Work Package 8

FUNDAMENTAL PHYSICS

Work Packages main aim

The second ESS source will generate very cold neutrons with 1000 times the intensity of any other facility on Earth. This has great importance for fundamental physics, which is often reliant on detecting incredibly rare particle behaviour in support of new theories: the greater the particle intensity, the greater the chance of spotting such behaviour. Led by Stockholm University in Sweden, this work package will provide a conceptual design for an experiment called NNBAR that will search for neutron–antineutron conversions. These conversions would provide the first experimental evidence for the violation of so-called baryon number. Baryon number violation is needed to explain the universe today is dominated by matter, with very little antimatter.

The experiment probes mass scales beyond those available at any collider and, in addition to addressing the matter-antimatter problem, could provide evidence for topical theories of new physics such as supersymmetry and extra dimensions. NNBAR is an international collaboration. The fundamental experimental goal is to provide a sensitivity to neutron to antineutron conversions with a sensitivity improvement of three orders of magnitude compared with earlier work. The unique nature of the Large Beam Port at the ESS together with advances in neutronics drive this improvement.

Conceptual design of the NNBAR experiment.
NNBAR will look for neutrons converting to anti-neutrons with a sensitivity 1000 times greater than previously achieved.
NNBAR is an international collaboration
The experiment probes open questions in modern physics such as the origin of the matter-antimatter symmetry.
NNBAR is made possible by a new lower moderator and the ESS Large Beam Port.
The Institut Laue-Langevin is mainly responsible for the design of the neutron focusing system.
Stockholm University is mainly responsible for the design of the detector and study of sensitive observables for an annihilation signature of anti-neutrons against a target.
The WP includes the quantification and optimisation of the experiment’s sensitivity, using simulations of the annihilation signature and background sources (spallation and non-spallation).

About

Drawing input from eight European research institutions, and with a budget of €3m over three years from the EU’s Horizon 2020 programme, the project will produce a groundbreaking design for a second source of ESS neutrons. As a result, it will show how the ESS can be not only the most brilliant neutron source in the world, but also the most intense, able to probe everyday materials and tackle fundamental questions in physics with up to 1,000 times the sensitivity found anywhere else.