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What good are muons?
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timrobinson@paradise.net.
science forum addict


Joined: 22 Sep 2005
Posts: 76

PostPosted: Sat Jun 24, 2006 1:39 am    Post subject: What good are muons? Reply with quote

How would the universe be different if there were only one grade of
lepton?
And how would our daily lives be different if muons had not been
discovered?
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ebunn@lfa221051.richmond.
science forum beginner


Joined: 21 Sep 2005
Posts: 38

PostPosted: Sat Jun 24, 2006 9:13 pm    Post subject: Re: What good are muons? Reply with quote

In article <1151108962.760596.111660@m73g2000cwd.googlegroups.com>,
Dr Tim <timrobinson@paradise.net.nz> wrote:
Quote:
How would the universe be different if there were only one grade of
lepton?

There'd be a bit less helium, for one thing. If there were only one species
of neutrino, the Universe would have been expanding a bit slower during the
time of big bang nucleosynthesis, when the light elements were being produced
during the first minute or so after the big bang. That means more neutrons
would have had a chance to decay before getting bound into helium atoms.

The difference in helium abundance would only be a few percent. You have
my permission to be unimpressed. Presumably others will come up with
something more exciting.

-Ted

--
[E-mail me at name@domain.edu, as opposed to name@machine.domain.edu.]
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tuppence
science forum beginner


Joined: 05 May 2005
Posts: 13

PostPosted: Sun Jun 25, 2006 2:20 am    Post subject: Re: What good are muons? Reply with quote

"Dr Tim" <timrobinson@paradise.net.nz> wrote in message
news:1151108962.760596.111660@m73g2000cwd.googlegroups.com...
Quote:
How would the universe be different if there were only one grade of
lepton?
And how would our daily lives be different if muons had not been
discovered?

As you know, the question asked by professor I I Rabi after the discovery of
the muon was: "Who ordered that?". I haven't yet seen a satisying answer.
But, I still want to believe that muon-catalyzed fusion of deuterium nuclei
is a viable way to achieve an "unlimited" safe energy source ... although I
know better, based on experimental evidence, etc. But, I wonder if anyone
else has calculated the properties of a lepton, mass and lifetime, that
would provide for optimum D-D-catalyzed fusion for energy production without
the possibility of being used in a sinister way?
SL
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Tom Roberts
science forum Guru


Joined: 24 Mar 2005
Posts: 1399

PostPosted: Sun Jun 25, 2006 12:53 pm    Post subject: Re: What good are muons? Reply with quote

Dr Tim wrote:
Quote:
How would the universe be different if there were only one grade of
lepton?

Probably not very much, at lest as understood today. But who can say
with any confidence what effects the first milli-microsecond after the
big bang have had?


Quote:
And how would our daily lives be different if muons had not been
discovered?

I don't know about yours, but _mine_ would be vastly different without
muons to think about. My current research interest is in designing and
demonstrating the feasibility of a muon collider, hopefully leading to
the construction of a machine to reach a whole new energy frontier.

The basic problem for the future of High Energy Physics is that the LHC
pretty much tops out what a proton synchrotron can do -- it seems quite
unlikely we will ever build a hadron machine with significantly more
energy in the center of mass. And electron machines have an inherent
limit around 0.5 TeV, including the hoped-to-be International Linear
Collider. While that's comparable to the LHC energy (because electrons
are elementary while protons are composite), its not a new energy regime
beyond the LHC.

A muon collider, on the other hand, could reach 5 TeV in the center of
mass, which is significantly above the LHC or ILC, leading to a new
energy frontier. The challenge, of course, is to capture, accelerate,
and collide muons within their short lifetime of 2.2 microseconds, with
enough luminosity to be useful. We're working on that, and simulations
show it appears to be feasible as long as the engineering details work
out. So we are preparing demonstration experiments to test and
demonstrate those details.

Some links:
http://www.muonsinc.com/index.html
http://mice.iit.edu/
http://www.fnal.gov/projects/muon_collider/cool/cool.html
http://www.cap.bnl.gov/mumu/


So my answer to "What good are muons?" is: they are potentially a
tremendous research tool for High Energy Physics, permitting access to
an energy domain that is simply unreachable without them.

The history of HEP is that _every_ new machine with an energy at least
~5 times larger than the previous machines has produced fundamentally
new phenomena. There are good indications that the Tevatron->LHC
increase will likewise provide surprises, and tantalizingly frustrating
indications that the LHC and ILC won't be high enough to teach us all we
need to learn....


Tom Roberts
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Tom Roberts
science forum Guru


Joined: 24 Mar 2005
Posts: 1399

PostPosted: Sun Jun 25, 2006 12:53 pm    Post subject: Re: What good are muons? Reply with quote

Dr Tim wrote:
Quote:
How would the universe be different if there were only one grade of
lepton?

I'm not sure about the universe, but consider life on earth:

Life on earth would surely have evolved considerably differently without
the constant bombardment of muons from cosmic rays entering the upper
atmosphere. At the earth's surface the cosmic radiation is >99% muons
(ignoring neutrinos), and they are an important source of the random
mutations in the genome that provide "raw material" for survival of the
fittest to work upon to generate the evolution of new species. Given the
idiosyncratic history of evolution here on earth, if it had been slowed
down by even 0.1% we humans would not be here yet; of course without
muon-induced mutations the history of evolution would surely be quite
different, with little likelihood of human-like creatures ever appearing
-- that's my point.


Electrons and hadrons produced in the upper atmosphere by interactions
of primary cosmic rays cannot reach the surface (electrons shower, and
hadrons decay or interact); neutrinos reach the surface but don't
interact enough to matter. Those primary cosmic rays are mostly protons,
and their interactions produce copious pions, most of which then decay
into muons which can and do reach the surface. There are other particles
produced, which ultimately interact or decay, and the only particles
reaching the surface in significant numbers are muons and neutrinos.


Tom Roberts
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Igor Khavkine
science forum Guru


Joined: 01 May 2005
Posts: 607

PostPosted: Sun Jun 25, 2006 5:28 pm    Post subject: Re: What good are muons? Reply with quote

Dr Tim wrote:
Quote:
How would the universe be different if there were only one grade of
lepton?
And how would our daily lives be different if muons had not been
discovered?

Probably the biggest impact the discovery of muons had was on the lives
of physicists who've written their dissertations and papers on their
properties. :-)

Aside from particle physics implications, muons are also a useful tool
in investigating magnetic (especially anti-ferromagnetic) materials.
The technique is called muon spin resonance or ÁSR. A muon's magnetic
moment is sensitive to local magnetic fields inside a crystal. Its
orientation and precession frequency can be measured by observing the
pattern of emitted electron or positron radiation that results when the
muons decay.

A couple of nice descriptions of the technique can be found here:

http://lmu.web.psi.ch/about/aboutmuons.html
http://msl.kek.jp/mSR/about_muon/index.html

Hope this helps.

Igor
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Ken S. Tucker
science forum Guru


Joined: 30 Apr 2005
Posts: 1230

PostPosted: Mon Jun 26, 2006 10:50 pm    Post subject: Re: What good are muons? Reply with quote

Tom Roberts wrote:
Quote:
Dr Tim wrote:
How would the universe be different if there were only one grade of
lepton?

I'm not sure about the universe, but consider life on earth:

Life on earth would surely have evolved considerably differently without
the constant bombardment of muons from cosmic rays entering the upper
atmosphere. At the earth's surface the cosmic radiation is >99% muons
(ignoring neutrinos), and they are an important source of the random
mutations in the genome that provide "raw material" for survival of the
fittest to work upon to generate the evolution of new species.

I should mention building codes now insist upon
a plastic sheet to keep radon gas - which is classed
as a mutating carcinogen - out of the house.
What has me puzzled is the optimum radiation
energy to accelerate evolution, for example, too
much is deadly, and too little ineffective, but can
the actual energy of the radiation itself be a factor,
intensity aside.
IOW's could the frequency of the radiation be a
significant factor in the positive mutation rendering
the evolution of the human species?
I'm wondering if radiation from the ground swamps
the muon radation where evolution is concerned?
Regards
KST
...
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mARK3
science forum beginner


Joined: 27 Jun 2006
Posts: 1

PostPosted: Tue Jun 27, 2006 8:06 pm    Post subject: Re: What good are muons? Reply with quote

Ken S. Tucker wrote:

Quote:
What has me puzzled is the optimum radiation
energy to accelerate evolution,

evolution runs on genetic variation. only a very small amount of that
is due to radiation, and only a small part of THAT is cosmic radiation.
sexual reassortment and chromosomal transpositions are more important.
and there is chemically-induced mutation too. radiation isn't really
any kind of evolutionary driver.
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Jman
science forum beginner


Joined: 16 Jun 2006
Posts: 6

PostPosted: Tue Jun 27, 2006 8:06 pm    Post subject: Re: What good are muons? Reply with quote

Quote:
Dr Tim wrote:
How would the universe be different if there were only one grade of
lepton?

Well, for one thing, our Standard Model of particle physics would have
a lot more problems...
If there was only one grade of lepton, then we would have four families
of quarks but only one family of leptons, which would quite succinctly
destroy all those beautiful multiplets that Gell-Mann thought up.

Moreover, we would lose several parameters in the QED Lagrangian,
ratios of particle to particle mass would no longer be coherent, the
CKM matrix would most likely not exist..

The list goes on.

J.
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markwh04@yahoo.com
science forum Guru Wannabe


Joined: 12 Sep 2005
Posts: 137

PostPosted: Fri Jun 30, 2006 8:21 pm    Post subject: Re: What good are muons? Reply with quote

Tom Roberts wrote:
Quote:
Dr Tim wrote:
How would the universe be different if there were only one grade of
lepton?

I'm not sure about the universe, but consider life on earth:

Life on earth would surely have evolved considerably differently without
the constant bombardment of muons from cosmic rays entering the upper
atmosphere.

If this is significantly affected by the question of whether there are
muons present or not in the universe, then the difference between the
two universes cascades much further down the line from here. Lightning,
as is now known, is triggered by cosmic rays.
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