User:Smilner2/sandbox

Sources of Dark Photons
Dark photons are particles that are weakly coupled to the standard model (SM) and are also known as the corresponding gauge boson A′ for the U(1) gauge group. This A′ can be produced in a number of ways, including radiative production in electron scattering from a nucleus, kaon decay and positron-electron annihilation. The A' can also decay invisibly which means the dark photon decays into a fermion and an anti-fermion pair into the dark sector, which results in a noticeable energy loss that cannot be detected directly by experiments. Kaon decay is a possible mechanism for production of dark photons through the decay of a kaon Κ to a pion π0 which then decays to a photon via the process π0 → A′γ. The number of kaon decays NK, which is equal to ħ divided by the lifetime of the decaying pion, is roughly (1.57 ± 0.05) x 1011 for the 98 m fiducial decay region. Electron-positron annihilation processes can be detected using collider experiments that collide positrons and electrons together to produce A' gauge bosons. These collider experiments use the total energy of the electron and positron pair in the center of mass frame to determine the corresponding mass of the subsequent A' boson. The A' boson cannot be directly detected by experiment due to the fact that it fails to interact with particles in the standard model or "visible world", meaning that the change in energy from the invariant mass of the electron-positron pair is calculated to be the mass of the A' boson or dark photon.

DarkLight Experiment
A new experiment titled DarkLight is currently being conducted at the Massachusetts Institute of Technology which will search for dark photons with a known energy range of ~10-500 MeV/c². DarkLight will also concern the search for a dark gauge field A' by examining scattering processes off a windowless hydrogen gas target. The intended target beam used for probing the dark gauge field is a free electron laser at Jefferson Laboratory in Virginia with a known emittance ε of. The experimental mass resolution M/ΔM has been calculated to be 1 MeV which is indicative of a high rest mass

Neutrino Experiments
A new search for U(1) dark photons of the dark gauge field A' is also currently undergoing development. This experiment will utilize the Compton like process γe- → A'e- for low energy interactions in nuclear reactors used for neutrino experiments. When the mass of a dark photon is larger than twice the mass of the electron (0.511 MeV/c2) then the dark photon will decay into a positron-electron pair (γ → e+e-). When photons of the order of 1-10 MeV are created in a nuclear reactor Compton scattering is dominant over photoelectric absorption and electron-positron annihilation processes. Using this information it is possible to use a Compton scattering cross section as the total scattering cross section σTotal of all possible dark photon energies. Two known neutrino experiments that have the potential to detect dark photons include the TEXONO experiment and the NEOS experiment, both short baseline reactors. TEXONO measures anti-neutrino electron scattering while NEOS is involved in the search for sterile neutrinos.