Re: new note on muon background

From: Joseph Formaggio (
Date: Thu Jul 14 2005 - 00:43:21 CDT

Hi Jon,

    Sorry I was unable to attend today's discussion. However, I wonder
if the following article might be of revelance to your discussions.

    Hope it helps.

Jonathan Link wrote:

> Greetings Alfred,
> Thanks again for looking into this interesting issue. I look forward
> to you following up on this problem as a Braidwwod collaborator.
> Unfortunately I don't believe that your calculation is correct. As a
> though experiment I considered the worst case muon (the muon that has
> the largest possible path length in the shaft and still make it into
> our detector. This muon enters the shaft at the top edge at the
> furthest point away from the center of the detector. The ratio of the
> muon path in the shaft to the total path to the detector is just
> proportional to the ratio of shaft diameter to the distance from the
> detector to the far wall of the shaft (proportional right
> triangles). Consider your rho of 3 meters and 5 meters radius case.
> Then this ratio is 10/35~0.3, so at most the muon sees 30% less
> shielding. If we consider that all muons see 30% less shielding then
> this is like going from 450 mwe to 315 mwe. This, of course, is a
> large overestimate because the entire shaft subtends less that 6% of
> the total azimuthal angle about the detector. Nevertheless, the muon
> rate for 300 mwe is only 2.7 times higher that at 450 mwe (not 4
> times) and the mean muon energy is about 63 GeV (not 44).
> Your methodology seems plausible, so I assume that there must be some
> bug and I encourage you continue working on this question so that we
> have a ready answer when we need it, but it appears to me that this
> real effect must be much smaller.
> Thanks,
> Jon Link
> Matthew Worcester wrote:
>> Hi all,
>> I've posted a new note, "Effects of a Vertical Shaft to Muon
>> Background", by Alfred Tang, currently at the Chinese University of
>> Hong Kong, to the Braidwood site. The note details his modified
>> Gaisser parameterization for surface muons, a different approach than
>> the fit to data used by Martina and Jim's study. His more detailed
>> MAND-sim talk on this work is also available at:
>> His note also gives very interesting results from a study of the
>> effect of a vertical shaft near the detector on the underground muon
>> flux. Thanks again to Alfred for graciously sending such a nice
>> writeup. If you have any questions on the note, please include him
>> on the email.
>> Cheers,
>> Matt

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