DONUT (Direct Observation of the NU Tau, E872) was an experiment at Fermilab dedicated to the search for tau neutrino interactions. The detector operated during a few months in the summer of 1997, and successfully detected the tau neutrino. It confirmed the existence of the last lepton predicted by the Standard Model. The data from the experiment was also used to put an upper limit on the tau neutrino magnetic moment and measure its interaction cross section.

A doughnut or donut ( or ; see spelling differences) is a type of fried dough confectionery or dessert food. The doughnut is popular in many countries and prepared in various forms as a sweet snack that can be homemade or purchased in bakeries, supermarkets, food stalls, and franchised specialty outlets. Doughnuts are usually deep-fried from a flour dough, and typically either ring-shaped or without a hole, and often filled. Other types of batters can also be used, and various toppings and flavorings are used for different types, such as sugar, chocolate, or maple glazing. In addition to flour, doughnuts may also include such ingredients as water, leavening, eggs, milk, sugar, oil/shortening, natural flavors and/or artificial flavors.