Sterile Neutrinos and Dark Matter By Christopher Simmonds
Sterile Neutrinos and Dark Matter By Christopher Simmonds
Discovery of Dark matter • 1884 Lord Kelvin estimated the mass of the galaxy from velocity of stars orbiting the galaxy • He found that this mass was much larger the mass of observed stars. • “many of our stars, perhaps a great majority of them, may be dark Bodies. ”[1] • The term dark matter comes from Henri Poincaré in 1906. • However he disagreed with the Idea of there being “dark mater” or if there was there could not be more of it then normal mater • More convincing observations started to appear in 1960’s and 1970’s Henri Poincaré (29/4/1854) to (17/7/1912) Quote [1] from Baltimore Lectures on molecular dynamics and the wave theory of light. By Kelvin, William Thomson, Baron, 1824 -1907
What is Dark Matter? • We do not Know • Dark matter makes up about 27% of the universe or 85% of “observable” matter • Does not react to EM waves • Found by looking at how galaxies rotate • Dark Matter is what holds a galaxy together • A great many hypothesis about what it could be • One of these is the Idea of sterile Neutrinos
Neutrinos in the standard model • They are a type of lepton • Three flavours • Half-integer spin • Electron neutrino • Muon neutrinos • Tau neutrinos • Have no electric charge • Interact with other matter through the weak force • In the standard model neutrinos are massless, however we know this to not be the case. • These are the active neutrinos • There are oscillations in the stranded model
Sterile Neutrinos • The sterile neutrino is a theoretical new Neutrino that does not interact with other particles using the weak force • Neutrinos need mass to oscillate • Sterile Neutrinos are often theorised to have more mass then other neutrinos • The frequency of neutrino oscillations depend on the mass of the neutrinos at the start and mass of the neutrino at the end of the oscillation • The idea of sterile Neutrinos came from experiments that found more Neutrinos of a certain type then expected or in same cases less • These missing neutrinos could be because they are oscillate into sterile Neutrinos
Oscillations
Quantum dynamics recap (hopefully)
Quantum dynamics recap (hopefully)
Finding probabilities
Oscillations part one
Oscillations continued part two
Oscillations continued part three
Oscillations continued part four
Discovery of neutrino oscillations • The first experimental observations of neutrinos was in 1998 • This was done by Super-Kamiokande in japan • Oscillations where detected from cosmic neutrino radiation • This was done by tacking advantage of the length dependence in the oscillation equation • Compered two detectors at different highs finding the proportions of flavours detected in each one was different • They then concluded that this was due to the difference in path length
Superkamiokande experiment http: //www-sk. icrr. utokyo. ac. jp/sk/detector/cherenkove. html
Connecting the two • We know that neutrinos are everywhere they come out as a by product of nuclear reactions • Suddenly we say they need to have mass in order to oscillate into different flavors • We have a lot of missing mass in the universe as dark matter • By connecting the two we solve the problem and dark matter becomes sterile neutrinos • At least in part, sterile neutrinos could be just one component that makes up dark matter • Still a very big problem observing sterile neutrinos
Chirality • Good way to thick about chirality • Right-handed if the direction of its spin is in the same direction as its motion • Left-handed if spin is in the opposite direction to its travel • This becomes more abstract when you consider that spin is not really in 3 D • Chirality is determined by whether it transforms in a right or left handed representation of the Poincaré group • Only left-handed fermions interact with the weak interaction (and right handed anti-fermions) • For massless particles like the photon, spin is always in the same direction as motion. Regardless of the point of view of the observer
Right Handed Neutrinos
The search for sterile Neutrinos • There a great number experiment under way looking at oscillations and sterile neutrinos • We will look at: • MINOS+ • Boo. NE (Booster Neutrino Experiment) • Both work with the same ideas, using high powered beamlines to create neutrino events • Compering the density and types of neutrinos to expected results from the oscillation equations • Boo. NE is practical open with its experiments and has a lot of information on its website https: //www-boone. fnal. gov
Creating the neutrino beam Image from https: //physics. aps. org/articles/v 11/122 • Set up of the Mini. Boo. NE experiment at Fermilab • Booster accelerates protons to high speed then fires them at a target • Protons hit the target and create pions which decay into muons and muon neutrinos • Muons and muon neutrinos hit dirt wall • Neutrinos passes through to hit the detector
Mini. Boo. NE’s findings
MINOS+
Summary • There is a lot of missing mass in the universe that we do not know a lot about that is “dark matter” • Sterile neutrinos could be one of the particle that make up dark matter as it fits many of the needed properties • There is evidence for and against the existence of sterile neutrons and experiments continue to try to find evidence for sterile neutrons • The evidence is very inconclusive • What do I think?
References: • https: //arstechnica. com/science/2017/02/a-history-of-dark-matter/ • https: //en. wikipedia. org/wiki/Neutrino_oscillation • https: //www-boone. fnal. gov • https: //www-numi. fnal. gov/Minos. Plus/minos. Plus. html • https: //physicsworld. com/a/sterile-neutrinos-are-a-no-show-in-minosexperiment/ • https: //en. wikipedia. org/wiki/Chirality_(physics)
- Slides: 25