Dark Matter & Experiements Flashcards
What are the equations for signal events & reaction rate?
- L Luminosity
- J Flux
- n No. Atoms
What is the minimum lifetime of an event where no signals are observed, up to some confidence level?
What are the different detectors used to measure WIMPs, in terms of charge, light & heat?
How do we calculate significance?
Name five possible dark matter backgrounds.
- Radon gas. Filter the air.
- Radioactive rocks. Shield the detector.
- Radioactive equipment. Assemble in clean room.
- Cosmic rays. Put detector underground.
- Directional detectors to eliminate solar neutrinos.
How does a Germainium dark matter detector work?
The germainium looks for direct interactions. Nuclear/electronic recoil will either ionise an electron or cause a gamma ray burst, which is detected by scintillation. The energy is of order ~keV
What are the differences between Belle and LHCb for flavour studies?
Belle
- Uses ee, which doesn’t relie on PDFs and so has high precision
- Uses traditional detectors that cover more of a solid angle
- Has lower backgrounds
LHCb
- Proton collisions can reach higher energies
- Produces higher cross sections
- Better resolution
How does a liquid argon TPC work to detect inverse beta decay?
First the neutron capture fires a gamma ray, which is seen. Then the electron ionises the material as it goes, detected by a drift current. The TPC lets us distinguish events by time, allowing for tracks construction and another dimension of resolution. Argon is also a noble gas, so doesn’t interact with its own scintillation light.
Describe how electron neutrinos were first detected.
Poltergiest (Reinies & Cowens) used a nuclear reactor as a source and looked for IBD. The two gamma detection was the signiature, from the nuclear recoil/neutron capture and thepositron annihilation. A liquid scintillator using heavy water was used, and the light was captured in PMTs.
How were muon & tau neutrinos first detected?
- Muon An accelerator turned protons & a fixed target to mesons & then to muon neutrinos. A spark chamber was used to detect muons.
- Tau An accelerator turned protons & a fixed target to mesons, of which we only keep the heaviest. They then decay into tau neutrinos and taus, detected by emulsion detectors (for sub mm precision).
What experiment first saw maximal parity violation in the weak force?
The Goldhaber experiment. It looked at the gamma ray helicity, which had to be the same as the neutrino helicity. An iron magnet ensured the gamma ray aligned with the B-field. It saw only LH neutrinos.
Describe the Homesteak / Ray Davis experiment.
A large amount of cleaning fluid was put in a mine, and the produced Argon was removed by helium pumping, and decays were observed with a germainium detector. Only 1/3 of the expected neutrinos were seen.
Describe the SuperK experiment.
Muon neutrinos are created in the atmosphere 2:1 with electron neutrinos, but when viewed from below the Earth they were 1:1. This delivered 5ò proof of neutrino oscillation. It used water Cherenkov and PMTs to distinguish the electrons and muons detected.
Describe the SNO experiment.
Heavy water was used in two phases. The CC phase on saw 1/3 of the predicted solar neutrino flux, then the NC phase saw the full flux.
Why are noble gases useful for detection?
- Scintillation & ionisation
- High granularity
- Electrons aren’t captured, so are detected by drift current
- Fast scintillation (ns)
- Transparent to their own scintillation light
- Drift electrons & scintillation allows for 3D reconstruction
How does indirect dark matter detection work?
We look for dark matter colisions, then detect them with Cherenkov dectors either on the ground or in satelites.
