Photo of Particles Interacting within a Bubble Chamber

Fermilab bubble chamber: 4.6 m in diameter in a 3 T magnetic field

How does a bubble chamber work ?

How can you analyze

this image ?

How does a bubble chamber function ?

How can you analyze the image ?

Apply the Conservation of Momentum to a head-on collision between

a positron and an electron

Relate the movement of the deflected particles with their charge

and the direction of the magnetic field

Relate the movement of the Compton Electrons with the direction of the magnetic field

Relate the materialization of particle pairs (matter & antimatter)

to the energy of the photon which preceded them

Relate the movement of the Compton Electrons

with the direction of the magnetic field.

Notice the trajectory of the spiraling lone electron, indicated by the arrow. This electron was knocked away from the atom that originally held it by a high energy photon.

Identify the other examples of this interaction in the picture above

Why isn’t the photon visible ?

What is the direction of the magnetic field?

Relate the movement of the deflected particles with their charge and the direction of the magnetic field.

Notice the trajectory of the spiraling lone electron, indicated by the arrow. This electron was knocked away from the atom that originally held it by a high energy photon.

Remember the Lorentz Force

BvqF

F

x

y

zF

vq

B

B

What is the relationship between the movement of the deflected particles with their charge and the direction of the

applied magnetic field.

Why isn’t the photon visible ?

• A charged particle travelling through the same medium interacts with it trough Coulomb’s Force. In this way it transfers enough energy to initiate the liquid boiling and leaving behind a trail of small bubbles.

• A photon does not possess an electric charge. Therefore, it does not transfer energy to the medium. Hence, it does not cause the initiation of boiling along its path, therefore you get no bubbles.

What other particles would not leave a track in a bubble chamber ?

Relate the movement of the deflected particles with their

charge and the direction of the magnetic field

B

A

B

An electron ( e - ) and a positron (e + )leave the tracks shown in the picture.

Which is which?

Relate the movement of the deflected particles with their

charge and the direction of the magnetic field

B

A

B

An electron ( e - ) and a positron (e + )leave the tracks shown in the picture.

The particle that deflects to the right ( track B) is an electron ( e- ).

The particle that deflects to the left ( track A) is a positron ( e+ ).

Explain the materialization of particle pairs (matter & antimatter)

to the energy of the photon which preceded them

One of the photons emitted at C travels to D where it interacts with a nucleus from the liquid and materializes into an electron/positron pair. To a good approximation, all of photon’s energy is shared by the e-/e+ pair.

Calculate the kinetic energy of the materialized system, knowing that the linear

momentum of the photon is 26531 MeV/c . ( me =0,511Mev/c2 )

DC

e-

e+

Calculate the kinetic energy of the materialized system, knowing that the linear

momentum of the photon is 26531 MeV/c . ( me =0,511Mev/c2 )

E =h

p=h/

Eo= mc2

E = 2Eo + K(e-,e+)

DC

e-

e+

Apply the Conservation of Momentum to a head-on collision

between a positron and an electron

E

At point E a rare event took place:the positron track changed into a negative track. What happened was that the positron made a head-on collision with an electron.

What is the linear momentum of the electron if the incoming positron’s linear momentum was 54±15MeV/c?

(melecton=mpositron)