Subatomic Physics

2.11. References 37
(b) Extreme relativistic energies.
2.21. Compare a typical colliding beam luminosity (∼ 10 34 particles per second) to
that for a beam of protons of 1 µA colliding with a stationary liquid hydrogen
target 30 cm long.
2.22. (a) Why is beam cooling important for pp colliders?
(b) Describe electron cooling.
(c) Describe stochastic cooling.
(d) * Describe the arrangement at Fermilab for beam cooling and pp collisions.
(e) Why can thin foils not be used for beam cooling?
2.23. Discuss heavy ion accelerators. What are the similarities and differences to
proton accelerators? How are the heavy ions produced? List some of the ions
that have been accelerated and give the maximum energies per nucleon.
2.24. Find the center-of-mass energy at HERA (see Section 2.7).
2.25. (a) An imaginary accelerator consists of colliding beams of electrons and
protons, each of 2 TeV total energy. What laboratory energy would be
required to achieve the same center-of-mass energy if electrons collide
with stationary protons (hydrogen)?
(b) Repeat part (a) for an energy of 2 GeV instead of 2 TeV.
2.26. An electron beam of 10-GeV energy and a current of 10 −8 Aisfocusedonto
an area of 0.5 cm 2 . What is the flux F ?
2.27. Assume that a beam pulse at a 100-GeV accelerator contains 10 13 protons, is
focused onto a 2 cm 2 area, and is extracted uniformly over a time of 0.5 sec.
Compute the flux.
2.28. A copper target of thickness 0.1 cm intercepts a particle beam of 4 cm 2 area.
Nuclear scattering is observed.
(a) Compute the number of scattering centers intercepted by the beam.
(b) Assume a total cross section of 10 mb for an interaction. What fraction
of the incident beam is scattered?
2.29. Positive pions of kinetic energy of 190 MeV impinge on a 50 cm long liquid hydrogen
target. What fraction of the pions undergoes pion–proton scattering?
(See Fig. 5.35.)