Muon Scattering Experiment - Muscat

The currently favoured technique for the cooling of muons for a neutrino factory and, particularly, for a muon collider is ionisation cooling. In this, the cooling is achieved by passing the muons through matter, in which they lose both longitudinal and transverse momentum via ionisation energy loss, dE/dx. In ionisation cooling, the lost longitudinal momentum is restored using rf cavities, giving a net reduction in transverse momentum.

However, this process is a delicate balance between the cooling coming from the energy loss and a heating effect coming from multiple scattering. Currently, there are no directly relevant measurements of the multiple scattering and all studies of ionisation cooling performed to date have relied on theory for this. However, the most relevant data, coming 55 year old electron scattering measurements, suggest there may be a problem with the theory for elements with low Z. A comparison between data and Moliere theory shows no problems for aluminium, a small discrepancy for beryllium and a big discrepancy for lithium. This trend with Z is worrying as the favoured element for ionisation cooling is liquid hydrogen.

As a result, an experiment to measure the multiple scattering of muons from various targets and compare it with a number of scattering theories has been constructed and run. The targets used are:

Liquid hydrogen
Lithium
Beryllium
Aluminium
Carbon
Polyethylene
Iron
Data were taken at the TRIUMF laboratory in Vancouver in 2000 and 2003. These have now been analysed and the results are being published in a paper.

A further experiment called MICE is currently under construction at the Rutherford Appleton Laboratory to measure ionisation cooling itself.

If you are interested in participating or would like more information, please contact Rob Edgecock

Further information:

Here are some photographs of the experiment in 2000 and 2003.

Mail the whole collaboration

Bill Murray's muon scattering page

This page is under development. If you have any additions to it, please let me know.

Rob Edgecock