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Science Forum Index » Physics - Particle Forum » Spin 1/2 Baryons Question?
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| Jim King |
 Posted: Sat Dec 02, 2006 2:18 pm |
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Guest
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Hello,
Could someone please give me an explanation for the fact that spin 1/2
Baryons in the octet
cannot consist of three quarks of the same flavor as the Delta++ for
example.
THX
Jim. |
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| Autymn D. C. |
| Posted: Sun Dec 03, 2006 9:14 am |
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Jim King wrote:
Quote: Could someone please give me an explanation for the fact that spin 1/2
Baryons in the octet
cannot consist of three quarks of the same flavor as the Delta++ for
example.
The spin of u is +1/2, so three of them make +3/2. Alike quarks repel,
so they don't orbit withwise to make +.5+.5-.5. Besides, the Deltas
decay into a nucleòn (1/2) and a piòn (1), so a Delta is not a
nucleòn by definition.
-Aut |
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| Meir Achuz |
| Posted: Wed Dec 06, 2006 11:26 am |
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Jim King Wrote:
Quote: Hello,
Could someone please give me an explanation for the fact that spin 1/2
Baryons in the octet
cannot consist of three quarks of the same flavor as the Delta++ for
example.
THX
Jim.
The three fermion quarks in a baryon are in a completely antisymmetric
state with respect to color. The Pauli principle then requires that
the spin-space wave function be completely symmetric with respect to
quark interchange for three identical u quarks. The assumption is made
that the spatial wave function is completely symmetric and has no
internal or total orbital angular momentum. This means that the spin
state for the three u quarks must be completely symmetric under quark
interchange, and the quark spins must add up to the spin of the
baryon.
The spin state for 1/2+1/2+1/2=3/2 is completely symmetric and
corresponds to the Delta++.
The spin state for 1/2+1/2+1/2=1/2 has mixed symmetry, and so cannot
exist for three u quarks.
--
Meir Achuz |
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| Jim King |
| Posted: Wed Dec 06, 2006 3:38 pm |
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Guest
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Thank You Meir,
But why cant the Baryon spin state for quark flavors (u,u,u) be this
symmetric combination.
(++-) + (+-+) + (-++)
?
"Meir Achuz" <Meir.Achuz.2iekfg@physicsbanter.com> wrote in message
news:Meir.Achuz.2iekfg@physicsbanter.com...
Quote:
Jim King Wrote:
Hello,
Could someone please give me an explanation for the fact that spin 1/2
Baryons in the octet
cannot consist of three quarks of the same flavor as the Delta++ for
example.
THX
Jim.
The three fermion quarks in a baryon are in a completely antisymmetric
state with respect to color. The Pauli principle then requires that
the spin-space wave function be completely symmetric with respect to
quark interchange for three identical u quarks. The assumption is made
that the spatial wave function is completely symmetric and has no
internal or total orbital angular momentum. This means that the spin
state for the three u quarks must be completely symmetric under quark
interchange, and the quark spins must add up to the spin of the
baryon.
The spin state for 1/2+1/2+1/2=3/2 is completely symmetric and
corresponds to the Delta++.
The spin state for 1/2+1/2+1/2=1/2 has mixed symmetry, and so cannot
exist for three u quarks.
--
Meir Achuz |
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| Autymn D. C. |
| Posted: Wed Dec 06, 2006 7:34 pm |
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