in the acceleration mechanism at the source / shift to heavier composition due to reduced acceleration efficiency of lighter nuclei
True or False: We have an observation that UHECRs come from extragalactic origin.
True: the anisotropy map at intermediate energies from Auger indicate so.
What did the g-2 experiment show?
It showed that the anomalous magnetic moment of the muon was deviating from values derived from the Standard Model with 4.2 sigma, describing a physical process that cannot be described with the Standard Model(https://cerncourier.com/a/an-anomalous-moment-for-the-muon/)
For which showers is geosynchrotron emission important?
For very inclined showers
List 5 notable experiments for gamma ray observations.
HESS, MAGIC, Fermi-LAT, VERITAS, LST (possibly more)
List 3 experiments that detect cosmic rays directly.
examples: AMS-02, PAMELA, HEIO, DAMPE, Fermi-LAT
How does the GZK effect work?
Describe the role of the CKM matrix for particle interactions
the CKM matrix describes the probability of flavour change through weak interactions. It is also used to show the existence of CP violation through the complex phase of the matrix amplitude
How can you differentiate between a neutron shower and a proton shower?
Neutrons are less prone to undergo electromagnetic interactions as compared to protons, so it can penetrate deeper before its first interaction -> will have a larger Xmax (although shower-to-shower fluctuations is larger than this difference so cannot distinguish well enough on event-by-event basis)
Why are understanding neutrino oscillations important for astroparticle physics?
To understand the flavour of the neutrino at the source, we need to understand how they undergo flavour change as they propagate so that we can better interpret neutrino fluxes.
Why would the neutrinoless double beta decay be important?
Neutrinoless double beta decay occurs when no neutrinos are produced through a double beta decay. This would mean that an antineutrino must have been emitted and reabsorbed as a neutrino within the nucleus -> indicates that the neutrino is a Majorana particle