Muon Collider Backgrounds
The backgrounds in the detector at a muon collider
are recognized as a critical issue for the feasibility
of doing physics at this machine. The challenge is to
design a final focus system (magnets plus shielding)
that will bring the backgrounds down to a reasonable
level. The main source of background comes from muon
decay. For example, with 2 x 10^12 muons per bunch at
a 2 x 2 TeV collider there are 2 x 10^5 decays per meter
and the mean energy of the decay electrons is 700 GeV.
Fortunately the decay angle of the electrons is very
small, which means that electrons born very close to the
IP stay in the beampipe untill they are well past the
detector region. For those electrons born further away
there is room to place sweeping magnets and shielding
to reduce the backgrounds they induce in the detector
region by many orders of magnitude.
The design of the shielding and final focus is an
iterative process, with an evaluation of the detector
backgrounds being made at each iteration. Two independent
background calculations have been developed: a MARS based
calculation (N. Mokhov) and a GEANT based calculaion
(I. Stumer). These plus the predicted backgrounds for the
final focus design considered at Snowmass 1996 are described
of the Snowmass muon feasibility study report.
Since then, further improvements to the final focus have
reduced the backgrounds by about an order of magnitude.
Although challenging, in many ways the predicted background
levels are no worse than the corresponding predicted
backgrounds at the LHC .... and we hope for further improvements
to the final focus design in the future.
Muon Collider Detector Issues
Chapter 9 of the Muon Collider Feasibility
Study for the 1996 Snowmass Workshop
Backgrounds and Detector Issues at a Muon Collider,
S. Geer, FERMILAB-Conf-96/313
Last updated July 9, 1998
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