Neutrino experiments Flashcards
(12 cards)
Neutrino experiments
What is the cosmic neutrino background (CνB)? What are common sources of higher energy neutrinos?
Relic neutrinos from ~1 s after the Big Bang with a temperature of 1.96 K and energies around 100 μeV. Only detected indirectly via Planck CMB data.
Higher energy neutrino sources: nuclear fusion in stars, supernovae, atmospheric phenomena, nuclear reactors, bombs, and particle accelerators.
Neutrino experiments
Who postulated the neutrino and why? How does SM describe neutrinos?
Postulation: Wolfgang Pauli in 1930 to explain the continuous spectrum of β decays.
Neutrino in SM: neutral particle, participates only in weak interaction
- three types, flavour determined from detected charged lepton flavour
- ℓ± flavour eigenstates also mass eigenstates but 𝜈 flavour eigenstates not necessarily mass eigenstates
- 𝜈 flavour oscillation: experimental proof that neutrinos have small but non-zero mass
Neutrino experiments
What is the KATRIN experiment’s goal?
Measure the absolute mass scale of neutrinos using tritium β-decay. Sets upper limit: mν < 0.45 eV (90% CL).
Neutrino experiments
What is neutrinoless double beta decay (0νββ)?
A hypothetical process where no neutrinos are emitted (neutron can emit and absorb the neutrino). Observation would imply Majorana nature and lepton number violation, showing the way towards the extension of SM.
- the GERDA (Germanium Detector Array) experiment searches for such processes
Neutrino experiments
Why are neutrino experiments conducted underground?
To reduce backgrounds from cosmic rays and natural radioactivity which interfere with detecting rare neutrino interactions.
Neutrino experiments
What are the Homestake experiment and KamLAND experiment and their results?
Homestake:
First solar neutrino detection using Cl-37. Detected only ~1/3 of expected neutrinos, hinting at oscillations.
KamLAND:
A large-volume scintillator detector that confirmed reactor neutrino oscillations and used a delayed coincidence technique.
Neutrino experiments
How can RICH detectors be used for neutrino physics?
They can detect Cherenkov light from neutrino-induced charged particles in water/ice, measuring energy, direction, and flavor.
Neutrino experiments
What was the Super-Kamiokande’s contribution to neutrino physics? How does it work exactly?
Detected neutrinos from Sun, atmosphere, and supernovae. Provided evidence for ν(μ) oscillation: the ν(μ) that arrived from above were more numerous than those that travelled through the globe, which indicates that these neutrinos had more time to change into another flavour. Measured direction, energy, and flavor.
Method:
- atmospheric neutrino produced by cosmic ray interactions in the atmosphere collides with a water molecule —» rapid, electrically charged particle is created
- particle generates Cherenkov radiation that is measured —» shape and intendity reveals the type, cause and source of the neutrino
Neutrino experiments
What did the SNO experiment confirm and how does it work?
Confirmed neutrino oscillations by comparing charged-current (ν(e), number smaller than expected) and neutral-current (all flavor, expectations met) interactions in heavy water.
Method:
- detects only neutrinos from the Sun where only electron-neutrinos are produced
- reaction between heavy water and the ν(e) amde it possible to measure ν(e) and all other types combined as well
What is neutrino oscillation and what does it imply?
A quantum effect where neutrino flavor changes as it propagates. Implies neutrinos have mass and mix, challenging the Standard Model. The question of CP-violation the the neutrino-sector arises.
- probability of changing flavour: P = sin²(2θ)sin²(Δm²L/4E)
Neutrino experiments
What are IceCube and ANTARES and what do they study?
IceCube:
A neutrino observatory at the South Pole using ~1 km³ of ice with PMTs to detect high-energy astrophysical neutrinos.
- detected the first likely source of high-energy neutrinos, a blazar
ANTARES:
A deep-sea Cherenkov detector in the Mediterranean for neutrino astronomy, complementing IceCube in the southern hemisphere.
Neutrino experiments
What are sterile neutrinos and how can we search for them?
They do not interact with ordinary matter, they interact only with other neutrinos, emerging and disappearing via oscillation. They can be detected only indirectly by monitoring a beam of ordinary neutrinos as they “oscillate,” or switch between different types, as sterile neutrinos would skew the process.
- need to measure neutrino energy spectrum in each detector to see whether the shape changes are consistent with oscillation
