bubble chamber work group

• Targets of our work group• Simple lessons with BC photographs• History of BC• Overview of 50-minutes lesson• FAQs

• To create simple lesson with BC photographs• To update webpage on history of BC• To create 50 minutes modular lesson for teaching BC

concepts• To create webpage of frequently-asked questions (FAQs)

• You can make your own cloud chamber and see tracks of particles produced by cosmic rays

• Click here for instructions• When a charged particle goes through a superheated

liquid, it ionises atoms along its path and makes the liquid boil, creating a trail of bubbles

• Click here for a simulation of bubble formation

A plane in the sky causes water vapour in the air A plane in the sky causes water vapour in the air to condenseto condense

Charged particle in BC causes superheated liquid Charged particle in BC causes superheated liquid to boilto boil

• The different coloured tracks are produced by different charged particles– Bright Green kaon K

– Red electron e

– Blue proton p

• Why are tracks curve? Click here for discussion

A

B

p

e

K

• A particle of charge q travelling through a magnetic field B with a velocity v experiences a force, given by

• We use the formula for the Lorentz force to calculate the value and direction of the force exerted on charged particles by the magnetic field

( )F q v B

• The thumb points in the direction of the force F

• First finger points in the direction of the magnetic field B

• Second finger points in the direction of motion of the positive charge v

• In principle, the momentum of a charged particle is obtained using the formula

p B q r

+ vB

��������������

F��������������

v

F��������������

• Spiralling tracks are common in BC photographs, caused by e or e+

• An e loses energy at a considerable rate as it travels through BC liquid

• All other charged particles, unless they collide with a nucleus, slow down very gradually – get more curved – as they lose energy by ionisation

• e are able to lose energy more quickly by another process in which all accelerated charges radiate

• Click here for more information

Dark tracks belong to a slow particleDark tracks belong to a slow particleSpiralling tracks are Spiralling tracks are ebecause of their very because of their very

small masssmall mass

Particles with large momenta are less curved

Particles with small momenta are more curved

• All physical laws must be fulfilled in every BC event– Momentum conservation– Charge conservation– Energy conservation– Behaviour of moving charged particles in magnetic field– Other physics laws

• The primary (orange) beam has –ve charge while one of the two secondary beams has –ve charge (green) and the other +ve charge (bright green)

• We also know that the two outgoing tracks have low momentum because they curve significantly in B-field

• What is the direction of the momentum of the primary beam?

• Estimate the momenta of the secondary tracks

• What is the total momentum after interaction?

• Clearly the total momentum of the outgoing charged particles does not equal to the momentum of the beam particle

• Draw an arrow to show the “missing” momentum

• Click here for more info

• In all BC photographs, the charge of the particle can be only +e or e

• Sign of particles can be determined by the direction of the track’s curvature

• Click here to find this• The primary beam is K

• What are the charges of secondary particles? [Hint: the red spiral is produced by an electron]

• Green is negative and bright green is positive

• If this event do not involve other particle, total charge before interaction (e) is not equal to the total charge after it (0)

• But the collision involves a proton (+e), so the total charge is conserved

• Here is another picture that could be used for a similar exercise

• Improve and publish a webpage on history of BC– Birth and evolution of BC and its main discoveries– Important photographs– 2 articles on history of BC and personal experience

• PowerPoint on history of BC

Cloud chamberCloud chamberAnderson (1932), positron (eAnderson (1932), positron (e++))

Nuclear EmulsionNuclear EmulsionPowell (1947), pion Powell (1947), pion ++

• It’s faster to reactivate than cloub chambers• The expansion of BC can coincide with the accelerator

cycle• BC were very small initially; only a few cubic centimetre

of liquid• Big European Bubble Chamber (BEBC) in 70’s has a

diameter of 3.7 m

• 1956. Discovery of 0 in a propane BC• 1964. Discovery of which gives acceptance of Gell-

Mann theory of ordering all subatomic particle “eight-fold way”

• 1973. Neutral current discovered at CERN’s 25-ton Gargamelle

• 1975. Discovery of “charmed” baryon in 7-foot Brookhaven

• Research on earlier particle detectors – cloud chamber & nuclear emulsions

• Design a PowerPoint presentation using the contents of the webpage

• Short biographies of the people who developed the BC

• Lesson 1 – “Introduction to BC and Basic Feature of the Interactions”– Photographs, Worksheet 1

• Lesson 2 – “Identifying the Particles and Conservation of momentum & Charge”

• Lesson 3 – “Particle Interactions – Collisions & Decays”• Lesson 4 – “Principle of determination of momentum”

• Lesson 5 – “Principle of determination of energy”• Lesson 6 – “More complex BC photographs”

What does LHC stand for? • Large Hadron Collider. Click here for further detail.

What are antiparticles?• To every particle that has a non-zero value of some

quantity such as electric charge, it is possible to create another particle with the opposite value – this is the antiparticle of the original one. For an example, click here.

• Profile of Jonni Fulcher• An example of a collision• Jonni Fulcher Stunts

You may need to install the xvid codec - you can download it from here