NEWS

1
NEWS

• Beginning Monday, Jan. 26, P4511 will meet in
  Folwell Hall Rm. 104.
• The enrollment cap on the class will be raised to
  45, so everyone currently wait-listed or
  otherwise shut out will be admitted.
• If you are not enrolled now, you can and should
  register on Monday, because permission numbers
  will be required beginning on Tuesday.

2
Lorentz Trans.?Energy-Momentum
Read Das and Ferbel Appendix A and Chap. 1.
Homework 1 is posted.

• Consider a particle at rest in S. What are its
  momentum and energy in S'?

3
Time Dilation and Particle Decay
CM
Proper Lifetime
Lab
If we know the speed (mass, momentum/energy), we
can determine the lifetime by fitting the
distribution of path lengths to the expected
decay distribution (exponential).
4
Example
CLEO-c Experiment
?
CDF Experiment
5
Build a Particle

• The sum of two 4-vectors is a 4-vector.
• Consider the 4-momentum of a system of two
  particles, for example the daughters of a
  decaying parent particle.

• Compute length2

m12 is the effective mass of the two-particle
system
6
Strategies for RK Problems

• Use full Lorentz transformation for boosts of
  4-momenta, but rely on invariants as much as
  possible to simplify computations.
• Specifically, for threshold calculations
• What is the minimum energy of _________to
  _________?
• Relate the initial state in one frame to the
  final state in another with invariants and
  4-momentum conservation.

7
Discovery of the Antiproton
Before
After
Lab
CM