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Golden Boar
science forum Guru
Joined: 17 May 2005
Posts: 651
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 Posted: Fri May 20, 2005 4:33 pm Post subject:
Electron and Positron Question
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"For each kind of particle, there is an associated antiparticle with
the same mass but opposite electromagnetic, weak, and strong charges,
as well as spin." from wiki.
Electrons and positrons can have a spin of +1/2 or -1/2, so if an
electron and positron both have the same spin, they are not
anti-particles of each other.
Is my statement correct?
Is the above definition wrong?
I am I missing something? |
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PD
science forum Guru
Joined: 03 May 2005
Posts: 4363
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| Posted: Fri May 20, 2005 5:45 pm Post subject:
Re: Electron and Positron Question
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Golden Boar wrote:
| Quote: | "For each kind of particle, there is an associated antiparticle with
the same mass but opposite electromagnetic, weak, and strong charges,
as well as spin." from wiki.
Electrons and positrons can have a spin of +1/2 or -1/2, so if an
electron and positron both have the same spin, they are not
anti-particles of each other.
Is my statement correct?
Is the above definition wrong?
I am I missing something?
|
Your statement is not quite right, and the definition is not quite
right.
The electron has spin 1/2 (only). It can have spin *projections* of
+1/2 or -1/2 with respect to an external axis.
In addition, antiparticles have the same spin quantum number as their
particles. Thus, anti-electrons also have spin 1/2.
PD |
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FrediFizzx
science forum Guru
Joined: 01 May 2005
Posts: 774
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| Posted: Fri May 20, 2005 6:35 pm Post subject:
Re: Electron and Positron Question
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"Golden Boar" <goldenboar@hotmail.com> wrote in message
news:1116614030.609788.156290@g49g2000cwa.googlegroups.com...
| "For each kind of particle, there is an associated antiparticle with
| the same mass but opposite electromagnetic, weak, and strong charges,
| as well as spin." from wiki.
|
| Electrons and positrons can have a spin of +1/2 or -1/2, so if an
| electron and positron both have the same spin, they are not
| anti-particles of each other.
|
| Is my statement correct?
| Is the above definition wrong?
| I am I missing something?
Your statement is wrong. Yes, you are missing something--a good
particle physics book. ;-)
FrediFizzx |
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Jim Heckman
science forum Guru Wannabe
Joined: 28 Apr 2005
Posts: 121
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| Posted: Fri May 20, 2005 10:09 pm Post subject:
Re: Electron and Positron Question
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On 20-May-2005, "Golden Boar" <goldenboar@hotmail.com>
wrote in message <1116614121.663692.217300@f14g2000cwb.googlegroups.com>:
| Quote: | "For each kind of particle, there is an associated antiparticle with
the same mass but opposite electromagnetic, weak, and strong charges,
as well as spin." from wiki.
Electrons and positrons can have a spin of +1/2 or -1/2, so if an
electron and positron both have the same spin, they are not
anti-particles of each other.
Is my statement correct?
Is the above definition wrong?
I am I missing something?
|
The above definition is incorrect, or at least very poorly worded. A
particle and its antiparticle have the same spin.
I'm also not sure how useful it is to say that particles and
antiparticles have opposite weak and strong charges, since these forces
are mediated by non-abelian gauge forces, unlike electromagnetism
whose gauge force is abelian. In non-abelian forces the gauge bosons
carry gauge-field charge and so interacting leptons and quarks are
constantly changing their weak and strong charges via exchange of real
or virtual W and Z bosons and gluons.
--
Jim Heckman |
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Old Man
science forum Guru Wannabe
Joined: 04 May 2005
Posts: 101
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| Posted: Sat May 21, 2005 1:00 am Post subject:
Re: Electron and Positron Question
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"Golden Boar" <goldenboar@hotmail.com> wrote in message
news:1116614030.609788.156290@g49g2000cwa.googlegroups.com...
| Quote: | "For each kind of particle, there is an associated antiparticle with
the same mass but opposite electromagnetic, weak, and strong
charges, as well as spin." from wiki.
|
The part about spin is wrong. With respect to spin
projection, the positron's magnetic moment may be
of opposite sign to that of the electron's, which to
zeroeth order, is given by the Bohr magneton:
mu_e ~ mu_B = e * hbar / 2 * m_e
| Quote: | Electrons and positrons can have a spin of +1/2 or -1/2,
|
That's not spin. That's spin projection.
| Quote: | so if an
electron and positron both have the same spin, they are not
anti-particles of each other.
|
Wrong
| Quote: | Is my statement correct?
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No.
| Quote: | Is the above definition wrong?
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Parrtly.
| Quote: | I am I missing something?
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Yes:
Lepton Spin ( S = 1 / 2 > 0 )
Lepton spin projection ( S_z = - S or + S )
[Old Man] |
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Edward Green
science forum addict
Joined: 21 May 2005
Posts: 95
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| Posted: Sat May 21, 2005 12:48 pm Post subject:
Re: Electron and Positron Question
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Old Man wrote:
| Quote: | Lepton Spin ( S = 1 / 2 > 0 )
Lepton spin projection ( S_z = - S or + S )
|
Hi Old Man. May I ask a question deeply mired in ignorance?
Ok. How can the "projection" of spin have the same magnitude as spin
itself? Unless of course the damn thing is alligned with the
projection axis: but somehow I never pictured that as being the case. |
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drnolittle
science forum beginner
Joined: 12 May 2005
Posts: 11
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| Posted: Sat May 21, 2005 1:39 pm Post subject:
Re: Electron and Positron Question
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Old Man wrote:
| Quote: | "Golden Boar" <goldenboar@hotmail.com> wrote in message
news:1116614030.609788.156290@g49g2000cwa.googlegroups.com...
"For each kind of particle, there is an associated antiparticle
with
the same mass but opposite electromagnetic, weak, and strong
charges, as well as spin." from wiki.
The part about spin is wrong. With respect to spin
projection, the positron's magnetic moment may be
of opposite sign to that of the electron's, which to
zeroeth order, is given by the Bohr magneton:
mu_e ~ mu_B = e * hbar / 2 * m_e
Electrons and positrons can have a spin of +1/2 or -1/2,
That's not spin. That's spin projection.
so if an
electron and positron both have the same spin, they are not
anti-particles of each other.
Wrong
Is my statement correct?
No.
Is the above definition wrong?
Parrtly.
I am I missing something?
Yes:
Lepton Spin ( S = 1 / 2 > 0 )
Lepton spin projection ( S_z = - S or + S )
[Old Man]
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my name says it all...
sounds like is related to why we cannot transport matter
target re-assembling has 50/50 chance of being correct position. |
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Old Man
science forum Guru Wannabe
Joined: 04 May 2005
Posts: 101
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| Posted: Sat May 21, 2005 4:38 pm Post subject:
Re: Electron and Positron Question
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"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1116686924.363278.120220@o13g2000cwo.googlegroups.com...
| Quote: | Old Man wrote:
Lepton Spin ( S = 1 / 2 > 0 )
Lepton spin projection ( S_z = - S or + S )
Hi Old Man. May I ask a question deeply mired in ignorance?
Ok. How can the "projection" of spin have the same magnitude as spin
itself? Unless of course the damn thing is alligned with the
projection axis: but somehow I never pictured that as being the case.
|
Been away and back a couple of times since hearing
from Ed Green. Nice to hear from one who enjoys
physics, the lack of which impels one to go-away,
while the want of such tempts one to return.
As for spin projection .... at times, Old Man's
knowledge base is on par with that of a parrot ....
spin and spin projection come in increments of
hbar / 2. So, if spin projection were less than spin,
lepton spin projection would have to be zero. Stern-
Gerlach says that's not so. Is that a cop-out ?
[Old Man] |
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Jim Heckman
science forum Guru Wannabe
Joined: 28 Apr 2005
Posts: 121
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| Posted: Sat May 21, 2005 11:02 pm Post subject:
Re: Electron and Positron Question
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On 21-May-2005, "Edward Green" <spamspamspam3@netzero.com>
wrote in message <1116686924.363278.120220@o13g2000cwo.googlegroups.com>:
| Quote: | Old Man wrote:
Lepton Spin ( S = 1 / 2 > 0 )
Lepton spin projection ( S_z = - S or + S )
Hi Old Man. May I ask a question deeply mired in ignorance?
Ok. How can the "projection" of spin have the same magnitude as spin
itself? Unless of course the damn thing is alligned with the
projection axis: but somehow I never pictured that as being the case.
|
Angular momentum states labeled "j" actually have total angular
momentum j*(j+1) (in units of h/2pi, of course) and possible
projections of -j, -j+1, ..., j-1, +j. So a spin-1/2 particle actually
has total spin 3/4.
--
Jim Heckman |
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Jim Heckman
science forum Guru Wannabe
Joined: 28 Apr 2005
Posts: 121
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| Posted: Sun May 22, 2005 12:53 am Post subject:
Re: Electron and Positron Question
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On 21-May-2005, "Jim Heckman" <wnzrfeurpxzna@lnubb.pbz.invalid>
wrote in message <118vmha3dm1b131@corp.supernews.com>:
| Quote: | On 21-May-2005, "Edward Green" <spamspamspam3@netzero.com
wrote in message <1116686924.363278.120220@o13g2000cwo.googlegroups.com>:
Old Man wrote:
Lepton Spin ( S = 1 / 2 > 0 )
Lepton spin projection ( S_z = - S or + S )
Hi Old Man. May I ask a question deeply mired in ignorance?
Ok. How can the "projection" of spin have the same magnitude as spin
itself? Unless of course the damn thing is alligned with the
projection axis: but somehow I never pictured that as being the case.
Angular momentum states labeled "j" actually have total angular
momentum j*(j+1) (in units of h/2pi, of course)
|
D'oh! Make that sqrt[j*(j+1)]. I was thinking of the eigenvalues of the
J^2 operator, not J itself.
| Quote: | and possible
projections of -j, -j+1, ..., j-1, +j. So a spin-1/2 particle actually
has total spin 3/4.
|
And make that sqrt(3/4).
--
Jim Heckman |
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srp
science forum Guru Wannabe
Joined: 30 Apr 2005
Posts: 198
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| Posted: Sun May 22, 2005 7:14 pm Post subject:
Re: Electron and Positron Question
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"Edward Green" <spamspamspam3@netzero.com> a écrit dans le message de news:
1116686924.363278.120220@o13g2000cwo.googlegroups.com...
| Quote: | Old Man wrote:
Lepton Spin ( S = 1 / 2 > 0 )
Lepton spin projection ( S_z = - S or + S )
Hi Old Man. May I ask a question deeply mired in ignorance?
Ok. How can the "projection" of spin have the same magnitude as spin
itself? Unless of course the damn thing is alligned with the
projection axis: but somehow I never pictured that as being the case.
|
Because S = + or - h_bar/2
And since h_bar is the unit angular momentum plus or minus half of it
ofsets you exactly 90 degrees in either direction.
S_z is also related to magnetism in the following manner:
S_z = mu_B m_e / e
Where mu_B is the Bohr magneton
m_e is the mass of the electron
e is unit electron charge in Coulombs
in this perspective, plus and minus refer to the relative magnetic
orientation of the electron with respect to the magnetic aspect of
other electrons, which can be either parallel (both are plus or both
are minus) or to antiparallel orientation (one is plus the other is minus)
the latter is how the covalent bound is established between two atoms.
André Michaud |
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Y.Porat
science forum Guru
Joined: 04 May 2005
Posts: 1809
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| Posted: Mon May 23, 2005 5:31 am Post subject:
Re: Electron and Positron Question
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if he electron is a 'point particle'
how can it have a 'parallel' or antiparallel' orientation??
parallel and antiparrallel are geometric properties
that is againt the HUP
that tell sus that we cannot know anything geometric about the
electron.
right?? .....
and
'ofsets of 9o degrees in either direction'
all the best
Y.Porat
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srp
science forum Guru Wannabe
Joined: 30 Apr 2005
Posts: 198
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| Posted: Mon May 23, 2005 10:49 am Post subject:
Re: Electron and Positron Question
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"Y.Porat" <maporat@012.net.il> a écrit dans le message de news:
1116833517.914937.187940@g44g2000cwa.googlegroups.com...
| Quote: | if he electron is a 'point particle'
how can it have a 'parallel' or antiparallel' orientation??
|
'Point particle' is only a handy mathematical representation, just like
in Newtonian gravitation, planets and sun are dealt with as if they
were points at their own center of gravity to calculates the orbits.
Obviously, if they can have orientation, and they do, then they cannot
physically be dimensionless points.
| Quote: | parallel and antiparrallel are geometric properties
that is againt the HUP
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I don't think it is. The hup only states that we cannot know at
the same time its localisation and velocity.
| Quote: | that tell sus that we cannot know anything geometric about the
electron.
right?? .....
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Well, we certainly do, in this case. Electrons are electromagnetic
particles, and as such, they have to conform to electromagnetic
orthogonality, which is definitely "geometric".
| Quote: | and
'ofsets of 9o degrees in either direction'
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Generally speaking, the spin can only be at the same time normal to
the velocity vector which, whether expressed or not, is at all times
normal to the electrostatic vector, which is directed towards the
nucleus.
André Michaud |
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Y.Porat
science forum Guru
Joined: 04 May 2005
Posts: 1809
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| Posted: Mon May 23, 2005 1:37 pm Post subject:
Re: Electron and Positron Question
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if so
can we say that in the Deutron nuc
the proton is located next to the Neutron?
is it geometric knowledge??
all the best
Y.Porat
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Y.Porat
science forum Guru
Joined: 04 May 2005
Posts: 1809
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| Posted: Tue May 24, 2005 2:35 am Post subject:
Re: Electron and Positron Question
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No answer???
---------------------
Y.Porat
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