Member States HST2000

The Creation of Particle Beams Paul Eaton -- United States Katarzyna Werel -- Poland HST 2000 CERN, Switzerland/France HST2000

Example of a Particle Hitting a Nucleus Scientists learn about the fundamental components of nature Best results occur between beams that consist of one pure type of particle By knowing what type of particles are interacting & what particles and energies are produced, conclusions are made HST2000

Pipe containing a Beam Pipes maintain a vacuum so that a particle beam can travel great distances HST2000

Target Area Particle beams are directed into various target materials to induce interactions Beam interactions with the atoms of the target can cause “cascades” of new types of particles HST2000

Particle Beam interacting w/ Hydrogen [H2] Scenes from the inside of a Bubble Chamber Charged particles leave a trail of bubbles after they pass through, similar to the trails left by jet airplanes HST2000

Particle Beam interacting w/ Hydrogen [H2] When particles come close enough to the nucleus of a target atom to interact, a variety of events could occur: 1. New particles could be formed. 2. Components of the original nucleus and particle could be scattered HST2000

Generalized interaction pattern The high energy particle penetrates the medium before a chance inter-action with the target medium HST2000

Generalized interaction pattern: electromagnetic cascade mass converted to energy and two photons (gamma) are produced  e HST2000

Generalized interaction pattern: electromagnetic cascade photon passes in proximity to another atom in the medium, producing an electron (e-) / positron (e+) pair e+  e- e  e+ HST2000

Generalized interaction pattern: electromagnetic cascade  e- e+  e- e+ this process repeats itself in a “cascading” fashion until there is not enough energy in the particles to continue e+  e- e+  e- e+   e- e+ e-  e- e+ e e- e+ HST2000

Generalized interaction pattern: electromagnetic cascade  e- e+  e- e+ this process repeats itself in a “cascading” fashion until there is not enough energy in the particles to continue  e- e+  e- e+  e- e+  e- e+  e- e+ *Notice: Only positrons, electrons, and photons are formed HST2000

Generalized interaction pattern: Hadronic Cascade The high energy particle penetrates the medium and fractures the atomic nucleus of the target medium K+ p n + - - HST2000

Generalized interaction pattern: Hadronic Cascade The high energy particle penetrates the medium and fractures the atomic nucleus of the target medium K+ p n + - - *Note: a large variety of particles could be produced, e.g., p, n, , , , ,  HST2000

Generalized interaction pattern: Hadronic Cascade - +  e  - +  e  The particles that have been produced may also contain high enough energy to either fracture another nucleus or further degrade itself K+ K+ p n K- - +  e   - +  e  *Note: a large variety of particles could be produced, e.g., p, n, , , , ,  HST2000

 Interaction Length Of a Hadronic Cascade The average distance a charged particle travels in a target medium before initiating a Hadronic Cascade - +  e   + e -  K+ - K+  p n K- - +  e  + e - -  HST2000

 Radiation Length Which results in an electromagnetic cascade The average distance a high energy particle penetrates a medium before initiating an electromagnetic cascade e+  e- e+   e+  e- e+ e-  e- e+  e-  e- e+ e+ e e+ e-   e- e- e+ e e- e- e+ e+ HST2000

Radiation vs Interaction Length in Lead [Pb] The radiation length in lead is only 0.56 cm long  e- e+     - K+ e - K+ + p n K-  - - +  e  e  - +  e  e + The interaction length is 17.1 cm  0 5 10 15 20 25 30 35 40 45 50 HST2000 -

Lead Target 0.4 cm in length High energy electrons and positrons will be produced  e- e+  e- e+  e- e+ p Virtually no hadrons will be produced 0 5 10 15 20 25 30 35 40 45 50 HST2000

Radiation vs Interaction Length in Copper [Cu]  e- e+ The radiation length is 1.5 cm   +  e - K+ - - e - K+ +  p n K-  e - +  e  + e - -  The hadronic length is 15.0 cm 0 5 10 15 20 25 30 35 40 45 50 HST2000

Length in Copper [Cu] target 40 cm  e- e+ Electromagnetic cascade occurs totally inside the copper target    K+ - e - e - K+ + + p n K-   e - +  e  + - -  The hadronic cascade begins within the target but critical energy is not reached and low level hadrons leave the target 0 5 10 15 20 25 30 35 40 45 50 HST2000

Lead Target 0.4 cm in length High energy electrons and positrons will be produced  e- e+  e- e+  e- e+ p Virtually no hadrons will be produced 0 5 10 15 20 25 30 35 40 45 50 HST2000

Path of Electrons/Positrons Most of the electrons and positrons exiting the target will be clumped together following the path of the original high energy particle  e- e+  e- e+  e- e+ = electrons = positrons 0 5 10 15 20 25 30 35 40 45 50 HST2000

Path of Electrons/Positrons some of the trajectories of the particles will cause them to be lost Most of the electrons and positrons exiting the target will be clumped together following the path of the original high energy particle  e- e+  e- e+  e- e+ = electrons = positrons 0 5 10 15 20 25 30 35 40 45 50 HST2000

Main beam is directed into a magnetic field = electrons = positrons  e- e+  e- e+  e- e+ A magnetic field, where the field direction () is pointing into the page 0 5 10 15 20 25 30 35 40 45 50 HST2000

Path of Electrons/Positrons  e- e+  e- e+  e- e+ 0 5 10 15 20 25 30 35 40 45 50 HST2000