Final Report Summary - GC4ICE3 (Search for high energy neutrino emission from the galactic center)
Over the past century physicists have developed – based on data from cosmic rays, nuclear reactors and particle accelerator experiments – a model of elementary particles (quarks and leptons) and forces (electromagnetism, the weak and strong nuclear force). This is modestly called the “Standard Model”. The physical properties of all “ordinary matter” around us can be described surprisingly well in terms of these Standard Model particles and forces, plus gravity as described by Einstein’s General Theory of Relativity. Even stars and their evolution can be adequately described using just these ingredients. Due to these successes, scientists have long thought that the Standard Model could account for practically all matter in the observable universe.
However, things do not seem to add up so nicely when studied on galactic scales, and larger. Most galaxies seem to be rotating so fast that we would expect them to disintegrate. But they don’t. The currently prevailing explanation is that a large fraction of the actual mass of galaxies is hidden in so-called “dark matter”, matter that manifests itself gravitationally through its mass but does not take part in ’normal’ interactions such as electromagnetism. Over the past decade this explanation has gained more support.
The nature of this dark matter is unknown, but there are good reasons to assume that it consists of so-called Weakly Interacting Massive Particles (WIMPs). These hypothetical particles are also predicted by the theory of Supersymmetry and might be produced in proton-proton collisions at the Large Hadron Collider. Being massive and only weakly interacting, WIMPs do not stick together like ordinary matter particles do, but are thought to form vast gas-cloud-like accumulations, held together by gravity. WIMPs may annihilate with each other when they collide, which should then mostly happen in regions where the dark matter density is high, for instance in the center of our Milky Way. From the energy released in the annihilation, observable Standard Model particles can emerge, in particular gamma rays and neutrinos.
Currently there are various efforts underway to detect dark matter. As the dark matter is assumed also to permeate Earth, detectors have been developed and installed in deep underground laboratories to witness rare events of WIMPs gently scatter off ordinary atomic nucleus. The observation of such a nuclear recoil event would constitute direct detection of dark matter, as opposed to the indirect detection method, in which we search for the high energy gamma rays and neutrinos from dark matter annihilation.
However, things do not seem to add up so nicely when studied on galactic scales, and larger. Most galaxies seem to be rotating so fast that we would expect them to disintegrate. But they don’t. The currently prevailing explanation is that a large fraction of the actual mass of galaxies is hidden in so-called “dark matter”, matter that manifests itself gravitationally through its mass but does not take part in ’normal’ interactions such as electromagnetism. Over the past decade this explanation has gained more support.
The nature of this dark matter is unknown, but there are good reasons to assume that it consists of so-called Weakly Interacting Massive Particles (WIMPs). These hypothetical particles are also predicted by the theory of Supersymmetry and might be produced in proton-proton collisions at the Large Hadron Collider. Being massive and only weakly interacting, WIMPs do not stick together like ordinary matter particles do, but are thought to form vast gas-cloud-like accumulations, held together by gravity. WIMPs may annihilate with each other when they collide, which should then mostly happen in regions where the dark matter density is high, for instance in the center of our Milky Way. From the energy released in the annihilation, observable Standard Model particles can emerge, in particular gamma rays and neutrinos.
Currently there are various efforts underway to detect dark matter. As the dark matter is assumed also to permeate Earth, detectors have been developed and installed in deep underground laboratories to witness rare events of WIMPs gently scatter off ordinary atomic nucleus. The observation of such a nuclear recoil event would constitute direct detection of dark matter, as opposed to the indirect detection method, in which we search for the high energy gamma rays and neutrinos from dark matter annihilation.
