4e : the quantum universemodphys.ucsd.edu/4es04/slides/4electure32-may28.pdf4e : the quantum...
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4E : The Quantum Universe
Lecture 32, May 28 Vivek Sharma
Quiz 5 will be based on Ch 8 from Serway BookPl. review HW problems from last 2 weeks
8
Cosmic Ray Smashing Through Nucleus
Nuclear debris
High energy Sulphur
Pions (16)
Fluorine
Hadrons !
11
Relativistic Force & Acceleration
21 ( / )mup mu
u cγ= =
−
( )
3/ 22
2
3/ 22
1 ( / )
: Relativistic Force1 ( / )
Since Acceleration [rate of change of velocity] a =
,
Fa =
Note: As / 1, a 0 !!!!Its hard
1 ( / )
e
m
r
dp d muFdt dt u c
mFu c
u c
dudt
dudt
u c⎡ ⎤−⎣ ⎦
⎛ ⎞⎜ ⎟= =⎜ ⎟−⎝ ⎠
⎡ ⎤⎢ ⎥=⎢ ⎥−⎣ ⎦
⇒
→ → to accelerate when you get
closer to speed of light
Relativistic Force And
Acceleration
Reason why you cant quite get up to the speed of light no matter how hard you try!
12
Linear Particle Accelerator : Parallel Plates With Potential Difference
V
+- F=-eE
EE= V/dF= -eE
Parallel Plates
d
e-
3/ 2 3/ 22 2
2 2
Charged particle q moves in straight line
in a uniform electric field E with speed u
accelarates under f F=qE
a 1 =
orce
larger
1
the potential difference V a
du F u qE udt m c m c
⎛ ⎞ ⎛ ⎞= = − −⎜ ⎟ ⎜ ⎟
⎝ ⎠ ⎝ ⎠cross
plates, larger the force on particle
Under force, work is done on the particle, it gains
Kinetic energy
New Unit of Energy
1 eV = 1.6x10-19 Joules1 MeV = 1.6x10-13 Joules1 GeV = 1.6x10-10 Joules
13
Linear Accelerator : 50 Billion Volts Accelerating Potential
PEPPEP--II accelerator schematic and tunnel viewII accelerator schematic and tunnel view
3 / 22eEa = 1 ( / )m
u c⎡ ⎤−⎣ ⎦
15
High Energy Proton smashing into a Proton Rich Target
Incident proton
Electron knockedOut of an atom
(road kill !)
Λ0 → p π-
7 charged pions
7 pions, 1 Kaon, 1 proton
16
Magnetic Confinement & Circular Particle Accelerator V
2
2
ClassicallyvF mr
vqvB mr
=
=BF
B
r
2
2
( )
(Centripetal accelaration)
dp d mu duF m quBdt dt dt
du udt r
um quB mu qBr p qBr
r
γ γ
γ γ
= = = =
=
⇒ == ⇒ =
17
Charged Form of Matter & Anti-Matter in a B Field
Antimatter form of electron = Positron (e+)Same Mass but opposite Charge
Positron curls the other way from electron in a B Field
20
Circular Particle Accelerator: LEP @ CERN, Geneve
circular track for accelerating electron
Geneva Airport
Accelerated electron through an effective voltage of 100 Billion Volts !To be upgraded to 7 trillion Volts by 2007
SwissBorder
FrenchBorder
30
Some Quantum Numbers of Quarks
Composite Particles are made of Quarks held by “glue”Proton = (uud); Neutron = (udd), Pion+ = (u dbar), K+ = (sbar d)
31
Some Open Questions In Particle Physics
• How do particles get the masses they have?– Physicists believe particle masses are generated by interaction with a
mysterious field that permeates the entire universe• Stronger the particle interacts with the field, the more massive it is
– It could be a new fundamental field called HIGGS field– Or it may be a composite object made of new particles (techniquarks) tightly
bound together by a new force (technicolor!)
• Whatever the nature of this mass mechanism, odds are solid that it will be produced when beams of protons with energy of 7 TRILLION eV collide at the LHC accelerator– Could be seen as one or many new Higgs particle
• If the Universe is made of >4 dimensions, some of the extra dimensions could “pop” out in these violent collisions
• Little blackholes could also be produced in these high energy interactions….and the detector will catch them in action !!