Scattering in Particle Physics, Form Factors of the Nucleons, Introduction to QFT, Partons, Particle Distribution Functions(PDF), Quarks and Gluons, Freymann diagrams, Meson decay & excitations, electron-positron collisions,
1) non-relativitic /i .
e no
spin)
2) charged point particles
3) no recoil
Rutherford scattering is not a
complete model ,
we need to modify .
it
, 1)
Introducing relativity
:
· In
Rutherford model , we have
neglected the
spins of the particle and the
target .
ISE is a non-relativistic &M a it does not involve
spin)
At relativistic energies , Rutherford cross-
section is modified by spin effects .
Mott's scattering describes electron
·
scattering
and includes effects electron
due to the
spin :
It matt =
Inlaut11-B-sin 1612)) .
where p=
When /
·
& >
-
It matt =
Int Cos
Helicity :
- normalized
So values : #
only have
2
·
Particles with
spin pointing in the direction of their
have
motion
helicity +1
J
, spin
> F
1
-
& > => n =
Particles direction
with
spin pointing in the
opposite
their have
of motion
helicity -1
pin F
>
= n = -
1
&
·
Helicity is conserved
.
H-momentum , spin momentum are conserved ,
then
So is
helicity .
·
Backscattering a
particle off of a nucleus :
spin
>
#
IIII
-
Before :
& 7
spin
= = h =
1
2- Proton
After
:
case I : Spin I
>
#
IIII
-
= h=
spin
=
& E
2- Proton
Not allowed , as
helicity should be conserved
spin
Lase 2 :
- E IIII = = h 1
spin
=
2- Proton
momentum should be conserved
Not allowed , as
spin
=> We need to involve the
spin of the
proton
both and
we can Conserve
helicity momentum
by flipping proton spir
, spin Spin
&
>
-
F
Before :
IIII spin
0 = h 1
= =
& 7
2-
Proton
After
:
spin
. spin >
t #
& E 1//I Spin
= o => h=
2- Proton
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