ISU Coloq 11-3-2014

Elastic -vs- Inelastic Collisisons

Elastic Collisions: Conserve P and E

Inelastic : Only Conserve P

4-Momentum vector definition using Ryder convention

$P_{\mu} \equiv \left ( \frac{E}{c} , - \vec p \right )$

$P^{\mu} \equiv \left ( \frac{E}{c} , \vec p \right )$

$P_{\mu} P^{\mu} = \left ( \frac{E}{c}\right )^2 - \vec p^2 = E^2-p^2 = m^2$ if you define the speed of light as unity

$P_{\mu} \equiv \left ( \vec p, -E \right )$

$P^{\mu} \equiv \left ( \vec p , E\right )$

or Kollen

$P_{\mu} \equiv \left ( \vec p, iE \right )$

$P^{\mu} \equiv \left ( \vec p , iE\right )$

Momentum transfer is defined as

$q_{\mu} \equiv ( \omega, \vec q) = P^i_{\mu} - P^f_{\mu}$ : conservation of momentum

$q_{\mu}q^{\mu} = (E_i - E_f)^2 - (\vec {P}_i - \vec{P}_f) \cdot (\vec {P}_i - \vec{P}_f)$

$= m_i^2 +m_f^2 - 2E_iE_f + 2 \left | \vec {P}_i \right | \left | \vec {P}_f \right |$