Muon decay

[elas]

The diagram on:

http://www.bnl.gov/bnlweb/pubaf/pr/2001/g-2_backgrounder.htm

shows the muon decay occuring in the direction of the spin axis, but the text states that decay occurs in the direction of the spin itself (i.e. at 90 degrees to the direction of the axis); can someone tell me which is correct.

[swansont]

QUOTE=elas;573020]The diagram on:

http://www.bnl.gov/bnlweb/pubaf/pr/2001/g-2_backgrounder.htm

shows the muon decay occuring in the direction of the spin axis, but the text states that decay occurs in the direction of the spin itself (i.e. at 90 degrees to the direction of the axis); can someone tell me which is correct.

 

I don't see where it says that the decay is 90 degrees to the spin axis.

 

"Direction of the spin" means the same thing as "direction of the spin axis"

[elas]

QUOTE=elas']The diagram on:

http://www.bnl.gov/bnlweb/pubaf/pr/2001/g-2_backgrounder.htm

shows the muon decay occuring in the direction of the spin axis, but the text states that decay occurs in the direction of the spin itself (i.e. at 90 degrees to the direction of the axis); can someone tell me which is correct.

 

I don't see where it says that the decay is 90 degrees to the spin axis.

 

"Direction of the spin" means the same thing as "direction of the spin axis"

 

Thanks for your reply which clarifies the issue.

I,m not going to ask why physicists think that clockwise or counter clockwise (i.e. the direction of spin) is the same as moving forward or backward (i.e. in the axial direction) or why a particle that decays is listed as elementary; I will just take that as read.

[swansont]

The page explains that the particles were prepared that way (spin polarized), so that the spin axis was aligned with the motion. Or were you talking about why the spin axis is the direction of the spin? That's by convention, because it's the classical direction of angular momentum, which is a cross product ([math]\vec{r} \times \vec{p}[/math])

[elas]

Checking out the discussion on:

 

http://en.wikipedia.org/wiki/Talk:Angular_momentum#Angular_Momentum_in_layman.27s_terms

 

I see that confusion reigns even amongst the well educated, but I also found:

 

http://www.g-2.bnl.gov/publications/ff/EPNd.htm

 

that, in my opinion; is more useful than the reference used to start this forum. The confusion seems to arise from the professional unification of 'spin' (rotation) and 'direction' which laymen would not expect to be connected. The relationship is of course, due to the nature of the (magnetic) field; no such connection exists in a gravity field as is shown by planetary spin.

 

Also missing from ‘the overview of the experiment’ is the important fact (stated in 2nd ref.) that the value of the magnetic moment varies in proportion to the energy of the muon.

Edited June 26, 2010 by elas

[swansont]

There are many things in physics that they layman would not be expected to understand. There are things in any field of study that a layman would not be expected to understand.

[elas]

There are many things in physics that they layman would not be expected to understand. There are things in any field of study that a layman would not be expected to understand.

 

We are of course back to our long standing difference, my view being 'that anything can be understood if it is properly explained in words'; but the mathematicians who have taken over from scientist in the field of physics say it can be understood only in numbers. People like Lee Smolin, who has gone to great lengths to explain string, bane, M and loop quantum gravity in words; are so few and so difficult to find: We desparately need a modern Dr. Brownoski.